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12 V Power Source Replacement
#1
Hey guys.

Simple question.  I’ve seen a lot of YouTube videos and posts.  Do you think it is better to use 3S or 4S for a 12 V power source?

3S gives me a 9 - 12.6 volt range (too low)
4S gives me a 12 - 16.8 volt range (too high)

What do y’all do?

I think a 3S with a voltage booster to maintain 12 V would work?
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#2
It'll depend on what you want to power with it.
If it's something like a kids ATV, going higher will provide a bit more power and fun. Some devices may handle higher voltages badly
For "delicate" devices that need a more stable 12V, you'll probably want to go 4S or higher and add a buck converter to lower the voltage down to 12V.
3S and boost converter will also work, but I think it's generally less efficient.
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#3
I been using 3s for years as a power source. Right now i have a small 3s16p 31 ah battery pack as a backup to my house battery, I use in cloudy weather. 3s works with all my 12 volt devices, I never had my inverter shutoff from low voltage. I find all my 12 volt devices work fine with 3s, even my high drain roadpro cooker works great with it. You probably wouldn't even need a voltage booster. I bought one years ago and never used it.

For me a 3s battery is easier to build then a 4s, also 3s works better when charging with solar. 4s voltage is too close to the max bulk voltage for a charge controller when charging a 12 volt system, it will charge but at very low amps.
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#4
If you are using Lithium Ion, don't use 3s. It's better to buck voltage down than try to boost it up. It's more efficient.

If absolutely needing 12VDC equivalent, use LiFePO4 if you can get them. They are far better for that voltage range than Li-Ion.

Generally speaking, 3s operates on a lower voltage range. This could have issues if your devices start having problems around 10.5V. Electric motors won't, but some electronics will. Diodes cause voltage drops and a lot of times they are used to ensure no backfeeding. So if your battery is at 10.5V and the diode is 1V drop, it's now at 9.5V and becomes unstable.
This is basically worse case, obviously. But if your devices start acting weird at lower voltages, just be aware that that is probably the issue.
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#5
Agreed... if you are going to use a DC-DC converter you are generally better off bucking from 4s than over boosting from 3s.

If you are going to consider building in that manner then you can buck from a 24v pack as well which might provide more equipment options.

For the money and added complexity, its generally better to start looking at LiFePO4 especially if you need to start moving more current.

I do build various 3s and 4s packs, but often times the decision has it has to do with equipment or accessory I intent to use with it. As an example LED light strip packs I build as 3s, and my ham radio I build as 4s because it can support up to 17v input voltage. Both are intended for a 12v source.

Victron 12v inverter can also handle a 4s input voltage, some other options can't.
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