Supertramp Flagship LT pop-up slide-in pickup camper

[K9LTW]

Thanks for the awesome TED Talk on internal heaters, @Chadx ! I had no idea there were different methodologies for internal heaters. Lots of stuff to ponder as I look for solutions for cold house batteries. I have self-heating Renogy batteries in our trailer, but an issue I run into is the REDARC's temp sensor is only looking at ambient temp and will cut charge off despite the batteries being happy to accept a charge. Need to figure out a way to insulate that. Not a huge fan of running the heat in the trailer while it's bouncing along behind me, but guess I could. The house batteries in the bed of the truck (have an OVRLND camper) present the same issue but I'll be getting an external heating wrap for them as they've no self-heating. I could, likely, just ensure the temp sensor from the REDARC is also kept warm.

 

[Chadx]

Ha. I've never been accused of being too brief. Glad there was some value there. Hard to dive deep without getting wordy.

There is a challenge in getting chargers and batteries "on the same page" regarding knowing internal battery temp and when to charge or not. Same for an external battery heat pad thermostat. Unless external heat pads or chargers can communicated directly with the internal battery BMS, and therefor access the internal battery sensor reading, there is no way for any external device to truly know the cell temp. There are ways to estimate and/or trick things to work, some of which were discussed in last post. But a reasonable way in your trailer battery, since they have internal heat, would be to place the REDARC sensor directly on the surface of the battery and then insulate tightly over it. Been a while since I had my OEV, which had a REDARC Battery Manager 30, so can't remember where that REDARC battery temp is located. In your trailer, is it attached to a battery terminal or some place else? If a terminal, that might make it a bit tricky to insulate around.

If you know your internally heated batteries are up to temp (by app, for example), but REDARC isn't charging because it thinks temps are too low, like you mentioned, you could intentionally create a false reading on the REDARC temp sensor (tiny 12v heat pad on an on/off switch). Or, simply make a temporary change the REDARC to a use a different battery chemistry charge profile that charges below freezing. You can change it to AGM and it will start charging. Looking at the REDARC Battery Manager 30 (is that what you have in the trailer?), the AGM profile has a perfectly acceptable voltage and would work fine for getting charge to your LiFePO4 battery as the AGM doesn't limit charging at freezing temps. Easy hack. See various charge profiles in owner's manual paste below.

And no worries if your lithium dips below freezing while charging is taking place as long as your lithium battery has a cold temp disconnect. If so, the battery BMS won't allow charging. But as long as you have first checked the internal battery temp with the app and the internal battery heaters have brought the cells up to adequate charging temp, then I'd just switch the REDARC to AGM charge profile to get it charging. It's only a few menu clicks to change the charge profile. Then, once at camp and camper is heating up, change it back to Lithium charge profile.