question

technomad avatar image
technomad asked

BP 12/24 100 + MPPT - disconnecting works but doesn't reconnect


I want to disconnect and reconnect my blue solar chargers from my lithium ion battery on different SOC‘s using the venus GX relay and a battery protect 12/24 100 instead of a Cyrix-Li-charge relay. This application is described in documents. 
The BP settings are on „C“, for lithium battery use where the under voltage thresholds are inactive. The battery is connected to the output and the solar charger to the input.

Disconnecting works fine but reconnecting does not work!
Measured voltages at disconnected state:
Battery voltage = 13,2V
MPPT charger output voltage = 14.2V (Bulk state when battery is 
disconnected)
There are no error codes visible.

Only after dismounting and remounting the input cable OR shorten the battery protects output and input manually for a short moment, the 
battery protect will reconnect.
It seems that the battery protect only reconnects when the voltage 
on the input is equal or less to the output?!

Do anyone have a suggestion for this?
MPPT ControllersBattery Protect
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2 Answers
nebulight avatar image
nebulight answered ·

I have this setup, but using my BMS rather than the relay on the venus controlling the BP. When I did my initial tests I didn't noticed any issues reconnecting although I have the smart BP so it may be different, but I can do some testing/simulated disconnect and check the results.

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technomad avatar image technomad commented ·

I would be very grateful if you could do this test and give a feedback about the result.

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Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

There is a switch-on delay:

"When in Li-ion mode the BP will connect the load 30 seconds after the remote input of the BP has been pulled high by the VE.Bus BMS. This delay increases to 3 minutes in case of frequent switching."

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technomad avatar image technomad commented ·

Thank you for this hint! I waited more than one hour after remote input pulled up to 12V, but the BP doesn't reconnect until I shortend input and output.

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