Electric standup jetski build

Boats, Jet Skis, Kayaks etc., including hovercrafts
Quinc   100 W

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Electric standup jetski build

Post by Quinc » May 07 2022 10:16pm

Built this over the winter with my 8 year old. He took every nut and bolt off the ski and did the fiberglass! So please give him a like and sub on youtube. :)

Couple things I could use some help with. My Ant bms/battery only charges to 4.158 per cell. Any tips on getting it to charge up to the full 4.20v per cell? 20s2p SPIM08HP battery

I have read through the votol thread a few times now, but if anyone has any tips on how to get the absolute max power out of this thing that would be awesome. After the kids riding for around 15minutes and me trying for a few minutes she only used 2ah and the motor never got warm. So I am thinking she is no where near her potential.




Top speed of 25mph! Going to try with a direct coupler next. Not sure the sprocket has another run left in her.



Ski ready to ride weight is 226lbs. Battery weighs 35 pounds! Once I figure out if I want to stay with sprockets or swap to coupler I will shave some weight off or maybe go to aluminum. Also thinking I can cut out the hood liner for a few lbs.


Specs:

QS-120 motor 2000w / Maximum Torque: 20N.m to 49.6N.m.
Votol em-100 controller
Battery 20s2p 16ah SPIM08HP
ANT 300a bms


Ski 1986 300sx


Motor sprocket 14T Driveshaft sprocket 10T (Did this so I could adjust rpm/torque with sprockets)


Still trying to Figuring out the rpms Vs Torque for a jetski.. In the video I think the top speed was around 15mph.
Last edited by Quinc on May 23 2022 6:32pm, edited 3 times in total.

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Re: Electric jetski build

Post by Hillhater » May 08 2022 2:26am

.My Ant bms/battery only charges to 4.158 per cell. Any tips on getting it to charge up to the full 4.20v per cell? 20s2p SPIM08HP battery.....
Seriously ?..why ?
There will be no noticeable change in performance from that 0.8 volt increase of pack voltage,..but you will likely seriously reduce the battery life.!
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4πr^2   10 W

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Re: Electric jetski build

Post by 4πr^2 » May 08 2022 8:44am

Interesting project!

Yes, I would second the post above - minimal gains in power or 'per charge' battery life from the 4.2V charge, and will most likely shorten the overall life of the battery by some amount. If you absolutely want to try it, there are likely some trim pots in your charger to control the stopping voltage. If your motor / controller can handle it, you could add more battery voltage and/or current. If you have the option, more voltage will generally get you more top speed and more current would get you a better hole shot / more torque.

Not sure on the chain/sprocket...seems like that would add a lot of weight/complexity and as you mention - gets hot, so a lot of energy wasted there. Any chance to run direct drive and make adjustments with different impeller pitches? For some skis you can also get different pump cones that help add torque or speed. Not sure on the 300, though.

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Re: Electric jetski build

Post by Quinc » May 08 2022 11:40am

Hillhater wrote:
May 08 2022 2:26am
.My Ant bms/battery only charges to 4.158 per cell. Any tips on getting it to charge up to the full 4.20v per cell? 20s2p SPIM08HP battery.....
Seriously ?..why ?
There will be no noticeable change in performance from that 0.8 volt increase of pack voltage,..but you will likely seriously reduce the battery life.!
Good to know! Didn't realize it was a feature. I thought there was something wrong. :)

Quinc   100 W

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Re: Electric jetski build

Post by Quinc » May 08 2022 11:42am

4πr^2 wrote:
May 08 2022 8:44am
Interesting project!

Yes, I would second the post above - minimal gains in power or 'per charge' battery life from the 4.2V charge, and will most likely shorten the overall life of the battery by some amount. If you absolutely want to try it, there are likely some trim pots in your charger to control the stopping voltage. If your motor / controller can handle it, you could add more battery voltage and/or current. If you have the option, more voltage will generally get you more top speed and more current would get you a better hole shot / more torque.

Not sure on the chain/sprocket...seems like that would add a lot of weight/complexity and as you mention - gets hot, so a lot of energy wasted there. Any chance to run direct drive and make adjustments with different impeller pitches? For some skis you can also get different pump cones that help add torque or speed. Not sure on the 300, though.
I am still trying to figure out how to get the absolute max power/torque out of the votol settings. If anyone knows hows? :mrgreen:

My original plan was to go straight coupler but went with the sprockets so I could adjust rpms/torque when/if needed. I may still do the coupler but I need to figure out the motor settings first. I also have multiple pitch impellers to try.

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Re: Electric jetski build

Post by Quinc » May 08 2022 9:16pm

Video of the motor out of the water. This is just over half throttle:

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Re: Electric jetski first test ride

Post by Quinc » May 10 2022 3:12pm

Going to get some graphite into the rollers on the chain. Hopefully reduce the heat and noise some. Also working on figuring out the best way to attatch a coupler to the motor splines.

