Hey guys, I built a board 3 years ago but after wiping out back in 2021 I didn’t touch the board till this spring. When I did I realized even though I took the loop key out of the board the BMS must have had some sort of power draw because my 10S3P Samsung30Q battery was at 0 volts… I did some research and it looked like everyone was building with 21700’s now so I bought some cells and am working on rebuilding the battery taking heavy inspiration from the build thread. The lingering question that I just can’t seem to find a clear answer to or even examples of is how does everyone mount the battery to their boards? Most of the pictures I found had the battery in a box on the top of the board but I’ve got an enclosure running the length of the bottom of my board. Previously I had two Velcro straps that held the battery to the bottom of the board but I can see after just a year of riding that battery there were lots of spots where the plastic has worn down off of the 18650’s. This time around I’ve wrapped each ‘P’ group in fish paper, and I’m thinking I’ll put some foam padding between the board and the battery but I’m still worried that the vibrations will wreak havoc on the welds. I’m thinking of trying to come up with some sort of ridged ‘clamp’ that will run the length of the battery and hopefully apply even pressure to hold it in place but I still worry about vibrations wearing down something somewhere causing an issue. I’d love to hear how others have mounted their batteries to their boards.
There are quite a few methods that have been used.
One is to just rely on the enclosure to support the battery. The downside is that if the enclosure isn’t strong enough, it can develop cracks from the added stress of supporting both its own weight, and the weight of the battery. I’ve used this method with a homemade thermoformed Kydex enclosure held on with M4 screws and washers, and it worked okay.
Another method is to use strips of industrial velcro between the battery and the deck.
Your method of straps is pretty good too, but I would recommend using more than two, probably three or four to support the battery more evenly.
You should definitely make allowances for the pack to flex slightly, by using flexible silicone wires or flat copper braid to connect the individual P-groups together so that there’s minimal stress put on the nickel and spot welds.
Yeah, my new pack is a much different design. I’ve got large tabs I will solder some heavy gauge wire to for connecting the groups. It should allow for more flexibility.
The enclosure I have has 22 screws going into wood inserts but I still worry about it failing and everything falling out lol I appreciate the insight though I’ll consider it as I ponder my final solution.
This, imo is the most important technique you should be looking at and I see that you’ve taken some key points of order from the battery builders thread (e.g. wrapping groups w fish, wide nickel strips and silicone wire series connections). Just be aware of the conductor current ratings when choosing your wires so u don’t add unnecessary bulk to your pack.
I’ll keep that in mind, I reference that list frequently to double/triple check I’m using the right stuff lol. Currently my board has a single motor but I’ve often thought about adding a second. I assume that would increase the current draw on the battery so I have been very briefly considering making the pack capable of a slightly higher discharge rate as I believe the P42A cells are rated for something like 45A. I had thought of making the pack capable of 100A or 120A but nothing has been committed to yet. I’m still caught up on how I want to mount the new battery to the board. I’m leaning towards a combination of more straps and the foam padding between the board and battery. Still hoping to see how others have their batteries mounted.
The inserts I have are long enough that I won’t be able to drill holes without going through anyway so I installed the inserts from the top so that the flange also serves as a stop. Then cover it up with epoxy; of course dabbing some epoxy as well on the sides of the inserts before installing them.
I just installed these yesterday, by the way, so it’s still curing.
If the enclosure is made from ABS this is more likely to happen. The best method to avoid any cracking from causing an issue mid ride is just to use more bolts that way if it cracks at one point the enclosure is still supported by all the other bolts. That way you can still make it home and can even putt of fixing the cracks for a bit after the initial cracks formed.
Just make sure to not use the easy and quick way to repair it with epoxy and fiberglass and you shouldn’t have any issues after the initial crack. If you go the easier way then the abs will just find another point to crack at. The easy way being to use fiberglass tape or just one layer of fiberglass within the epoxy to fix the crack.
Fiberglass work is a pain in the ass if the epoxy you use is thicker/more viscous but if you use an epoxy that flows more than it is easy to repair the crack with several layers of woven fiberglass material that is saturated with epoxy.
With thicker epoxy, if you soak the epoxy in epoxy it will want to stick to your hands/gloves and any mixing stick used to apply the epoxy. Making it near impossible to apply several layers of impregnated fiberglass even if the epoxy has a long working time.
I say this because I 100% made easier repairs with epoxy and less fiberglass on my board which did hold up for a while before the abs cracked again. I used a dremel to remove more abs and replaced it with fiberglass and epoxy and haven’t had any cracking issues since then. Also when I had cracking issues from the “easy” repair the fiberglass did keep the material from just cracking and falling off mid ride. The cracked pieces of abs only came off once I was trying to remove them
I want to eventually use my current enclosure as a form to make a new one made only of fiberglass and epoxy but right now I don’t have the space needed to do that. I also want to make a new enclosure so I can properly take advantage of the height of my board so I can fit a larger battery under the board. I use 1" of risers and right now the enclosure is way shorter than my board can fit under it.
Ohh and I prefer using bolts with nuts over threaded inserts when it comes to enclosures. for other parts having a threaded hole and bolt works fine, but I’d prefer not to take that risk when it comes to batteries or speed controllers since they’re very expensive and having what holds them onto the build fail could be a catastrophic failure that destroys the board. (via fire from the battery)
new battery is just about done, just need to add the power leads and shrink warp. I went a little overboard thinking maybe I’d add a second motor eventually but after trying to see where everythign would fit in my enclosure I don’t think I’ll have room for another one lol I’m much happier with this battery but I’m still not sure how I’m going to go about holding it to the bottom of the board. I don’t feel super comfortable letting the enclosure hold it. and I don’t want to subject it to the two straps… I’m thinking of maybe using a piece of 1/4" plywood between the straps and the battery? Not sure yet still brainstorming ideas.
