[Archived]

My understanding is the built in tank heaters only work on batteries when they’re being charged

[Larry]

Correct. Li batteries can be discharged (used) when the battery cell temps fall well below zero F, and can be stored unused in very cold temps (battery dependent), but can be safely recharged only if battery cell temps are above about 28 degrees F. Built in battery heaters turn on when battery cell temps go below about 28 degrees F and there is charge current present at the battery. If no charge current is detected the heater does not come on so you can store your bus without discharging the batteries even in very cold weather. Once the battery cell temps go above the set point (battery dependent) then the Battery Management System turns off the heater and will allow charge current to flow to the battery to recharge it. So, other than the additional cost, it is a transparent process that is very beneficial for the user with no downside. I highly recommend you consider adding this option if you are considering conversion to Li batteries.

BTW, many Li batteries are now being supplied in stainless steel cases. Make sure the lids fit properly and are attached with SS machine screws going into threaded inserts in the case. Watch out for some using cheaper SS sheet metal screws to attach the lid which can potentially result in sharp points present inside the battery – not a good idea!

Jerry

[Jon]

Thanks for the info. In my coach I have a pair of 12V EG4 racks and a pair of 48V SOK racks. All metal. I know some BMSs log temps and iv under 0deg even when not used it can void warranty. I’m hoping all packed tightly in front bumper with all other electric components they’ll stay warm in winter with just a couple tank heaters.