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james-ward avatar image

Connecting Lithium in parallel

Hi.

I have an issue with a victron 150ah LiFePO4 (600ah bank of 4 at 12v) not balancing after several attempts. It balances after about 6 hours on hook-up via the multiplus 3000/12/120 but as soon as we boat off it won't balance the next time I charge via engine or geni/multiplus, and BMS shuts down due to one cell (always the same one) going OV at 3.76v

The guy (pro) who fitted the system (now unwell) thinks its a duff battery and has asked that I swap 1 and 4 over to see what happens (cell 4 in battery 1 is the issue)

Now having a look my black BMS cables aren't wired like anything I've seen.

All diagrams I can see the left black cable of Battery1 goes to the left BMS port; the right black cable or B1 goes to B2 left cable; B2 right to B3 left, B3 right goes to battery 4 left and lastly battery 4 right to BMS right port (a 4 battery version of this link https://www.victronenergy.com/blog/2019/07/11/new-veconfigure-manual-new-detailed-marine-schematics-and-dvcc-explained/)

Mine goes B4L-B2R; B4R-B3L; B3R-B1L; B2L-BMSL; B1R-BMSR

I can't find anything wired vaguely similar ANYWHERE. The only possible reason I can see why it was done this way is that my left hand black cable is too short to go to the BMS left port and needs the 2m victron (https://www.victronenergy.com/accessories/m8-circular-connector-male-female-3-pole-cable-2m) extension cable

Q1) is my wiring enough to mess with the cell balancing?
Q2) should I buy the extension cable and wire it as per the diagrams I can find regardless of whether I have a duff battery on not?

Lithium battery Smartwiring diagrambattery bms
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2 Answers
stefanie avatar image
stefanie answered ·

Hi @James Ward,

A1) If you untangle the virtual mess with the BMS cable on a piece of paper, it looks right. The BMS does not care/know about battery numbers.

A2) No. Unless you want to relocate your batteries and really need the extension cable.


For the other problem with balancing, can you please take a look at the batteries with VictronConnect, using bluetooth to see which firmware version is installed on the batteries?
There was a problem with version prior to 1.19.


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james-ward avatar image
james-ward answered ·

Hi batteries v1.19; BMV v4.03

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Sounds good to me.

Then you should proceed as per manual Lithium Battery Manual - especially section 7 and 8.

Balancing needs time and could take several hours. I recommend setting the charge voltage to 14.2V and charge with low current, like 2A per battery (assumed they are in parallel). Even with the low charge current it can happen that one cell might reach high voltage threshold and the BMS stops charging for a couple of minutes. But it will resume charging as soon as the voltage drops below the threshold. The low charge current should prevent cell voltage rising too quickly.