Over the last few weeks we have noticed that our Home built Lithium Battery pack, that is 1400AH and has run perfectly for us for nearly two seasons now, was showing ever so slightly raised cell temperatures on just a few cells.
When you dealing with large currents, in our case as much as 220A for charging and quite normally 100A during the middle of the day, every single connection on your battery bank comes under pressure.
Electricity is tricky stuff and always looking for a way out, but more important, when you have big Amps available its also looking for a way through any slight resistance, which will generate power losses but more importantly heat.
With this in mind I went hunting for connections that might have loosened over time with hot/cold cycles during the past seasons.
The one thing I wish I had done with my battery bank was not create it as a single combined unit with all the cells in a compression box and the circuitry on top of this. The reason for this is that it means its a major job to remove the top of the battery bank, get to the cells and check the torque on each terminal and then put it all back together.
But that is what I did and sure enough, whilst not loose, a few had lost their torque setting tightness and once this was fixed the cells went back to running at normal temperatures again.
I also found a major fuse connection had vibrated itself loose exposing a 95mm crimp that had developed movement, so a new cable was crimped for that to prevent any future issues on that high load connection.