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Charging my cells

benja.min47

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Joined
Oct 25, 2020
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Hi,I just got 4 Lifepo4 100ah cells. With the voltmeter I have 2.99v on the 4 cells. Only the thousandth varies on a cell. Can I directly plug in my BMS and charge without going through the balancing phase? thank you,
(i'm french and i use google translate, sorry for the language).
 
Hi,I just got 4 Lifepo4 100ah cells. With the voltmeter I have 2.99v on the 4 cells. Only the thousandth varies on a cell. Can I directly plug in my BMS and charge without going through the balancing phase? thank you,
(i'm french and i use google translate, sorry for the language).
No. Even though the voltages are the same, the states of charge are probably not matched good enough.
If you don't balance, one of the cells will hit the BMS voltage limit long before the other cells are fully charged.
 
No. Even though the voltages are the same, the states of charge are probably not matched good enough.
If you don't balance, one of the cells will hit the BMS voltage limit long before the other cells are fully charged.
thank you for the answer. so I plug in in parallel and I let it rest, is that it? can I use a small diameter cable to connect?
 
Hi,I just got 4 Lifepo4 100ah cells. With the voltmeter I have 2.99v on the 4 cells. Only the thousandth varies on a cell. Can I directly plug in my BMS and charge without going through the balancing phase? thank you,
I did. My thinking was it's the BMS's job to do that, so it can do it better than me and trusted those end digits on my voltmeter.

Silly me... now I know better.

At the time I didn't realize how poorly the voltage was as a measure of SoC at anywhere other than the ends of the curve. For example, in the image below a 3.2V reading could be most anywhere along 10 to 60, a pretty wide range of SoC.
Google Translation
J'ai fait. Je pensais que c'était le travail du BMS de faire cela, donc il peut le faire mieux que moi et a confiance en ces chiffres de fin sur mon voltmètre.

Silly moi ... maintenant je sais mieux.

À l'époque, je ne me rendais pas compte à quel point la tension était médiocre en tant que mesure du SoC ailleurs qu'aux extrémités de la courbe. Par exemple, dans l'image ci-dessous, une lecture de 3,2 V pourrait être la plupart du temps entre 10 et 60, une assez large gamme de SoC.


discharge.jpg

Hope that helps!
 
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