12v portable jump starter issues?

Trestle

Active member
When stored, low temperatures are generally not too harmful to the longevity of lithium batteries. Stored in excessive heat will have a bigger effect in degrading their capacity. Especially heat over 150f for prolonged times (gets pretty hot in an enclosed vehicle sometimes).

In use, lithium batteries do hove low temp issues that you have to account for. Most will put out juice safely down to about 4f, and accept a charge down to about 20f. Early batteries did not have protections in place to prevent charging and discharging at low temps, and will be damaged very quickly. Some cheap newer ones still don't have those protection built into the BMS, which is in my opinion just poor engineering.

Other failures seen in low quality units have to do with the connection size and configuration. A low quality connection (under sized or poorly connected) will work for a while, but usually fails when it heats to the point where the connection fails. You're putting out amps quickly to fire over an engine, often at quite low voltage, so connections heat up quick if not appropriately sized. They have to cut costs somewhere to get to a low price point, and this is often the place they do it. It could be connections between cells, connections from the combined cell to cables, often both. One failure in the system results (hopefully) in an open circuit which is doing nothing for you. Better than a short and fire though.

Last point of failure is likely the battery management system. It could be that it has a bad program, or just poor connections choosing so save $ in manufacturing by using a low quality unit.

Some things to ponder when shopping for a unit and comparing prices. Hard to see what's under the hood too, so a long standing reliable brand OR lots of good reviews from various sources is probably a good idea.
 

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