How many solar panels do I need?

This question is best answered by asking, how much do you use?

By building a load profile that outlines all the power you intend to consume during a day and estimating the duration of each device and its power draw you can build a power profile. A power bill is similar but not to the same level of detail as it only shows a total for the month which you divide by the number of days in that month. That gives you a kWh value. That number is sometimes referred to as the number of units. It's what you are charged for on your power bill. i.e. 500 units for the month at 20 cents per unit (1 kWh) would be $100. 500 units divided by 31 days equals 16.12 units per day. So that's 16kWh, and in New Zealand, the peak sun hours over winter are only 2 hours. So you'd need an 8kW solar array which will produce on a clear day 8kW per hour and with the 2 hours of usable sun energy in a day you'd generate 16kWh of power.

This would generate enough power to offset your consumption, but it's not all at the right time. You use power at night from the grid so you'll be charged for importing power to your house. But during the day while you aren't at home or your power usage is low you'll be exporting to the grid which may result in you receiving a small credit to your account.

You can see how the real way to benefit from solar is to utilise the sun's energy during the day and limit your need for it at night. This is where batteries can help as they store the day's energy for you to use at night.

Which is better Optima or Odyssey

The choice between Optima and Odyssey batteries depends on your specific needs and preferences, as both brands offer high-quality batteries with their own unique features and advantages.

Optima Batteries:

  • Optima batteries are known for their distinctive spiral-wound design or different coloured tops, Yellow, Red & Blue
  • They are designed to deliver a high burst of energy, making them suitable for starting applications and providing strong cranking power.
  • Optima batteries are also spill-proof and maintenance-free AGM design with pure lead.
  • These batteries are known for their reliability and are often used in performance and enthusiast vehicles and are lighter weight than the same sized Odyssey because of the lower capacity (Ah).

Odyssey Batteries:

  • Odyssey batteries are recognized for their robust deep cycle capabilities because of the increased Ah, making them suitable for applications that require continuous and deep discharging, such as RVs, boats, and solar systems.
  • They too are designed to deliver a high burst of energy, making them suitable for starting applications and providing strong cranking power because they are pure lead AGM.
  • Odyssey batteries are known for their long service life and strong performance in demanding conditions.
  • They are versatile and can be used for both starting and deep cycling applications.

The choice between Optima and Odyssey batteries depends on your specific needs. If you require a battery primarily for starting applications in vehicles and prefer a unique spiral-wound design, Optima batteries might be a good choice. On the other hand, if you need a battery that excels in deep cycling and can handle sustained discharging, Odyssey batteries are a strong option. Consider the requirements of your particular application and select the battery that aligns with those needs. Both brands are known for their quality, so you can't go wrong with either choice.

Charging efficiencies

In this article, we will discuss so of the losses when power is converted or transformed or used. Our niche is the conversion of energy and with that there are losses. For example, a light bulb was designed to provide light. It does this by making a small filament of wire glow. The glowing generates the light that's wanted but also heat and that is a wasteful by-product of a light bulb.

With battery charging which is a chemical reaction, there are losses through the chemical conversions of electrons moving between plates and acids. These losses are minimalised with improvements in the technology with over 100 years in development. Losses in charging lead-acid vary from 12% for AGM batteries to about 20-25% for wet cell batteries. That means a 100Ah battery requires 112-125 Amps to recharge and store 100Ah of usable energy.

When you convert DC power from a battery into AC mains power using an inverter the equipment inside the inverter uses power and that accounts for a 5% loss in available power. The same happen when converting AC power into DC power, these devices are called power supplies, or chargers, or power rectifiers. Switch-mode supplies are typically used in all modern-day equipment to help reduce these inefficiencies but they need to be calculated and allowed for.

An example of this might be an off-grid solar system with a small inverter for charging a cellphone.

Solar panels generate DC power 18-20% efficient, that's run through a solar controller 95% into a battery for storage 85% efficient. The mains power inverter converts DC power into AC mains 95% and you connect your phone charger in here. The charger is only 90-95% efficient which then connects to your phone's Lithium battery. Let's just say here it's 99% efficient at charging. All in all, you have four pieces of equipment all with up to 10% losses so your generation of the panels needs to be almost twice the power you want to consume.

When using mains power or grid-tie to power your home but have batteries for backup energy there are losses. You also lose more power in converting them back from DC stored energy in the battery back into usable mains power. This highlights an issue with grid-tie and battery backup. Multiple conversions, the storage, use and generation all have efficiencies and losses.

In future articles, we'll discuss DC versions much like our DC to DC chargers. Direct DC Coupling in a renewable energy system and more.

