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Volt difference in a series parallel installation


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is following ok?
4x 6v fla’s. 5yrso.

usual 2s2p config.

except split port/ starboard. 

Strb = 6.39, 6.37

port=6.35, 6.36v

panel collectively sayes 12.72.

Open circuit 4days rest.

 

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0.04V difference between them?  Thats almost measuring error levels - less than 1%.

I'll bet that if you check with a hydrometer you will find slightly different pH levels across them too.

I wouldn't sweat it. but I would monitor it (without getting paranoid).

 

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Cheers.

Didn't think error came into it as it is comparative, using sharp probe to lead bat terminal.

Googled first but couldn't find acceptable variance.

What triggered my interest was some oscillation of current from multiple shunts as it neared tail current.

All in unison.

Thought perhaps I had an intermittent fault in a cell.

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13 minutes ago, lateral said:

Thought perhaps I had an intermittent fault in a cell.

very unusual if it was - batteries are only slightly advanced on rocks as complex devices.  Best tested under load - 20 - 25A (more if you can get it) draw of the entire bank, look for a battery that has significantly different readings to the others

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11 hours ago, lateral said:

Didn't think error came into it as it is comparative, using sharp probe to lead bat terminal.

Correct on the comparative, and in your situation the absolute readings were not particularly relevant.

Every DVM has a measuring and sampling error.  Once you are down into hundreths of a volt, that error is significant for everything except lab-calibrated equipment.

For day-to-day stuff in a 12 or 24V system, 1/10ths of a volt is all the resolution you will ever need and most digital meters (even cheap ones) should be reasonably accurate in that range.

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So, that is why my $300 fluke is only one decimal place. Haha.

I was using the Uni -T @$35 which is two.

amazing what another decimal place does to ones perception

 

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I thought I had replied to this thread. I typed a post and must have forgotten to post it.
The important point when hooking up Series/ Parallel is to ensure the bank gets an equal charge across it. To ensure this takes place, ALWAYS connect the Positive feed from one end of the bank the the negative from the other end, so as the current is drawn equally across all the bank.
So for the situation of seperating the bank to two different sides of the Boat, you need to take one feed across to the other pair. As the Negative feed should be running down to the Engine Starter motor mounting Bolt anyway and thus be able to take a different path, that is the best cable to take from the pair on the "far side" or furtherest away. The Positive cable can remain shorter and be the direct feed to the breaker and switch panel. Thus you will also need a cable to run from the negative of the pair you are feeding the Positive to panel from and across to the other pair where it will connect to that pairs Negative. If it is a long run, make that cable a decent size so as you have no voltage drop across it.

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