Parallel vs Series Charging

[TRTC360]

I've always wondered, what makes a battery bank of 12v batteries wired in series be able to charge at 24v or 26v just fine but if you wire it in parallel and try to charge the bank at 18v you'll have batteries ballooning and melting all over the place? nothing is changing internally as in the structure of the battery so what allows the charging voltage to change so drastically?

[SnowDrifter]

You can't charge a 24v bank at 18v. You'd get the batteries to .05% capacity

Wire them in series parallel and charge with a 12v charger

[TRTC360]

You can't charge a 24v bank at 18v. You'd get the batteries to .05% capacity

Wire them in series and charge with a 12v charger

i'm not sure if you understood my question, take the same battery bank, for example 12 D3100's wired in parallel can be charged up to 15.6 iirc, take that same battery bank and wire it in series and you double the voltage, so they can technically be charged at 24v-26v

edit: I don't plan on doing this by any means it's just that I read it a while ago and i've always wondered why the voltage can be doubled depending on how you wire them and they don't balloon or melt, without changing any of the internal structure of the battery

[meade916]

I've always wondered, what makes a battery bank of 12v batteries wired in series be able to charge at 24v or 26v just fine but if you wire it in parallel and try to charge the bank at 18v you'll have batteries ballooning and melting all over the place? nothing is changing internally as in the structure of the battery so what allows the charging voltage to change so drastically?

because when you wire batteries in parallel, you basically have one big 12v battery still.

when you wire in series, every battery you add to the mix double's the voltage. 3 12vdc Batts in series is not 12v anymore, it is 36v. You would need an appropriate charger for a 36v system, if you had something that could run off 36v. Hydraulics (you know front back, side-2-side) would be the only thing i can think of where you would do that, with a CAR.

[meade916]

You can't charge a 24v bank at 18v. You'd get the batteries to .05% capacity

Wire them in series and charge with a 12v charger

wait wait.....i think you have a typo bro.

do NOT wire them in series and charge with a 12v charger. Wire in PARALLEL and charge with 12v charger.

[TRTC360]

ahhh I did not know that, I thought you could only double the voltage of the original battery

[SnowDrifter]

You can't charge a 24v bank at 18v. You'd get the batteries to .05% capacity

Wire them in series and charge with a 12v charger

wait wait.....i think you have a typo bro.

do NOT wire them in series and charge with a 12v charger. Wire in PARALLEL and charge with 12v charger.

Yessir. Good catch! Lol

Yeah... Do NOT wire them in series

[SnowDrifter]

You can't charge a 24v bank at 18v. You'd get the batteries to .05% capacity

Wire them in series and charge with a 12v charger

i'm not sure if you understood my question, take the same battery bank, for example 12 D3100's wired in parallel can be charged up to 15.6 iirc, take that same battery bank and wire it in series and you double the voltage, so they can technically be charged at 24v-26v

edit: I don't plan on doing this by any means it's just that I read it a while ago and i've always wondered why the voltage can be doubled depending on how you wire them and they don't balloon or melt, without changing any of the internal structure of the battery

Yes, you can do that. Typically, you want to charge between 2.3 and 2.4 volts per cell, which in a 6 cell 12 volt battery is 13.8-14.4 volts.

Us audio guys like to push things a bit farther - charging closer to 15v. But know that some batteries don't tolerate this well and will bulge

If you wire in series, you are doubling your voltage. So you would charge between 27.6 and 28.8v. Or 30v if you are simply doing double 15v

Keep in mind you do need a specialized charger for 24 volt applications as your 12, 14, and 16 volt chargers don't even come close to charging high enough

[n1ghtsn1p3r]

To use the water analogy:

Voltage = water pressure

Current (amps) = flow rate

Battery = pump

In series, you are doubling the pressure, but the second pump cannot double the flow rate, since it can only use what the previous battery is giving it.

In parallel, you are doubling the flow rate, while the pressure stays the same.

This explains it better: http://www.madsci.org/posts/archives/1999-08/935725864.Eg.r.html

Edit: I missed the charging part, but this at least covers the why the drastic difference between voltages.

[Tarball]

a 12v battery is basically six 2volt batteries wired in series.

when you add a second battery in series you have 12 - 2volt batteries in series = 24v

when you add a second battery in parrellel you still have 12v but double the storage capacity

So, your 24volt charger wont blow your series because its designed to charge 24v batteries which is what you are presenting the charger with

In parellel you are still at 12v for the batteries but you are now trying to present 18volts to those batteries = buldge, meltdown etc.