Victron Battery Protect 100a Failure

[Dave McCampbell]

Our Victron 100a Battery Protect has just failed after about 6 months use in our charging circuit. 

It is positioned between the charging buss and shunts to the 4S2P LFP cell pack.  The charging buss has only solar, grid charger and alternators wired to it, but normally only the solar charging is in use.  None of the charging sources exceed 60a at 12v.  The load buss is completely separate.  The BP is wired correctly with IN toward the charging buss and OUT toward the battery as recommended in other posts here.  We understand that the BP can only accept current IN to OUT, not the reverse.  It is controlled by the SBMS0 using the over voltage lock parameters.

The BP was programmed for Lithium/C when it failed, and we have reprogramed it to that, but it will not pass current now.  Removing it from the circuit and shorting the charging wiring allows the charging circuit to work normally.

We would like to determine the cause of the failure so we can prevent this in the future.  Is there something about shutting down the system for recycling the SBMS0 that could cause a reversal of the power going through the BP.?  Normally we shut down the solar panels first, then the MPPT (24v panels and 12v system), and then disconnect the battery from the circuit all with circuit breakers.

Anyone have an idea as to what might have caused this?

[Dave McCampbell]

Found the problem.  It was a programming error.  Somehow the BP program got switched from C, lithium, to B, relay, with no relay connected.  Now we are back on C with the SBMS0 controlling the BP.  Probable cause operator error.

[Timmeh]

So with the battery protect if you set to lithium then it relies on the two wires to be switched via the bms and ignores voltage settings? If i was to set B relay mode and operation normal then i could have bms switch the bp220 and should bms not switch then the internal voltage cut off setting i define would be a backup? 

[Dacian Todea]

To turn OFF the SBMS will just make that EXT IOx open circuit so if one of the two wires will be broken then the BP220 will also default to OFF.   That backup will not be needed and it will be fairly useless anyway as total battery voltage is no indication of anything as you can have all cells above 3V and just one cell well below 2.8V (it is almost guaranteed that is what will happen when battery is discharged).

[Timmeh]

Ok so if sbms turned off for some unknown reason then it would open circuit by default and sb220 would turn off anyway. I was thinking altho the sb220 would not protect against a low cell it would be better than nothing as a back up to shut off at pack low voltage if for some reason the sbms did not shut off.   

[Dacian Todea]

The Toshiba TLP172GM are the optoisolators used on the EXT IOx and they need power to be close circuit else they will be open circuit so if SBMS0 power is lost for some reason then yes all EXT IOx will be open circuit thus all devices will be OFF.

You can program the BP220 anyway you want as long as it has as priority to be OFF when remote port is open circuit.