Robust and Reliable with Odyssey Batteries

Odyssey batteries are renowned for their exceptional robustness and reliability. These high-performance batteries are engineered to meet the most demanding power needs, excelling in various applications such as automotive, marine, and industrial equipment. Their design incorporates Absorbent Glass Mat (AGM) technology, ensuring superior vibration resistance, shock tolerance, and long-lasting endurance. Odyssey batteries are built to endure a wide range of environmental conditions and extreme temperatures, making them a trusted choice for off-road enthusiasts and those seeking reliable power sources in challenging scenarios. With impressive deep cycling capabilities and quick recharge times, Odyssey batteries consistently deliver dependable and long-lasting performance, earning their reputation as a top-tier choice in the world of battery technology. Whether you're looking for a reliable source of power for your vehicle or equipment, Odyssey batteries have proven time and again to be a robust and trustworthy choice.

Hardware differences for Grid Tie and Off Grid

With a grid-tie connection, the property uses mains power provided from the nationwide power grid as a secondary power source. It generates DC power from solar panels, sends that power through an inverter which converts it into mains power which is used within the home or passed back to the national grid. This is passed back power is referred to as selling back.

With an off grid setup other than your solar panels you'd use some other source of secondary power for times when the sun's not shining. Options include a generator, wind turbine, hydro-power or battery backup each of these systems has its own pro's and con's but each situation for their use and or cost, duration, return on investment will differ. The main schematic difference between a grid and off-grid though is an off-grid generates DC power which it stores in batteries using a charger (the name of the charger will change depending on what your charging source is. A solar array uses a solar controller, wind and hydro both use controllers (in fact all 3 use the same model controller in different ways so if you have multiple sources of generation you will require multiple controllers) All these controllers essentially charge your batteries, one might say solar/charge controller or wind/charge controller. These batteries are used to provide power and flatten out the curves of either low power generation times or high power usage from multiple appliances all being used at the same time. The second part of an off-grid system is the generation of mains power onsite, rather than coming from the grid it is converted from DC power (the batteries power). This is just like the inverter used in a grid-tie setup to convert the solar DC power to mains AC power.

Are Deep Cycle batteries good for cars

Deep cycle batteries are not typically used as the primary starting batteries in cars. Instead, they are designed for applications where the battery needs to provide a steady, deep discharge over a longer period, such as in RVs, boats, golf carts, solar power systems, and electric forklifts. Deep cycle batteries have thicker plates that are better suited for these deep cycling applications.

Starting batteries, on the other hand, are designed to deliver high bursts of energy to crank the engine and then quickly recharge. These batteries have thinner plates and are optimized for providing the high current needed to start the vehicle's engine.

Using a deep cycle battery as the primary starting battery in a car is not recommended because it may not provide the necessary cranking power and could lead to difficulties in starting the engine. However, some vehicles, especially hybrids and electric cars, use a combination of a starting battery and an auxiliary deep cycle battery for accessories and electric power. In these cases, the deep cycle battery is used for different purposes and not as the primary starting source.

If you're experiencing issues with your car's battery, it's best to consult with a professional mechanic and choose the appropriate battery type for your vehicle's specific needs, which is typically a dedicated starting battery.

Difference between Grid-Tie and Off-Grid

In its simplest form "the grid" is the power grid that connects homes all over the country which provides them with mains power.

When you are connected to the mains power grid you are referred to as grid-tied or vice versa tied to the grid. So Off-Grid simply means operating your own power not tied to the nationwide grid.

When you go bush or remove yourself from your device people quite often refer to this as going-off-the-grid. Not quite the same but it might be where some people associate off-grid with being remote or removed. It doesn't mean without technology though as a modern-day off-grid setup can actually be smarter and more intuitive than your current smart meter.

In-fact building your own power source with battery backup, solar and grid independence gives your location the ability to store, sell, distribute, manage, monitor, and action your power in almost unlimited ways. All with the benefit of resilience to outside infrastructure, outages, or scheduled power cuts. The components and hardware used in grid and off grid should be from a quality internationally recognised brand as the hardware should be assessed as a system costs that you can calculate over a 20 year period for a good return on your investment.

There is another variation from grid or off-grid. It's really a hybrid of the two systems taking the best of both and in recent years its becoming more and more common. Grid-tied with battery backup has been around for some 15+ years but marketing by Telsa and the Teslawall has made everyone aware of its existence. LG chem and others have similar "wall" designs which give people options for internal or external system storage designs.

Are Deep Cycle Batteries AGM or Gel

Deep cycle batteries can be either AGM (Absorbent Glass Mat) or gel batteries. These are two common types of deep cycle batteries, each with its own characteristics and advantages.

  1. AGM (Absorbent Glass Mat) Batteries:

    • AGM batteries use a special type of glass mat separator that absorbs and holds the electrolyte (acid) between the battery plates.
    • They are known for their sealed design, making them maintenance-free and preventing acid leakage even if the battery is damaged.
    • AGM batteries are typically more resistant to vibration and shock, making them suitable for various applications, including recreational vehicles (RVs), boats, and renewable energy systems.
  2. Gel Batteries:

    • Gel batteries use a gel-like electrolyte that is immobilized within the battery cells.
    • They are also maintenance-free and spill-proof because of their sealed design.
    • Gel batteries are known for their deep cycling capabilities, making them ideal for applications where a steady and deep discharge is common, such as in solar power systems and electric wheelchairs.

