MGL Avionics User Forum

Has anyone used Lithium-Ion backup batteries for their iEFIS systems?

Looking to add a backup battery and AVIOGuard to my existing iEFIS system. Does anyone know if the AVIOGuard can charge Lithium-Ion batteries?

The AVIOGuard manual specifically mentions lead-acid and I know the two battery types require different charging. A 7AH LiFePO4 battery is about 2 pounds lighter that an equivalent Lead Acid version.

It's going to depend on the battery management system that is implemented by the battery manufacturer. In most cases, Lithium batteries will need a 13.8V or higher input before the logic will allow a charge. The AvioGuard will sit around 13.6, and so could disqualify most of your battery options.

I had already purchased my (standard) AvioGuard and my lithium backup battery (EarthX ETX-104) before I saw this question. I went back and checked the EarthX documentation. It said "normal" charging voltage was 13.9 - 14.6 V, but I could not find anything that said it would not charge on a voltage lower than this. So I did a test. I hooked up the AvioGuard input to my car battery (through the power outlet). I hooked up the backup battery as the only thing on the AvioGuard output. The car battery was at 12.14 V. The initial backup battery voltage was 13.33 (EarthX says 13.2 V is fully charged). I turned on the AvioGuard and found the initial output voltage was 13.39 V, lower than the open circuit voltage, so maybe it was charging? After 20 minutes, I again measured the output voltage and it was now at 13.71 V. After an hour, the output voltage was at 13.76 V. I turned off the AvioGuard and disconnected everything from it. The backup battery voltage did read 13.76 V. So it appears that at least this particular lithium backup battery will charge from the AvioGuard and therefore should perform properly as a backup for this system. (It will be a fair while before everything is finally installed to truly verify this.) It is just one data point, but it seems that at least some lithium backup batteries will work in place of the lead-acid batteries. Hope this helps someone.