How I built a 12ah Battery for my BGT

First of all I want to make it clear that this is the first battery I have built, so take everything I say with a grain of salt.

After around 150 cycles the stock battery in my BGT was pretty much flogged, so I thought I would build a much larger replacement with higher quality cells. This is how I went about it.

What I built
I made a 12ah battery which is almost twice the capacity of the stock battery, it is comprised of 40 x LG HG2 18650 cells setup in a 4p10s configuration. This new pack experiences very little voltage lag and does not seem to overheat causing cut offs like the stock pack (this happens when you are pushing hard in long grass for an extended period of time). This new pack is longer and thicker than the stock pack so significant modifications to the plastic battery case was required. It also reuses the stock BMS and uses the stock charger.

Finished project (well mostly finished)


The idea:
this should give you a conceptual idea of how the battery works. Note the order of the balance wires in this diagram are not how they appear in reality.


Checking the cells:
I started by individually testing and charging each cell to make sure they were all genuine and at the same voltage. to do this I used a "AccuPower IQ338 Battery Charger Analyzer Tester".


Making groups:
Once I was happy my cells were all good I selected 20 of them and added an extra layer of heat shrink to them, these 20 cells would be on the outside of each parallel pack so I wanted them to have an extra layer of protection. I then grouped all the cells in groups of 4. Then the cells were glued together with hot glue then reinforced with fibreglass tape.


The next step was to add insulator rings to the positive ends of the cells for yet another layer of protection.


Welding:
In preparation I had designed and printed a couple little tools for holding two groups of cells together, these are shown below. These allow you to perfectly lineup the groups for welding.


I used 10mm x 0.15mm nickel as it was the thickest I could weld and the widest I could find. For the series connections I doubled up layering the nickel 2x thick to allow loads of current through. Then I added one long parallel strip to stabilise and current share the pack (I had already soldered on a balance wire to each of these long strips, its best to do this before you weld the strip on because batteries don't like heat). I was welding on pretty much max settings on my welder doing 4 welds (8 spots) for each connection. I also cut the corners of the strips on the positive end to reduce the chance that it would cut its way through the insolation.

After welding I ended up with this.


I then "butterfled" each double group like this.


Then I added more tape parallel to the cells to make sure the nickel did not feel any stress, also I covered up the nickel with tape.


After doing this 5 more times I had these.


Now each of these double groups was effectively a rigid block and I needed to allow them to flex on each other as the deck flexed, so I designed and printed these little spaces. These spaces were covered in tape then taped between each double group.


This allowed the battery to flex a lot.


Now I needed to make the rest of the connections on the outside of the battery. These ones were a little more tricky as they needed to allow for some flex. So I soldered (using a 80W iron) some 10AWG high strand (flexible) silicone coated wire to long strips of nickel like shown below. The small gaps between the nickel is very flexible. I made 4 of these and welded them on. Then I soldered some long runs of wire to more nickel which was welded to the ends of the battery.


More tape, so much damn tape


Wiring:
Then it was just a matter of wiring up the stock BMS to the new battery which was pretty straight forward. Just make sure to label everything as you are going along.


Required background reading (seriously if you are going to do this read all of this stuff and understand it, also watch all the videos.)
Endless-sphere.com • View topic - Evolve Carbon AT with 50km+ range
Endless-sphere.com • View topic - Landyachtz TopSpeed 90mm 10S4P DualRearDrive
Endless-sphere.com • View topic - 18650 spot welding -how to- ULTIMATE REPOSITORY







Materials
40x LG HG2 18650 cells ($400)
Nickel strip 10mm x 0.15mm ($30)
Fiberglass tape 20mm wide ($20)
10AWG high strand flexy silicone wire 3m ($20)
Good quality solder
18650 insulator rings
Heat shrink

Tools
Spot welder
Soldering iron 80W
Soldering iron adjustable low wattage
Heat gun
AccuPower IQ338 Battery Charger Analyzer Tester

Battery case:
The other part of this project was the battery case extension, I figure people will do this in there own way, but all I did was purchase a Bamboo Gen 2 battery case from Evolve and used parts of it to extend the stock case. I did this about in inch in the front and an inch at the back of the battery.


To accomodate for the extra thickness I added some printed spaces, shown sitting on the deck.


Thats about everything I can think of right now, if you have any questions let me know. I will upload the 3D files in the next couple of days.

Big thanks to Spartan117 and paulfulwood for inspiration and help in the design process, plus all the Guys that helped out on this thread Custom battery for Evolve Bamboo GT

 

Dude, this rocks. there is great potential in this, it is exactly what we need as a plug and play after our cells are spent.
why Evolve has not used 18650's in there battery i will never know

 

They use unbranded rectangular cells because they are cheap and compact, one of my cells was way worse than the rest and pulling the entire pack down with it.

 

Wow Nick bravo.. this is really well done Not sure if evolve anticipated so many people either using the bigger abec wheels or AT wheels more, so the battery thickness/clearance to ground doesn't need to be as slim as they've made it?

Too much of an ask to include cost of material (+source of batteries) & your time it took?

Although I imagine it'd be much quicker as you've almost made the how-to guide.

 

Thanks Mate, yeah I think they needed to accomodate for the smaller wheels. Speaking of wheels this happened yesterday

 

wow hipster..

was going to ask where you got your front greenies from? (As they didn't look like abecs?).. are these the knock off ones I see on eBay? How do they go?

 

The build time was around 24 hours and total cost of materials was around $500, but I also needed to buy new tool like the welder which set me back and extra $300-$400

 

The off color green wheels are 97mm clones, I run them in the front and save the genuine ones for the rear. The pink ones are genuine 107mm.

 

Wheels : Abec 11 Flywheel 107mm

 

As you bought a welder now are you looking to do more packs for refine technic. That's quite an investment for one battery pack.

What kind of welder did you get? Some kind of spot welder?

 

I'm not keen on the idea of making packs for other people if that is what you are asking, mainly because I don't want the liability and it takes ages to make one so the labor costs would be crazy high.
This is the welder I used, it worked a treat.
Mobile Phone Notebook Battery Microcomputer Pulse Spot Welding Machine MCU Pedal Welder Machine 787A+-in Spot Welders from Home Improvement on Aliexpress.com | Alibaba Group

 

What a great idea and design! The board looks gorgeous, is that a different deck or did you just throw a coat of stain on the original deck?

 

Thanks Mate, it's just a stain, super easy to do.

 

This is phenomenal! probably every BGT owners dream to have your custom battery setup inside their board now. My battery is really showing it's age after only 5 months. I skate every day.

 

I think EVOLVE must be working on this. Allot of there commuter customers are asking for a higher capacity battery. I travel 46km a day back and forth to work and although it gets me there and back after a charge at work, I pretty much baby the battery both ways. If I could run in FAST mode all the way averaging 28 / 30km I would save 30 min on my time. A real game changer and I would'nt be arriving home in the dark.
I think its could be well on the cards that they might make available a higher capacity battery in the next 6 mths. It would be a very smart business move and they could market their boards as a world leading commuting alternative. Ow and make it water proof of course :}

 

Did you have to modify the 107mm wheels to fit?

 

Yeah you need to shave around 10mm off them

 

Slight update, I have routed out some of the deck to allow the battery pack to sit flat with the deck and not need the 3D printed spacer.

 

Just a little extra info on how the balance wires are put together

 

I want to do this so bad. When my battery tanks I'll definitely be giving it a try, if I can't find a premade battery somewhere (I am completely new to all of that stuff. Lol). Currently I cart my fast charger around, and it's ok... But it would be amazing to just not care.