Custom battery for Evolve Bamboo GT

Yeah I will put them up On thingiverse when I'm happy with them

 

We were pushing pretty hard most of the time, they made it probably 22-23kms.

 

Clear grid, it seemed easier than spray on.

 

Hey- great write-up. I have made several big packs for my high-performance e-bikes, so I feel I'm ready to tackle this. Question - took the old pack out and laying out everything. I am using a new BMS (keeping old pack to use). What did you do with the two extra connections to the controller from the pack - UART, and BAT_SW? Did you leave them disconnected with your DIY pack, and board worked OK?

 

Looking more closely at your photos, I see that because you used the old Evolve BMS, it must have onboard connections for UART and BAT_SW, and you connected to those, yes? So I guess I'm screwed if I want to use my 3rd-party BMS?

 

Yeah that's correct, I reused the stock BMS, I think its the only way to do it.

 

Thanks for the reply. Well, cool, I now had to buy the Evolve BMS because you can't use one without the UART connection (which negates some of the cost savings - my main reason for doing this). And I just found out, it doesn't come with the balance wire harness. Awesome. I've purchased about 12 BMSs for my battery projects, all of them came with balance wire harnesses. I guess if you're just replacing the cells from an old pack and harvesting everything else, you're OK, if you are building a new, separate pack like I am, you're kind of screwed.

 

Yeah sounds like it, so Evolve was fine selling you a BMS?

 

Yeah, I have a pretty good relationship with them I think. They know my name well over there Assuming the connector is a standard 10-pin JST harness, I can use the balance harness that came with my BMS. Do you remember, when you connected your harness to the BMS, did it look like this standard kind of JST connection (pictured)?

 

Other side of it. Note this is an 11-pin harness because many BMSs, like most of the ones I used for builds, have the first wire as B-. Then series 1+, series 2+, etc.

 

GT BMS. To be honest that doesn't look like a JST connector to me.

 

Interesting, that looks a little different to mine, I didn't have the metal on the top. If you can check it for any marking that could let us find them online. My BMS had 11 wires to but I never took the plug out as it was glued in. How much did Evolve change you?

 

Could you take a closeup picture from the other side of the BMS? And bonus points if you could remove the heatsink and take pictures of all the chips etc.. I'm also interested in the BMS for a different reason. Thanks!

 

So this is coming along, but has been a true *****. Mainly because it has to be way over-engineered to account for the vibration, the close proximity of cells to each other, etc. I didn't have those paper sleeves for cells but I do have adhesive fish paper, so used that between cells. Did the 'butterfly' method but that was another snag - by habit, I double all my nickel strips. When folding the cell groups over, the 2 layers of nickel are bending at different radii and the top layer wants to pop off. Add to that another completely different problem - the BMS. I guess if you're just replacing cells in an old pack and gutting your old GT pack to build a new one, it's not an issue. But if you are doing one from scratch like me (as a backup pack, for 2nd home), then you have a huge pain in the butt. Because, you can't use a 3rd-party regular BMS as I had purchased for it. You must use the Evolve BMS, due to the UART connection. And besides that, their BMS is not sold with a balance wiring harness, like every other regular BMS sold is. After much research, I found the wiring harness (I think). Waiting for a BMS, to finish this up.

I've built 7 huge packs now for my fast e-bikes and scooters, and this small one is BY FAR the biggest ***** (and most time-consuming) of them all. Can't really say if all the work and frustration and hours and research is worth it, to save a few hundred bucks. Before, I thought the replacement packs from Evolve were way overpriced when you look at the parts cost. Now after building one and seeing the labor required, they don't seem so overpriced to me anymore!

PS - for other battery geeks - I do have the paper insulators that go on the positive terminal. After test-fitting, I did not use them. On the 25R, the top is actually recessed a bit already from the top of the cell body, and by using the insulators (at least the ones I got, they're thick), it forces the nickel to bend down drastically to reach the positive terminal. To me this makes a force opposite of how the welds are holding the nickel, and over time might cause the strips to loosen or come off. Chose to not use them, for the sake of stronger welds.

 

Looking good mate, running the balance wires in the middle is a good idea. You may find this helpful, but it looks like you have it all sorted anyway.
How I built a 12ah Battery for my BGT

What cells are you using?

 

Also are you cutting those slots in your nickel? Or can you buy it like that?

 

Thanks. Samsung 25Rs, I bought about 500 of them for all the battery projects I have to do.

Great supplier of pure nickel strips:
18650 Cylindrical batteries nickel belt 18650 cell nickel strip lithium battery pure nickel tape Used for 18650 battery holder on Aliexpress.com | Alibaba Group

 

Cheers they look good. Have you checked them to make sure they are pure nickel?

 

Yes, tested in salt water. Perfect.

 

Well, got it done, took for first test drive today. Have to say that overall I'm really pleased with the performance. But the entire process has been extremely time-consuming and difficult. Yes, there was a sense of accomplishment, and I did save some $. But it took better than 2 full days of my time, and to save less than $300, hard to say if that's worth it... plus Evolve has us all by the nuts because you can only use their BMS with the battery pack. Makes it much harder to DIY a pack, which is probably the intention.

Anyway, back to performance. For a little 10S3P pack, not bad at all. In general, I got 11.5 miles on AT tires, a full 1.5 hours of riding, on mixed pavement and hard-packed off road. I was hoping for 10-12 miles, so it's right about there. The one very interesting thing - the discharge curve from the 25Rs is much different than the stock Evolve pack - much more linear. It drops off of 100% sooner than the stock pack, but then goes down steadily and gradually from there. No drop off a cliff around 45% like with the stock pack. I was amazed to get several more miles out of it once I was down to 40% or so - usually at that point with my original pack, it's time to get ready to pack the board up and go home. That's one good characteristic of the 25R cells - their low-voltage performance is excellent. They have very little voltage sag under load, and at the low end of the voltage range.

All in all, I'm glad it's done and working properly. I had planned to build a 2nd, 2nd pack for my CGT - I will keep one pack at home here and one at my 2nd home in Ukraine. But after the ordeal that was building this pack... not sure I'm ready for it just yet. Not to mention, not even sure I could get a BMS for it (or the balance wire harness).

Photo of the new pack being charged by the King of all chargers, the Cycle Satiator. Really cool charger.