So what will it be AGM or Gel?

Both AGM and gel batteries are considered deep cycle batteries, which means they are designed to handle repeated charging and discharging cycles without suffering from reduced capacity or performance. The choice between AGM and gel batteries depends on the specific requirements of the application and the preferences of the user, as well as factors like cost, maintenance, and environmental conditions.

Some products to consider might be:

Dual Battery Options in Boats or Motorhomes

Many industries have similarities and principals of one that can carry over to the other. Marine industry or marine electricians to be precise can carry over their ideologies to motorhomes and remote off-grid setups.

Boats have utilised batteries since their invention to power electronic equipment onboard including starting an engine. Later people added living luxuries like lights, heaters, pumps, cooking. More recently GPS, Radar, Satellite Radio, auto-pilot, air condition, these are high demand and long duration discharge applications. Batteries have been used in full electric and hybrid electric installations also. These types of batteries all have a different purpose and you'd typically use one battery type for each installation for each system. Motorhomes while on land have many of the same systems and therefore are relatable.

When it comes to trailer boats here in NZ anyway it's pretty standard to have a dual battery system, one battery to start and one battery to discharge electronics from. In motorhomes we have one battery to start the petrol engine which was factory fitted and another to discharge from for running everything behind the driver. This is referred to as the house battery or the service battery, it's normally the large deep cycle battery used to run everything and is often connected to solar panels to recharge just like in a boat.

Marine industry made the VSR or Voltage Sensitive Relay famous (also called Voltage Control Relay) as it was seen as a way to charge the house battery using diverted energy from the alternator. As time went by these got smarter to include a delay before switching to the house battery so that the start battery would charge a little first. Later versions include a parallel connection of both batteries so they would charge together. This works OK if both batteries are of similar physical size and similar state of charge but is a terrible idea when a house battery bank is upwards of twice the capacity. Even worse when the house bank is 5 times the capacity of the starting battery as they never charge correctly and the variances in voltage could take days to equalise meaning the relay will open and close repeatedly for days while switching between the two banks which can lead to the VSR failing.

Better solutions today are DC charging systems where energy is taken from one power source to charge the other. In this situation, the first battery is being recharged by the alternator and the second battery is being charged by the first battery.

Other things to consider are:

  • If the battery types are different do you need to use different voltages for flooded vs. AGM
  • If you have a lithium house bank what voltage is needed to charge but more importantly does the BMS have alerts or a cut out if something is wrong
  • If the lithium house bank is very large how long will the alternator running at 100% of max output
  • How far away from the start battery is the house battery because voltage loses should be accounted for
  • different types of batteries have different price points and some might be better or more suited than others

Lastly a consideration of design and purpose, batteries can be dual purpose, it's not that they are really designed that way it's more like a very large 260Ah deep cycle battery still has a 1350CCA rating so while it might be deep cycle, used primarily for a house bank doesn't mean it can't be used as a starting battery. Therefore you can simplfy a system design if you needed say 100Ah of starting battery, but 200Ah of house battery. Normally a VSR might be a good idea but what if your house battery or spare battery didn't have enough power to start your motor if your main start battery failed? This is why having a good quality house battery is important. It's your spare "get me out of jail" battery. It's not like you can hop out your boat and push start it like you can a car or motorhome. So you can build some insurance into your design and maybe rather than worrying about needing a good DC to DC charger you could use a better start battery which matches the house battery size or type (both being AGM) and therefore you have more usable power and less requirements on electronics.


Why you can't use a Lead Acid charger on Lithium Batteries

The importance of using the correct charger for lithium batteries becomes apparent when comparing standard 12V lead acid batteries used for deep cycle applications with their lithium counterparts. Although the nominal voltages may seem similar, with lead acid ranging from 12.5V to 12.9V and lithium exceeding 13V, it is essential to understand the differences in charging behavior and requirements.

Lead acid chargers typically allow a longer duration for bulk charging, around 20 hours, while lithium batteries require a much shorter time, usually 4 to 5 hours. This discrepancy arises because the charger's capacity should be within 20-25% of the lithium battery's fully rated capacity. Rushing the charging process for lithium batteries can cause overheating, potential faults, and failures in the Battery Management System (BMS).

The subsequent charging stage, known as the Absorption stage, differs significantly between lead acid and lithium batteries. Lead acid batteries exhibit increased internal resistance as they approach their maximum capacity, absorbing every last bit of energy. This process, accounting for 40% of the total charged capacity, brings the battery to around 80% state of charge (SOC). However, lithium batteries do not require this absorption phase. Instead, the charger algorithm typically transitions straight to a float voltage as the lithium battery is already at 80-90% SOC. The purpose of the float voltage is to slowly balance the remaining capacity without overloading or overheating the BMS. During this absorption charge, the balancing system may activate, and the BMS may initiate a shutdown to allow the unit to cool down and the cell voltages to return to nominal levels. These additional stressors on the BMS can compromise its functionality and longevity.

