homemade battery pack using laptop batteries

I have heard it is possible to make a rechargeable battery pack for my electric handcycle using old laptop batteries it is a 36v powabyke not sure what the wheel is I think its 200 watt brushed motor on s l a batteries I was wondering if anyone has heard of or made a battery pack at 36v with laptop batteries I know they have to be stripped out of there casings but am unsure how to configure them or how many id need I have read on google that they make a 24ah rechargeable pack is it possible and can anyone please point me in the right direction thanks

A few of us have done it. You have to spend a lot of time testing them, for which you need the right equipment. Then you need to find a way to wire them up successfully. It's great to do it as a project, but it's a lot easier to make a battery out of new Hobbyking lipos.

Not as easy as it sounds I'm afraid.

 

For starters, you need at least 50 cells. You will need to harvest them, and check them. There's about 8-10 18650 cells in each pack. Normally one is a dud, but this depends on your battery source.

 

Then you need to solder them all together. 5 x 10 in series. The soldering need to be accurate. Too Much heat could screw a cell up.

 

Then you will need to add Battery management System of some kind, and also solder wires to each cells for balancing.

 

At this point you will have a 36v, 8ah battery, if you are lucky but I don't think it will be able to deliver much more than about 10 - 12a. But that depends on the cells.

 

It might last for a bit, or a cell might go belly up first time out.

 

Oh, and it might go a little bit on fire if you get anything wrong.

 

I don't intend to spoil your fun, just saying it as it is.

 

I have loads of old laptop batteries that I power stuff with. Very useful for low/medium drain stuff.

I'm building one at the moment but using Makita drill cells, a bit more ooomph than the laptop ones. I'm doing a 4p 10s pack to begin with to see how it goes. On my second soldering iron this week! Trick for me is, high powered iron (60w-100w) and quick decisive solder joints so as not to heat the cells up too much. I'm then charging up the single 4P sets and testing before incorporating into the pack. just building a discharge station as well with an amp meter and an hour meter (essentially electromechanical clock mechanism).

I have built a couple but as others have said it's very time consuming ! And they can't really deliver much amp before they start to sag - the c rating just isn't there

 

Matika cells are different as they are designed for high drain - more oomph as pdarnett says !

 

I learnt a huge amount by building them though - invaluable on that level frankly

 

I find that using laptop cells for other low / medium drain as per mike works very well - my shed stereo runs forever practically !

 

Also, IMHO , they work better as booster batteries when the sag is not so noticeable. Partly as you can parallel up enough to overcome some of the sag issue

I have powered the following things from old laptop 18650 cells:

 

USB power supplies (numerous)

Radio's (various)

Drills (when the ni-cd packs are fer-knackered)

High powered Cree torch (awesome!)

Handheld VHF marine radio (25 Years old, works great now).