Soon attempting to make a 9s5p by salvaging a Psychotiller 10s5p with a broken p group
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To be determined soon, still need to buy a bms and charger.
37.8v charger and 9s bms? 
Good luck with the searchš
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@Flasher, BMSās and chargers are available in almost any flavor.
https://litechpower.com/product-detail/HCX-D140LI09S15A.html
Mainly an experiment to see if I can save the pack and still push a skate around. Conceptually easy, but weāll see
I know the bms is available. And if it werenāt itās just a matter of removing a few components to make it a 9s. But Iāve never seen a liion 37.8v charger
Lol ya I tried looking for 9s BMS and chargers before and couldnāt find a good one so I just went with 8s and added another p group due to the number of cells I had
Guess I missed this site but ya I couldnāt find a charger either
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Hm maybe I never searched by the voltage, and instead only did 9s - who knows.
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Weirdā¦ guess I have to change my search methodsā¦ @Dareno i need to learn internet again. Care to join?
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Hi guys, reading and learning, learning and reading.
I bought a couple of pre-made 10s packs when I built my first ESK8, now seeing how itās really done I have questions about my packs.
Doing a bit of google-foo I believe my packs were built with this BMS
Chinese BMS
The specs are:
Input voltage DC42-45V
Charging current max.10A
Output current up to 30A
Over charge voltage test: VCU 4.25V Ā±0.05V (4.20-4.35V // each 0.05V per step)
Over charge voltage resume: VCD 4.10-4.00V
Over discharge voltage test: VDD2.50V Ā±0.1V (2.5-3.0V // each 0.05V per step)
Over discharge voltage resume: VDU 2.80V Ā±0.V1
Operating current: ā¤300UA
Short circuit protection: 40AĀ±3A
Short circuit protection duration: 500MS
Temperature protection: 55 / 65 / 75 degree
Typical output current: 30A
Max. output current: 45A
Balance voltage for single cell:4.19V Ā±0.02V
Balance current for single cellļ¼ā¤ 55MA
Charging currentļ¼ā¤10A
I realize there are better BMS available, and Iām researching and Iām planning to replace, but my question, anyone have any experience with these? Anything I should be made aware of?
Iām cool with the 30A max discharge, but the ā¤ 55MA seems a bit low.
30a discharge is low for most skates built around here, typically people bypass the BMS for discharge to remove this limitation.
The balance current it typically very small since this is only the amount that is bled off a cell that is on the high side compared to the other cells in the group. But Iām not sure how this BMS compares with others on the market regarding balance current spec.
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Yeah, I know 30A is low, but right now Iām limited to 30A by the cheesy ESC that I bought at the time. I really didnāt know at the time what I didnāt know and just bought cheap to see if I even wanted to pursue ESK8.
From what Iāve read 100mA is more typical 55mA is basically half 
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Building and building. Easily more. Work here than the rest of the build.
Not a fan of the folded tabs. Cosmetically they bother me. However I thing they do keep sharp edges of the tabs away from the batteries. If I could start over I would use a single tab per battery/cell folded over the holders and then solder the wire before putting in the cells. But solder the wire such that it sits exactly on the edge of the holder and there are no extra lengths
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those 18650 sleds are nice, but the metal tabs will blow at like 6A. so for your 4p groups, i wouldnāt set it any higher than 25A batt max.
Each cell gets a tab to the 12 awg wire. Iāve run 10A through my strips continuously (15 min through 6") and they get slightly warm.
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If I were to have nickel coming up to a buss bar or wire, Iād double it up for each cell at least. Iām sure you will be fine with one strip per cell though, but itās a peace of mind thing for me, and 2 reduce resistance and voltage sag caused by resistance.
The main thing I see that scares me is the nickel folds hanging out over the plastic, over the cells. Once this pack gets shrink wrap and road abuse, I see those wearing down on the thin cell wraps and shorting. Strips of fish paper underneath those folds (between the cells and wire) may just prevent a fire in the long run.
if thatĀ“s a 8 or 10mm .15 nickel it should be more than enough.
you donĀ“t want to draw more than 20A per stripe because of the 30q and you will not do that for a real āconstantā time anyway as we skate, so the load change.
Thatās not what voltage sag is
Thatās been addressed as per above.
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I am aware this is not what voltage sag is primarily, but any additional resistance in the battery itself will further contribute to the cells voltage sag.