AGM batteries were first designed to be float life batteries as used by UPS companies and the telco's. So we're always on float (13.6v) with varying current as required to supply the current draw this is why the VRLA lid is important to capture and recombine those gases/water once recondensed back into the batteries acid.

Hop on over to our dedicated OdysseyBatteries.co.nz website for all the latest from Odyssey.

International companies like CTEK, Sterling Power, Enerdrive, RedArc, Mastervolt manufacture chargers that allow solar and either DC charging from an alternator or AC charging from mains supply. The reality is if there was no current being discharged regardless of the charging source (solar or AC/DC) if a battery is floating at 13.6v that's because it's almost fully charged and both devices will within minutes both settle at 13.6v to float charge or maintenance charge the battery. At night the solar controller will be off and the mains charger will finish charging the battery. By the second day the solar controller will turn on as the sun rises, voltage will quickly rise to its pre-set bulk voltage before dropping back to float voltage for the rest of the day. While the solar boosts voltage to its bulk amount the secondary charger depending on the charge algorithm the unit may stop supplying current as it's not in control of the rising voltage to bulk. (the current is what's pushing voltage up, so it regulates voltage at 13.6v but cuts current) But once voltage comes down again and additional current is required it will settle back at 13.6v or float voltage.

Monocrystalline were typically more expensive and produced in larger numbers for a residential house or industrial applications. This is no longer the case and the costs aren't that different so consideration could be made regarding the purpose, site, installation, orientation to the sun etc for a year-round yield benefit. There are always differing opinions in this debate but if your panels aren't going to be mounted at 90 degrees to the sun then a wider sunlight collection method should be considered. In which case Monocrystalline may give a better year-round energy gain.

Polycrystalline, however, performs better in direct sunlight so if mounted at the correct angle facing directly north (if in the southern hemisphere) then your peak daylight yield will be greater. If this is matched to discharge cycles then performance could be measured in usable power during collection rather than stored energy which has to allow for electronic equipment conversions and losses and chemical conversion losses in turning DC energy into battery stored energy. Most small panels which are 36 cell under 200w are Polycrystalline so the decision of which is best suited to your installation might become a whole lot easier.

Most of what's discussed here is our own opinion as this topic has so many variables from manufacturing materials, cell connections, place in the world, installations, angles, colour, strength, quality, performance over years (25 year warranty on some panels) and rated output after 20 years.

We have many auto electrical companies that use, buy and ask our advice.

We have this info to offer:

Auto electricians test their batteries for cranking power, the ability to start the vehicle. Even a battery of only half-life remaining will accept a charge and work off an alternator. A CCA test normally indicates a lack of power which is what is required to turn over an engine. Let's not forget they are used to testing start batteries, alternators, and starter motors and their CCA testers are used to test cranking power and not reserve capacity. Many are also advised on what's needed to test by the battery supplier they are affiliated with. Only if they speak to a specialty product manager within the distribution business will they be given info regarding the requirements to discharge test a battery correctly.

We are also aware of one major distributor only using a 75A discharge current to calculate capacity. Many batteries smaller than 100Ah won't even have technical data to support a discharge of this large capacity so the test results aren't accurate.

You need to visit a marine electrician or a well-trained motorhome service centre to get specific info and ensure it's a discharge test done to industry standards. If the test is free it isn't being done right because it takes time and effort to do this properly and most businesses require payment for their services.

Depth of Discharge is something that's relevant to all rechargeable batteries. This type of battery is specifically designed to perform and discharge before being recharged and is commonly referred to as a deep cycle battery.

Deep cycle batteries quite often don't advertise a CCA (cold cranking) rating as this is more typical with starting batteries. Dual-purpose batteries like some AGM batteries, however, have good deep cycle ability and a large surface area of active material which gives them high cranking output when compared to equivalent-sized starting batteries. Remember, the purpose of the battery is the most important consideration here.

Battery spec sheets of deep cycle batteries will show a cycle life that is expressed by a graph showing different depths of discharge with a corresponding life expectancy. When the depth of discharge is deeper the number of times that battery can cycle reduces. So general-purpose batteries might only be 50-70 cycles at 30% depth of discharge. These are sometimes referred to as Leisure batteries but in fact, are just standard typical starting batteries. 400 cycles at 50% D.O.D. is really where a purpose-built battery might be advertised as a deep cycle. This will extend to 80% D.O.D at 700-800 cycles before you get to the internationally recognised quality brands that might be as much as 1000-1200 cycles at 50% which is similar on the graph to the 80% at 700 cycles but shows the manufacturers intent of the battery to be longer-lasting over 1200 cycles than say once a day for 2 years until end of life.

