FAQs

Ampere Ratings or Amp Hour Rates

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.

DC Isolators in Solar Arrays and Circuit Breakers

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.

Smart Alternators what are they?

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.

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