Custom battery for Evolve Bamboo GT

Edit: I ended up building this and it works a treat info at How I built a 12ah Battery for my BGT


So it looks like I'm going to end up replacing my stock battery in my BGT with LG HG2 18650 cells in a 10S4P formation.

Details of the swap:
I will be using the stock BMS as it would be a massive pain to replace it.
The LG HG2 18650 cells have a max continuous discharge rate of 20 amps with 4 of these paralleled the pack should have a total continuous discharge rate of 80 amps. LG HG2 Review (20A, 3000mAh)
The length of these pack will be slightly longer than the stock pack so I will need to extend the battery case.
The diameter of these cells are also slightly too large to I will need to cut some wood out of the deck.
I plan to build the pack in the same manner as this guy Endless-sphere.com • View topic - Evolve Carbon AT with 50km+ range
LG HG2 18650 cells cost about $10 each so the battery alone will cost $400.
I believe the stock pack is rated at 6.5Ah this new pack should be 12Ah.
Our motors are rated at 3000w, and batteries at 36v. 3000 / 36 = 83 amps

Things I still need to sort out (and I would appreciate some help with):
Work out which spot welder to buy
Where can I buy 40 genuine LG HG2 18650 cells
Is a 10S4P pack with an 80 amp continuous discharge rate going to be enough for our 83 amp motors

Anything I'm missing or should be aware of?

 

I love the idea, please take pictures once you work it all out. Am tempted myself

 

I don't think there's any danger of the motor controller sucking more juice than it can handle - that's where the bottleneck would be - so meet the minimums at least of the stock pack (and the basics - voltages / amount of cell banks presented etc) and you should be fine - interested to see how the BMS and remote handle the larger capacity - should be fine - as based on voltages - and maybe the only side effects would be longer charge time and even better - longer run time

 

I'm actually getting started on the same project!

Got the batteries today. Welder is coming in tomorrow, but I'll still be waiting on some additional materials (heat shrink, nickel plating, etc.) for a few days before I can get started on it.

Others have had success with building LG HG2 10S5P packs for CGTs. As far as I know the CGTs include the same hardware so I don't see any problem with building a 10S4P to drop into a bamboo.

The only thing I'm a little concerned with is how it'll fit in the enclosure. It seems like there is enough room in there for a 18650 10S4P pack without having to do any alterations, but to be honest I haven't done my own measurements, so I could be wrong about that.

 

west please keep us updated on how you are going, I'm very interested, from my measurements I think you wont have enough length to fit them in. My current plan is to get a replacement battery cover and add the front of it to the stock one for a little extra length. Which spot welder did you buy?

 

Very interested in what you guys got going on here. Please keep us posted.

 

+1, maybe we can use the new tesla 2170 battery cells in the future

 

Sure I'll keep you in the loop. I got a Carejoy 709A spot welder for 180USD. I haven't had a chance to try it out yet. As soon as I do I'll let you know if its worth buying.

I'll probably get started this weekend.

 

Very cool Mate, good luck!

 

Hey west if possible can you take some pics of the build process?

 

would like to see the build process and see how your board range changes

 

Maximum discharge your pack has to cover is 65A. That's the current limit the motor controller has. 30A per motor, 5A is just heat on the controller. You can test that by going on to the secret battery menu while in GT-mode then accelerate on a hill and the current draw still not exceed 65A. Now go into secret motor menu and you will see that each motor takes 30A

 

Thanks for that Spartan117 that's good news

 

So after a couple more days of thinking about the design I think I have it all worked out now.
The diagram shows how it will be wired


I had a couple test cells arrive in the post so I test fitted them.


This all looked pretty good so I ordered 42 more, this gives me 4 for redundancy sake.
I have also ordered a spot welder, nickel plate (0.15x10mm), 8 AWG silicone covered flexible wire, 18650 insulator rings and a couple other bits and bobs. A lot of this stuff is coming from China so it will probably be a good month until I have everything I need.

 

So just an update. There isn't quite enough room in the case. The existing case has just enough height & width to fit a new battery, but once you account for the size of the BMS it lacks 2-3cm of the space needed to fit a 10s4p.

I'm going to start looking into some ways of creating a little more room.

 

I've hit 40+ amps in full acceleration from a standstill in GT mode. I weigh about 150 pounds (68 kg) so I doubt weight is the reason causing it.

 

Thats interesting, I measured it out today and thought I would have about 3-4mm free between the motor controller and the BMS, either way I have ordered a replacement plastic battery case from evolve and if it comes to it I plan to extend the front of my case by using a bit of the new case.

 

Hers a pic of the case with 20 batteries side by side. As you can see there's just not quite enough room for the BMS and the last battery to fit side by side.

 

Damn ok, thanks for the pic, any chance the BMS will got behind the motor controller?