Supposedly the Adafruit one is +/- 1%.
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How many thermisters can be read. I would like to do at least one per p-pack
The BMS linked above has two thermistor ports.
I had the pleasure of seeing this in person on that Prototipo I did the rebuild. Pretty cool to see.
Donât threaten me with a good time.
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@Battery_Mooch
Just did a test from a full charge. Here are the results. The first couple of bursts, I was giving it everything it had.
I know itâs not a very long ride, but the temp probe says it got to 28c.
Looks like it was doing a lot better, perhaps 3.65V lowest?
So you can charge fully and go hard or charge to a lower voltage and go easy.
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Yah, it does seem to look better.
Is there any harm riding it hard when the battery is at a lower voltage, as long as the cells donât go below 3v?
Not unless theyâre overheating and/or you are above their continuous rating (which can age them faster).
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And I would even go so far as to say that it would be fine down to ~2.5v/cell under heavy load. Thatâs the datasheet minimum rating anyway.
Obviously the harder you are on it, the faster it will wear, just like any other physical object, but I wouldnât expect it to self-destruct at that level.
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Before I finalise this is there anything Iâve missed?
The P groups have fish paper, the welded ends have kapton and anywhere the positive tab overlaps the negative can has kapton.
Iâm in the process of adding kapton to the edges of the tabs just in case the adjacent ones somehow contact each other. The internal edges where the adjacent groups touch also has kapton, does that work? The balance wires are going on last on a raft of fish paper and not overlapping
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Follow-up: anyone know off hand how much an imbalance can or should be treated by just charging a pack with a BMS? Each cell in each P group was matched to within 0.05v before welding, but the different P groups vary by ~0.2V
1s charge boards. Charge each group to desired voltage. Pay close attention to groups after doing this. If they stay within .05v thereafter, Iâd say youâre good.
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Great thanks, I think I have a few of those from 18650 power banks so they even have micro USB ports wired in already. Should definitely have thought of that myself but ah well
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Whatâs seperating your p-groups in the spaces as below? It looks like youâve used kapton?!
Edit: Re-read your post. Kapton is a good insulator and holds up well to heat but for a spot like that where there will be a lof of friction I would put something more robust. Fish paper on top of the kapton is good. Some people print custom spacers. I fish paper and then secure w some double sided foam tape.
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Ah shite, I just finished soldering them when I saw this. Thanks for the info though, the pack isnât covered in heat shrink or super jammed together so thereâs still quite a lot of flex, Iâll go through and add fish paper now
Progress image in case Iâve missed anything else
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All of those points are at the same voltage potential so a short would do nothing but lower the resistance between the two p-groups, kapton is more than enough in those spaces unless I misunderstood what is at hand here. I would be more worried about a divider in between the two rows of p-groups (dollarama cutting board, fishpaper, abrasion resistant anything) since the nickel has some points that sticks out past the cells.
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You dont need any kind of insulator in those places. As you will notice, those nickel tabs are already going to be shorted together with those large wires soldered on top of them 
Jokes aside, @itsrow is right, those two nickel pieces have the same voltage potential, thereâs no need to insulate between them. You only have to insulate between two spots with a different voltage potential.
@mr.shiteside if youâre ever in doubt, poke a multimeter around and see if you measure a voltage difference between two spots. If you do, then insulate.
This of course assumes that everything in the pack is well secured and wont move around. Anything that can move could potentially bridge two points with different voltage potentials, causing a short.
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Yeah theyâre at almost exactly the same potential, but if thereâs high current flowing and youâre making and breaking a connection (even if thereâs almost no voltage across it) it sparks
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In my experience, two layers of Kapton is totally fine in those spots.
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