High Voltage Charging Cut-off
After some good basic Electrical Engineering 101, Jane now has a charging cut-off circuit that monitors each cell individually. This involved designing and wiring a circuit (schematic will be posted soon), that takes the alarm output from the CellLog monitor and uses to turn off a high-current contactor between the charger and the batteries. As part of this enhancement, a couple of relays have been added to only turn on the CellLog monitor board when either 220V (charger) is connected or when the key is turned on. This should solve the slow drift that the CellLogs were causing on some of the cells, since they don't draw evenly across the sub-banks. Also, put on push-button switch to provide a quick check option for the batteries. Pushing the button, powers up the CellLogs.
The relay controlling the charging contactor require two special considerations:
- Latching - Wired it so that it would latch ON once the alarm triggered. This way, even if the alarm condition clears, there is no way to resume charging without disconnecting the 220V supply.
- Delayed-On - Added a cap (4700 µF) across the coil and a resistor (50 ohm) in series with the coil to require the alarm to sound for about 2 seconds before the relay will activate. This filters short alarms and any temporary issues that may occur at power-up.
The CellLog Monitor has a buzzer attached to alarm if a cell is out of range. A quick connection to the original Alternator indicator on the dashboard now provides the driver a red warning light (replaced with LED bulb for extra brightness) if an alarm condition is in effect. The buzzer is audible inside the cabin but if the windows are down or music is up, it may be missed.
Also, added a heavy-duty marine-quality manual cut-off switch on the positive side of the battery pack. This provides a quick, secure cut-off of the high-voltage pack, making it safer to work on the systems.
The CellLogs are set to the following:
Voltage Range: 2.5V - 3.6V
Delta P (maximum cell variation): 100mV
Alarm Type: Normally Closed (this provides a safety if a unit become disconnected or is not functioning, since the alarm will open up, triggering a alarm condition)
Pack Voltage:
- 6 Cell sub-pack = 17.5V - 21.0V
- 7 Cell sub-pack = 20V - 25.2V
2 CellLogs have 6 cells connected to them, 2 have 7 cells to cover 26 total cells.
Completed one charge cycle and the system performed well. One cell was slightly higher than the rest and hit 3.6V, shutting off the charge current. Next is to test it while driving. All of the cells are within 25mV of each other.
No comments:
Post a Comment