Will this battery bank circuit work with these batteries?

[skillz21]

I took these batteries out of an old laptop battery pack:






It's a parallel array of four 3.7v lithium-ion cells (it was originally used in series in the laptop). Each one is at 4.2v. I tried to connect this to a small single cell power bank circuit, but for some reason, some component on the circuit released the magic smoke after a few minutes (which confused me, because when I connected it to a single cell, the circuit worked properly.

Anyway, I want to get a power bank circuit for this, because this is currently lying around, and all of these cells combined made a 42 wh pack. Would something like this (http://r.ebay.com/ufzmfL) work if I connected this battery pack directly to it? Would it have all the needed protection for the batteries?

[ogden]

Anyway, I want to get a power bank circuit for this, because this is currently lying around, and all of these cells combined made a 42 wh pack. Would something like this (http://r.ebay.com/ufzmfL) work if I connected this battery pack directly to it? Would it have all the needed protection for the batteries?

It depends. That power bank module is sized for 18650 Battery which is usually in 2..3 Ah (6..10WH) range. Most charge controllers have charge safety timer which dos not allow charge to be longer than some predetermined time. It may simply shut-off after 4 or 8 hours or whatever timeout time is. Your problem is that your pack is 20x 4x bigger than 18650 and obviously will need longer time for that poor controller to do the charge job. So... your mileage may vary. There's slight problem about protection circuit which is undersized for your pack, but it's IMHO minor problem.

Try it if you can afford it, share your results.

[skillz21]

Anyway, I want to get a power bank circuit for this, because this is currently lying around, and all of these cells combined made a 42 wh pack. Would something like this (http://r.ebay.com/ufzmfL) work if I connected this battery pack directly to it? Would it have all the needed protection for the batteries?

It depends. That power bank module is sized for 18650 Battery which is usually in 2..3 Ah range. Most charge controllers have charge safety timer which dos not allow charge to be longer than some predetermined time. It may simply shut-off after 4 or 8 hours or whatever timeout time is. Your problem is that your pack is 20x bigger than 18650 and obviously will need longer time for that poor controller to do the charge job. So... your mileage may vary. There's slight problem about protection circuit which is undersized for your pack, but it's IMHO minor problem.

Try it if you can afford it, share your results.

Thanks for that, I'll try to buy that and have a look... but will it be safe? All the necessary protection for over discharge and overcharge?

[ogden]

All the necessary protection for over discharge and overcharge?

I can't tell you that - have no experience with that particular controller. Overcharge protection for sure, overdischarge most likely. You shall investigate - try to find PCB pictures where IC markings are visible, check datasheets to see what kind of protection particular controller IC  offers. When you buy it - do not leave unattended for first runs, check how it does it's job. [edit] 42WH is s**tload of energy - be safe. Note that I modified battery sizing info in original post as well.

[skillz21]

Thanks for the info, I'll have a look.