I want to store my extra traction battery cells for future transplantation. I have a extra Gen II EV Traction battery that sat with out recharging for almost two years. I just scavenged one it's good (7.35 Volt) donor cells to transplant into my "failing" Gen II Traction battery. The one bad cell (6.33 Volts) was triggering the Triangle of Death warning code was removed from the middle of the traction battery stack of the car & replace (with a 7.35 volt donor cell from and extra EV battery). My car is up and running again. Questions: 1. For best shelf storage longevity of these back-up (donor) cells; should I reconstruct the old battery connections making all the cells link in series as designed or should I not use the battery pole connector plates and leave the cells sit on the shelf (effectively not linked to each other)? 2. Interesting side note, the donor battery had three cells that had zero charge while the rest of the cells were at 6.5 to 7.34 Volts. 3. Should I take the time to recharge each viable cell up to 8.0 volts before placing them in storage? 4. What recharge system is recommended to charge the cells?
Question #1 leads me to believe a lack of basic electrical knowledge. Which makes me have to say, be very careful. You're dealing with high voltage DC. If you make a mistake, it could be fatal. 1) It makes absolutely no difference because there isn't a return path. Without the safety disconnect switch in and without something attached to the big (+) and big (-) cables, it is just free floating. It's free floating with high voltage DC though between the 2 ends of the terminals. For storage it is best to not connect them all up. The only reason for this is that the human that finds it 10 years from now when it has been long forgotten may pick it up not knowing what it is and have a very bad day... 2) It's nearly impossible to get to zero volts. All the cells in the module would need to be completely dead/shorted and then run down. If this is the state of your donor battery... The whole thing is seriously suspect. 3) You should take the time to charge them up before storage. Once you charge to about 80%, you're good for roughly 6 months. You will be doing this every 6 months. If not, then don't even bother keeping one in storage. 4) The recommend individual module charger is a Keithley 2281S-20-6. It has the power and smarts required to charge (and discharge) NiMH batteries intelligently. Link here: 2281S-20-6 Dynamic Model Battery Simulator | Tektronix
