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Newbie struggling to sort through fake listings versus real listings
(08-08-2019, 10:28 PM)kc8adu Wrote: make it 4s.
gives it a bit more power and wont hurt it a bit.
you would be surprised to see what those motors will tolerate.

Thanks, I'll keep that in mind here. I found a person giving away a broken ATV that was identical to his so I picked it up so I have one I can tinker with without risking destroying his.

I haven't finished taking it apart, but I was able to crack open the motor housing just enough to peek in there and it looks basically like it has the equivalent of two cordless drill motors; one on each wheel. I had expected one larger motor and some sort of differential, but I was wrong. The interesting thing is that fitting a much bigger motor in there would actually not be that hard since it appears to have quite a bit of unused space.

(08-09-2019, 12:56 AM)ajw22 Wrote: I've never played with electric ATVs, but here are some thoughts.

You'll definitely want to add a BMS to protect the lithium cells from various conditions that could lead it to catch fire.  I've not used this particular one, but the 45A version seems like a reasonable choice.  Lacks over-temperature protection tough.

Probably a good idea to add a fuse in there.  A BMS can fail, too.

You might want to add ceramic capacitors to the motors to reduce voltage spikes that might otherwise kill nearby electric components.  The parts cost virtually nothing.

Some inspiration:

Thanks for the reply. I was considering putting fuse wire to each cell. I have a ton of wire sitting around of various sizes so that shouldn't be hard to accomplish. I certainly have tons of old electronic devices around that I could take capacitors off of. Is there anything wrong with using large caps off a computer power supply? I honestly don't understand capacitor ratings as well as I would like to. I'll try to get myself educated on that as fast as possible. Safety is extremely important on this since my kid will be sitting on top of it. I'll probably fabricate some sort of steel shell to go around it all.
Yes, they don't really degrade, so any old part will do, but it needs to be a "ceramic capacitor". They're typically blue or yellow/brownish in color... google for pics.
Make sure it's not a "tantalum capacitor" - they have a printed "+", dot or similar sign.

It's not an exact science, but 3 capacitors anywhere in the 47nF ~ 2uF range seems to work well. Ie. it should have any of the following numbers printed on them: 473, 683, 104,154,254,224,334,474,684,105,155,205. Probably no harm in mixing, if you can't get 3 of the same type.

Solder might not stick well on the motor case. Try scratching the surface where you want to solder.

Here are some more info:
Amish_Fighter_Pilot likes this post
Modular PowerShelf using 3D printed packs.  50kWh and growing.
Hello again! I've been super busy trying to get our tiny home ready to move, but tonight I took apart the motor housing on the junk ATV that is just like his. I took out the two motors and their gear boxes. I'm still trying to find data on these motors but they're clearly some sort of permanent magnet DC motor. They remind me a lot of the motors used on car windows actually.

Anyway here are the pictures of them:

I was fairly surprised to open this thing up and not just see one motor with some sort of cheapo differential. They share an axle, but the axle seems to just serve as a spindle for the wheels to rotate around and the hexagonal plastic parts on the opposite side of those gear boxes do the actual driving of each wheel. These things are like a puzzle to take apart though unfortunately; its absurd how you have to take almost every part of the thing off to detach the motor housing. Dumar seems to no longer be making these things and may even be out of business. Its surprising how little info there is on the internet about the internal workings of these things.

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