Portable jump starters

David113

Member
The battery on my 2004 tdi90 was flat so I used a fully charged Halfords portable 2L lithium ion jump starter for the first time. The instructions ask you to connect the positive jump lead to the positive terminal of the dead battery and the negative to a suitable unpainted point on the chassis or engine of the vehicle. I couldn’t find a suitable point in the boot of the car so I connected to the negative terminal on the dead battery but I wonder whether the electronics risk being ‘fried’ or is there a negative terminal other than the one on the dead battery? Incidentally, the portable unit didn’t get the car going but an old school set of jump leads did, thank goodness.
 
Connecting across the battery terminals is just fine.
It's the same principle as when using jump leads.
 
Oh good, thanks for that. The leads supplied with the portable unit are so short there really aren’t any other options.
 
Those portable units are just three 4.2v lithium cells in series. When you connect the croc clips directly to the battery it pushes 12.6v so should be enough to help a slightly poorly battery but once the ‘peak’ voltage is off the lithium cells it’ll drop to around 3.7v each - 11.1v.

You aren’t going to fry anything electrical with these. Your alternator pumps 14v into the circuit.


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