Rushed through my physics homework and got a little bit started 
typical domino pattern.
Iâm a bit stumped by this problem, the bms isnât getting accurate reads on the first two cells but I checked the bms leads harness with a multimeter - Iâm getting the correct voltages there, low resistance, everything âlooks correctâ. I tried plugging in a different smart bms, same problem not reading first two p-groups
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Very high possibility one or both of those two wires is not getting connection properly.
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I thought so too so I checked the resistance on all of the leads and they looked pretty similar. Not satisfied with that I actually re-crimped and replaced the lead going into group 2, still same problem.
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yello dont worry its just the main battery - isnât connected. like the one on the side of the bms. atleast it was for me 
Oh shit I havenât wired the charge leads yet just the balance then checked the app, let me try that.
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i did the same thing. maybe just grab a wire and âtouchâ the two ends to check if that fixes it
That was right on, crisis averted!
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Well bulk battery sorted me out! Free delivery took 2 days to get to Uk only ordered on Wednesday night!
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Dang! How much was shipping, may I ask?
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Free and so far I dodged import duties so I got 100 cells for ÂŁ365
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So if someone, has an old pack with a bad pgroup. ( charges up faster and drains faster than the rest. )
Is it a bad idea to try to replace the pgroup with new cellsâŚ
I told them the usual you sholuld probably get a new pack. ( 12s12p ). but having bought the board used they give me the âholy shit thatâs gonna be expensiveâ style response.
I feel like the zeitgiest in this group has been never put new cells in and old pack, and if you have to do it to all pgroups evenly. or tear apart the whole pack and rebuild it evenly, at which poiknt the labor suggest going ahead and doing new cells anyhow.
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Yep this is pretty much my opinion on it as well. However there is a 3rd option that I think doesnât get much credit:
Just remove the bad p-group and have an 11s battery. Your top speed will be a tad lower, and you will need a new BMS, but itâs way cheaper and easier than rebuilding the whole pack.
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the 11s idea is pretty interesting.
so why is it bad to replace pgroup with new cells? seems like it canât be worse than having run with a bad pgroup for a while before noticing?
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It is bad in a very similar way to that. Basically you are putting all that time and effort in fixing a pack with one p-group way out of wack with the rest, only to end up with one p-group still way out of wack with the rest.
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Yep, I made all the steel damascus for Jeff. Not the ti or mokume though, unfortunately one of my great danes got cancer and it derailed me from any large orders for a while. I actually sent him some experimental patterns a while back, to make us a couple of lights and see how it looks, but, theyâve been busy, as I have.
That light in the photo was supposed to be mine, but apparently a couple of rabid customers begged for the two he made from that particular pattern, and we ended up SOL. 
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Yes, it is bad to do that.
The reason why is that the new cells probably have different characteristics to the old ones - The manufacturers are always slightly tweaking the recipe, and also they are brand new, so no wear!
The old cells have wear, so their internal resistance and capacity wonât match.
That means your new â4ahâ cells may be 4.05Ah, and your old â4ahâ cells might be 3.95Ah, so youâll end up with one p-group that charges and discharges more slowly than all the rest, exactly the opposite of the problem you were trying to fix.
To fix this, the recommended solution is to replace a number of cells that is evenly divisible by your S-count (for a 12s battery that would be multiples of 12, for a 10s multiples of 10, etc), and rearrange the cells so each p-group has the same number of new cells. That way no one p-group will have more or less capacity than any other due to the new cells.
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If I want to use onsra dd kit https://onsra.eu/collections/all-electric-skateboards-and-longboards/products/direct-drive-motor-electric-skateboard-12s-kit?variant=32283554709553 with 12s3p Molicel P42A and BMS only for charging, what fuse should i use to not blow it randomly when riding for example up hill full throtle? On Onsra website there is hardly any information about ESC and motors.
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