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hydrogen avatar image
hydrogen asked

Battery Bank Voltage Recommendation (12V vs 24V)

I am considering a 24V Multiplus with 12V batteries in series or 24V batteries in parallel, or even a 48V Quattro setup and looking for battery voltage recommendations.

This would be a LiFePO4 based bank.

A 24V battery setup would make a 24V system simple and provide for smaller 'sets' of batteries run in series for a 48V system (should I go with 48V now or upgrade to it in the future).

A 12V battery setup provides a secondary, 'fallback' option of using AGM batteries in some future scenario if I ever had a failure across the LiFePO4 bank and LiFePO4 was hard to come by or cost prohibitive.

What I don't care for with having too many 12V in a series is dealing with the need for all packs in series set to be 'matched' and if one goes bad, replacing it pulls the entire set out of 'spec' to some degree.

I am considering Battle Born 12V and 24V batteries, but open to hearing opinons here.

Thank you!

chargerbattery
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3 Answers
wkirby avatar image
wkirby answered ·

Higher Voltage is always better. Lower current means lower cost cabling and smaller dimension DC components in general.
48V is what I'd recommend. There are a wider range of 48V commercial batteries available.
As you are considering future upgrades then this is another reason for 48V since the higher power levels are more easily accommodated on the DC side.
You need to decide your battery Voltage early on. Once you buy in to 12V for example then it's expensive to move to a different system Voltage as your existing MultiPlus would be unusable. I have made this mistake myself in the past......

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shaneyake avatar image shaneyake commented ·
I agree with wkirby, higher voltage is always better. Not always possible in van/small systems but I would go 48V if your PV array can run at around 100V or higher. 48V tends to work out cheaper as you need lees MPPTS for the same power, cabling is smaller etc.
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Trevor Bird avatar image
Trevor Bird answered ·

It depends upon what power level you are considering. Anything up to 5kVA I would go for 24 volt batteries in parallel. I would try to avoid putting batteries in series to acheive the correct voltage (like 2 x 12 volt to acheive 24 volt) as they may get out of balance. If this happens and the BMS becomes very active it seems to cause unusual consequences. If you need to consider cable size a good referecne is the Victron Wiring Unlimited booklet. https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

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Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

In my opinion it also depends on what kind of system you are planning.

In a caravan or boat I would recommend 12V or 24V to easily use the alternator to recharge while the engine is running.

In a house I would recommend 48V.

To your PV question: The open circuit voltage is rising very quickly even in low light conditions. A "24V panel" has typically 36-40Voc, so you have 72-80Voc with two in series. That's enough to start the MPPT. But there are also panels available with higher Voc.

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