question

timharper avatar image
timharper asked

Low Voltage Reconnect - LFP BMS

Also another client has a a question that I cannot answer with confidence.

Using a Victron 100/50 SmartSolar, if a LFP battery falls below the point that the BMS disconnects loads, can the 100/50 still get the battery to reconnect and accept a charge?

Is this dependant on the BMS/Battery or does that function work as stated in the Victron documents regardless of brand?

MPPT ControllersBMS
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1 Answer
Louis van der Walt avatar image
Louis van der Walt answered ·

You get 2 types of BMS. Common port and Seperate port.

With a common port the charging(input) and discharging(output) is on the same connection, and if the BMS disconnects this common connection for both charging and dischanging is disconnected and your MPPT will not charge in that state.

With seperate port the charging(input) and discharging(output) is on two different connections, and if the BMS disconnects the discharge port charging can still happen on the other connection and vise versa.

In most cases on the default settings the the common port BMS will still reset and accept charge after the disconnect delay passes (normally a few seconds) as the voltage in the cells/battery will be lowered when there is a load triggering the disconnect, but will rise again when there is no load.

If the BMS is connected to the ESS (either official supported/branded batteries or like with my driver) this will raise an alert and the ESS will not immediately draw from the battery again and let it first charge. If it is not in comms the ESS will not know about the disconnect and draw power again as soon as the battery connects causing ripples.

So best to have a connected battery or not work your battery to the limits if it is not connected)

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