It is important to note that other charging issues, such as thermal runaway, can occur when using the incorrect charger. These issues further strain the cells and contribute to the premature degradation of the battery. Lithium battery lifecycles are typically measured in years rather than cycles. While the claim that "it works fine" may initially seem valid within the first year, a lithium battery is often sold with the expectation of a 10-year lifespan and 6000 cycles. Evaluating its usable power and performance at the five-year mark will reveal whether the battery is still functioning as originally advertised.

In summary, using the correct charger for lithium batteries is crucial due to the significant differences in charging behavior, absorption stages, and BMS requirements. Neglecting these considerations can lead to safety risks, compromised performance, and a shortened battery lifespan.

Total Loss Ignition Systems

What is a Total Loss Ignition System? Its using a petrol engine without an alternator.

Effectively you are running your vehicle's electronics from your battery which includes any spark to the ignition system, gauges, lights, fans, pumps, transponder or data logger, GPS, radio, comms etc etc.

Again we'd highlight the purpose of this battery is the most critical thing to consider. Do you want to have enough cranking power to start the vehicle or do you need to drive for a few hours without a recharge? (the latter being something to consider if your alternator dies while in competition or along way from home. Its referenced on the specs of a battery as being the reserve capacity (RC). It's measured at 25 amps and simulates SLA which was considered the essential requirement to operate a vehicle some 20 years ago. (Starting, Lights, Accessories). So the 25 amps could be discharged for X number of minutes (i.e. 90RC) until there is no usable voltage remaining in the battery.

With high flow fuel pumps and water cooling systems on high power engines a fully charged 12 volt battery might only be 11.5 volts under discharge load. This is to low a voltage for the ignition system to operate effectively and it makes current draw that much higher that it is far from ideal. An alternative would be to run a higher voltage battery like our XS Power 16 volt battery. Underload the voltage would still be 14 volts which is similar to the voltage output of a high powered alternator without the overhead of the alternator drive belt loading the engine or the extra weight being carried.

This is ideal for systems like drag cars or midget vehicles used in speedway which are push started. The 16 volt batteries also make for excellent jump start batteries on 1400 plus horsepower engines used in Hydroplanes, river racers and jet sprint boats.

Will 540 watts and a big battery bank allow me to go off-grid full time?

We get asked questions like this all the time and I guess most would say yes that will be fine, some might say it depends on your load requirements, few would say no. The answer lies within the maths and calculations of your power consumption which is subtracted from your power generation. To work this out you take the power of each device and how long it's used for to get a daily demand. Now there are also peak loads and hours of minimal usage but for now, let's just work with a total figure for the day then divide that by 24 hours. 

We recently investigated a system where the customer had spent over $6500 on multiple replacement batteries & upgrades to the charging and solar system on top of the base installation the motorhome came with to resolve their shortfall. Only a few years ago a 150W panel and a 220Ah or 260Ah battery were all your motorhome came with which would be considered only a mid-sized occasional off-grid solution now. Many still don't have anything more, especially those vehicles out of Europe built for the rental market unless upgraded locally.

Their new setup included 540W (3 x 180W) Solar panels and 2 x 270Ah AGM batteries, DC charging from the alternator but it turns out they don't actually travel that much. The panels are connected in parallel into a 20A solar controller and they have 50A of AC Battery Chargers they run off a generator if the batteries get low. As it turns out that means they run the generator every second day to ensure they keep the batteries above 12.5 volts so they will get 5 years cycle from them.

With a moderate 5A discharge per hour, 24 hours a day the performance figures of their new system look like this:

540W-Solar-w-540Ah-batteries Did you know...

We didn't want to alter the chart in any way to correct the errors we can see but we will explain something to clarify. The last column is headed LOLP meaning Likelihood Of Lost Power. in the months of May through to July there is Zero % of the system working and Battery State of Charge will be 100% discharged. But you will notice in Jan - Mar then Oct - Dec there is less than 1% chance of the system failing. April it's 50/50 and in August an 80% chance based on the last few years sun hours in the Coromandel when the panels are mounted flat on the roof of your motorhome. The reason the chart is displaying errors is nobody with this level of information would actually design-build, or implement a system that is shown to fail. The system would require over 1kW of solar to be able to maintain a 5A continuous load (120Ah but 133.3Ah when losses are included daily). You can see days carry over for the batteries is only 3 days without sun and that in summer months in the southern hemisphere you'd have plenty of excess power.

That might lead some people to figure out that 540W of solar far exceeds the 20A controller included. But over the summer months, the battery will fully recharge from the max 50A discharge from overnight in the first 3 hours of sun in the morning so will be in float mode only supplying discharge load at midday in the full summer sun. With the large array size, you have the benefit of collecting more of the low-level power for longer over the winter months. It's just not enough to meet demand.

Marine Batteries and CCA requirements

Have you ever wondered why a 100HP outboard requires a 800CCA battery? It actually has nothing to do with 800 cold cranking amps and the 30 second discharge time at minus 18 deg centigrade.

