Has someone on this forum studied this temperature difference issue, how serious it is and how it affects the balance and cell life in a battery pack ?
I don't think anyone has made any scientifically rigorous study comparing cell temp difference and its affect on balance thru numerous cycles. The only data point I can contribute is:
I have one rack with 15 Thundersky 100ah cells in a 'block' one cell wide without a cover all summer, rear rack has been completely enclosed. I really only saw a little (5 degrees) temp difference with similar outdoor temp probes taped to the copper bus bars attempting to get a clue of internal temp compared to ambient after 20 minutes of extended highway drive at 200amps. That being said I have not seen any significant relative cell drift in the first 3000 miles in either rack or compared to each other. I have developed a 'method' of cell level checking that *should* show drift if it occurs, but so far nothing has drifted anywhere.
I run my cells BMS-less, using a low end Elcon 1500 with finish voltage set to 3.65vpc. Typical daily discharge is around 30% DOD. Vehicle is in the garage at night.
I have checked cell voltages twice. Once at 1000 miles, once at 3000 miles. Method is to catch system just post charge when it has partially settled from a peak of 139.0 to 136.0... because it slows down enough for me to measure all the cells before settle much more and I want to try and catch them as high as possible to see variations. The cells were initially top-balanced to +/- .02v at the post charge voltage.... and they settle even closer than that longer after charge.
so.... my initial conclusion on limited data is that there is not tha tlarge a temp differential, and it does not seem to have any affect on cell balance over time.