Smart BMS will be able to fit on top of the pack as I’m using a 1/4 inch rubber gasket. Which helps a bit.
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No.
fuses are voltage-agnostic in normal operation. The voltage rating is only there for when the fuse has to actually do its job and interrupt an overcurrent event. If the voltage rating is too low, the fuse may fail to extinguish the arc created by breaking the circuit in a reasonable time.
This is also why a lot of fuses (and circuit breakers) have different AC and DC voltage ratings even if the current is the same: an AC arc is easier to extinguish than a DC one of the same voltage.
With all that said though, a fuse with an insufficient voltage rating is still far preferable to no fuse at all, and will probably be just fine. It’s edge case shit where that rating really matters.
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Capacity (and thus state of charge) is not linear across the voltage range of the cell. If you want to actually nail those numbers, you’re going to need to dig into the discharge curve of the exact cells you’re using at the average current you’re going to be using them at, or use a coulomb counter.
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I’m going to be using the model 3 cells in a 16s12p. I don’t really know what current I will draw with bn gear drive 5.2:1 with 225mm wheels and spintend esc and I’ll be going steady at an average of 25km/hr over hilly neighborhoods but it seems like most people average 40-60amps? The only curves I know of for these are from moochs test?
Battery test-review 18650 comparator also does discharge tests.
Dunno if either they or Mooch have done model 3 cells, but you could get close by matching the cell size and capacity to a different cell that they did test.
I’m not an expert at battery discharging by any means - I can’t tell you the exact best way to go baout it. I just know enough to know that a straight linear volts = SOC approach will put you wayyyy off the mark.
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Excellent information, thanks Ryan.
throws mini blade fuses and holders in the bin.
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The 12v mini blade fuses would probably be fine. Just don’t overspec the current thinking that will somehow compensate for the lower voltage rating.
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Got a 12s llt bms new in package
(Can’t be bothered making a sale thread)
Pm if interested and I will send pics
Cheers
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Guys I need your help.
I have a power bank to make for my mom was supposed to be for her birthday (it already passed) but now I want to at least give it to her for summer, got pretty much all the essential 60 of Those1s2p batteries to make a 3s20p(if I can) I’ll have to test them all to make sure they work good.
They pretty much all have connectors with them (even tho I bought the w/o wires. So I was thinking about making a pcb so it could also be modular and some 3D printed holders, but I might scratch that as it would be in a car, wouldn’t want it to wear out.
It’s gonna be enclosed in an Ammo box, I’ll repaint it and remove the rust that started to eat the metal.
I’m pretty sure I could fit 80 or even 100 of those batteries inside.
I had a 3S BMS but I can’t find it in my mess of a room( is there smart 3s bms? )
And I also got a small 150W inverter from 12V to 110V and 2 USB ports, Cheap made in china
I think I’ll have to upgrade for sure, will gladly take any recommentations.
I forgot to tell you, it would be used as a camera battery, laptop and Phones charge station and ofc in case of emergencies when at home. She loves her wireless charging So I’ll also include that and probably an ambiance light (idk about this one honestly)
There’s more than enough space in the box so yeah. I know I’ll need help for this, I never really tried doing my own 3D designs and absolutely clueless of how to make a PCB / circuit design, This could work too
Thanks for reading through 
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Even with the increased size you can still fit a fairly big 18s pack in something like DS evo enclosure and a stormcore
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Hey everyone, I’m planning my 12s2p build, and I’m considering attempting to add cell level fusing.
Here’s an image example of what my pack will be like. This example is a 10s2p pack, split into two 5s2p halves, however mine will be two 6s2p halves. (stolen from ebikeschool - intended for a vruzend kit, but principles are the same for welding)
What I’m wondering is how to actually add the cell level fuses. A common approach I’ve seen is to run a bus bar across the parallel group, then solder thin wires from the positive terminals to the bus bar (in this case soldered to the cell, but I would be soldering to a nickel tab on top). This example is a 14p group.
How exactly can I incorporate a bus bar like this into a flat-packed battery? I’d rather not create 12 small bus bars - could I have two bus bars running down the whole length of each 6s2p pack, then connect the positives of each side to their respective bus bar?
Here’s a quality GIMP mockup of what I mean. I’m new to pack design, so please don’t snipe me if this is completely incorrect
Whoops, forgot to say: in the bottom image, red = bus bar, green = nickel strip, blue = thin wire.
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Cell level fusing isn’t a great idea for an esk8, because of the resistance of the small wires you’ll get a bigger voltage drop. Cell level fusing is common in diy powerwalls which use way lower currents then we do, so it doesn’t really make sense for us to use it.
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Interesting, I was linked to this page https://electric-skateboard.builders/t/fishpaper-and-cell-level-fusing-use-it/35026 and assumed it was a pretty common safety measure.
That would create a dead short.
The buzbar used for eatch p group. Your said you wanted to use 2p so you want to link 2 cells with a buzbar witch is not really adding any thing.
Cell level fusing works far a couple of amps you want to use a 80 amp motor?
Why are you so determined to use 2p li-ion. Is it cost? If so we been down this road befor and most people end up spending more than a pre built.
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Would a 12s3p pack with 40t’s be ok? I know 3p isn’t the greatest, but with the added capacity and discharge of the 40t over the 30q cells, would it be fine? I used to have a 12s5p, but i want to lower weight and size.
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Where can I find large clear heatshrink to cover my pack?
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