Battery bank with voltage differences

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ibot asked Apr 18, '24

Battery bank with voltage differences

Hello,

i have 12v battery bank with 3 200Ah lithium batteries. The system is running since two years and the batteries are connected with same cable length and in parallel. I preloaded all batteries before setting up the powerbank. All batteries have a different voltage: 13.28V, 14.25V and 13,.4V.

Most of the time charging is done by solar, but i also charged by landline (multiplus).

Is that a tolerable difference or do i have to fix smth? Also where do i have to set the cable for midpoint measurement?

Thanks and best regards, Tobias

(A bit of a mess, had to save space...)

voltage

screenshot-20240418-072603-firefox-nightly-1.png (80.7 KiB)

screenshot-20240417-223824-victronconnect.png (314.4 KiB)

2024-03-01-18-45-09-189.jpg (3.6 MiB)

screenshot-20240418-074409-victronconnect.png (152.2 KiB)

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klim8skeptic answered · Apr 18 at 09:27 AM

@iBot All batteries have a different voltage: 13.28V, 14.25V and 13,.4V.

Your pics show batts A,B,C show voltages very close together, about 40mV deviation.

More importantly the batts show "balanced" meaning that they have been fully charged to the point that each battery considers itself fully charged and balanced in the last 30 days.

Your mppt shows a full charge with a complete absorption charge, before settling to float.

What seems to be your concern?

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Alexandra answered · Apr 18 at 09:30 AM

@iBot

BTW typo in your post about the voltages. My heart did a skip there then i checked with your screen shot. Phew.

Answer is it is tolerable. Thay are all at 13.2v. It is quite literally 0.04v difference between highest and lowest. Probably a little to do with lugs stacking there. (But I understand space issues)

You can't do mid point measurement with your set up and bank voltage.

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Modifications Space

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Answer 1 · 2024-04-19T07:12:00Z

ibot answered · Apr 19 at 07:12 AM

Thanks to you both. My concern was about the 0.04v difference. Good to hear that this is acceptable.

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Alexandra ♦ commented · Apr 19 at 09:07 AM

Worry more at 0.3v and 0.5v difference

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