I previously had a 200 Ah AGM battery in my van with a Renogy solar controller and BMV 700. The SOC always seemed to give fairly stable & accurate readings. I recently installed a 200 Ah lithium battery and replaced my solar controller with a new Renogy MPPT with 50A DC-DC charger. All other connections remain the same. I updated my BMV settings to reflect recommendations for lithium batteries, but now it gives very inconsistent readings.
A few examples:
- The voltage is often above the charged voltage for many hours and the SOC does not increase. Right now I've had 13.5V for over 4 hours but no update to SOC.
- The SOC no longer shows incremental increases. It only goes down, then jumps back to 100%. With my AGM battery it would show incremental increases when my solar was charging or the battery was charging off the starter battery
- The SOC doesn't seem to reflect reality either. Just the other night, it read 60% battery, but then my inverter's low voltage alarm rang and I had to unplug everything.
Here are the settings I have:
- Battery capacity: 200Ah
- Charged voltage: 13.2V (as recommended by Renogy w/ the MPPT I have)
- Tail current: 4%
- Charged detection time: 03
- Peukert Exponent: 1.05
- Charge efficiency factor: 97% (as recommended by Renogy w/ the MPPT I have)
- Current threshold: 0.10
Can anyone recommend a settings change to help me get more accurate readings?
