why i call Li fussy

You don't need to be able to draw power from the battery while heating as they only heat when being charged (ie power is flowing into the battery). When the BMS detects the temperature is below a certain value, and current is flowing into the battery, it shunts that current to the heater until the temperature is above the set point, then it switches off the heater and charges as normal.

In practice, you turn on the charger (or the sun rises on your solar) and for the first minutes to a couple of hours (depending on the temperature) the charge power is actually going to the heater. Once the battery is up to temperature, the heater turns off and the battery charges like normal. This is superior to the BB scheme of just always heating the battery to maintain temperature. There is no need to heat the battery if it is not being charged.

BFL13 wrote:
Don't know who makes this brand, but the CANBAT with heater blurb says:

"In cold temperatures, the BMS ( battery management system) disconnects from the cells to protect your battery. Prior to charging, the built-in heating systems draw power from the charger in order to heat up the battery."

I have not watched that BB video yet, but does that mean you lose your 12v to the rig during the heating phase of the recharge?

Or do you still get 12v from the converter since the charger must be getting 120v and you don't need the battery when the converter is working? Unless it is an inverter/charger--where do you get the 12v to run that?

http://www.wegosolar.com/products.php?product=12V-100Ah-Cold-Weather-Lithium-Battery-%28LiFePO4%29

I see their spec balancing voltage is only 13.6v. Relion spec is higher. They claim it works down to -35C but very muddled as to what it really does for when you can draw from it as opposed to when you can charge it--badly written blurb!