[bobbyboblington]

The cell actually used in the Model 3 is the 2170 format cylindrical - 21 mm x 70 mm - made by Panasonic at the "Gigafactory".

2170 sorry, is it correct they are rated at 5000mAh? Point taken about the pouch cells. I haven’t seen a DIY pouch battery made from scratch and as this is a DIY EV forum, the suggestion was to make one from 18650s which is far more common.

 

[brian_]

I haven’t seen a DIY pouch battery made from scratch and as this is a DIY EV forum, the suggestion was to make one from 18650s which is far more common.

Sure, that makes sense if completely from-scratch pack construction is required. On the other hand, welding fine leads to every one of those cylindrical cells is a real pain for DIY manual construction... which is one reason that people were using prismatic cells (with a small number of connections, using screw terminals) and now avoid building packs from individual cells at all, instead assembling OEM modules (consisting internally of of pouch cells) to suit their needs. Even when people use 18650 cells, most of those cells going into recent projects are within complete Tesla modules, not as individual cells; some people do modify the Tesla modules (to change them from 6sNp to 12s(N/2)p), but even then they don't touch the individual cell connections.

Since sdb's intent is to convert a camper or van, it should not be necessary to custom-build a pack to suit some oddly shaped cavity; reconfiguring the modules of a production EV pack (whether those modules contain pouch cells or cylindrical cells) seems like the most practical approach.

 

[bobbyboblington]

Sure, that makes sense if completely from-scratch pack construction is required. On the other hand, welding fine leads to every one of those cylindrical cells is a real pain for DIY manual construction... which is one reason that people were using prismatic cells (with a small number of connections, using screw terminals) and now avoid building packs from individual cells at all, instead assembling OEM modules (consisting internally of of pouch cells) to suit their needs. Even when people use 18650 cells, most of those cells going into recent projects are within complete Tesla modules, not as individual cells; some people do modify the Tesla modules (to change them from 6sNp to 12s(N/2)p), but even then they don't touch the individual cell connections.

Since sdb's intent is to convert a camper or van, it should not be necessary to custom-build a pack to suit some oddly shaped cavity; reconfiguring the modules of a production EV pack (whether those modules contain pouch cells or cylindrical cells) seems like the most practical approach.

Absolutely makes sense if you are going for the simplest/most compatible solution, however sdb’s just purchased the £500 remy cartridge motor and building a custom housing and cooling unit, along with a DIY motor controller. Either he’s going for an incredibly bespoke EV build or he’s looking to save money. If it’s the latter you can’t get a much cheaper LiIon sollution than recycling used 18650 cells, albeit very time consuming and requiring a lot of scrutiny. Tab welding is not difficult with the right equipment, and as you say if it is the former it does give some modularity to your battery pack design, but if you could get your hands on reasonably priced battery packs that would be the best option.

 

[Kevin Sharpe]

if you could get your hands on reasonably priced battery packs that would be the best option.

A quick look on eBay has Tesla 5.3kWh Modules at $1199 (here) which equates to $2.70 for each 3400mAh cell. I don't know what current prices are for complete 85kWh Tesla packs in the US but in Europe we can typically buy them for 11,000 Euros (~13,000 Dollars) which equates to 1.55 Euros ($1.86) per cell.

It's hard to imagine that you can build a lower cost battery pack if you factor in the hardware required for the case, cell fuses, BMS, etc. I also doubt you can produce something as compact as the Tesla design if you include cell heating/cooling (IMO a critical safety requirement).

 

[Kevin Sharpe]

Since sdb's intent is to convert a camper or van, it should not be necessary to custom-build a pack to suit some oddly shaped cavity; reconfiguring the modules of a production EV pack (whether those modules contain pouch cells or cylindrical cells) seems like the most practical approach.

If we're talking about a VW camper then it would be trivial to fit Nissan Modules beneath the floor and above the motor without cutting the bus. Indeed it's possible to fit 14 Tesla modules with only minor cuts