Electric Skidoos

1349 Views 7 Replies 4 Participants Last post by brian_, Apr 28, 2018

matt4x4

Discussion Starter · Apr 4, 2018

We have 2 very old Skidoo's up at the family cabin, circa 1970's thats been sitting for years in the quonset. We get by without them with our 4x4 quad in the winter. We have a four Trojan 12V 150Ah to make 48V 150Ah lead acid golf cart that I think we should use the batteries on one Skidoo. I know L.A. need to be derated, to 0.80 which leaves it with 120Ah on 48V. A silent snow mobile would be ideal for our cabin.

Weight - Guessing on the weight but I'd say close to 500lbs for the Skidoo itself the way it is.

Motor - The question becomes what motor would be adequate for the Skidoo. I believe I should start looking for a used forklift motor locally. Are forklift motors brushed or brushless?

Terrain - Flat, Skidoo'ing on the lake back and forth from fishing hut to cabin, around the community itself and neighboring cottage community. All flat.

Speed - I would like to have it go up to about 50kph (31mph) but would really ride it most of the time at 35kph (21mph).

Distance around the lake is about 65km(40m), which I'd like to do on the skidoo, but if its not practicle in terms of battery Ah, then a midway charge is not a deal breaker, so say 35km(20m)

No cargo, just perhaps having 2 adults which would be 225lbs each, so 450lbs total weight.

Controller - What controller should I be looking for when purchasing a used forklift motor.

This is a spring/summer/fall project to be ready for next winter.

Thanks

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brian_

· #2 · Apr 4, 2018

matt4x4 said:
I believe I should start looking for a used forklift motor locally. Are forklift motors brushed or brushless?

When people in this forum refer to a "forklift motor", they mean old brush-commutated DC motors, typically with series field wiring. Modern forklift trucks use AC motors, but that is not what is being salvaged for EV conversions.

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matt4x4

Discussion Starter · #3 · Apr 5, 2018

I sent out some emails to forklift companies for used motors. If I can find some for a $100-$250(CAD) then I will buy locally. Are they usually rated for 20-35kw?

I have also run across some 18kw+ motors for 300euros and 25kw for 470euros and a matching 165euros ESC 3-12S for 300A, which I think would suit my needs for 48V 150Ah batteries, leaving my with 7200Wh derated by 0.8 is 5750Wh, so hoping the setup uses 50-75Wh/km that is 115km, 75km and if I rate it at 100Wh/km then that is 57km. More then enough.

So a $1000-$1250 and some welding fabrication work. Pop the old motor out, rebuild if I want to, pop the new electric stuff in and done deal.

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brian_

· #4 · Apr 5, 2018

matt4x4 said:
... leaving my with 7200Wh derated by 0.8 is 5750Wh, so hoping the setup uses 50-75Wh/km that is 115km, 75km and if I rate it at 100Wh/km then that is 57km. More then enough.

That seems like very optimistic energy consumption to me. It depends heavily on the snow conditions, of course, but generally snowmobiles use a lot of energy per distance for their size, because

it takes more energy to slide skis than to roll wheels,
it takes more energy to break trail or churn in snow than to roll on a hard surface, and
there is some sliding friction in the track mechanism.

There's a reason that high-performance snowmobiles have as much power as much faster high-performance street motorcycles. I wouldn't be surprised if a snowmobile takes as much energy for the same distance and speed as a compact car... which is much more than 100 Wh/km.

But maybe I'm overestimating the energy requirement.

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madderscience

· #5 · Apr 8, 2018 (Edited)

I would strongly recommend not bothering with the lead acid. The extra weight will only increase energy use, especially when plowing through soft snow.

instead, consider nissan leaf modules or volt modules, series / paralleled as necessary to get the voltage and AH you want. With any DC motor you are considering, there probably isn't any reason not to go to 72V as well (10 leaf modules in series are 66ah, so 10s2p would be 133ah usable. The controller will step down the battery voltage anyway.

Note that the 80% derate on lead acid is just for depth of discharge, and the same rule of thumb applies to the lithium. However what will really kill you is the peukert effect, which means the faster you use power from lead acid, the less overall energy you get. for full size roadgoing EVs, NEW lead acid you could get about HALF rated capacity in normal driving. Colder makes it WORSE. we are talking about snow machines here

a single leaf module (7v, 66ah) weighs about 8lbs. So the pack of 20 I am recommending, with bus bars and tie downs would probably be about 200lbs.

a single T-1275 trojan weights 80lbs, so the whole pack with tie downs would be pushing 400lbs.

a 72V, 130ah lithium pack with leaf modules would probably have 3-4x the usable energy capacity of a 48v, 150ah trojan pack under those conditions. Not to mention weighing half.

on motor selection, an AC setup (even a real AC forklift motor

) might be a bit more reliable long term than brushed DC, but the usual roadgoing benefit (regen) aren't likely to apply in this situation. However if you can find a fully enclosed frame motor, that might help keep dirt/moisture out of it which would be a plus.

Good luck

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madderscience

· #6 · Apr 8, 2018

one way to estimate range vs. fuel efficiency -

This is a good rule of thumb for cars, I don't know how it might apply to motorcycle/snowmobile engines though.

For cars, a lithium battery weighing 8% (cells only) the overall weight of the vehicle will give approximately the same usable range as 1 gallon of gas for the un-converted car. So for a 3000lbs vehicle with a 240lbs of cells, if the car originally got 30mpg you can estimate a 30 mile range on that pack. My scion xB with a 600lbs pack in a 3000lbs vehicle gets about 100 miles range under ideal conditions and 80 miles cool and wet. I see quite a few conversions with 300lbs lithium packs (about the weight of 100ah, 156v LiFePO4) that get around 50 miles. So its roughly proportional.

So if you know how long you can run on 1 gallon of gasoline for these skidoos, a 240lbs lithium pack will give you similar range/autonomy. So that 160lbs leaf pack (cells only) would be 2/3 of gallon. you can do the math.

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dain254

· #7 · Apr 9, 2018

The only thing you really have going for you is that your terrain is low resistance (frozen lake) as opposed to deep snow. You are likely replacing a 200-300CC 2 cycle engine... which would give you somewhere between 20-40hp. A forklift motor/lead acid setup will be far too much weight and take up too much space, you need something like an etek brushed DC motor and minimum of 4kwh of lithium batteries, and a reasonably high power controller/inverter if you want to hit your speed and distance goals on hard pack snow. Batteries also don't like cold conditions, especially lead acid batteries.

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brian_

· #8 · Apr 28, 2018

matt4x4 said:
...hoping the setup uses 50-75Wh/km that is 115km, 75km and if I rate it at 100Wh/km then that is 57km.

brian_ said:
That seems like very optimistic energy consumption to me.

Taiga Motors of Quebec announced an electric snowmobile a couple of months ago...

It’s electric motor is fed by a 15 kWh battery pack that’s good for 100 kilometres of range.

That's 150 Wh/km.

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