Cheap jump starter teardown

April 2023

"High Power" TM188 jump starter

A couple of years ago I was looking for a compact jump starter for my car in case of emergency. I found that lithium ion jump starters were available on the market, and purchased a cheap one from an online store. It was a "High Power" brand model TM18B.

Unfortunately, this jump starter has proven to be completely ineffective at jump starting, although it has been handy as a USB power bank, laptop charger and light. I already have all of those things in other devices, so I decided to pull this apart, as I couldn't use it as a jump starter.

First up, the label of the device claims it is "68800mAh". That's 68.8 amp-hours! If it were lead acid, that would be the size of a small car battery. Lithium can pack a lot of energy in a small package, but nothing is that good!

Inside the case. Click here for a larger view.

Information label

Once inside, I found that there was indeed an unmarked Lithium cell, but its capacity was probably more like 4000mAh (4Ah), as I have another (confirmed) Lithium battery of the same voltage that is slightly larger and has a 5Ah capacity.

The unmarked Lithium cell connects directly to the plug for the jump leads, without any protection. It should be noted that the jump leads have a small enclosure part way along, and this contains a line of what look like power diodes connected in parallel. Perhaps an attempt to provide basic reverse polarity protection?

The main PCB of the unit is connected to the battery using the load balancing connector from the battery. It would appear this is done so that the charging circuit can do cell balancing (which is needed for Lithium), and also draw power from the pack as a whole. The PCB itself appears to be well made (except for a lack of cleaning) and effectively secured, which was a surprise at this price point.

The main boards. Click here for another larger view.

I didn't spend any time trying to trace out the circuit on this one or measure the stability of the charge outputs.

Overall, this is pretty useless as a jump starter, but could be of some use as a power bank or laptop charger.