rocwandrer
100 W
When a NiMH cell is reversed by overdischarge in series with higher capacity neighboring cells, what happens after recharging the pack? Does this cell act like a resistor in series? Can you get an open circuit? Something worse?
Background:
I bought a 1g insight with the factory 120S1P NiMH D-cell battery pack (sticks of 20 in series, with rudimentary BMS on the sticks, but not individual cells). The pack worked fine 6 months ago, before it was put in storage. It was stored at 168v and wall charges to an indicated 184v peak. It immediately trips the IMA light on discharge, suggesting a bad cell. Many people have success with deep discharging the pack (well below 120v) and then grid charging it fully to make the pack function within the bounds of the factory control system again, allowing the car to work as intended.
On the face of it this sounds like a TERRIBLE idea. But it is reputed to work. I wonder if this process completely kills the bad cells such that the BMS in the car no longer registers them dropping out and stops faulting, but rather just works at a reduced voltage and with a resistor in series with some of the sticks of 20 cells.
Background:
I bought a 1g insight with the factory 120S1P NiMH D-cell battery pack (sticks of 20 in series, with rudimentary BMS on the sticks, but not individual cells). The pack worked fine 6 months ago, before it was put in storage. It was stored at 168v and wall charges to an indicated 184v peak. It immediately trips the IMA light on discharge, suggesting a bad cell. Many people have success with deep discharging the pack (well below 120v) and then grid charging it fully to make the pack function within the bounds of the factory control system again, allowing the car to work as intended.
On the face of it this sounds like a TERRIBLE idea. But it is reputed to work. I wonder if this process completely kills the bad cells such that the BMS in the car no longer registers them dropping out and stops faulting, but rather just works at a reduced voltage and with a resistor in series with some of the sticks of 20 cells.
