Overkill BMS with Midnite charge controller/Magnum Energy inverter

jjhdtv

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Joined
Jul 22, 2021
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20
Need some help figuring out the Overkill BMS and Midnite charge controller.
I seem to lose the ability to solar charge the Lifep04 pack once the Overkill BMS low cell voltage trips. I need the ability to have the system to start charging once the solar power comes available. As the system is in a remote location, accessing the BMS is not possible once the power is off.

I'm not sure if this is an issue with the BMS (not allowing a charge current once low voltage is tripped) or an issue with the Midnite charge controller stopping charging current if it does not detect a battery (since the BMS has cut the power from the pack).

Trying to figure out how to set the BMS and the Charge Controller to work after a low voltage trip. Thanks,
 

sunshine_eggo

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Oct 26, 2021
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This is a pretty common issue. The Midnite is POWERED by the battery, so once the battery hits LVD and prevents discharge, the Midnite loses power and can't charge.

You might try:
Use an external method to stop pulling loads before the BMS trips.
  1. Have the inverter disconnect at a higher voltage
  2. Use a Victron Battery Protect to disconnect DC loads.
These have a lower chance of success:
  1. Raising the LVD value to ensure there is capacity remaining when it trips.
  2. Lowering the release point, so the BMS will turn itself back on sooner.
 

jjhdtv

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Jul 22, 2021
Messages
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Thanks. I suppose I will try to set the low voltage cutoff on the Magnum inverter higher than the BMS value. Any suggestion what this delta should be for a 24volt lipe04 battery?
 

sunshine_eggo

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Thanks. I suppose I will try to set the low voltage cutoff on the Magnum inverter higher than the BMS value. Any suggestion what this delta should be for a 24volt lipe04 battery?

Good plan. At 3.0V/cell, there's not much left, so 24V is probably good provided your loads aren't too high. Probably set reconnect at 25.6V if you can. Might need to play with the numbers.

The Midnite shouldn't pull much power waiting to charge, so I wouldn't worry about that.
 

Mahendra Gomanie

Solar Enthusiast
Joined
Mar 8, 2021
Messages
178
This is a pretty common issue. The Midnite is POWERED by the battery, so once the battery hits LVD and prevents discharge, the Midnite loses power and can't charge.

You might try:
Use an external method to stop pulling loads before the BMS trips.
  1. Have the inverter disconnect at a higher voltage
  2. Use a Victron Battery Protect to disconnect DC loads.
These have a lower chance of success:
  1. Raising the LVD value to ensure there is capacity remaining when it trips.
  2. Lowering the release point, so the BMS will turn itself back on sooner.
Use midnite wbjr. To switch off inverter using aux for soc.
 
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