question

I have a superpack 20Ah paired with a bluesolar 75/15 MPPT charger. I connected the battery inputs in reverse, and the charger's 20A fuse blew. I corrected the polarity. When I then replaced the fuse the charger started smoking. Upon disconnecting everything the battery output was fluctuating between approx 0.2V and 1.5V. Presumably the BMS detected a short circuit condition and has disconnected. I've tried applying 14.2V using a PSU, and the battery draws just a few hundred milliamps. The battery voltage will always mimic the PSU voltage, dropping to 0V if I turn the PSU off.

Any ideas on what's going on and how to resolve this would be hugely appreciated.

Here's what happened in more detail:

1. We connected a Victron Energy superpack 20Ah to a victron energy MPPT blueSolar 75/15 charge controller the wrong way around.
2. Upon flicking the switch the system remains off, and we discover our mistake and a blown fuse. We did not check the battery at this point.
3. The battery is then reconnected to the charger with the correct polarity and the fuse replaced.
4. We flick the ON switch once again, and this time the charge controller starts smoking. We disconnect everything.
5. When inspecting the battery we discover that the output voltage is low (0.2-1.5V) and fluctuating; presumably the BMS has tripped.
6. Typically, when this happens you either need to disconnect the load and wait several seconds, or apply a sensible charging voltage.
7. When the battery did not auto-recover we applied 14.2V (recommended charging voltage) with a PSU and noted that the current draw was low, although was gradually dropping as would be expected if the battery was charging.
8. When turning the PSU voltage down the battery would track it. Turning the PSU causes the battery to read 0V. When physically disconnecting the PSU the battery returns to its fluctuating state.

• The charge controller appears to lack reverse polarity protection.
• Ultimately, neither the fuse nor the battery BMS reacted fast enough to defend the charger.
• The battery should be easily capable of withstanding a brief short circuit condition through a 20 amp fuse, even without a BMS.
• The BMS is not auto-recovering as it presumably (no user manual) should.