Hi everyone! I was wondering what would be a good way to test a cell for experimenting with cell level fusing. Just looking for a way to pull a constant 20A or so to see how hot the fuse bit gets under load.
i needed this…thx
The balance wire doesn’t deliver the charging current, that goes through the main leads and the entire pack.
The balance wire only sees around 100mA, wich is typical balancing current. That’s why you can use small gauge wires for balance connections.
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Ah that makes sense. Just drains off the top when necessary.
Check all balance lead voltages again? Could have lost continuity on one or more when tightening the enclosure?
Overall, you can set up the BMS to be “always on” or the unity to be “always on”. Then use the other component to do the on-off. If you lock bms on, you get the unity’s push-to-start. But then you have more things that are “on” when the board is off.
If you can get your hands on a lab psu that can output 20a, that’s the ticket. Set the voltage low for safety, like 2v should be okay. Voltage does not affect heat and fusing. Set current limit close to zero, short across the strip, slowly turn up the current until you see what you want. Most reasonably priced lab PSUs stop at 10a. You might be able use half thickness fuse to test. Not sure if things are linear enough with heat affecting things.
There’s also Ruideng DPS-5020 which might be cheaper and more compact if you can feed it enough power.
Alternatively you can also try one of these
There are many variants with different prices. The limit for the linked one is 150w or 20a whichever is reached first. If you set voltage under 7.5v you can pull 20a. Might need to watch the cooling.
IIRC the one I linked (purple fan with pretty displa) is analog controls. The display shows what’s happening, and you twiddle the knobs to change parameters. No digital control.
The one below has an ugly display and is only 10A, but has digital control (you set the parameters you want numerically, then hit the “on” button).
Maybe 2 of those in parallel to get 20a of load…
All that said, I think you should skip the cell level fusing.
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Replaced BMS, everything works well now.
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@tyesk8 There are different ways to fix your pack/cells.
I used silicon other use velcro tape.
Pack number 1 starts where the main negative wire is connected, the last pack is where the main position wire is connected.
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Out of curiousity what BMS did you end up using? I see that you were initially using the HCX D223v1 (I’m using those in my builds). Assuming the D140 based on your charge only statement?
Rock on, thanks.
I’m assuming that count is then linear starting from main negative terminal on the pack. I have a 13 wire BMS for my 12s pack I would then do the following based on my diagram moving from left bottom to top left:
B- on BMS would go to main negative
1 would go to positive side on P group 1
2 would go to positive side on P group 2
…
6 would go to positive side on P group 6
7 would then continue top right working my way down each positive until I reach 12 on main positive.
You should get a wiring diagram with your bms. There are different kinds. It can be that B- is shared with b- or b0 (different Label but First Balance wire) so you need only the main B- and the first balance wire goes to first pack plus. There other bms where you need the first balance wire to connect to the first pack minus and than go on with first pack positive, second pack positive and so on
Dont overthink and just use regular glue, if you dont go cheap on it and put a reasonable amount it will be stronger than the heatshrink, and if you try to remove it it will break the heatshrink, especially if its really hot when you apply it
Any brand name hot glue will do it, but dont go with the cheap sticks from ebay
No need for this
I would personally use 10awg because its much easier to solder
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who can design a pcb!? so frustrated trying to get someone to put my hand drawing into a gerber file. help me do it and i’ll put the pcbs up for sale at cost.
similar to this but 48 cells instead of the 24.
dm if you can help.
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What are you using to make your diagrams? Visio? I’m using Google sheets and I hate it.
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Thanks!
The very first balance wire is marked as an uppercase B-.
It’s pretty straight forward, but only the order in which the P groups were numbered is what confused me based on other wiring diagrams I had seen.
Thanks again for the help.
PowerPoint 
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When I’m building my battery pack do I connect the power cable between the p packs first or do I connect the balance cables from each pack first? Note, I’m not connecting a BMS.
Doesn’t matter as the balance wires are not plugged in the bms (you said you don’t connect the bms 
)