Monday, December 5, 2022

Magnum Issues

Warning, very tech-y post...

Sunday - The Magnum inverter/charger ran on the “Flooded” setting yesterday and it got the batteries up to 14.6V in absorption mode. It then dropped to float and kept the batteries at 13.4V for the next four hours. After four hours, the charger switches to “battery saver” or standby where the current drops to zero. By design, the charger will remain on standby until the voltage drops to below 12.8V at which time another four-hour float mode is initiated. Current will be supplied to get the batteries back up to 13.4V.

The problem with this system is voltage won’t drop to 12.8V until the state of charge (SOC) is ~17%. Clearly, this isn’t going to work. Today, I turned off the main breaker for a few minutes and when I turned the breaker back on, a four-hour float charge cycle was initiated. This got the SOC up to 82% from 60%. 

Monday - Today, the goal was to get the battery voltage down to around 12.7V. At this time, I can turn off the main breaker for five minutes. When AC power is switched back on, the Magnum charger should go into bulk/absorption and charge the batteries up to 14.6V before switching to float. 

This happened at 6:18pm. The voltage was down to 12.68V. I turned off the main breaker for 5min. After it was turned back on, the charger went to bulk charging mode at 100amps, of which 70amps were going into the batteries. The remaining 30amps were the 12V draws within the RV. When the batteries were fully charged, the voltage jumped to the absorption voltage and the current dropped to zero. The charger will sit in the absorption mode for an hour before dropping to the float mode for four hours. After this, the charger will shut down. This was a test to see if I understood how the Magnum inverter/charger works. If dry camping, the generator would end up running for five hours to charge up the battery bank.

I did go out and check temperatures and all was good. No hotspots. The Victron temperature sensor on the negative post registered a max of 107°F at the end of the bulk cycle. The warmest thing was the inverter/charger. 

I think I have found a solution to this problem. The inverter is a model ME2012 with version 5.9 firmware. I ordered a new wired remote panel which should have more options. At least enough to create a custom charge profile compatible with LiFePO4 batteries. The remote has been ordered. 


  1. Yes, a bit on the technical side, and I admit reading the first time a day ago and becoming hopelessly lost and bailing on the post. This morning, in spite of just a little coffee, managed to understand enough to comment. Given my existing meager power budget and setup, it'll be sometime before I go to LiFePO4 batteries I think. Having said all that, I'm not sure what the problem is? It's doing exactly as you thought it would right?

    1. The only problem is the amount of oversight and manual fiddling to get it to work. Lithium batteries have a very stable voltage during use. The voltage doesn't drop until the batteries are almost discharged and the voltage doesn't rise until the batteries are almost charged. If the charger has a Lithium profile, then charging will start before the batteries are almost discharged. By upgrading the remote controller on the Magnum, I believe that I will have enough control to enable a Lithium-friendly profile.