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[Doctorbass]

Have you ever wondered how to make a capacity discahrge test on your zero battery?

As well to do this it require to have the battery protection enabled to avoid overdischarge. and what make complicate to acheive is the MBB that is connected thru a harness to that battery.

I have investigated about the signal from the BMS that is sent on the MBB to cut power when there is one or more cell bank reaching the Low Voltage Cut.  I have found that ton the 2011 battery connector number C80 ( it have 10 pins), that the throttle signal engage ( also called Battery throttle enable) pin IS the important pin i need. It's pin 7  black wire.   when the battery is operational  without any alarm or LVC, this pin is at the Vbatt+ relative to the  NEG batt. when the battery is fully discharged and that one or more cell bank is reaching the LVC, this pin 7  fall to 0V.

I also found wich signal from the MBB is activating the BMS in the battery. in fact when the key is turned ON, the BMS become active and protect the battery from overdishcharge by monitoring each of the 14s cell bank..

So this is answering me a great question i was wondering about the possibility to test some zero battery alone without the MBB to measure their capacity and also have the BMS operational to cut it to protect from overdischarge.

 To activate the BMS the pin no 2( brown wire) on the C80 connector must be connected to Vbatt+. when it is done, the BMS will do this little short "bip", same as when we turn ON the

The Battery Throttle engage pin is only working of the BMS is active so to test a 2011 battery  the " ON SIGNAL TO BMS" must be connected to the Vbatt+,  This activate the BMS
Then the "BATTERY THROTTLE ENABLE" pin will become active and have the proper siganl according to the battery  fully dishcharged or charged. ( this pin could be connected to a 48V coil relay and the contact of that relay could activate the contactor insid ethe battery so once the LVC is activate by one or more bank the main relay will cut the power during the capacity test to avoid overdisharge =)

I have attached a little schematic to make a MBB fake to have the battery main current output active but to keep the protection of the battery.

This bypass can be really usefull for battery capacity test or if you want to use a zero battery on another project as backup power or main power.

Please see teh attached schematic i have madeé It only require a relay with 48V coil and a switch

With this configuration, the main power contactor will be energized  and will have  few more volt on the coil. it is not too drastic since the coil is made for 48V and that with this bypass the coil will receive 58V max wich represent few more watt to dissipate but should drop as long as the battery voltage drop.

Doc