You can not test deep cycle batteries with handheld test equipment in a matter of minutes. It takes 8 hours to ensure your batteries are fully charged before spending 8 hours or more discharging them before another 8 hours to recharge. (assuming the batteries are OK), if they cannot hold capacity these tests can be done in hours once you have ensured the battery is first fully charged because the discharge and recharge time will take a much shorter time due to no capacity.

How do you perform a test, there are many variations, some include:

1. Reserve capacity test. Reserve capacity is a discharge at 20deg C and 25A constant for X number of minutes which will be stated on your battery as RC. If RC is 200 then that's 200 minutes at 25A discharge until the battery reaches an end voltage of 10.75v. If your test lasts 100 minutes then your capacity is 50% of its rated new Ah.

2. AH rating test. If a battery is rated at 200Ah @ 20 hours that's 5 amps per hour for 20 hours till an end voltage specified by the battery manufacturer. They often quote in VPC or volts per cell. So for a 12v battery you need to multiply the number by 6. 1.8vpc = 10.8v when testing a 12v battery. You need to discharge a fully charged battery at 5 amps for 20 hours and if the battery lasts 10 hours before the voltage reaches 10.8v then that's 50% of its rated capacity.

3. Not recommended but some distributors supply 75A discharge testers because that's a test used on golf cart batteries that they distribute. Golf cart batteries are also normally 6v 250Ah or larger (can be 415Ah) so a 75A discharge test is only 1/2 or less the batteries rated capacity. If you perform a 75A constant current discharge test on a 100Ah battery you certainly aren't going to get a real-world test result on a 100Ah battery when the test would only last 30 mins on a brand new healthy battery but your tested battery only lasts say 17 mins. It's easy to quote a large percentage number differential or failure when you've only tested for a few minutes and each minute represents 2-3%. So this test needs to be put in perspective of reliability to your situation. It is, however, a great way to ensure you buy a new battery from the battery test company.

Last point, a discharge test is using a deep cycle, your battery only has X number of those depending on how you've used your battery so they really only need to be done when there's an issue or if performing a system upgrade and you want to assess the suitability of the batteries to perform their new duties.

State of charge refers to how high a percentage of fully charged a battery is. An example would be if you were to discharge 25% of a batteries capacity the battery would be 75% S.O.C (state of charge). The same example would show a 25% depth of discharge.

Batteries are classed, categorised and rated to international standards. Those standards can also be manipulated when published if you state your variances, the trick is to know what's important and why.

In the Aviation industry battery is rated at the 1 hour rate because if your batteries fail while in flight you better hope you can get on the ground within 30 minutes before you lose communication or navigation instrumentation. This means a battery rated a 10Ah @ the 1-hour rate can provide 10A until it's voltage reaches 10.02 volts or 1.67 volt per cell and is considered completely flat. (sometimes the end voltages are much lower to make a batteries capacity seem better).

Traction batteries like used in Electric Forklifts are rated at a 5 or 8-hour rate because depending on the type of products being picked the equipment might average 5 used hours in one shift. Other products might require more handling in an 8-hour shift so you would use the 8 hour rate. Either way the end result would be flat batteries by the end of shift, which once recharged is 1 cycle. If you use larger batteries you can lift the depth of discharge from say 50% to 60% and that will manipulate the depth of discharge (end voltage when flat) and the increased cycle life from say 2000 cycles to 2500 cycles will extend the replacement time (in years) and your Return On Investment (R.O.I).

Industrial Applications use power over a working day with lunch breaks so a 10 hour rate is used. i.e. 18Ah battery at the 10 hour rate will provide 1.8A of power for 10 hours until the voltage is reduced to 10.02 volts. (If the temperature is higher or lower it will change the batteries rated capacity).

General use, deep cycle & Automotive/Marine batteries use the 20 hour rate or Amps over 20 hours so again you divide the stated Ah by 20 hours to get the average current discharge per hour. 100Ah / 20 hours = 5 Amps per hour. (All to often we see all the ampere ratings, temps, end voltages, and battery purposes cross over to confuse and or mislead a buyer as to how good a battery will perform not to mention the variations in a batteries weight).

Solar use the 24 hour rate for daily averages, but the 100 hour rate or 120 hour rate are more common as they refer to a better average use over 4 or 5 days.

You can see how when batteries are advertised at a rate that differs from these industry standards that the designed purpose of the battery may have been for a different use and that it may mean the charging rates need to be different, the voltages might need to be different or that the cycle life could be more or less than your expected use with consequences good or bad.

An IP rating is an international standardised test to describe how dust and waterproof a piece of equipment is.

The numbers indicate the dust ingress/resistance and the second number refers to its water-resistance / repellant. The number scale from 1 to 8, 8 being of the highest protection and 1 the lowest.

