gas tank filling dreamstime xxl 55387059 691x405It’s a simple and common task for anyone owning or operating a vehicle with a gas tank. You pull up to the pump, stick the nozzle in the filler, pull the trigger, and then wait for either the auto-stop mechanism to operate, or you get a boot-full of gas. The math is simple: Since the last time you filled up you have used x gallons of gas, and now you add exactly x gallons to the tank to bring it back up to the level it was previously. There are no losses other than the boot-full you might have got thanks to the faulty nozzle.

Refilling batteries is a very different kettle of fish.

piggy bank being charged
We received an inquiry recently from a customer who is contemplating installing a large 12v (volt) AGM (Absorbed Glass Mat) battery bank, and he asked a pertinent question: Which would be better; several 12v batteries wired in parallel to multiply capacity, or large capacity 2v, 4v, or 6v cell groups wired in series to produce a high capacity 12v bank? Good question.

This customer estimates he needs around an 800 A/hr (Amp/hours at the 20 hour rate) 12v battery bank to achieve the holy grail of running his air conditioning overnight from batteries through an inverter in addition to supplying the regular daily house loads. This is a popular dream of boat owners these days, and highly achievable with the equipment we have available, and there are several battery configurations to consider. Typically it will all come down to what will fit where, so first let’s look at space constraints and then focus on the technicalities. Cost will not be considered in this article as you can’t put a price on creature comforts, now can you?

What does a mousetrap and winterizing your boat have in common?

cat and mouseThat’s what I’m working on right now. Well, not exactly a better mousetrap, but one with additional functionality. The mousetraps I’m using now are extremely well designed and work so much better than the old spring-and-fling models, but like all mousetraps that I’m aware of, they require checking periodically for “yield”.

So what I’m working on is some form of remote indication of when a trap is sprung. That should be easy, right?

battery-tight-rope-walkingNow that we have the option to install true non-sulfating Partial State of Charge (PSOC) AGM batteries like the Firefly and the Blue Plus range from Meridian/Northstar, we are faced with a new dilemma. These batteries could be at risk of failure due to voltage imbalances when connected as multiple units in a series configuration.

Read the specs of any lithium ion battery and you will see that the individual series-connected cells employ some sort of voltage balancing mechanism. Without this balancing act, some cells would end up working at different voltages and be charged at different rates, and if this situation gets too far out of whack with lithium ion batteries, well .... you know he rest.

Cells in AGM batteries work in a different way to lithium ion cells. Small imbalances between the individual 2v lead-acid cells (six of them in a 12 v battery) do not create any real inherent danger, but stringing together numbers of unbalanced 12v batteries in a series connection to raise the voltage does present the real possibility of premature battery death. The same potential exists also with 6 volt batteries connected in series, but the imbalances should in theory be much smaller, so for simplicity we'll consider only 12 volt batteries here.

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