louis avatar image
louis asked

Batterie Balancer and charging AGM slow discharge batteries on a 48V bank of 4x12V


Being new here and after searching the forum, I didn't find an answer and I am looking for some help. Thank you very much for your time and answers.

I am planning to wire in serial, 4 Hankook 12V - 65Ah to get to 48V in order to drive through an Alltrax SR 48300 controller a DC Motenergy ME0909 Motor ( 48V - 100 Amps ).
1) Is it a mandatory to use Battery Balancers (like BMV-702 or 712 ) in a serial AGM Battery Bank ( 4 x 12V ) as I have read somewhere that AGM batteries don’t need equalization ?
2 ) I understand these batteries balancers work when charging but do they work also when running the motor and therefore discharging the batteries ?
3) What is the best way and easy way to charge these batteries ? Is it by charging them one by one with for example a Blue Smart IP22 ( 12V ) or directly with a 48V charger like a MEC ( 48V Charger )

Thanks again

battery chargingAGM Battery48v batteryBattery Balancerequalisation
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Warwick Bruce Chapman avatar image Warwick Bruce Chapman commented ·

That’s a big battery bank @Louis ! How about a photo?

Ps. I’ve wired in 3 x balancers into my 2 x 4 battery bank. Too soon to tell how effective they are.

@Daniël Boekel (Victron Energy Staff) has been very patient with me advising how to get this right.

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2 Answers
JohnC avatar image
JohnC answered ·

Hello Louis.

1) It's not 'mandatory', it's your choice. Cost vs perceived benefits. Note that the BMV units are not balancers, they're monitors. You'd need 3x of the Victron balancers:

2) They'll only work above a set V (in the spec sheet), so no, under a load they won't. And with a load like that they couldn't help much anyway.

3) Best to charge them in a 48V block, same way as you load them. (considering your mental health here). :)

65Ah @48V suggests ~10A capacity charger sufficient (batt manufacturer specs you could check).

Back to the BMV. Would be nice to have anyway to monitor your charger/load flows and batt condition, especially if you went without balancers. You could set it to also measure mid-point V of your 48V string to prewarn of imbalance.

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louis avatar image
louis answered ·

Hello John,

Thank you very much again for your answers. I really appreciate !

1) OK. The choice is quickly made as it will be easier to deal with. Thank you for correcting me on the BMV / Balancers. I understood the differences but somehow did confuse the references while writing.

2) I understand

3) Good as this was the preferred way but I was not sure if this was acceptable for batteries life. I must been missing something here with "... same way as you load them. (considering your mental health here). :) " The smiley means to me that this was a joke but I am not getting it. French is my mother thong and I know I still have a long way to go ... Can you please explain a little more ?

4) Regarding the BMW, that's clear now in my mind and that's the way we will start without the balancers as we can always add them up in the following weeks once we have the machine working

Once more, Thank you !!!

Kind regards

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JohnC avatar image JohnC ♦ commented ·

Yes, we Australians are said to have a twisted sense of humour. (Some also say we have to have to live here). What I was meaning was that trying to charge each battery alone would eventually send you insane, and we wouldn't want that. :)

When considering battery balance, remember that 12V Pb's have 6x cells, so can't be balanced internally. The Victron balancers can deal with those 12V blocks, but can't get to cell level anyway.

I really do like the BMV centre-point-monitoring. If a bad cell occurs, no amount of balancing can fix it anyway, but at least you get a warning of it.

What you now propose doing seems fine to me.

Bonne chance mon ami.

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