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Re: Electric standup jetski build

Post by liveforphysics » May 10 2022 3:52pm

Ive made this mistake, its only fixed by making both sides sprockets larger in diameter is the way to make your chain more quiet. The link below shows the effect of tooth count vs chain vibration. It looks like you have room to package 2x the number of teeth at least, doing that will knock out most of that vibrational power.

http://chain-guide.com/basics/2-2-1-chordal-action.html
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Re: Electric standup jetski build

Post by DogDipstick » May 10 2022 4:24pm

Quinc wrote:
May 07 2022 10:16pm

Motor sprocket 14T Driveshaft sprocket 10T (Did this so I could adjust rpm/torque with sprockets)


Even drive / Even driven.... sprockets... requires a chain with an ODD number of links or.... else your wear will be 2x faster, or even more. Just like if you have an even number of links, a even driving number of teeth, you need an odd number of teeth on the driven sprocket.. to keep the chain rolling around the sprockets and not wearing the chain prematurely. This keeps the same link from hitting the same spot on the same sprocket every time.

Most OEM manufacturers follow this pattern too. kawa, Honda, soozook, ect. Ducati, Ktm. Aprilla. Ect.
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Re: Electric standup jetski build

Post by Quinc » May 11 2022 10:10am

DogDipstick wrote:
May 10 2022 4:24pm
Quinc wrote:
May 07 2022 10:16pm

Motor sprocket 14T Driveshaft sprocket 10T (Did this so I could adjust rpm/torque with sprockets)


Even drive / Even driven.... sprockets... requires a chain with an ODD number of links or.... else your wear will be 2x faster, or even more. Just like if you have an even number of links, a even driving number of teeth, you need an odd number of teeth on the driven sprocket.. to keep the chain rolling around the sprockets and not wearing the chain prematurely. This keeps the same link from hitting the same spot on the same sprocket every time.

Most OEM manufacturers follow this pattern too. kawa, Honda, soozook, ect. Ducati, Ktm. Aprilla. Ect.
Well known by motorcycle mechanics. Often overlooked by motorcyclists.
Very interesting! This is the first I have heard that information. However, shouldn't chain slack determine how many links you have? And if I throw a half link in there am I covered either way. :mrgreen:

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Re: Electric standup jetski build

Post by Quinc » May 11 2022 10:12am

liveforphysics wrote:
May 10 2022 3:52pm
Ive made this mistake, its only fixed by making both sides sprockets larger in diameter is the way to make your chain more quiet. The link below shows the effect of tooth count vs chain vibration. It looks like you have room to package 2x the number of teeth at least, doing that will knock out most of that vibrational power.

http://chain-guide.com/basics/2-2-1-chordal-action.html
Thank you! Only thing is this QS motor has some oddball shaft size and after ordering multiple sprockets I cant find any that fit. Any chance do you have any tips on how to attach a coupler to a spline shaft? Right now I am thinking I will bolt the coupler to the sprocket that is on the motor shaft and run direct drive.

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Re: Electric standup jetski build

Post by SlowCo » May 11 2022 1:26pm

Great build :thumb:
Weld a 20+ tooth sprocket on to the motor sprocket.

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Re: Electric standup jetski build

Post by Quinc » May 20 2022 12:13pm

Worked with the ElectroBrapp guys yesterday and got the controller settings dialed in. 6500 rpms, instant power, (in the video it had soft start) and will hit the motors full power of 33ft\lbs of torque. If the motor can reach 6500rpms the impeller will be spinning around 9100rpms.

First video I had the controller maxed at 65amps. The controller is now set for 165amps.

Any guesses on top speed with a 75lb kid riding it? And will it get it my fat 230lb arse up out of the water?! =)

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Re: Electric standup jetski build

Post by liveforphysics » May 21 2022 8:56pm

Quinc wrote:
May 20 2022 12:13pm
Worked with the ElectroBrapp guys yesterday and got the controller settings dialed in. 6500 rpms, instant power, (in the video it had soft start) and will hit the motors full power of 33ft\lbs of torque. If the motor can reach 6500rpms the impeller will be spinning around 9100rpms.

First video I had the controller maxed at 65amps. The controller is now set for 165amps.

