Quote:
Originally Posted by bdserv
Hope this helps. Part numbers are from DigiKey.
In the diagram on the left the color green represents stock cart wiring and the red indicates what was added.
The diagram on the right shows how I wired in the modifications.
The relay is SPDT and we use the normally closed contacts to operate the alarm. Normally the ALARM DISABLE switch is in the ON position. When the BMS is allowing discharge the relay will be ON and the normally closed contacts will be open = no alarm. If the BMS stops discharge such as in a low cell voltage fault the relay will turn OFF and the normally closed contacts will close, sounding the alarm. The disable switch is there so I don't have to drive home with the alarm blaring.
Charging current flows through the BMS and the BMS can terminate the charge if necessary. However, I added a supervisory circuit to my DPI charger that terminates the charge when the highest cell reaches 3.55 volts. This makes the BMS a backup if the supervisory circuit happens to fail - the BMS is set to 3.60 volts max cell voltage. This way I do not have a single point failure possibility.
The 10 volt zener diode keeps the relay coil voltages within specs. The 1N4007 diode clamps voltage spikes that occur when the coil is de-energized. The alarm is a piezo type rated for 48 volts nominal but will tolerate up to 60 volts.
My battery pack enclosure has 3 external connections:
Pack positive
Pack negative
BMS C-
All of the added items in the diagram except for the BMS are external to my battery pack enclosure.
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Thank you for taking the time to explain! Very much appreciated!