A 100HP outboard these days has an electronic ignition system and a high torque starter motor which only draws about 150-200A. It will start in 1 second so you could actually use a 7Ah alarm battery you use on your fish finder to start the outboard. It might, however, record a low voltage warning in the engine management ECU, and that if done repeatedly will void your mechanical warranty of the outboard. The low voltage happens when you draw high current from a small capacity battery, the voltage dips but when the discharge turns off the voltage goes back up.

So this is why you are told 800CCA. A few things to note also, have you ever noticed that there are plenty of batteries just under the magic 800CCA that are $80-100 less? That's because back in the day the outboard manufacturer being local to a country had to determine what was locally available and suitable. Many times that lead to supply agreements and those agreements were made to benefit one brand over all the others with not quite enough CCA. Anyway I digress, the reason for 800CCA is that a typical battery would have to be approx 80-90Ah to achieve that kind of spec and if its 80 plus Amp Hour then even if the battery is a few years old and is half discharged, you've got some electronics on prior to turning the key and the temp is a chilly few degrees above freezing. The battery will still have enough power to start your outboard.

There you have it, a worst-case scenario used to resolve a starting point and avoid liability of being sued. (a genuine concern if you are in America)

We only have a small space for solar what can we power?

We have been designing Marine & Motorhome charging systems for over 12 years and have seen many changes in the industry and new inventive solutions are developed to address known shortcomings of traditional solutions. The biggest is the inclusion of DC charging from the vehicles alternators, programable regulators, MPPT as a standard for solar and arrays getting larger to meet today's power-hungry demands.

Subsequently with the recent demand for off-grid tiny living, we have been asked how to power a tiny home? The same information applies in all 3 instances as the demand for power generally exceeds the available roof space which isn't that much different from a motorhome or boat, it just doesn't have an engine to power it.

One of the most common questions is how much power do I need? Then how much solar do I need to support that amount of power? Given every person's needs are different maybe it's best to just give two examples of what's common for a Marine or Motorhome installation and you guys find out where you fit on the consumption scale.

In this first example, we investigate how much solar is required when we have a very modest 30W (2.34A) current draw 24 hours a day like what a small fridge would consume with 300W of solar mounted flat on your roof or deck with a latitude across the country in Christchurch which has average sun hours for the country.

300W-Solar-with-35W-load- Did you know...

You can see that in February with an array/load ratio (which means the amount of excess power available) you are going to start to have issues if the weather isn't sunny every day. Depending on the size of your battery bank it will change how many days it is until your bank is 100% discharged. But just important is it will take 5 days of full sun to recharge a completely flat battery bank is sized as we had with a small 100Ah battery. By March you will remain in deficit till September and your batteries will be severely damaged and not able to function correctly throughout summer again if it was not for the arrays power running devices during the day.

In the second example we increase the power drain to 40W per hour continuously (24 hours per day) which might reflect a fridge freezer, or LED lighting, USB chargers, TV or radio, recharging a notebook, occasional use of a water pump. We used a 200Ah battery bank and kept the same 300W solar array using the same MPPT solar controller.

300W-Solar-with-40W-load Did you know...

You can see above power might start to become something to savour throughout January but you won't see enough again till October and that month will really be all about trying to maintain a full charge even if you did charge on a generator or mains power on the 1st Oct. Your battery would have had an average State of Charge of just 76% and would most definitely be sulphated. These deficit charging won't fully be noticed till February in the second year when things all start going wrong and you start complaining about how poor the batteries performance has been. Of course, the opposite is true, the solar arrays ability to collect the required amount of power required has been lacking, resulting in battery failure.


Winch Vehicles

We often work with clients incorporating a winch on a vehicle. The winch manufacturer's specification includes recommendations of a battery, given they often aren't specific to brand or type of battery there are many considerations the owner needs to address. Here's a simple guide to help you through the process:

1. Purpose of the battery - in this instance the battery is needed to provide high current for a sustained period of time (much like a CCA rating over 30 seconds). The issue with CCA ratings is a high-quality battery like an Odyssey Battery will have a high CCA but will also be small Reserve Capacity or Amp Hour because it has a high power density and a small battery can output as much power as a larger wet cell or gel battery.

2. How often you use the winch - if it's occasional use then a similar-sized battery to your factory battery but with a higher performance spec might be all you need. You aren't reducing the Reserve Capacity and hopefully are increasing the battery's high power output.

3. If you run the winch for more than 30 seconds - you need to consider these as long duration discharges at high power, which means you are cycling the battery and therefore need to consider a deep cycle battery so you can repeatedly discharge and recharge. Remember though, a flooded deep cycle battery won't have a high CCA if the same physical size as your normal start battery. To compensate you'll need to increase the size of the deep cycle battery to get a higher CCA.

4. Vehicles charging system - Charging of the vehicles alternator would typically be fine but if you go off-road for the day and use your winch 5 or 6 times with a lot of low RPM driving and long duration winch pulls your battery will be quite flat once the surface voltage has dissipated. The alternator maintaining a voltage above 13 volts artificially leads you to believe the battery is fully charged. But if you leave it for 24 hours without using then check the voltage again you might find your voltage below 12 volts which is over 50% discharged. You'll need to use a maintenance charger after such days to keep the battery in good health.

