Today, for the first time, I had my complete electrical system all connected in my cargo trailer so I made my first attempt to charge my LiFePO4 batteries using the Multiplus inverter/charger while connected to shore power. After roughly 90 minutes of charging the battery monitor has detected excessive difference in voltage between the batteries and charging has been stopped.
Details:
Two SOK 12V 206Ah batteries in series for a 24V system.
Victron Multiplus 24/2000/50 inverter/charger.
Victron BMV-712 battery monitor and shunt. I have this setup to do midpoint monitoring to ensure the two batteries stay close to the same voltage.
Lots of other parts but everything was turned off during most of the charging.
Before I started charging, both batteries were reading the same voltage at roughly 13.2V and the battery monitor showed roughly 26.4V. The shore power was connected, through an extension cord and adapter, to a normal 15A, 110V outlet at my house. Once the inverter/charger was connected it started showing that it was bulk charging the batteries. Through the VictronConnect app on my phone I could see the batteries were getting charged at roughly 40A. The charging battery voltage was initially showing 27.53V and slowly going up. The last value I noticed, which was about 10 or 15 minutes before the alarm, the charging voltage was up to about 27.77V. I had left the trailer during that 10-15 minutes and it is when I came back that I heard the alarm. The inverter/charger has stopped charging and the battery monitor was reporting an excessive voltage difference between the two batteries of just under 2%. I turned the inverter switch off and stopped the alarm. Using a multimeter I measured the voltage of the two batteries at their terminals. One battery was showing about 13.4V and the other was roughly 13.7V. Again, both had the same voltage just before I started charging. The battery with the lower voltage is the one connected to the shunt.
What am I doing wrong here and what needs to be changed to help ensure the two batteries charge equally?
My electrical schematic is attached (hopefully it's clear enough as attached).
During the time I was charging both of the two big red switches were on. The battery protect was turned off via VictronConnect so no 12V or 24V loads were being used. All of the AC breakers were off so no AC loads were being used. The breaker to the charge controller was open so effectively that was out of the picture and my solar panels are not yet installed. So the only components in play should have been the batteries, shunt, inverter/charger, battery monitor, and the smart dongle.
Details:
Two SOK 12V 206Ah batteries in series for a 24V system.
Victron Multiplus 24/2000/50 inverter/charger.
Victron BMV-712 battery monitor and shunt. I have this setup to do midpoint monitoring to ensure the two batteries stay close to the same voltage.
Lots of other parts but everything was turned off during most of the charging.
Before I started charging, both batteries were reading the same voltage at roughly 13.2V and the battery monitor showed roughly 26.4V. The shore power was connected, through an extension cord and adapter, to a normal 15A, 110V outlet at my house. Once the inverter/charger was connected it started showing that it was bulk charging the batteries. Through the VictronConnect app on my phone I could see the batteries were getting charged at roughly 40A. The charging battery voltage was initially showing 27.53V and slowly going up. The last value I noticed, which was about 10 or 15 minutes before the alarm, the charging voltage was up to about 27.77V. I had left the trailer during that 10-15 minutes and it is when I came back that I heard the alarm. The inverter/charger has stopped charging and the battery monitor was reporting an excessive voltage difference between the two batteries of just under 2%. I turned the inverter switch off and stopped the alarm. Using a multimeter I measured the voltage of the two batteries at their terminals. One battery was showing about 13.4V and the other was roughly 13.7V. Again, both had the same voltage just before I started charging. The battery with the lower voltage is the one connected to the shunt.
What am I doing wrong here and what needs to be changed to help ensure the two batteries charge equally?
My electrical schematic is attached (hopefully it's clear enough as attached).
During the time I was charging both of the two big red switches were on. The battery protect was turned off via VictronConnect so no 12V or 24V loads were being used. All of the AC breakers were off so no AC loads were being used. The breaker to the charge controller was open so effectively that was out of the picture and my solar panels are not yet installed. So the only components in play should have been the batteries, shunt, inverter/charger, battery monitor, and the smart dongle.