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Batt go BG-8S issues

Jwtravel

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Jul 5, 2021
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Hello folks. First post here, although I’ve be reading for months. I have some AC electrical experience but I am a total novice on DC.
So, I just started working on my 24v battery bank (8 times 3.2v Eneramp cells).
The batteries arrived pretty close to consistent voltage, connected in parallel for a day and they all balanced out at exactly 3.209. Then I connected them is series.
I connected the input cord for the BG-8S per the schematic. I plugged in the monitor. It turned on, immediately gave me a low voltage alarm. I saw that the #8 cell was around 1.8 and dropping, thought “oh crap”. Double checked my connections, used the voltmeter to check the pins on the connector. Everything checks out.
Is it possible I have a brand new monitor that is bad?
 

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Does your multimeter indicate that cell #8 is not below 2V? If the cell measures fine except on the BG-8S, I would first suspect the connection of the balance lead to that cell. If that is not the problem (on either the cell end or the JST connector), it may be something wrong with the BG-8S.

Not what you asked, but you really should top balance those cells before hooking them up into a series pack.
 
Does your multimeter indicate that cell #8 is not below 2V? If the cell measures fine except on the BG-8S, I would first suspect the connection of the balance lead to that cell. If that is not the problem (on either the cell end or the JST connector), it may be something wrong with the BG-8S.

Not what you asked, but you really should top balance those cells before hooking them up into a series pack.
I conenected the cells in parallel for little over a day (they were was only .11’s discrepancy the begin with). I disconnected them and tested each cell. They 7 were 3.209 and 1 was 3.210. I felt like that was balanced. Did I miss something?
I did double check all pins and connectors. I found (see photo) what appears to be an arc on the #2 pin on the monitor side, also smells a little burnt.
I have removed all leads and double checked my cell voltages, they are all still @ 3.209. I feel like I must have gotten a dud 8G-8S? Thanks
 

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Does your multimeter indicate that cell #8 is not below 2V? If the cell measures fine except on the BG-8S, I would first suspect the connection of the balance lead to that cell. If that is not the problem (on either the cell end or the JST connector), it may be something wrong with the BG-8S.

Not what you asked, but you really should top balance those cells before hooking them up into a series pack.
And yes, my multimeter said 3.209.
 
I conenected the cells in parallel for little over a day (they were was only .11’s discrepancy the begin with). I disconnected them and tested each cell. They 7 were 3.209 and 1 was 3.210. I felt like that was balanced. Did I miss something?
Hooking the cells together is not top balancing. Search the forum resources for how to top balance. Top balancing makes sure the cells are all at the same state of charge near the highest. Cells can be at the same voltage but not the same SoC. It's pretty important to do top balancing (or bottom balancing if you are doing very high current applications).
 
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