Hey guys I’ve been lurking on this sub for a while, and finally got the Boss Level Spot welder to spot weld the batteries together. Could you guys check if this seems like a safe battery? I only hot-glued the 3 batteries together, and left each parallel group to get some flex. I used separate nickel strips for the balance wire for the BMS besides the last one B10 (36V). Did not realize the amount of time and care it takes to build these things before I started lol All I need to do is connect the positive and negative to the batteries and connect the charge port. I’m thinking of adding some neoprene foam and fish paper before I wrap this in heat shrink. Does this look good?
I’ll be building a very similar battery, using the same cells when I get to building my electric longboard. Good luck and be careful!
Yeah I almost burnt my cells when I was careless cutting the nickel strips near the cells hahaha thank god I only got away with a burn.
I would certainly recommend adding another layer of fish paper where your batteries touch in the middle just to be safe. That is an easy place a short could occur. You can never go wrong by always wrapping all battery terminals in fish paper and using heat shrink tube to keep everything tight.
I know fish paper is available on Amazon but I don’t think they have any with adhesive backing so you have to tape it around each row of cells. I bought my adhesive backed fish paper in a in a 5’ roll.
I would ship you some for the cost of shipping but I just ran out.
Looks good to me! Only thing I would change was to put fish paper under all the balance wires. And that last balance wire on the other site would I cut a bit shorter.
Why didn’t you put the balance wires on the side with the series wiring? Now you have two sides with protrusions instead of only one and a flat side.
Yeah I was actually worried about that I think that’s actually a great idea. I already put fish paper, but I think I’ll untape and add another layer just like you said. There’s so many cases of DIY batteries going bad and catching fire. @legend27 I didn’t even think to cut the balance wires instead of bending them great idea! Thanks @Maxid I heard that separating the balance wires from the series connections were vital because it heats up and could cause shorts in the circuit. at least that’s what @Eboosted said
Looks reat but you need to use additiona fish paper here:
These two strips are too close together, if there’s a crash or some accident they could touh each other and start a fire.
Also use fish paper between cells and balance wires.
You also must use fish paper between each P-Group, remember this is the main cause of fire.
Thanks for your input @Eboosted I did what you said and put some extra fish paper in between the parallel groups so there would be no shorts. But I’m having some problem trying to power the VESC using the BMS P- and positive lead straight from the battery. I shorted the eswitch and plugged it into my VESC to check if it works, but I don’t get any lights. I tried to see if there was a problem with the wires so I shorted the pins from the back of the BMS like this, which didn’t help the problem. ’ I also checked the voltage for each cell from the balance wires to see if there were any shorts, but there were no irregularities from cell to cell. I’m charging the pack right now to see if a fully charged pack would resolve the issue (it might be triggering nominal voltage, but I doubt that’s the case because the voltage of the pack is 37V right now.) , but one thing I notice is the heatsink gets extremely hot when I’m charging it. I can’t even touch it for more than a second without pain. Is this normal? The only way to get the pack to power the VESC is when it is only charged and as soon as I unplug it it doesn’t work. I wired everything correctly, but I can’t seem to find a solution. @kuphjr @legend27 @Maxid @Namasaki I could really use your help. or anyone else.
Okay new update. The charging stopped working for some reason. I have no clue what is going on with this.
I’m really out of my depth since I have never used this specific and BMS before, but are you sure the switch is supposed to be shorted? Most buttons I have used for anti spark switches are momentary buttons and do not act like a switch.
Honestly, completely disconnect your BMS. You might need a new one.
I highly recommend the discharge only BMS. Cheap, small & easy. If you did indeed break this BMS or if you recieved it damaged, you can get one with super fast US shipping from BuildKitBoards.com @JLabs.
Since the VESC is really reliable about cutting off before the battery is over discharged, there isn’t much benefit to a discharge BMS. Just get a $2 50-60A auto fuse to protect your battery in case too much current is drawn for some reason.
I’ve read a couple of posts saying shorting the E switch would solve their problems of their battery not turning on. Yeah I think so too it’s so annoying to find out I gotta redo everything and it wasn’t even my fault. If ai buy a new one I gotta open the pack up and redo all the balance wires so I might just end up getting the same on I bought I hope I can get some compensation
Think you wired the bms wrong.
This would have been a great post to put in this thread, I created it to try and get all the battery build info in one area so it could be a more convenient resource for all.
I think you did pretty good on your first pack and most of all the extra tips you needed have already been said above. I would just add that the silicone wires you used to connect the p-groups, I would use a two thinner gauge instead of one thick one. As it’s easier to solder, more flexible and less thickness. Or braided strap.
Although already said, insulate between each p-group. If the cell shrink is compromised between two p-groups it can short. It is not really obvious at first.
Here’s how I wired the BMS
- BMS P- to VESC Out -
- Battery + to VESC Out +
- Battery - to BMS B-
- Battery + to Charger +
- Charger - to BMS C- Isn’t this correct?
@Irdesigns Maybe I can post a post on this thread on that thread to find a solution. I mean I already put some fish paper between the p groups and if there was a short, there should be some discrepancy when I measured the voltage of each cell through the balance wire right? it just doesn’t add up. All I can say is that it just might be a faulty BMS, but that doesn’t seem likely either.
There should be no shorts in the battery at this stage. Pack looks fine. All the extra precaution / insulation is mostly vibration / crash proofing, an esk8 is a harsh environment for a battery.
You probably have some BMS issue. Tricky to solve over forum. Usually need to see the manufactures diagram and really clear photos of where all the balance leads /power wires go. And maybe even hand drawn diagram of how you think you wired it.
You may have killed it also . Many people have on their first go don’t feel bad. Could have been dead on arrival.
Im not BMS expert, but if you have the manufacturer diagram and really clear photo of all the wires leading to the BMS maybe someone here can figure it out.
who makes the BMS, model number?