That's a great basis for discussion and one many variables can be considered and put into play. Remembering the purpose of the battery is actually more important than it's spec sheet. 600CCA is great for instant power but not reserve capacity. Large capacity is great but not if there isn't a high power discharge available. Physical size may be important if under the bonnet of your vehicle. Large alternators only work if the battery has a low internal resistance to accept a large load current. All these reasons are why we recommend Odyssey Batteries with their extensive range.

Things you need to know about batteries

Batteries are built with a specific purpose in mind. This encompasses the materials used in the manufacture of the battery, the glues/adhesives used. The types of plastics used in the case and many other physical attributes. But there are things that can't be seen or measured easily like, the thickness of plates, Specific Gravity (SG) of the acid which has a huge impact on the battery's ability to give a high CCA when new, but if a high SG also limits the batteries longevity.

The next is true of all batteries and brands but we'll generalise one brands product offerings to give an overview of how their models within the range differ. And we'll be even more specific and limit this article to just AGM batteries within a single brand to give a better overview of the variations.

The first and cheapest entry-level AGM would be a 3-5 year design life battery (which means typically a 1 year warranty) it also means traditionally a battery manufactured with cheap labour and high volumes of turn over. Design life does not mean it will last 3-5 years either, the product will typically last 2-3 years in its desired application. Please note if you use it in the wrong application it might only last 6 months to a year. These batteries are also always referred to as float life batteries as they are meant to be connected to a charger or power supply full time like used in an alarm or UPS system.

Next would be a float life battery with a 10-year design (meaning it might last up to approx 8 years if conditions are suitable). These are occasionally used as an entry point deep cycle battery as they will give approx 250 cycles to 80% which would be similar to use of an occasional user in a cyclic application like a weekend motorhome or boat enthusiast. They might advertise 400-500 cycles at 50% but this can rarely be proven.

Then you'd enter step up to the next design of thicker plated batteries with a lower SG level to give the batteries a better reserve performance over a longer duration. This is really where true deep cycle batteries start. They might have an advertised performance of 800-1200 cycles at 50% depth of discharge. They are also flat plate construction and in a general statement we'd say are the high end of Chinese production. These batteries will however all look the same as the above 5 and 10 year design float life batteries so you really need to know what to look for and test yourself to prove the claims of capacity and longevity.

If you were to try comparing one brand with another you must first match the above 3 characteristics before reviewing and matching apples with apples the following technical specs: Amp hour, C rate (number of hours discharged to calculate the Amp hour rate), end voltage of discharge rate, temperature of discharge rate, start temp of discharge rate test, weight of the battery. Again, like for like as in AGM with AGM, not AGM with Lithium or AGM with Lead Carbon). Cycle life vs. depth of discharge. Once you have worked your way through that nightmare, brand, warranty or number of pages and exclusions, after sale service, advice given up front vs. retrospective, cost, location, distribution, ability to diagnose or test if there is ever an issue. All these need to be reflected to get a sense of value or worth in a battery.

That typically brings us to the end of the upgrade path by a single brand as the technology doesn't change for a 6 volt or 2 volt cell if its AGM. There are other chemistries available from the same said manufacturer like OPzV which are typically a tubular gel and in many cases far superior to the 12 volt AGM deep cycle batteries with cycle life charts normally starting at 1000+ for 80% Depth of Discharge. Do not even confuse these with traction batteries, they are used very differently from a reserve capacity battery.

As far as OPzV or traction batteries are concerned do not think they are better for you though, it's all about the balance of charge time, current and discharge rate. Mostly there is a cost difference and which point you might consider Lithium. This is where expert advice is required to match your use with the intended purpose of the battery and your available charging systems.

Returning to traditional 12 volt batteries or the slightly higher capacity 6 volt cells we then move to high-end global brands where the reputation of the brand is world-renowned. Like Odyssey, SunXtender, Lifeline, Optima, Trojan, Sonnenschein. These batteries typically use industry-standard systems for measuring performance, life cycle and are well proven and offered by distributors like ourselves because of the brand's reputation and the requirement to service and support with adequate ability.

Solar Installation Component Glossary

Here's a quick rundown on parts used in a variety of solar installations and what they are used for:

Solar Battery - to store energy for later use

Solar Panels - Framed cells with a series of silicone wafers which generate DC voltage used to charge batteries

Solar Array - A collection of solar panels connected together to provide DC voltage

Frame rails - Support structure used to build a platform to place solar panels on. They can be mounted on walls, roofs, ground, tilted frame rails.

Solar Controller - (also called Charge Controller) connects the solar panels to the battery bank. The cheaper version use PWM (Pulse Width Modulated), the better versions use MPPT (Maximum Power Point Tracking) to harness the variable energy from the sun during a day and convert it into the correct charge voltage which is put into the batteries.

