question

Hello Stefan,

I asked some weeks ago the same question, because I really don't like, that when one single batterie fails, the complete bank fails. On a boat for example, it can never be installed this way.

I was told that there is no solution. Not even the Victron small BMS on every battery should work. I don't know why this shouldn't work.

Thanks for your response offshore. Hopefully someone else can answer and guide us correctly.

I have created a diagram so that there is no confusion.

My concern is the Load Battery Protect might receive some reverse current when connected to the bus bar. So should these be replaced with Cyrix-Li-load?

The Cyrix-Li-load will disengage when its control input becomes free floating. If the battery voltage recovers after disconnection (which will happen when no other loads are connected to the battery), the output of the BMS will become high and the Cyrix will reengage after 30 seconds. After 3 attempts to reengage, the Cyrix will remain disengaged until battery voltage has increased to more than 13 V (resp. 26 V or 52 V) during at least 30 seconds (which is a sign that the battery is being recharged). Alternatively, a BatteryProtect can be used (advantage: very low power consumption).

Hi Stefan,

"my concern is the Load Battery Protect might receive some reverse current when connected to the bus bar. So should these be replaced with Cyrix-Li-load?"

I would say this is no problem, the load Battery protect is perfect for this case, because it is unidirectional and only allows current to pass in one direction. (so for Charge protect you only have to reverse the IN & OUT)

What kind of charging sources do you have? For example, if you have an inverter with a charging option (Victron Quattro), I don't know how to connect it, as it is both a load and a charger.

The battery protect only likes current flowing from the IN terminal to the OUT terminal. When the batteries are connected to the bus bar, even when all fully charged there will be some differences in voltages and each pack attempt to balance. ie some current from Battery Pack 2 could flow into Battery Back 1, which is in the opposite direction preferred by the Battery Protect.

Datasheet states: * The BatteryProtect is not designed for reverse currents from charging sources

Manual states: Reverse currents from OUT to IN terminals are strictly forbidden, and will damage the device

Caution: uncontrolled reverse current will flow through a Battery Protect if Vout > Vin. Therefore never use a Battery Protect for battery to battery charging.

Charging will not be a problem as the battery packs will be swapped out as needed and charged elsewhere with a mains charger with no load connected, using the red charging connector through the second Battery Protect.