Thor Forums

[RonRM]

Originally Posted by Chance

Are your lithium batteries located inside coach? If so, as is the case with most RV Lithium batteries I have seen, you can start the vans engine and warm the inside of the van like you would any car until it reaches a comfortable temperature around 70 F or thereabouts. Given a little time batteries should also warm up enough to allow charging. After initial cold start, house heater (whether propane or gasoline) can keep inside of van warm enough for camping in cold weather, which should also keep batteries fully functional for charging.

Unless batteries are located outside camper, I don’t see this being a significant problem for cold weather camping as long as there are safeguards to prevent charging a cold battery bank.

I’m not saying Thor did an adequate job because I have no idea how they wired safety interlocks to protect batteries from damage. In many cases batteries can be charged from shore power, generator, alternator and or solar, so there is a lot to consider. From my perspective easiest solution is to make certain batteries remain above 40 F before any charging is attempted.

ditto - 2023/20L batteries are under the coach - 9/10 degree of difficult to remove. Thor just repurposed an AMG system added sophistication and didn't consider the combinations of situations and care/feeding required by lithium.


So, just to recap.

Batteries have hard wires to both +/- always powered devices (they do not cut off with master DC switch). So, batteries can never be 'stored'...they will discharge to 0 in a few days. Modification of wiring needed -- at your own risk.

Stock solar even on the brightest day, is not enough to run the heaters in the batteries. Best if it is disco'ed in cold. No way to do that, without pulling a fuse - good luck finding it and then once you see it...requires very specific yoga poses to remove.

Temp is measured on UHG (on non gen models) - this feed back regulates alternator field and keeps UHG in temp range. Good stuff, keeps the smoke inside the alternator where it belongs .

Temp is measured on outside of battery - this is feed back to the UHG regulator. Prevents UHG output when temp is below 0C. Marginally stupid - since BMS handles this. In theory, this protects from a couple of other conditions...but that's going out on a limb (read below field dump issue). It's mostly just stupid.

Temp is measured by the internal BMS - this feedback is internal, no interface no bluetooth...nada. At threshold, it diverts charge to heaters, until internal battery temp is 40f+. It appears the 12vdc output is cut off when heating. Nice, but...without this information being available to the charging devices, can actually cause other issues (read below field dump)

It appears on gen units, when the battery goes into low temp cutoff, it kills the generator as there is no 12vdc when heating.

On UHG units, UHG (via regulator temp low temp cutoff) will never deliver charge to batteries below 0C. So, no way to charge (via UHG) below 0C with regulator at low temp cutoff - solution modify low temp cutoff on regulator...easy to do, but please be careful...at your own risk.

UHG/regulator does not have 'field dump' protection. If the UHG is charging and the battery BMS cuts off 12VDC (technically both batteries would have to disco) - instantaneous field dump may occur, pretty much guaranteeing 12VDC device damage throughout coach. Balmar now sells a device (around $65) to protect from this (big zener diode in waterproof case). This can occur if the battery outside temp is above low temp cutoff (above 0C regulator will deliver charge) and the inside temp goes below BMS low temp cut-off...hard to imagine it is even possible...but if it happens there is nothing to protect from what happens next. Given where/what and accuracy of temp measurements - there can be differences in temps, causing an issue.

When on shore power, everything is done with voltages...none of the devices feed back/talk to one another. MV inverter/charger just does it's thing and the batteries do their thing...batteries, when internally are below 0C, divert change to heat, MV is suppling 12vdc so coach 12vdc stuff stays alive - even if batteries are not delivering 12vdc. When at 40F+, batteries charge...they never get above 13.5/13.6 - top end charge voltage set on MV. MV continues to 'float' or bounce back and forth between battery heat and charge cycle,...not ideal by any means.

For me, too cold out to fix. I'll have to live with the consequences of being plugged in all winter. First chance, I'm going to yank all the crap directly wired to the batteries, add disco switch, so I can completely disconnect them. Second, install new parts that will provide a bit more intelligence about what happens when (shunt, monitors, Rpie with some ESP32's - I've got a smart RV project on the board for spring). Tweak the UHG low temp cutoff. Add the Balmar zener diode pack ($65 field dump protector). While I'm under there, replace all the connectors/splices etc. with waterproof marine grade stuff. Oh yeah, the connector on the UHG has only 2 wires in a 4 wire connector -- apparently the Thor assemblers do not plug those MT holes...water gets into connector...plug those with silicone or better.

If $$ was no object...I don't think I'd buy a different unit, might be stupid on my part...but I kinda like the Ram and most of the Thor stuff on the inside. It's just the power system that is an issue in cold temps (setting aside all the abysmal manufacturing practices/execution). My $$ is going into fixing/adjusting the battery system (replacement would be pretty expensive).

The 20L actually might have enough room behind the fuse panel ,and near the water pump to move the batteries (or additional) inside...that's an option too.

rm