diy solar

diy solar

Eve 280Ah battery, strange behavior from one cell

Sure, at those values. He's maxing at 60/150. When I run at 150, those terminals are maybe 100F (and that's at 48vdc - more heat).

Even at 100-200A, they get hot. The contact area isn't huge. Wire rating temperatures are all above the pain threshold. Ever subjected your skin to 60, 75 or 90°C continuous exposure? Anything over 45°C results in pain.

Also, just going by his numbers...

.15V drop, 150A = 0.001Ω or 1mΩ - not at all an unreasonable resistance in a switch.
 
Even at 100-200A, they get hot. The contact area isn't huge. Wire rating temperatures are all above the pain threshold. Ever subjected your skin to 60, 75 or 90°C continuous exposure? Anything over 45°C results in pain.

Also, just going by his numbers...

.15V drop, 150A = 0.001Ω or 1mΩ - not at all an unreasonable resistance in a switch.

I totally hear you -- I'm just saying that 200F for 150 amps isn't reasonable because if it were 300 amps it would be a fire. My personal experience with this same switch is 100F at 150 amps. Maybe the switch is OK but the crimps on the wires aren't. Who knows. But 200F (93C - higher than most insulation ratings) for 150 amps isn't right IMHO.
 
Hey all. A couple months ago I put together a 560Ah 12v pack (2p4s) using the 280Ah Eve cells (It is possible that I actually have the 272ah Lishen cells....the vendor on alibaba was a bit unclear).

Today I was charging up the pack from ~60% to 100% using my victron compact multiplus 12/2000. The charge rate was ~70A, and at around 80% SOC I noticed something strange. The voltage on one of the cells (actually 2 parallel cells) in the pack was rising and quickly hit my BMS cutoff of 3.65v. The other 3 cells were all around 3.35v. I figured that maybe I have a weak cell or they somehow got out of balance.

In order to keep charging I reduced the charge rate to about 15A, which kept that first cell voltage from hitting the cutoff. It hovered around 3.55v for almost the rest of the charge cycle while the rest of the cells stayed at ~3.35v. However at about 98% SOC when the other 3 cell voltages started to rise, the voltage of the "weak" cell dropped down. All four cells are now at around 3.45v, with the weak cell just slightly higher at 3.48v.

Is this normal behavior for a weak cell? Why would the voltage spike high earlier but then drop back down as the pack nears 100% SOC?

These voltages are measured by my BMS (daly smartbms) in case that is a factor...
First thing I would do is verify the readings with a dmm. Could be that you just need to clean the terminal, tighten a connection, fix a bad crimp, or any combination of the above. I suggest reassembling with oxguard or some other kind of anti corrosive.
 
Back
Top