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Tibor Johancsik avatar image
Tibor Johancsik asked

Battery bank monitor as one, or batteries monitored individually?

Dear All, I would like to monitor the status of my boat batteries. I have a service battery bank of 4x150Ah (12V in parrallel) + one 50Ah starter battery. In all posts I see, that battery bank are considered as single large batteries and are monitored as one (now let's leave the starter battery). Is it not neccessary to see the individual battery statuses, as they might go wrong one by one, thus need to be replaced one by one? Or as installed at the same time you would change them at the same time, thus a single monitoring is enough?

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3 Answers
Alexandra avatar image
Alexandra answered ·

@Tibor

I am going to say it will depend on how you have wired them to know if it is even possible to monitor them separately.

We have 5 in parellel current daisy chained and one bmv for the entire bank SOC. As jonnado said it then is actually one big battery now. Like this it is difficult to spearately monitor each one. Generally if your batteries are rated to work in parallel and your interlinks are nice and beefy your bank will be fairly well balanced or will balance out of the course of the charge.

For individual monitoring and best practice current sharing, you would have to wire and fuse each one separately to a bus bar. Then use a smart sense if you just want basic status of each one. Or a bmv on each one, but that is more expensive option.

But really if your set up is good then not really something to stress about.

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johanndo avatar image
johanndo answered ·

You cannot monitor individual batteries in parallel by voltage as the voltage is shared across all batteries, you may install a shunt per battery to monitor the currents, but they will correspond to the capacity anyway, current is driven by voltage. On LFP batteries with BMS you could measure cell voltages as long as they are in strings, parallel cells have the same voltage. You see the point I guess.

Measuring currents for individual devices in series makes no sense, they are voltage dividers, while the current is everywhere the same, measuring voltages in parallel devices doesn't make sense as they are current dividers.

Parallel batteries act as one big battery, they are equally charged and drained as they share the same voltage. So using a single battery monitor makes sense.

You usually are interested in the total amount of available energy, so a single battery monitor for the bank is convenient too instead of adding the values of multiple monitors.

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Tibor Johancsik avatar image
Tibor Johancsik answered ·

Thanks for the quick replies! Clear and understood!

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