Some examples:

Commercial TV IP20

Notebook IP21

Submersible in water items end with a 7 or 8. Splash proof ends with a 5. Water tends to do more damage to electronics than dust (in small amounts) which is why we have focused on the last number but dust can also short out electrical equipment so ensure items remain clean and free of dust.

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The Electrical standards for ultra-low voltage state that both the positive and negative conductors (wires) of a solar array need to have a disconnection function. (this means the ability to be turned off) When the panels are producing energy disconnecting under "load" will cause an arc as the contacts are opened. Automatically reconnecting circuit breakers can become welded in place while connecting or disconnecting under load which is why DC Isolating Switches are used, being manually operated you will know it's still working correctly as you turn the rotary on and off. However, these DC Isolators are expensive, more expensive than using a manually operated circuit breaker which you can manually trip and reconnect. This is why we supply double pole (pos and neg) circuit breakers in housing as its a 2 birds with one stone approach. Protection and Isolation.

Solar panels themselves can't short circuit even if you connect the two outputs of the panel together as the internal wiring is rated higher than the panels output. If, however, you have 3 panels in series and one fails. The power output of the other 2 panels will be more current than what a standard 16A circuit breaker would be capable of handling. For this reason, circuit protection may not be required, but isolation is. On 1 or 2 panels a single 16A 500VAC circuit breaker is adequate. But with 3 panels, you should isolate each panel with a circuit breaker to ensure safety and isolation can be achieved.

At this point, 3 circuit breakers cost more than 3 fuses and 1 x DC Isolator so the choice is yours to make. Isolate and protect yourself.

Start Stop refers to a vehicle's engine stopping when a vehicle comes to a standstill and restarts automatically when the driver releases the brake or presses the accelerator.

A typical alternator that most people might have a basic understanding of generates power that is used to recharge a vehicle's battery. Why that's correct in principle the reality is that when the voltages are only 13.3-13.8 volts as typically found after the first 5 minutes of starting a vehicle. This is why an alternator is only used to replace the energy used to start the vehicle in the first place. Many people may make short journeys to and from work and have already found how quickly their battery needs a replacement this is due to it not getting adequate charge.

Also if you revise charging voltages why are they important in our FAQ you see this isn't enough voltage to fast charge (or bulk charge) a vehicles battery. This problem is compounded if a secondary battery is attached.

Now for the Smart Alternator, it goes one step further and is controlled by the engine management system which controls when the turning of the alternator by the motor is applied. This additional load that is placed on the engine also consumes fuel, therefore, increasing emissions and that costs the manufacturer Carbon Credits so they now actively limit the time the alternator is on. Which means more flat batteries which is why we see the rise of EFB or AGM batteries as start batteries to try to counter the problem.

The engine management system knows how much power is drawn by every factory fitted item in the vehicle and therefore if you turn on lights, wipers and are using electric fans to cool the motor the vehicle knows to provide just the right amount of current the vehicle needs to operate with little wasted energy. Unfortunately, that previously wasted energy was actually absorbed by secondary battery banks needing a charge. These days this doesn't occur as much, in fact, with recent tests we have found a factory Iveco van only outputs a maximum of 22A above the engine management system requirements. That's typically the same amount of current required to run a DC powered fridge while driving. So your batteries aren't really getting any charge while driving from the alternator. Many vehicles now have smart alternators like Mercedes, VW, Fiat, Renault, Ford & more.

To try and combat this problem DC chargers draw their power from the start battery and by design try to flatten the start battery while the engine is running by feeding the secondary battery bank the correct voltage up to the max current of the charger. This in-turn causes the start battery to flatten which in-turn forces the alternator to come on and recharge the start battery While this is a very crude overview of the process the result is the alternator running for longer charging the secondary battery bank with the added benefit of being charged at the correct voltages for the secondary batteries which may be more than the output of the alternator. All in all that can lead to batteries being charged 30% quicker than the old alternator systems and est. 80% quicker than the new smart alternator setups.

Many charger manufacturers have taken note of the increased demand on a battery to charge in cold weather conditions but high temps are just as important to note. While the voltage variants may differ from one battery manufacture to another a general rule of +/- 0.03 volts per degree C above or below 25⁰C per cell.

This feature requires a temperature sensor to be located near the batteries and or on the batteries. Which is best? Well if it's cold conditions you face often then between a pack of 2 or more batteries is ideal because the batteries will be cold in the middle. You could just as easily argue that if the cabinet is cold and the batteries were being used that they would still be warm internally which we'd have to agree with also.
You could also state that in high-temperature conditions the compartment would be hotter than the batteries so reducing the battery voltage prior to thermal runaway would be advantageous. Just as if you are monitoring the temperature of the batteries directly if there was a dead cell the battery would be hot and potentially gassing (which is bad). So early indication of this is best. But we'd add that a warm gassing battery would also heat up a battery compartment so the ambient temp would increase anyway.