Any guesses on top speed with a 75lb kid riding it? And will it get it my fat 230lb arse up out of the water?! =)
The easy way to find out is a test! Make sure you go above and beyond for corrosion protection on the pack and inverter.
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Re: Electric standup jetski build

Post by goatman » May 22 2022 10:39am

i havent blown my shaft coupler yet and were running about the same motor torque
3d printed a pla carbon fiber coupler to match the electric motor shaft splines
then used a propeller hub kit brass insert to match the outboard motor shaft
when i was looking for the spline adaptors, jet skis have splined impeller tools
viewtopic.php?f=39&t=107045&start=25#p1660189


ive got 8 spare of these printed couplings on the boat but it just runs smooth like butter
viewtopic.php?f=39&t=107045&start=50#p1674699

theres better/stronger filaments you can get if the pla isnt strong enough

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Re: Electric standup jetski build

Post by Quinc » May 22 2022 3:15pm

goatman wrote:
May 22 2022 10:39am
i havent blown my shaft coupler yet and were running about the same motor torque
3d printed a pla carbon fiber coupler to match the electric motor shaft splines
then used a propeller hub kit brass insert to match the outboard motor shaft
when i was looking for the spline adaptors, jet skis have splined impeller tools
viewtopic.php?f=39&t=107045&start=25#p1660189


ive got 8 spare of these printed couplings on the boat but it just runs smooth like butter
viewtopic.php?f=39&t=107045&start=50#p1674699

theres better/stronger filaments you can get if the pla isnt strong enough

That is awesome! Great work you are doing. Do you know if those will fit the QS shaft threads? I have ordered a ton of mx sprockets and cant find anything that fits. My only plan so far is to attach the coupler to the sprocket on the QS motor. Or cut a keyway into the motor shaft.
sprocket_shaft.PNG
sprocket_shaft.PNG (454.8 KiB) Viewed 1200 times

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Re: Electric standup jetski build

Post by goatman » May 22 2022 6:42pm

my motor shaft is tapped in the middle so i can screw the coupling to it, yours looks like a twist-on lock ring with 2 bolts

looks like only about 6mm of spline would be taking all the torque and would probably just shear the filament.
you could try 3 d printing a coupler and if it fit, send the file to a cnc shop to get one made in aluminum with a couple holes in the side for something like a u-clip to lock it to the shaft.

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Re: Electric standup jetski build

Post by j bjork » May 23 2022 9:08am

Just look in the thread for the qs3000 (or what it is called) or my ktm thread, I have posted some fitting sprockets there.
Maybe just 428, Im not sure. It seems to be a rather common spline, so it shouldn't be to hard to find the ones you want.

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Re: Electric standup jetski build

Post by Dui, ni shuo de dui » May 23 2022 11:15am

Quinc wrote:
May 07 2022 10:16pm
Built this over the winter with my 8 year old. He took every nut and bolt off the ski and did the fiberglass! So please give him a like and sub on youtube. :)
Very cool build mate and kudos to the kid :thumb:
Can't wait to see more videos with the new settings
Quinc wrote:
May 07 2022 10:16pm
Couple things I could use some help with. My Ant bms/battery only charges to 4.158 per cell. Any tips on getting it to charge up to the full 4.20v per cell? 20s2p SPIM08HP battery
I suppose it might be that the maximum total voltage of the pack that is set up too low in the BMS settings. Your pack reaches this value before any cell has time to get there.
Maybe you could post screenshots of your current settings of the BMS, that way we could check that there isn't anything wrong with it.

As other people already pointed out, in this case it's not a big issue, the very marginal difference in voltage should be more than compensated by battery lifetime, so in the end it's probably a good thing.

Ah and also I second whoever said that you need to waterproof your battery, didn't do it on mine and it got corroded pretty bad. Corrosion gets way faster when there are electricity and liquids involved. Also I suggest you drop in some humidity absorbers in there when you store it, if possible.

Anyway, that thing looks like a blast :thumb:
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Re: Electric standup jetski build

Post by Quinc » May 23 2022 5:33pm

Got the controller dialed and took her out for a speed run. Even got my fat arse up out of the water... for a second.. lol

top speed of 25mph! Going to try with a direct coupler next. Not sure the sprocket has another run left in her.

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Re: Electric standup jetski build

Post by Quinc » May 23 2022 6:31pm

Dui, ni shuo de dui wrote:
May 23 2022 11:15am
Quinc wrote:
May 07 2022 10:16pm
Couple things I could use some help with. My Ant bms/battery only charges to 4.158 per cell. Any tips on getting it to charge up to the full 4.20v per cell? 20s2p SPIM08HP battery
I suppose it might be that the maximum total voltage of the pack that is set up too low in the BMS settings. Your pack reaches this value before any cell has time to get there.
Maybe you could post screenshots of your current settings of the BMS, that way we could check that there isn't anything wrong with it.
Ah and also I second whoever said that you need to waterproof your battery, didn't do it on mine and it got corroded pretty bad. Corrosion gets way faster when there are electricity and liquids involved. Also I suggest you drop in some humidity absorbers in there when you store it, if possible.
The battery is held in by two bungees (just like the gas tank would have been) When we are not riding the jetski the battery is on my bench in the open air. :)
Anyway, that thing looks like a blast :thumb:
Thank you! It's been a fun build.
I suppose it might be that the maximum total voltage of the pack that is set up too low in the BMS settings. Your pack reaches this value before any cell has time to get there.
Maybe you could post screenshots of your current settings of the BMS, that way we could check that there isn't anything wrong with it.
Battery died when one of the cells dropped to 2.9v. and battery showed 6%. when I got home the battery was back up to 11%.

