Battery building for a conversion project

[paintboy]

Unless you want a specific cell or shape then one will likely be better off buying a battery or going to Jimmy at ebikebatteries .co.uk to build one.
If one has a few spare quid to burn then as an experiment one learns better how a multi cell battery works and how it is connected.


First of all one needs to carry out weld tests to see that the weld doesn't penetrate or burn the cell ends, the more expensive spot welders have adjustment to vary the energy /weld strength. For this. welding nickel or copper to kraft knife blades (the snap blade variety) will tell you if too much energy is being used, once done turn the blade over to check for damage.
One doesn't want to see blued/burnt metal as this means penetration is to deep/hot, the ultimate test is to use pliers to see how strong the welded nickel is to the blade used. A good weld is one where the nickel tears leaving small /sharp spikes of weld left behind.

The items needed are more then just cells and spot welder.
DVM.
Cells.
Cell holders. (Glue/hot glue is really not suitable).
Cell insulators for v+ end.
Soldering iron, solder etc,etc.
Shrink wrap.
Kapton tape or fibreglass tape.
If not using a case then fibreglass 0.4mm protection sheet top and bot before using shrink to wrap.
A BMS.
Pure Nickle or copper strips with weld slits (strip thickness or layers need to be capable of carrying the current rating, so one needs to calculate the area to know it's capability).
Silicone awg wire suitable to carry the current rating.
Wooden or plastic tools to work with ( I use wooden implements, like take away forks, lolly sticks flat and round or wooden kebab skewers.

Yes, I've spent many evenings watching YouTube. Some solder, some spot weld, some use car battery s and short circuit it. YouTube has many videos on which the person hasn't a clue. Dunning Kruger effect.

 

[vfr400]

Gotcha. Ok I like a challenge, but maybe building a pack isn't the route to take. I could weld the cells, I get that, but the BMS would be a problem. Let alone the fact I need to suss out the controller wiring, I don't need to complicate everything

I'd recommend that you buy your first battery, then if you feel you want to do a lot of messing about with bikes, you can consider making your own battery. It only makes sense to build one if you're going to build a few or if you want/need a special shape one.

 

[WheezyRider]

Paintboy, if you have never owned an e-bike before, my recommendation would be to take a second hand push bike, buy a basic 250W rated motor kit and battery, put it all together for about £400 and ride it around for 6 months and see how you get on. Until you have done that, you will have no idea what you want/need.

The route you seem to be taking is one that could cost you a lot of money and you'll end up with something that is not any good for what you want it to do. Reading and watching the theory is all very well, but until you get your hands dirty, it's just academic. To do the hands on learning, you want to do it in a way that isn't going to break the bank, or end up with you getting hurt.

 

[paintboy]

Paintboy, if you have never owned an e-bike before, my recommendation would be to take a second hand push bike, buy a basic 250W rated motor kit and battery, put it all together for about £400 and ride it around for 6 months and see how you get on. Until you have done that, you will have no idea what you want/need.

The route you seem to be taking is one that could cost you a lot of money and you'll end up with something that is not any good for want you want it to do. Reading and watching the theory is all very well, but until you get your hands dirty, it's just academic. To do the hands on learning, you want to do it in a way that isn't going to break the bank, or end up with you getting hurt.

Good advice mate

 

[Woosh]

I like to take things to bits and I have not been that impressed with the commercially available packs I have taken apart.

if you can take a commercial pack to bits then that commercial pack is not up to date.
For at least two years now, commercially produced packs can no longer be taken to bits. They are all disposable packs now.
that seems to be the way forward to achieve better product safety. If there is a whiff of anything untoward, throw the whole thing away.