Lithium Ion Battery Jump Starters

[tmontague]

I thought I'd post this as a heads up to those who have a lithium ion battery jump starter pack in their car for emergency use.

For xmas this past year my wife bought me a jump pack from Costco - The Type S jumper. I wanted one since I have a parasitic draw on my battery (~275-300mA) and if I let thre car sit for about 6 day in the summer or 2 days in the middle of winter, it doesn't have enough juice to turn over the car.

Well I fully charged the jumper and left it in my car in case I ever needed it. I needed it a couple week ago and went to use it and the jumper battery was almost completely dead. It had less voltage than my car battery so it automatically wouldn't jump the car. I took it inside and once it warmed up it read full charge. I ended up having to use my battery charger/75A jumper that I have and after 5 tries it finally turned the car over and started. 75A isn't as much as you think when it is -20C.

I have since kept my jumper in the house at night and if I think I may need it later in the day I bring it inside with me where ever I am. This morning my battery didn't have enough charge to turn over the engine and I pulled out my (room temperature) jumper. Hooked it up and the battery turned over like it was brand new and the car started.

Anyways, my point is, don't trust those lithium ion jumpers to do anything below 0C, during the winter bring them inside in case you actually need it. This is nothing new, Lithium ion batteries don't do well in cold, but something to keep in mind none the less.

I think my parasitic draw may be due to my aftermarket keyless entry but it is way too cold outside right now to test that theory.