So I’m traveling at 35 KM an hour and my deck does the dreaded power jolt / cut out. I keep riding for a few more KM and it cuts out altogether
So I get home, change my underpants pants and decide to revisit the first battery pack I’ve ever built and I cant believe it didn’t catch fire! BMS leads were crossed over (One of the leads was disconnected) and P group connections being severed and hanging on by a thread were a couple of the issues.
Now that I have a half decent setup going I’m looking to lift my game. I was using Chinese tips on my welder although upgrading to the KWELD tips made a world of difference. I put together a 12S3P pack without burning my fingers.
The hardest part was trying to get the P group wire soldered on as a smooth blob. I still have some work to do although I’m happy with the results so far.
I place my balance leads on the opposite side of the pack than my series connections. Sits mutch better and avoids most pinch points.
I would also avoid any Kevlar tape touching any of the nickel or any thing that conducts. The adhesive on fish paper and keption tape is a insulator (why it doesn’t stick as well) Kevlar adisive sticks better but could carry some micro current
Place some keption tape under any nickle you soldering I fined it helps protect the fish paper from starting to brake down from the heat when soldering.
Not sure where to ask this question and I understand if an admin needs to move this post. Regardless, thanks for the help.
How reliable are 5.5 x 2.1 mm DC power jacks? I went for a ride this morning on my DIY that has over 1k miles on it. When I got done I went to plug it in and I got a big arc from the power port. I open up the board and nothing seems wrong minus the power port looking like it arced. The charger was not on when I plugged it into the port.
The BMS is a smart BMS LLT. Should investigate the BMS. Everything looks fine inside of the app.
It’s not wet outside but maybe moisture got into the port…?
The charger not beeing turned on was your problem. The charger has big capacitors on the output side which will be charged instantaneously when you connect it to the battery. Therefore always turn on the charger first before plugging it into your board.
Hmm, I just got a new charger about a week ago that is a lot larger. That has actual on/off switches. I’m guessing this is how I’ve never come across this issue.
haha don’t be too hard on yourself, I still have a build using a barrel due to space constraints. They just don’t survive many arcs compared to something like a GX or LP connector
@Darkie02@SmokeNEsk8
The best way to prevent this is to put a diode in series with the charge port, to prevent any current from flowing in reverse.
This also safeguards against sticking something conductive in the port and shorting it out.
Only drawbacks are that you can’t check the battery voltage by poking the charge port with a meter (which you shouldn’t do anyway), and the voltage the battery sees/gets charged to is reduced by an amount equal to the forward drop of the diode (0.3 to 0.7 volts). Of course, that can be remedied by adjusting your charger’s voltage up an equal amount, or just left as-is with the understanding that you will lose a couple % of maximum capacity/range, and extend the lifespan of your pack by not charging to 100%.
Some “smart” chargers don’t like it though, since they can’t sense the battery voltage through the diode prior to beginning the charge.
Can I get some advice on my welds? I did on empty cells to get some practice before doing it live but still not entirely sure what I should be looking for to see if these are good or not.
Good, potentially ever so slightly hot, and be careful with how close you get to the edges of the electrode, like the lower welds of the right-most cell.
at what joules/ ms are you ? the one at the middle left side seems a bit burned and like @marketthrowaway said make sure to not spot weld on the edges and don’t forget to put the + terminal rings if you have 'hem. to be sure you spot weld at the right place you could make like a stencil out of fish paper so you know where to weld
