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I have a ES cordless drill and it has a Li-Ion battery (model is ES GB118L20).

The original battery charger is missing and there is almost no way for me to get one in my country.

The Battery has 5 Samsung INR18650-20R 3.7v cells connected in series.

Inside ES GB118L20 battery Inside ES GB118L20 battery

The battery pins are BATTERY+, BATTERY- and 4 pins marked BATTERY1, BATTERY2, BATTERY3 and BATTERY4 which are connected between + and - of batteries (probably used for balanced charging). Also there are T, BS and ID pins which I'm not sure of their role.

I tried charging the cells one by one by connecting a TP4056 charger to each battery pin (for example [BATTERY- and BATTERY1] or [BATTERY1 and BATTERY2], but was not successful. It didn't even start charging it.

Can anyone help me how to charge this thing?

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  • \$\begingroup\$ it is unclear what is the brand name of the cordless drill ... is it just ES? ... is there another name? \$\endgroup\$
    – jsotola
    Commented Mar 14, 2018 at 17:09
  • \$\begingroup\$ Yes, the brand is ES. It's a Korean brand (probably LG Industrial branch). the website is es-is.co.kr/html_e/index.html \$\endgroup\$
    – Euphoria
    Commented Mar 14, 2018 at 17:17
  • \$\begingroup\$ And this is the link to the original charger: es-is.co.kr/bbs/… \$\endgroup\$
    – Euphoria
    Commented Mar 14, 2018 at 17:17
  • \$\begingroup\$ Can you measure any voltages across the individual cells? \$\endgroup\$
    – Finbarr
    Commented Mar 14, 2018 at 18:04
  • \$\begingroup\$ Are those cells as easy to remove as they look? If so, you could easily get a charger from any vape shop. Perhaps not the most convenient option, but it would save you from having to reverse engineer the system. \$\endgroup\$
    – Phil C
    Commented Mar 14, 2018 at 18:06

1 Answer 1

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Quick answer: connect a constant current supply, with suitable voltage limit (4.25Vx5=21.25V), and leave it until pack voltage is high again. Clearly this will take forever (4+ hours) to charge, and will invalidate any warranty with the pack etc.

Longer answer: while there are many different chargers, there are two ways to charge li-ion cells, either using constant current only, or constant current followed by constant voltage. The quick answer method uses the constant current method where it pushes current into the cells until they are charged. This is the method used in my of the basic battery powered equipment out there, such as vacuum cleaners and some basic drivers. The more complicated method, which is used in the more power sensitive devices, pushes a fixed current into the cells until they reach somewhere around 80-90%, and then a fixed voltage and let the physics of the cells control the current.

In your application, I would suggest that your best bet is to use a desk top power supply, current limit it to something around 0.5Amps, and leave it to charge the pack. This isn't exactly a clean idea, but it works.

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  • \$\begingroup\$ Thanks. Finding a 21v charger is not easy. I probably need to find one with one of those imax b6 chargers and ask him to test it for me. if ok, i would buy one myself. \$\endgroup\$
    – Euphoria
    Commented Mar 15, 2018 at 10:40

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