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juliian-buss avatar image

Balancer installed - still huge voltage difference at the end of bulk phase

I have 4 x 230Ah lead acid batteries (closed, but not gel or AGM). Two in series, both pairs in parallel for a 24V system. The batteries are at least 5 years old, exact age unknown.

A couple of weeks ago I discovered that there are voltage differences in each pair, for example the lower battery had 11,9V while the upper battery had over 13V.

Then I bought the Victron Balancer and installed it. In general it works fine: When the bank is notable discharged (say by 50Ah) and then charged with my Victron Centaur 24/70 the voltages are pretty similar during the process.

But a the end of the bulk phase, when there is only about 4A charging current left, something weird happens: The upper battery gets more and more voltage up to 15,1V while the lower battery gets less voltage of around 13,6V.

After a short discharge when there was for example an huge load while using the inverter it's even more weird: Then first the lower battery has an higher voltage than the upper with up to 14,5V (lower) / 13,9 (upper). While charging this is reversed so again the upper gets much higher voltage (up to 15,1V), just as described above.

Has anyone an idea what happens?


Battery Balancer
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2 Answers
JohnC avatar image
JohnC answered ·

Hi @Juliian Buss

This won't be good news for you, but I think you have at least one faulty batt.

It may be 'lazy', and it's partners (either in parallel or string) doing all the work. Hence the reversal in V between charge and load.

And if you can detect a different temp with your fingers, that's it for sure. And it's not necessarily the hot one that's faulty, but it will die anyway from the heat.

Try isolating each string in turn (no balancer) for a few hours and checking each batt for V after standing. Something obvious should show..

At 5yo, you've reached a place where this becomes more common. Such are pb battery evils..

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juliian-buss avatar image
juliian-buss answered ·

John,

thanks for your reply! I already thought so but wanted to make sure the I made to error in installing the balancer.

It seems it's time for a refit of the whole bank with Victron Super Cycle :D

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