It's a bit of a monster...

[gords1001]

Their all parrallel, hence 4.2v on firing. Its a real elegant solution to me

 

[doobedoobedo]

Putting cells in parallel divides the effective internal resistance by the number of cells. That's why I get such a low voltage drop under load.

 

[Raguri]

... I am tempted to make this my project over the easter holidays.
No longer have access to a lipo charger, but that's easily changed
Only problem is, I'd need to balance them right?

 

[doobedoobedo]

They will 'self balance' when they're connected. Basically make sure they are all at exactly the same charge level before you build the pack, otherwise the lowest voltage cell will be charged by the others as fast as they can which can be bad news as you shouldn't really charge above 1C, which is 750mA. Once the pack is built they act as a single cell and require no further balancing.

 

[Raguri]

They will 'self balance' when they're connected. Basically make sure they are all at exactly the same charge level before you build the pack, otherwise the lowest voltage cell will be charged by the others as fast as they can which can be bad news as you shouldn't really charge above 1C, which is 750mA. Once the pack is built they act as a single cell and require no further balancing.

Aaaaaah okay! So basically, check the charge from factory, then join them pretty much straight away if they're level. Got it (y)

 

[doobedoobedo]

Yes. They should come at a storage charge of about 3.8V. Don't connect anything that's not within 0.1V at the most otherwise you might get some hot wires or worse.

 

[doobedoobedo]

To be perfectly honest, unless you're used to LiPos and good with a soldering iron I wouldn't advise anyone to build their own packs. Even a slip with the soldering iron can short them.

 

[Raguri]

Aah alright
Will have a look for a box to put it all in (I have no wood working skills)...
What's a rough idea of internal dimension needed?

 

[gords1001]

The load is also shared amongst the cells so each cell only sees 1/7th of the load. I think its brilliant. Plus you dont need to think of building coils any different to a mech mod, or remember which attys suit the box mod.

 

[doobedoobedo]

The pack itself is 63x45x24mm. Everything would fit in a Hammond enclosure. But I'd coat the inside of the enclosure with something non-conductive first I think.