In general, the thing this is really important is the upper and lower temperatures. Below Zero you shouldn't be charging and above 40⁰C you shouldn't be charging what happens in the middle is your applications use are an ongoing variable that either extends or reduces battery longevity.

It's important to note though that Temperature Compensation is the ability to automatically alter the charging voltage due to the environmental temperature the batteries are stored/housed in and not anything to do with charger temps, this is typically understood when an external temperature sensor is available and or provided.

A 12v battery is made of six 2 volt cells. When we discuss charging we have to consider the application in which they are used and how long you want them to last. This ties in with Depth of Discharge (D.O.D.). Many variables exist but the gist is the faster you discharge and the higher the voltage on recharge or higher the current is on recharge the quicker the active material deteriorates which causes end of battery life.

Batteries typically have voltage ranges to charge for bulk / cyclic applications and float life applications. There is also a stipulation on the max initial charge current, the larger the battery the higher the current. If comparing brands an initial inrush current that is higher than another brand may be an indication of a better quality product with a lower internal resistance if made with better raw material which will also be reflected in its cost. Alternatively, it will indicate a thicker plate which is ideal if you require a deep cycle battery.

AGM batteries should bulk charging voltage between 2.4 and 2.45 volts per cell, and float voltage charge between 2.25 volt and 2.31 volts per cell. That is 14.4-14.7 volts bulk and 13.5-13.9 volts float. These figures are not temperature compensated and this needs to be factored in.

See temp. compensation charging FAQ but in short, allow for the addition of 0.03v per degree C below 25⁰C and the reduction of 0.03v per degree C for every degree above 25⁰C. Temperature compensation can not be calculated if you do not have a temperature sensor which is typically an optional extra on many chargers. It does come standard on all CTEK chargers above the 7A rating.

Well I guess there's a few ways to look at this and considerations.

The largest 12 volt batteries are 260Ah (approx) @ 20Hr rate. 6 volt batteries can be 420Ah as they have half the plates but twice the capacity. So one answer might be yes 6 volt is better if you need 400Ah of battery because you could use two large capacity 6 volts instead of two mid-sized 12 volts. The 6 volt battery at 400Ah is quite often an L16 case size which is tall, these batteries in a flooded battery require the height to store them and also need to be deep cycled regularly to keep the acid from becoming stagnant (see stratification).

From an electrical point of view a 12 volt battery is actually six 2 volt cells in series. There is no difference between 2 x 3 cells (2 x 6 volt) or 1 x 6 cells (12 volt). The physicall size of these cells is quite often an issue for different installations so sometimes one form factor is better than another.

Lastly, if one of your batteries fail in a 2 x 6 volt installation your voltage drops dramatically (normally 2 volts per dead cell) or if there is an open circuit (just like a fuse blowing) the voltage will be zero volts. That may render your vehicle useless. Whereas if you have two 12 volt batteries in parallel the voltage will appear normal but your capacity will be reduced by 50%. This later is harder to detect if you don't have a battery monitoring system because you can't see the capacity reduction vs. voltage.

Absorbed Glass Matt - its a type of Lead-acid battery. There is a microfibrous matting placed between each plate to ensure there is no shorting of the plates. AGM batteries are commonly confused with Gel batteries (which look similar but have a different usable purpose).

Just like a normal mains powered charger which is AC input but a DC charger is DC input voltage.

Some of the considerations are when the charger should turn on, so ignition inputs or input charge voltages in excess of OCV are used to initiate the charging process. Additional programming or hardware design has been made in some cases for regenerative braking systems and the fast surge input power generated. In some cases, the input voltages on a start battery with regen braking are in excess of 17 volts DC, which is very high on a 12v system.

Some manufacturers include multiple charge profiles or relay control systems or low voltage disconnect features to isolate discharging equipment.

Head over to our dedicated website at CTEKNZ.co.nz for all your product, specs, prices etc on CTEK chargers.

While different manufacturers will each build and design their EFB batteries differently the general concept remains the same. EFB (Enhanced Flooded Battery or Extended Flooded Battery) takes the Maintenance Free battery one step closer to AGM batteries by either using more plates to increase Ah capacity, thicker plates to increase deep cycle ability or a combination of both. They may also be enveloping the plates which are similar to Absorbed Glass Matting between the plates or enveloping. Either way, the result is a flooded battery with characteristics more in line with the advantages of AGM and a performance heading towards that of AGM but at a lower price point.