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24 volt in series and parallel


Bigal10

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I current run two 24 volt 220 amp battery banks separately,( one for domestic 24 volt services and the other bank for my inverter) for historical reasons the Banks are 2 foot apart. What size cables should be used to connect the banks to give me 440 amps ?

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2 minutes ago, Bigal10 said:

I current run two 24 volt 220 amp battery banks separately,( one for domestic 24 volt services and the other bank for my inverter) for historical reasons the Banks are 2 foot apart. What size cables should be used to connect the banks to give me 440 amps ?

Just over 600 mm then :)

  • Haha 2
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15 minutes ago, TheBiscuits said:

Just over 600 mm then :)

Don't confuse the poor new member, just because he doesn't understand the difference between current flow "amps" and battery capacity " amp-hours" - as many folks do.

I'd suggest - but subject to folks comments who have cable tables to hand,  "the same size as you use for the cable run to the inverter"

(24V users are to be savoured and encouraged as they are an endangered species)....

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PEDANT ALERT!!

 

will the batteries really provide 440 amps?

I think you mean amp.hrs

 

.................. only you can decide the 'size' of cable - depends on the maximum load you put on the batteries......  for starters consider using the same cable as you presently use for each bank, but we don't know if that was/is sufficient.

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33 minutes ago, Bigal10 said:

I current run two 24 volt 220 amp battery banks separately,( one for domestic 24 volt services and the other bank for my inverter) for historical reasons the Banks are 2 foot apart. What size cables should be used to connect the banks to give me 440 amps ?

What we really need to know is what do you intend to run from the batteries, (eg do you have a 3Kw inverter)

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36 minutes ago, Bigal10 said:

I current run two 24 volt 220 amp battery banks separately,( one for domestic 24 volt services and the other bank for my inverter) for historical reasons the Banks are 2 foot apart. What size cables should be used to connect the banks to give me 440 amps ?

 

Welcome to the forum. Ignore all the fun-poking, confusion between Amps, AmpHours and Amps/hour is common on here and always draws humourous comments.

Taking your question at face value, if you really do need to draw 440A from the newly combined battery bank, the new interconnects will be drawing a nominal 220A. For this, the 'one third' rule of thumb suggests 70mm2 cables will be fine. 

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Just now, Bigal10 said:

Thanks Mike I was of course simply quoting the total maximum amps from the 4 batteries. Your response confirms my thoughts Thanks again

But it isn't - that is the amphour (Ah) rating ie you can draw 440 amps for one hour, or 220 amps for 2 hours etc., or the reverse (if you get a short) you could be drawing 26,000 amps for 1 minute.

 

 

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4 minutes ago, Alan de Enfield said:

But it isn't - that is the amphour (Ah) rating ie you can draw 440 amps for one hour, or 220 amps for 2 hours etc., or the reverse (if you get a short) you could be drawing 26,000 amps for 1 minute.

 

Not with 70mm2 cables you wouldn't!

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12 minutes ago, Alan de Enfield said:

Well - not for long.

I was just pointing out that 440 ISN'T the maximum amps available (which the Op appears to think that it is)

 

And I was just pointing out that your 26,000 Amps probably isn't the maximum either... :P

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Gentlemen My original post was simply to seek your advice as to the size of cable required to connect two existing battery banks which incidentally have operated separately for over 10 years. I have no wish to start WW3. Thanks again Mike

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2 minutes ago, Bigal10 said:

Gentlemen My original post was simply to seek your advice as to the size of cable required to connect two existing battery banks which incidentally have operated separately for over 10 years. I have no wish to start WW3. Thanks again Mike

 

Yes but we LIKE having WW3 over terminology. It's not your fault!!

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34 minutes ago, Bigal10 said:

Gentlemen My original post was simply to seek your advice as to the size of cable required to connect two existing battery banks which incidentally have operated separately for over 10 years. I have no wish to start WW3. Thanks again Mike

You need to answer Alan's question for the correct answer;  it's all guess work otherwise.

 

1 hour ago, Alan de Enfield said:

What we really need to know is what do you intend to run from the batteries, (eg do you have a 3Kw inverter)

 

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3 minutes ago, Robbo said:

You need to answer Alan's question for the correct answer;  it's all guess work otherwise.

I agree. To do anything else is just guessing.

If you really do mean 440 Amps then mike may well be correct, but if you mean 440 Ah then Alan is correct, you need to answer his question. Its nothing to do with WW3 and everything to do with getting you the correct answer.

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6 minutes ago, Robbo said:

You need to answer Alan's question for the correct answer;  it's all guess work otherwise.

 

True, but from the info given so far, its 99% certain that 70mm2 cables will be fine. 

For 100% certainty, full disclosure about the current loads to be drawn from the freshly paralleled battery bank will be necessary.

Even if a 3kW inverter is to be used on the newly extended battery bank, I hold that 70mm2 interconnects half way along it will still be adequate. But I agree, boaters can sometimes have truly mahoossive expectations form their battery bank so to be sure, we need to know the loads(s). 

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53 minutes ago, Mike the Boilerman said:

 

 

True, but from the info given so far, its 99% certain that 70mm2 cables will be fine. 

For 100% certainty, full disclosure about the current loads to be drawn from the freshly paralleled battery bank will be necessary.

Even if a 3kW inverter is to be used on the newly extended battery bank, I hold that 70mm2 interconnects half way along it will still be adequate. But I agree, boaters can sometimes have truly mahoossive expectations form their battery bank so to be sure, we need to know the loads(s). 

70mm2 will be way over spec for most instances.  50mm2 should do it if the OP has a 3Kw inverter.

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26 minutes ago, Alan de Enfield said:

But the OP specifically asked for 'size' not length.

But volt drop depends on "size" (Conductor cross sectional area), current flow and LENGTH so when specifying cables length comes into it but at a total length of 4 ft, as per the OP, I doubt length comes into it. I would just go by the cable rating IN THIS CASE.

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