diy solar

diy solar

New 8S lithium system wont charge above 26V

Ah, so...

I owe a sincere apology to my Daly BMS...

I made up a lead to bypass the BMS, thinking that I would try and get a reasonable charge into it with the solar panels. Imagine my surprise when the charge stopped at 26V.

Out with the multimeter... what followed was five minutes of me beginning to doubt that I had even a basic understanding of electricity. The MPPT was outputting 28V, but the battery itself was only at 26V. What? How was this possible? I traced the voltage back from the MPPT to the positive busbar, and found the voltage on the busbar was 26V but the voltage at the MPPT breaker was 28V. More confusion...

Then I noticed that the nut holding the wire from the breaker was slightly discoloured, and the heatshrink on the wire was a bit shiny. I gave the nut an experimental turn... it moved easily but with a kind of crunching feel. I removed it and found pitting from what I assume to be sparking. My theory is that as the voltage increased so would the sparking, until eventually the charging device got spooked and shut down.

I'm such a knob. I checked all the connections at the battery several times but didn't check the other parts of the system. Lesson learned.

I cleaned everything up and now the system is running beautifully - charging from the solar and B2B without issues.

Thanks for your help especially Mike. Attached a couple of pics.

20211015_100202.jpg
20211015_100315.jpg
 
Glad fault found, that buss bar must have been glowing in the dark.

Mike
 
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