This post is going to deviate a little bit from my typically long-winded format and present a list of observations and measurements so far. In short, I’m very pleased:
- The charger charges at a constant rate until it reaches the upper voltage shutoff
- After shutting off the charger, voltage drops by less than 0.2V (in 48) over the next several hours with no load. This suggests that the surface charge effect is small.
- When the charger is on, there’s no immediate spike in battery voltage. Turning the charger on/off only influences the voltage by about 0.1V, meaning that even if it is on, we can still use voltage as an indicator of state of charge.
- At each of several measurements, all cell voltages stayed within 0.01V of each other.
- The self-discharge rate is (for all practical purposes) zero. After 2.5 months in storage, the voltage was unchanged.
- Charging or discharging a 4kW module at 1500W results in no noticeable heating of the battery pack, cables, or connectors.
Coming soon (not necessarily in this order):
- Overall system objectives
- Discussion of battery management/monitoring systems
- High and low voltage disconnects
- Over- and under-temperature disconnects