Steve’s car battery died, and he needed to get to an exam.  He needed to be on his way quickly, so we decided to jump start his Nissan Sentra with a tiny handheld lithium battery!

The battery was 100% dead on this Nissan Sentra.  The LIPO battery started it right up!  WARNING: We do not recommend using this exact battery on a car if you are concerned about the electronics. It is at least 2v higher than max alternator charging voltage.  We are aware of this, so we disconnected it the moment it turned over.  If you want to jump your car with a lithium pack, use 4S LiFePO4 lithium instead.

The battery used in the video is 5AH 4S LIPO with cobalt cathode (LiCoO2).  These are 14.8v nominal, 16.8 full charge.  Manufacturer states they are 20C rated.  RC forums have supposedly got 30C out of them, or 150A discharge.  Basically, it’s a tiny 1.16 pound jump starter!  If you plan on doing this sort of thing, I highly recommend doing 4S LiFePO4 variety.  Although less energy dense, they are inherently safer and the nominal voltage is closer to a car’s (~13.2v nominal, 14.4v max).  The only thing keeping a LiFePO4 battery from being a direct drop-in for a car would be excessive charge rate and cell balancing requirements, easily remedied by a BMS.

If you insist on using LiCoO2 because they are cheaper, a 3S pack would be safer for your car electronics (11.1v nominal, 12.6v max).  However, you would need to remove the battery the moment it started to keep the alternator from damaging the pack (with a huge fire risk).  I don’t recommend it, which is why I suggested 4S LiFePO4 instead.

People who race their cars on the track would benefit from the weight reduction of using one of these batteries.  You could replace a 30 pound Pb battery with a 2-5 pound LiFePO4 Lithium pack.  Along with reducing the weight, it could improve the weight distribution on a front heavy car for improved handling.  Or, you can just use them to jump start your old beater in a pinch like we did!