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Post by smileypete on Jan 30, 2017 22:28:11 GMT
Just seen this on Youtube, shows how to check balance of a 12v batt bank with a clamp meter, might be handy for someone:
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Post by Telemachus on Jan 30, 2017 22:51:25 GMT
I did this when we had 4 x 110AH batteries in parallel with the 175A alternator and 2.5kw inverter connections at one end. I could never detect any imbalance which is why I don't agree when lots of people on CWDF bang on about convoluted connection methods to equalise conductor lengths.
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Deleted
Deleted Member
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Post by Deleted on Jan 30, 2017 22:58:45 GMT
I have one of those. Good bit of kit. Mine does amps as well.
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Post by JohnV on Jan 31, 2017 8:40:04 GMT
I did this when we had 4 x 110AH batteries in parallel with the 175A alternator and 2.5kw inverter connections at one end. I could never detect any imbalance which is why I don't agree when lots of people on CWDF bang on about convoluted connection methods to equalise conductor lengths. I have often looked at some of the connection diagrams and wondered, (never actually bothered checking) and always thought there had to be an element of pedanticism, especially when heavy gauge jumpers are used |
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Post by cuthound on Jan 31, 2017 9:24:21 GMT
If you already have a multimeter capable of reading millivolts, and with the batteries feeding a heavyish load you can measure millivolts drop on the paralleling cables. More accurate than a clamp meter.
Best to check all connections all recipes lean all rend tight forster though.
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Post by Telemachus on Jan 31, 2017 10:58:32 GMT
If you already have a multimeter capable of reading millivolts, and with the batteries feeding a heavyish load you can measure millivolts drop on the paralleling cables. More accurate than a clamp meter. Best to check all connections all recipes lean all rend tight forster though. Yes this is true, although ultimately it is the current imbalance that is relevant and unless you know the cable and connection resistances precisely, you can't work out current from mV drop. As to your last sentence, could you translate it from autocorrect-speak please? |
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Post by Telemachus on Jan 31, 2017 10:59:28 GMT
I did this when we had 4 x 110AH batteries in parallel with the 175A alternator and 2.5kw inverter connections at one end. I could never detect any imbalance which is why I don't agree when lots of people on CWDF bang on about convoluted connection methods to equalise conductor lengths. ...especially when heavy gauge jumpers are used So not in summer then, presumably. |
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Post by cuthound on Jan 31, 2017 13:27:29 GMT
If you already have a multimeter capable of reading millivolts, and with the batteries feeding a heavyish load you can measure millivolts drop on the paralleling cables. More accurate than a clamp meter. Best to check all connections all recipes lean all rend tight forster though. Yes this is true, although ultimately it is the current imbalance that is relevant and unless you know the cable and connection resistances precisely, you can't work out current from mV drop. As to your last sentence, could you translate it from autocorrect-speak please? Best to check all connections are clean and tight first though. Bluddy Autowrong! With regards to your other point, when the millivolts drop is the same, the current flow will be the same, assuming that paralleling interconnects are the same length. |
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Post by Telemachus on Jan 31, 2017 15:34:56 GMT
Yes this is true, although ultimately it is the current imbalance that is relevant and unless you know the cable and connection resistances precisely, you can't work out current from mV drop. As to your last sentence, could you translate it from autocorrect-speak please? Best to check all connections are clean and tight first though. Bluddy Autowrong! With regards to your other point, when the millivolts drop is the same, the current flow will be the same, assuming that paralleling interconnects are the same length. No I don't think that's right, but my mental picture is struggling a bit! Let's consider the final (remotest) connection in a bank of batteries. Compared to the other interlinks, the current is inevitably less - the first should be carrying 3I, the second 2I and this last one I (where I is the current going into each battery) So the mV drop wont be the same between all the batteries. But let's assume that you really mean the mV drop is proportional to the current so between the first pair it's 3kMv, 2kMv for the next and kmV for the last (k being a constant). But how do you really know that the kmV arises from the current I? Could it not be that the current is less than I and the resistance is more, due to a poor crimp etc? i think my point is that ultimately it is the current that is relevant. The voltage is a byproduct and depends on the resistance. |
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Post by tonyb on Jan 31, 2017 19:15:03 GMT
I think that Cuthound is probably correct in what he says BUT unless the connections are made in such a way that all carry the same current then he is probably wrong. That is he is right if the pos and neg are on opposite ends of the bank AND the interlinks are all the same length, size and with low resistance connection to the terminals. If the pos and neg are on the same end then Telemachus is probably correct because the current will differ down the bank as voltdrop is proportional to current flow.
I agree with Mr T that its the current that is important but the voltdrop may give allow and inference as to the current flow in the link.
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Post by Telemachus on Jan 31, 2017 19:18:55 GMT
I think that Cuthound is probably correct in what he says BUT unless the connections are made in such a way that all carry the same current then he is probably wrong. That is he is right if the pos and neg are on opposite ends of the bank AND the interlinks are all the same length, size and with low resistance connection to the terminals. If the pos and neg are on the same end then Telemachus is probably correct because the current will differ down the bank as voltdrop is proportional to current flow. I agree with Mr T that its the current that is important but the voltdrop may give allow and inference as to the current flow in the link. No, if the batteries are in parallel with connections at opposite diagonals, the current in the interconnects will still be 3I, 2I, I. Only if the batteries are connected in a star manner to a bus bar or terminal post will the Is (hopefully) be the same. |
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