Electric standup jetski build

Boats, Jet Skis, Kayaks etc., including hovercrafts
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Dui, ni shuo de dui   10 kW

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Joined: Jan 29 2016 3:21am

Re: Electric standup jetski build

Post by Dui, ni shuo de dui » May 24 2022 2:18am

A few remarks/suggestions from the screenshots provided:

-Cell High protect is ok at 4.2V, but cell high recover is a bit low, meaning if after charge the battery stabilizes at a voltage higher than this then the BMS will remain shut off, not allowing you to ride. I suggest you put is a bit closer to 4.2V than it is right now.

-Pack voltage is ok at 84V, it's correctly set up. Though you'll probably never actually reach this voltage, the cell cutoff voltage will get there first. On my battery packs I prefer to have the total pack voltage reached before the maximum cell voltage in normal conditions, but I guess it's a matter of preference

-Cell low protect and recover should be set up according to the dischage curve of your cells. I don't have the data for your cells so I can't say if it's correct. Here also, there's really nothing to gain to set it too low, seaching for the last tiny percents of capacity will really decrease your battery life, so I usually suggest to cut off right after the voltage starts to decrease at the end of the curve (hopefully you'll get what I mean by looking at a discharge curve, if not already done :wink: )

-Cell diff protect is too high in my opinion. When your cells drift apart so much that it reaches one volt they are already long gone and it's very, very risky to keep using them, especially during the charge process. I'd set it up at 0.2 or 0.3V, which is already a lot. If at any point in your battery's life you see the difference between the best and the worst cell reaches this value then it's time to stop using the pack immediately and sent it to be repaired.

-Cell high warning should be lower than cell high cutoff. You want the BMS to beep and alert you before it reaches the cutoff value. But if the beeps annoy you then you can also leave it like this, up to you. I like for it to beep because it can tell if there is an issue while riding (in this case it would signal an issue with regen for example).

There are also some other very important parameters like current discharge, short circuit protection and stuff like that but I don't see them on the screenshots so I can't comment on those.

Hope this helps, :wink:
:bolt: New Build in Progress: Electric Roadster, Kelly KLS72701, 24S2P A123 cells, 3000W QS273 :bolt:
viewtopic.php?f=12&t=109246

:bolt: My Ninja 250 clone: FarDriver 841800 Track Edition, 23S2P A123 cells, 3000W QS273 : :bolt:
viewtopic.php?f=12&t=90032

:bolt: My Electric Scooter: Sabvoton 72200 Unlocked, 72V 20Ah 24S1P A123 cells, 2000W QS273: :bolt:
viewtopic.php?f=12&t=75912

Quinc   100 W

100 W
Posts: 273
Joined: Apr 18 2016 11:21am

Re: Electric standup jetski build

Post by Quinc » May 25 2022 3:11pm

Dui, ni shuo de dui wrote:
May 24 2022 2:18am
A few remarks/suggestions from the screenshots provided:

-Cell High protect is ok at 4.2V, but cell high recover is a bit low, meaning if after charge the battery stabilizes at a voltage higher than this then the BMS will remain shut off, not allowing you to ride. I suggest you put is a bit closer to 4.2V than it is right now.

-Pack voltage is ok at 84V, it's correctly set up. Though you'll probably never actually reach this voltage, the cell cutoff voltage will get there first. On my battery packs I prefer to have the total pack voltage reached before the maximum cell voltage in normal conditions, but I guess it's a matter of preference

-Cell low protect and recover should be set up according to the dischage curve of your cells. I don't have the data for your cells so I can't say if it's correct. Here also, there's really nothing to gain to set it too low, seaching for the last tiny percents of capacity will really decrease your battery life, so I usually suggest to cut off right after the voltage starts to decrease at the end of the curve (hopefully you'll get what I mean by looking at a discharge curve, if not already done :wink: )

-Cell diff protect is too high in my opinion. When your cells drift apart so much that it reaches one volt they are already long gone and it's very, very risky to keep using them, especially during the charge process. I'd set it up at 0.2 or 0.3V, which is already a lot. If at any point in your battery's life you see the difference between the best and the worst cell reaches this value then it's time to stop using the pack immediately and sent it to be repaired.

-Cell high warning should be lower than cell high cutoff. You want the BMS to beep and alert you before it reaches the cutoff value. But if the beeps annoy you then you can also leave it like this, up to you. I like for it to beep because it can tell if there is an issue while riding (in this case it would signal an issue with regen for example).

There are also some other very important parameters like current discharge, short circuit protection and stuff like that but I don't see them on the screenshots so I can't comment on those.

Hope this helps, :wink:

This helps a ton! You can fill the outside of a barn with what I dont know. So I appreciate all of the knowledge being shared with me and will go back through my settings and adjust. Thank you! :D

Quinc   100 W

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Posts: 273
Joined: Apr 18 2016 11:21am

Re: Electric standup jetski build

Post by Quinc » Jul 18 2022 10:28am

Making progress!
Thing is very quiet now with the coupler. Just barely a slight hum if you are close enough to hear it. And still no issues with motor over heating. Also got closer to getting my fat arse up on plan. Going to try swapping the skat 16 to a 15 next and see how she does.
e-ski.jpg
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Quinc   100 W

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Joined: Apr 18 2016 11:21am

Re: Electric standup jetski build

Post by Quinc » Aug 12 2022 10:32am

Took her out and only hit 18mph with this setup. So thinking the motor is not getting anywhere near the 6500rpms. Question now is do I go down in impeller pitch so its less work for the motor and more rpms OR do I go up in pitch so even though its spinning slower I will get more speed?

