Uv 26 conversion

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treasurehunter

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I am planning to modify my Uv 26 with the post 2007 motor using lithium ion cells and cutting down the hull so as to reduce the weight by 30ish pounds. With the 2 battery packs I will build, I will be able to remove about 9'' to 10'' of hull effectively reducing weight of scooter. If i can remove 10'' it will reduce buoyancy by 31.8 pounds so scooter will be 62 pounds.If i can only remove 9'' then will be 65 pounds. That is enough weight removed to make me feel young again.
I would need some advice on the battery pack which I will be building myself.

Battery: Sanyo 18650, 3500mah 10amp continous discharge @ 3.6 Volts nominal in 8s12p configuration = 28.8 volts,42Ah, but a full charge at 4.2volts per cell will give me 33.6 volts.

My Question particularly for @TBone and @superlyte27,since you both are very well knowledgeable in battery and dpv motors and anyone else that has experience with these motors.

Can the post 2007 Uv 26 take a voltage of 33.6 volts or will this be to much and fry the board and motor.
I have options of reducing the voltage charge to a max 29.4 volts which will be good for increased cycles on battery and occasionally fully charge to 4.2 volts for battery cycle health and drain back down to 29.4 before use.
The battery packs will be 2 packs of 8s6p connected in parallel.
 

tbone1004

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@treasurehunter when you are trying to tag someone, make sure you start with the @ symbol so we get the notification. @Superlyte27

The stock vipers are a 7s configuration and I would recommend staying with that configuration. It will still give you a meaningful power increase over the stock UV lead batteries, but I would not put the extra cell in there. I don't doubt the motor could handle it, but I'm not sure about the ESC.

I would build the packs as 7s and give them a full charge. They will age out before you ever hit their cycle limits
 
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treasurehunter

treasurehunter

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Thanks@Tbone for the quick reply.
I mistakenly calculated my battery design with nominal voltage not thinking of max charge voltage. Also realized if I under charge, the bms probably will not balance the cells until I perform a full charge.
One other thing if it makes a difference,I don’t have any speed control at the moment, straight on off and adjust pitch, but am considering it if I find a used one at a reasonable cost.
 

Superlyte27

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This is the battery I use. You will fry the controller if your voltage is much higher.

LiFeMnPO4 Prismatic Module: 3.2V 40 Ah, 3C Rate (128 wh) - UN38.3 Passed

All of the scooters I’ve built are still running. That’s coming up on 10 years I think.

if you make the scooter the same length as a UV18, you’ll add a ton a lead, but can eliminate ballast to put a massive lighting/camera system on it.

And the scooter will have a longer range than you do :)
 

tbone1004

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Thanks@Tbone for the quick reply.
I mistakenly calculated my battery design with nominal voltage not thinking of max charge voltage. Also realized if I under charge, the bms probably will not balance the cells until I perform a full charge.
One other thing if it makes a difference,I don’t have any speed control at the moment, straight on off and adjust pitch, but am considering it if I find a used one at a reasonable cost.

I don't think I've ever seen one used for sale... If you don't have an ESC then you need to stay with a 7s pack not 8
 
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treasurehunter

treasurehunter

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Thanks @Superlyte27

My main goal in this project is #1 max weight reduction and realistic power/speed gain without frying my trusted UV 26. Its been good to me and does not deserve to go down in flames. The prismatic batteries you use will have a full charge at 3.6volts/cell to 3.8volts/cell, at 8s full charge = 28.8volts to 30.4volts.

My 7s pack will be 29.4 volts full charge.
Is it imperative that I keep the full charge at not more than 28.8 volts? if so I can charge at 98% and reach 28.8 volts.
Also when you say fry the controller are you talking about esc or the brush board,because on my Uv-26 does not have a speed controle modual. Does that make a difference?

I have spoken to Rodney about using Lithium ion batteries and he did confirm that the motor can take it no problem as all the motors beyond 2007 are all the same from UV-18 to the vipers. Also Dan at Divetech in Mallorytown Ontario has done a few modification with lithium ion and he too has total confidence that the motors can take the extra voltage.

I will error on the side of caution and charge less than full charge.
This scooter will be my spare and/or back up and sometimes lend to dive buddies that don't have one.

@TBone
Yes, I will be configuring the battery packs in 7s.
 

tbone1004

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@treasurehunter you're tagging the wrong tbone :p

If you are making a 7s lipo pack or an 8s lifepo4 pack, then you can run them to full voltage no issue. If you are using it as a backup scooter or loaner then you probably don't want to charge it fully since the packs prefer to live around 1/2-3/4 charge for storage
 

Superlyte27

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Brush Board. Some of them were pretty weak
 
https://www.shearwater.com/products/peregrine/

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