String Inverter - is really a solar controller that you'd use connected to the national grid across a larger array at a residential voltage up to 600VAC. In commercial installations, the string inverter can be up to 1000VAC. These higher voltages allow the solar panels to be connected in series to add voltage while the current remains the same as that of just 1 panel. These units only convert DC energy from solar to AC and connect to your main switch board. If the mains power stops for any reason these inverters also stop working for safety reasons.

Grid-Tie or Grid-Tied or Grid Connected - means a system connected your onsite power generation to the national grid.

Off-Grid - means your system is stand-alone with no national grid network attached. Typically used in remote locations.

Hybrid Inverter - allows a string inverter which only generates AC power from DC solar, to also be able to use the DC power from solar to charge a battery bank.

DC Coupled System - Uses the DC power from solar panels to be put straight into batteries with only the MPPT controller ensuring the voltages are correct to charge the batteries and minimilising conversion inefficencies. It then uses the stored DC energy in batteries to pass through an AC inverter to power the AC load. It can also export this power to the national grid once its in AC if you configured your system to do so.

AC Coupled System - Inverts the DC power from solar panels into AC and supplies the main switchboard and any loads attached. When there is excess power from solar available it can either export the AC power to the national grid. It could also convert the AC power back into DC power and charge a battery bank. When the stored power is needed it converts the DC back to AC to supply the main switch board.

Zero Export - this is when the national grid carrier doesn't want you to export any of your excess power back to the grid. Many regions in NZ now have a 5kw Max. export limit managed by Transpower and many power retailers only pay back a certain number of units of energy back to the grid per day.

Fuse - Fuses need to be held in place so use some form of fuse holder, they have different current ratings and each rating is typically a different colour. So if your blue fuse blows then you need another blue fuse to replace it. There are many different style of fuses from Class T, NH, Auto Blades, Maxi Fuses, Midi Fuses, Mega Fuses, ANL or FBT tag Fuses. The right type of fuse should be used for each instance.

Circuit Breakers - These are like a fuse, used to protect your circuits from over current. A fuse breaks and needs replacing but a circuit breaker can be reset and used again. There are 3 types of circuit breakers, automatic (which disconnect when blown but reconnect once they have cooled down). Manual Reset meaning it blows (opens the circuit) if tripped, then requires manual switching on to reactivate the circuit. Lastly PTT (Push to Trip) You can manually open the circuit and then re-close the circuit just like using a switch but with current protection builtin. Variations include double pole which means a breaker for the negative cable and a pole for the positive cable so total electrical isolation is achieved. There are also polarised and non-polarised, the later meaning they do not have an inward direction or outward direction in which the energy should flow from battery to loads.

Charger - A device that provides voltage above the open circuit voltage of a battery. This could be a solar controller, mains powered charger or DC power charger (DC to DC charger). Modern-day chargers would have charge profiles and can be set to best match the charge voltages required by the batteries manufacturer.

Cables - These are used to connect all the components on the DC circuit, normally multi-string copper cable which might also be required to be tin-coated. This cable is measured by its cross-section in mm squared. The number of strands is important for flexibility and ultimately affects its maximum current capacity. The insulation is also important, many require double insulated where there might be a coloured (blue or red) plastic around the copper, then each colour, if the cable is 2 core (a red and blue together), is then moulded inside an outer insulation like black for instance as seen in twin-core solar cable. They can also be built to be circular when cut cross-section, cheaper and more popular is a figure 8 shape when you look onto the end of the cut cable. This outer layer might also include a high content of silicone so the cable slides easily during installation. It can also be manufactured to include a UV protective material so it doesn't break down in sunlight. This outer is referred to as PV1. AC power cables are normally solid core cables in 1.5mm or 2 or 2.5mm2 and are either 2 or 3 core TPS in white or purple outer colour. With the Life, Earth & Neutral wires inside (Red/Brown, Black/Blue, Green/yellow)

5 things you need to know about importance of correct sizing and purpose

  1. When you select a battery charger you need to first choose a style or form that is appropriate for the task at hand. A desktop charger isn't suitable in an application where the charger needs to be retained or mounted. These form factors may include dust or water ingress considerations or power cables in and out of the unit.

  2. When selecting a battery the capacity required for you to run with a few day's autonomy needs to be matched with a batteries need to be recharged with the appropriate sized current. As a general rule we say use 1/10th batteries AH for its charging rate given you have 12 hours to recharge overnight. If you have less time then you need a larger charger if the battery can accept a higher rate of charge. Or if you are using some of the charging power to run equipment while the charging is simultaneously occurring.

  3. The intended use of the battery is a key factor in the life you will get from it if you use a starting battery in a deep cycle application then be prepared for an early end of life. If you have recently increased your Ah capacity because you required a longer autonomy and used a deep cycle battery but have not increased your charging current to match you can also expect issues. Using any battery charger or regulator which doesn't use the factory recommended recharge voltages of the battery you are charging will lead to an early end of life issues also. These are not covered by the manufacturer's warranty which covers physical defects in production.