Quinc   100 W

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Joined: Apr 18 2016 11:21am

Re: Electric standup jetski build

Post by Quinc » Aug 12 2022 6:01pm

Been using the battery/bms now a few times but it is showing the battery dead after using only 6.8ah out of the 16ah and 66v out of the 84. Is that normal? Any suggestions on my settings? I took the screenshot when I got home from the lake and it now shows 12% but a few hours before that it was showing 2%. *I recharge it at 1amp and hit the auto balance option on the bms.
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crab   1 µW

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Re: Electric standup jetski build

Post by crab » Aug 12 2022 7:59pm

Subscribed buddy! Now I need to get one going over the winter for sure.

Quinc   100 W

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Joined: Apr 18 2016 11:21am

Re: Electric standup jetski build

Post by Quinc » Aug 13 2022 10:50pm

crab wrote:
Aug 12 2022 7:59pm
Subscribed buddy! Now I need to get one going over the winter for sure.
Welcome! And let the overwhelming amount of learning and confusion begin! :)

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Dui, ni shuo de dui   10 kW

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Joined: Jan 29 2016 3:21am

Re: Electric standup jetski build

Post by Dui, ni shuo de dui » Aug 15 2022 3:10am

Could you show us all the settings in the BMS app? The ones you showed don't have much to do with the battery state of charge or the current metering.
It is possible that the current sensor range is off, thus displaying wrong informations.
:bolt: New Build in Progress: Electric Roadster, Kelly KLS72701, 24S2P A123 cells, 3000W QS273 :bolt:
viewtopic.php?f=12&t=109246

:bolt: My Ninja 250 clone: FarDriver 841800 Track Edition, 23S2P A123 cells, 3000W QS273 : :bolt:
viewtopic.php?f=12&t=90032

:bolt: My Electric Scooter: Sabvoton 72200 Unlocked, 72V 20Ah 24S1P A123 cells, 2000W QS273: :bolt:
viewtopic.php?f=12&t=75912

Quinc   100 W

100 W
Posts: 273
Joined: Apr 18 2016 11:21am

Re: Electric standup jetski build

Post by Quinc » Aug 17 2022 1:37pm

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Quinc   100 W

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Joined: Apr 18 2016 11:21am

Re: Electric standup jetski build

Post by Quinc » Sep 03 2022 5:40pm

These are the battery specs:


Material Li-ion

module specs

Typical capacity 16AH
Nominal Voltage 3.7V
Internal Resistance ≤0.8mΩ
Recommend Continuous Discharge Rate 400A
Pulse Discharge Rate(3 seconds) 800A
Fully Charged voltage 4.2V
Discharge cut off voltage 2.5V

Quinc   100 W

100 W
Posts: 273
Joined: Apr 18 2016 11:21am

Re: Electric standup jetski build

Post by Quinc » Sep 05 2022 3:54pm

Much better! Went up in impeller pitch from 16 degree to 17 degrees and spent a couple hours hogging out and blueprinting the pump (cleaning up casting marks and sharping exit side of the pump veins) Kiddo was able to take off like a rocket without cavitation issues this time. *Also increased the max amps on the Votol 100 from 160 to 180.

Looking through the ANT bms system log I found out what is killing power early on the battery. CellLowRecovery: 2.80v(need to figure out which cell it is so I can replace it if needed. So for now I changed it to 2.60v. (cells are good to 2.5v) So hopefully give him a few more minutes of riding. Also interesting after almost 24hrs of sitting the battery was back up to 68v with an average of 3.4v per cell. Also still using less than 7ah before cutting off.

15 degree 16 degree 17 degree
impellers.jpg
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SlowCo   10 MW

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Location: The Netherlands

Re: Electric standup jetski build

Post by SlowCo » Sep 07 2022 3:03pm

Great result :thumb:
Maybe add another parallel string to the battery pack so the voltage sag is less and riding time increases?

Quinc   100 W

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Re: Electric standup jetski build

Post by Quinc » Sep 08 2022 10:56am

SlowCo wrote:
Sep 07 2022 3:03pm
Great result :thumb:
Maybe add another parallel string to the battery pack so the voltage sag is less and riding time increases?
Parallel string? Like another row of batteries to increase AH or is that a wiring thing? :)

SlowCo   10 MW

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Re: Electric standup jetski build

Post by SlowCo » Sep 08 2022 3:01pm

Quinc wrote:
Sep 08 2022 10:56am
Parallel string? Like another row of batteries to increase AH or is that a wiring thing? :)
Yes.
I don't know how your battery pack is built but adding extra Ah will "stiffen" the pack leading to less voltage sag (keeping the cells at higher voltage and less stress) while being able to pull more amps.

Quinc   100 W

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Joined: Apr 18 2016 11:21am

Re: Electric standup jetski build

Post by Quinc » Sep 09 2022 10:37am

SlowCo wrote:
Sep 08 2022 3:01pm

Yes.
I don't know how your battery pack is built but adding extra Ah will "stiffen" the pack leading to less voltage sag (keeping the cells at higher voltage and less stress) while being able to pull more amps.
I dont think another row will fit also this thing already weighs 35lbs! Might have to spend more and build a battery with some better cells.

battery.jpg
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