I also changed all the low volt settings to 2.8v NOT 2.6v. :) (battery is good down to 2.5v)

After riding for 20minutes
bms1.png
bms1.png (221.55 KiB) Viewed 1143 times
low volt settings are 2.8v NOT 2.6v
bms2.png
bms2.png (225.52 KiB) Viewed 1143 times
low volt settings are 2.8v NOT 2.6v And pack low volt is 54v
bms3.png
bms3.png (235.06 KiB) Viewed 1143 times

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Re: Electric standup jetski build

Post by Quinc » May 23 2022 6:32pm

j bjork wrote:
May 23 2022 9:08am
Just look in the thread for the qs3000 (or what it is called) or my ktm thread, I have posted some fitting sprockets there.
Maybe just 428, Im not sure. It seems to be a rather common spline, so it shouldn't be to hard to find the ones you want.
I went through your thread but didn't see anything to the motor sprocket. Do you have a link to one? I will order it and try it. :)

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Re: Electric standup jetski build

Post by 4πr^2 » May 23 2022 8:50pm

Quinc wrote:
May 20 2022 12:13pm
Worked with the ElectroBrapp guys yesterday and got the controller settings dialed in. 6500 rpms, instant power, (in the video it had soft start) and will hit the motors full power of 33ft\lbs of torque. If the motor can reach 6500rpms the impeller will be spinning around 9100rpms.

...
Not sure what impeller you have settled on. 9100rpm strikes me as a bit fast. Not sure what the original motors run. My 550sx doesn't seem like it would be running much above 5000-6000. Likely most any impeller would be matched to the expected rpm of the original gas engine.

I guess if you can make power with it at 9100, then it might not be an issue. But at some point, I'd worry that cavitation or just overall inefficiency of the jet pump would kick in and you'd actually be loosing power with such high rpm.

Overall, I think the 'ideal theory' is that impeller pitch x rpm should equal speed... sort of like a screw pulling itself through wood. Then how far below that 'ideal' speed you fall is the overall inefficiency.

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Re: Electric standup jetski build

Post by Quinc » May 23 2022 10:54pm

4πr^2 wrote:
May 23 2022 8:50pm
Quinc wrote:
May 20 2022 12:13pm
Worked with the ElectroBrapp guys yesterday and got the controller settings dialed in. 6500 rpms, instant power, (in the video it had soft start) and will hit the motors full power of 33ft\lbs of torque. If the motor can reach 6500rpms the impeller will be spinning around 9100rpms.

...
Not sure what impeller you have settled on. 9100rpm strikes me as a bit fast. Not sure what the original motors run. My 550sx doesn't seem like it would be running much above 5000-6000. Likely most any impeller would be matched to the expected rpm of the original gas engine.

I guess if you can make power with it at 9100, then it might not be an issue. But at some point, I'd worry that cavitation or just overall inefficiency of the jet pump would kick in and you'd actually be loosing power with such high rpm.

Overall, I think the 'ideal theory' is that impeller pitch x rpm should equal speed... sort of like a screw pulling itself through wood. Then how far below that 'ideal' speed you fall is the overall inefficiency.
I figure it is probably spinning around 5500rpm. I think these pumps will only process around 7000rpms worth of water without a lot of work put into them. Hoping with the direct coupler to driveshaft the motors torque will be able to shine a bit more and get her up in the 6000rpm range. :)

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Re: Electric standup jetski build

Post by j bjork » May 24 2022 2:06am

Quinc wrote:
May 23 2022 6:32pm
j bjork wrote:
May 23 2022 9:08am
Just look in the thread for the qs3000 (or what it is called) or my ktm thread, I have posted some fitting sprockets there.
Maybe just 428, Im not sure. It seems to be a rather common spline, so it shouldn't be to hard to find the ones you want.
I went through your thread but didn't see anything to the motor sprocket. Do you have a link to one? I will order it and try it. :)
It seems I was to quick. I found it on page 4, but it dosent fit your shaft: http://www.jtsprockets.com/catalogue/part/JTF1263/
It is for 20/16/4. I dont really understand the spline on your shaft, 4-6?

If it is the same as the 180 90h with a 5mm spline: http://www.jtsprockets.com/catalogue/part/JTF1264/
There are sprockets for 520 too, but you find those in my yamaha thread :lol:

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