  4. Chargers are a logic programmed electrical device that uses timers and measurements of voltage and current to determine the charge cycle. They are therefore pre-programmed with time limits for each stage, or current (amps) and a minimum value before the stage is complete then moving to the next stage of a charging cycle. If you haven't sized your charger correctly to your batteries these rates can be either too long because of undercurrent causing issues with recharge. Or just as annoying if the charger is too big you can reach high voltages quickly but not be able to change modes for a minimum number of hours which can lead to unnecessary overcharging.

  5. Purpose of the system design, simplicity, effectiveness, and efficiency are all core factors in power storage and conversion. Choosing the correct components from the outset might cost a little more upfront but the return well worth the effort in getting it right.

Solar Installation Guide

Many people are interested in renewable energy and are installing it themselves. Here's a quick guide on electrical components and their connection order to install.

1. The battery, it's the heart of the system. It's where energy is stored, it's charged via a solar panel and powers equipment from devices attached to its terminals. So this is always the first place to start. You should be using fuses on all cables which would have a direct connection to power. If you also have a switch panel you should include 1 large fuse directly off the battery to the switch panel, then smaller fuses for each circuit running of each switch.

2. Charging circuit, this normally consists of 2 scenarios, either a solar panel and solar controller, or a mains powered battery charger. Both are OK to use at the same time to charge up a flat battery.

For Solar Panels connect the battery to the solar regulator first. Connect the battery neg to the controller battery neg. input/output, then connect the pos. terminal of the battery to the battery input/output. (we say input/output as you might be using the solar controller devices outputs which are normally indicated as a lightbulb to power your devices). If you have any equipment that exceeds the current rating of the solar controller you shouldn't use these lightbulb outputs but instead connect your discharging equipment directly to the battery terminals so you don't overload the controller).

If you are connecting a mains charger that can be connected to either a generator or a mains power source you just need to connect the positive and negative terminals to the battery. If it's a permanent installation it would be best to use eyelets and not the alligator clips as they can come off easily.

Now for the solar panel - a 36 cell panel outputs around 17-18 volts which is too high a voltage to connect directly to a panel so it needs to be connected to a solar controller. It should also be fused and switched so you can turn it off when necessary. Connect the negative terminal first and then the positive terminal.

With that done your solar controller should have the solar panel input indicating its working and the battery being connected will be charging. If the battery is already fully charged then there won't be must current flowing and it might only indicate a voltage up to 13.6 volts but that's OK. A fully charged battery doesn't need a charge. If however, the battery was flat, let's say the voltage was only 10 volts, it will take many hours, maybe days to get the voltage up to 13.6 volts. That's not uncommon if using one small panel on one large battery. Just let it do its thing until a full charge has been done prior to you discharging energy from the battery.

Direct DC Coupling

Morningstar has released a 600V MPPT Solar Controller that allows for direct battery charging in DC rather than going via the  inverter charge controller in a typical grid-tie solution. The intent is to eliminate the double conversion from solar panels being DC power through the inverter to mains then back through a charge controller into the batteries.

This isn't really something new its more of a variable option, it allows you to use your house's power via your distribution power board in the event of the grid going down.

Many people won't know that when the power provider or mains power line is not working if power is cut, that stops your solar panel system from functioning. If power is purposely disconnected because of rolling blackouts or accidental line failure or like in California U.S.A power has been cut to prevent fires from failures in the national grid in dry summer environments.

The Direct DC Coupling allows you to be more efficient and charge your storage batteries directly and keep your grid-tie system live. Other manufacturers call this an "island", an island is where you can operate independantly of the grid and distribute and manage your own resources.

Reconditioning a battery?

CTEK chargers have 2 conditioning charge states.

The first is the desulphation stage 1, its a pulse charge but is only used if the 12 volts open circuit voltage is below 10 volts when first connected to the charger. The idea behind this type of pulsing charge is to slowly bring the battery back up into normal charging conditions by slowly bringing the voltage up and not by overheating the battery or ramming large current into plates not wanting to operate outside normal conditions.

The second conditioning state is a mode selected by the users on the following models. MXS 5.0, MXS 10, PRO15, PRO25, and other professional series chargers. Mode 5 is added to the otherwise 7 stage charger to increase the voltage to 15.8v (on a 12 volt battery) and maintain a low absorption charge to ensure the battery cells are equalised and that every possible area of the plate is fully saturated with energy. Much like leaving a sponge in water to ensure it soaks up every last little piece of water it can.

Vehicle's electrical systems are designed to operate within industry standards which on 12 volt systems includes voltages up to 16 volts. In fact, we know of many vehicles that peak at over 17 volts but still use 12 volt batteries. In general anything above 2.45 volts per cell (14.7 volts) is a maximum charge rate but for short periods of time a higher voltage helps desulphate lead crystal build-up and can be very helpful to extend batteries usable life. It can also be the treatment that pushes a battery too far and it fails from drying out so the frequency of use should be managed.

Keep in mind a recondition charge is only performed once on a battery when the battery is stored for a long period of time as the stage is only initiated the once.

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