what do you mean by both sets of cells are outside their comfort zone? I’ll be running dual 6355 street wheels. id be setting batt amps max to 65. Also trying to figure out if i need to make a bigger pack (12s3p 21700 instead of 12s2p) would rather stick with the original packs listed because of lighter weight and size
hmm, sagging hard does not sound great. you reccommend upgrading to 3p p42a? Im dual 6355, street and really just hoping to get 7 miles per charge without stressing battery too much, but i do like to go fast. only prefer 12s2p bc its a pretty light and small pack
Anybody know of any suitable 26650 li ions for esk8? only ones I could find are too expensive compared to comparable 18650/21700. also i know batteryhookup is a great place for lightly used cells but it seems its mostly lifepo4, anybody know of a site for lightly used li ions?
So there’s a couple of things
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There’s a pretty big difference between setting battery max to 65 and pulling 65 as a sustained load. As I said unless you explicitly state that you are gonna pull heavy currents a lot, it’s very likely you’ll be in the 2000W zone most of the time. Also my comment was given with “if semi-consistently drawing 60-80” which is even higher
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65A from 2P is 35A each, and mooch has tested the P42A saying that above 30 it gets too hot. He elaborates a bit more in the report, and said 30 is his rating, so 32.5 for continuous periods you’re gonna have a bad time.
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You’re a bit safer with P26A in 3P, because the low end of the range I have is 20A per cell. But as I said 80A is above the sustainable continuous rating
Reports here
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gotcha, thats very good to know, thanks for the info. I currently use 65a batt max and almost never go full throttle just 90%ish for big hills, so i think i could pass with either of these small packs and not have to move up to a 21700 12s3p
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Yeah so even at full throttle you’re not usually drawing full power from the battery. It’s only really full throttle at full speed that would draw max power, hopefully the distinction doesn’t sound too nitpicky
Pushing 70A through a motor that’s not rotating is comparitively quite easy. Pushing 70A into it when it’s spinning at 5-10krpm is much harder because the spinning magnets in an electromagnet field create a voltage against the supply, referred to as back EMF. If you want an explanation from the perspective of the ESC check out the thread below
What this translates to is veeery roughly:
- Throttle = motor current. Full throttle, you’re at your motor current max
- Battery current ≈ (current speed as a percentage of max speed) X (motor current)
If you have a logger (metr, robogotchi, ilogger, the VESC app paired to a phone) then you can check how much current you’re actually pulling
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that makes sense, I want to get one of those logging tools at some point. need to research them
Standard li-ion 26650’s are old technology, manufactured only by the smaller China factories now (who don’t need to, and never will, change over to a better performance battery chemistry). Their performance is only suitable for lower power applications…in spite of some rather optimistic ratings.
There are a couple of very high performance LiFePO4 (LFP) cells but their lower voltage and low energy density (low capacity for their size and weight) can make them a tough choice for many PEV’s. Some here use them though, @b264 for example, and could give you more feedback.
The equipment you will need to buy to test each used or salvaged cell, and the time it takes to remove the spot welds, makes buying cells like these much more expensive than it initially seems. And any of those cells could fail at any time since you don’t really know how they were treated.
My recommendation is to stick with new cells, from a known manufacturer, purchased from a known/trusted source. In the long run it will be less expensive and a lot more worry free.
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Mooch is right, as always.
If you’re making a powerwall for a building you might be able to get by with a boatload of used cells. Key word: “might”.
For an esk8 you need to use new cells. And, if used cells is going to be something that will work for you, then you won’t need to ask 
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good to know about those used cells. I actually built a 26650 pack after seeing b264’s posts about it, but the extra weight and size vs li ion is making me want to make a ion pack. asking about 26650 ions because my lifepo4 battery is a nese module. Lifepo4s been good to me but looking forward to lighter weight and longer range. starting to see why lifepo4 is rare in this community
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typically you would pick one, not both
You could get both under the right circumstances (though not too much of either one) but either way you will be also getting reduced lifetime and decreased safety
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well, i meant, li ion is overall lighter and has longer range than similar sized lifepo4
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“Lighter per watt*hour” is not the same as “lighter”
“Range per weight” is not the same as “range”
A 10S67P li-ion is absolutely not lighter than a 12S5P LiFePO4, but if you lock it to about 12Ah then a 10S4P li-ion battery (30Q) would be much lighter than a 12S5P (A123) but it won’t go much further, if any
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Ahh…okay. Yea, that’s an investment that would be nice to keep. Or perhaps sell the 26650 NESE’s and buy the 21700 version? You would lose some money but gain the performance of 21700’s.
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Idk how I’ve gone this long without knowing, but what’s actually modulated in a phase signal? Is it voltage or current or is it frequency? What’s the sine wave actually sine-waving?
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My solution would be to embiggen the bearing pockets enough that you could epoxy in a metal bearing-cup with the actual proper tolerances. Would be pretty easy to do if you have access to a metal lathe, or you know somebody that does.
You could also probably rough up the inside of the bearing seat, apply some mold release to a bearing, coat the bearing and seat with epoxy and install the bearing. Once the epoxy sets, you have a perfect fit, and the bearing can be removed thanks to the release agent.
Metal shim stock could also work. It’s available in a wide range of thicknesses down to less than 0.001", and the thinner stuff can be cut to size with scissors (Don’t use your good ones, it does damage the blades). Be wary though, the edges are RAZOR sharp and will slice the fuck out of you if you aren’t careful.
Or, you know, MBS could get their QC game together. Shouldn’t be hard to have them molded slightly undersize and then cut to fit, rather than relying on molded-in tolerances.
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Some bearings are slightly rounded on the lips and that would cause it to be stuck if that’s the case
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Just for a point of reference, I have a shortboard 6354 100mm thane 12s3p p42a. I get about 15-17 miles riding at good speed (sustained 20-35mph) and can eek out 20-23mi cruising at lighter speeds.
I think you’d get your 8mi range on a 12s2p p42a as long as its thane.
I’d keep it at 20-25a bat each side though, and run 60a(ish) motor.
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Maybe use a wider bearing of the same od to a avoid the lip problem
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