Battery pack first build

Ordering all the sheet metal

After pondering over the design of the battery box it was time to bite the bullet and just order it. This was for the outer enclosure panels and also the cooling layers. 

I used a company called Fractory, there are many like it, you upload your CAD designs and get back in instant quote to cut and also bend your parts. Services like this are amazing now for people wanting to engineer their own solutions, I imagine I'll be using them again for a HVAC unit I need to design. 

All the loose parts, note the cooling layers have bars running across them to prevent distortion during the laser cutting, I'll have to cut these out and deburr them before bonding the 3 layers together.

Assembling the pack

I needed to first make my special bolts with the fittings I have turned welded onto the end. The idea behind these is they are a 12 point 17mm hex socket fitting and also have a female M8 thread in them so the layer above can be bolted down onto the layer below. So the layer below supports the cooling layer above while also bolting down this layers battery module, only 108 to weld.....
The idea behind these though is all 27 battery modules will then be one structural lump so I don't have to worry about any movement in the pack.

Each battery module has a heat pad underneath to promote the most efficient transfer of heat from the cells to the cooling plates. So it was a case of cleaning down the plates with IPA then sicking the thermal pad in place before bolting down the modules. After the first layer I began to get concerned that the thermal pad was going to put pressure on the cells themselves as there is no structure under the modules. So I 3D printed in PLA+CF some little spacers that go under the structural part of the module and prevent pressure on the cells themselves. 



1 full layer down, it almost looks like it did on CAD.


You can see here the small little adapters I welded onto each of the fixing bolts stand just proud of the modules and support the next layer then that goes on top. 



This is what the cooling layers look like on the pack, There is a solid top and bottom layer with the finned layer in the middle, these will all be bonded together to make a radiator in effect. 

Well there we have it, 27 battery modules, 71Kwh and 487V (I'll limit it to 427V for a few reasons)



The outer box was then very satisfying to assemble around the battery modules. 

Underneath the battery pack there will also be a support frame I'm currently fabricating, all of the bottom layer battery modules will bolt to this then he support frame will bolt onto the car Chassis. Also allowing the whole pack to be quickly and easily removed if I ever need to. 

Progress is slow but still progress, Now I've done the dry build of the pack I have just taken the outer casing over to GD so no battery's but just the fabricated outer, one for safety reasons and also one person can happily move it around rather than it weighing 300kg.

Jobs for me now while GD are fabricating the chassis:
Busbars, round the edges, bend and then off to powder coat.
Finish fabricating the lower support frame
Test the cooling plates, do they actually work?