Field charging LiPo batteries

[Pathfinder075]

Just bear in mind that a jump starter is designed to produce lots of CCA but probably doesn't have the biggest sized battery.  So maybe a 40-50Ah.  You need to work it out, as 50% of that capacity is what you should use at the most.

Yes you could connect the jump leads to the 12v connector if it has croc clips or plugs (tape them if using these to stop the two sides touching/arcing).  Do not let the two terminals touch, the worst case if they do is the battery explodes, which would mean A) shrapnel, B) sulphuric acid and C) some sort of sulphorous gas, probably hydrogen sulphide (egg smell).  None are a good thing.

Another suggestion.  Put an inline blade fuse in between the positive jump lead and 12v lead going to the charger.  To work out the size of blade fuse, work out how many amps the charger will pull at 12V and round that up to the nearest sized fuse.  So probably you'll end up with say a 15A fuse or 20A fuse. If something goes wrong, the blade fuse will pop before you have a fire.  If you decide to do this a lot, get a proper midi or mega fuse and build something specific.

Basically the charger will use whatever the limit of it's power input is.  So for example, say 100W @ 12V = 8.3A, so if you put a 10A fuse in between the jump lead and the charger, if it ever decided to try and pull more amps than it should do the fuse would pop.  This could happen if the charger overheated and maybe went into some sort of thermal runaway type situation where by some components got cooked and it just started pulling as much power as possible, but having the fuse inline means the second power requirements go past the size of the fuse it will pop and break the connection.


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