Battery level inside not reflecting Lithium level

[aparrothead]

I just finished installing lithium batteries, inverter, etc. in my 2024 MLE. Everything works great, icebox runs for 6 days on solar/batteries without any issues and that is with the inverter periodically running. However, after day 6, the batteries registered at 12.5V on the solar charger and 12.3V on the Connect App, icebox still running. When I look at the battery level on the control panel, it shows fully charged. The electrical panel does state auto-switching from lead-acid to lithium. I'm assuming thta means the converter will charge as if batteries are lithium but shouldn't have any bearing this particular issue. If the connect app reads correct, and the solar charger reads correct, why doesn't the panel? Has anyone else seen this behavior?

[Jlawles2]

if you are referring to the lights on the panel, good luck on ever having them tell the truth.

Let's start with how they determine % charge. They simply look at the voltage (note 50% is technically DEAD) then turn on the proper number of lights. What KILLS this is any external source of charging throws off the measurement. If you really want to know the "charge level" of the battery using those lights, first thing is to kill all incoming charging. WHY b/c charging voltage is higher than the full capacity of the battery and remember the lights are "dumb" in only being able to measure the voltage it can see not what the actual battery voltage is like a charger that cycles the feed to the battery or measures internal resistance to determine full charge.

[Cate&Rob]

This may have to do with the gauge of the wire between charge sources and batteries . . . and where your voltmeters are tied in. When I went to lithium batteries, I first started with the (new in my case) lithium capable converter in the original location. Some 10 ft away from the batteries and connected with 6 ga OE wire. I had a voltage measurement at the converter and at the batteries and these never agreed. Charge rate would never go over 30% of converter capability. (I do not have solar panels.) I moved the converter to within a foot from the batteries and connected it with 2 ga wire. Charge rate increased to the nameplate rating of the converter, charge time decreased dramatically and all the voltage measurements agreed with each other.

Rob

[TedS]

Voltage compared at either end of wire carrying current will be different due to resuting voltage drop. The shorter and larger the wire, the smaller the voltage drop for the same current.

[steveluannj]

The lights are a simple voltage indicator, and are not "smart" in my understanding. Lithium has an almost constant voltage until the BMS shuts off current to protect the battery. The panel is set to something like 13V for 100%, 11.5-11.7 should be "out". As you can see from the graph, the voltage to charge is relatively linear for SLA, so they use that for something simple. Lithium is different, and as you can see from the graph, the voltage will result in a "full" reading on the lights almost until it shuts down. If you want to know how much you have with lithium, you will need a shunt current meter that measures each amp leaving the battery and keeps track.

[aparrothead]

I already have a shunt and can use my phone. I just don't carry around my phone everywhere, especially when we are camping. SInce the camper is supposed to auto-detect the litium batteries, i was hoping that would as well. Not too worried about, just an annoyance. Thanks