KTM65 Electric Conversion

[snydes]

I was thinking 20s as well, but the capacity doesn’t add up for me with any of the parallel configurations. I’m likely missing something though.

 

[C5tor]

'Lots of battery pack questions. Here's a challenge, sorta. Our pack is around 1.81Kwh, 72v Nominal, and we're running around 125 amps right now. Can you calculate (SWAG, scientific wild ass guess) what cell configuration we're using?

This should do it!

 

[F451]

Wow! Super impressed. Great work guys.

PLEASE post the links to the vids when you can.

And how about charging? How is that done? How long to re-charge to 100%?

 

[F451]

And all this electron business. So many new words. After riding dirt bikes and motorcycles for I don't know how many years I was finally getting a handle on jetting basics and suspension tuning. With the electric bikes I feel like I was left back, then we got a new teacher that is skipping over all the easy stuff and I'm lost, Lol. Learning a ton though! Slowly...

 

[snydes]

And all this electron business. So many new words. After riding dirt bikes and motorcycles for I don't know how many years I was finally getting a handle on jetting basics and suspension tuning. With the electric bikes I feel like I was left back, then we got a new teacher that is skipping over all the easy stuff and I'm lost, Lol. Learning a ton though! Slowly...

I know the feeling. I’m way behind the curve too. All I can say for sure is we have some very talented members here.

 

[F451]

I know the feeling. I’m way behind the curve too. All I can say for sure is we have some very talented members here.

Absolutely. And I really appreciate how willing everyone is to take the time to share the knowledge. And how easy going everyone is.

Thread jack! Sorry, Lol.

 

[C5tor]

I know the feeling. I’m way behind the curve too. All I can say for sure is we have some very talented members here.

Me too. The sum total of my battery knowledge is that if you lick it and your tongue gets all tingly, then it's got some juice left in it.

 

[Mark911]

Assuming your 18650 cells are 3.6 V & 2.6 amps for each cell I calculate you battery is 20 S (series) & 10 P (parallel)

Close, but your assumptions about the cell are probably off. The cell you modeled wouldn't be a good candidate for this application. Another clue, think original ALTA cell. Isn't this FUN! Lol.

 

[ElectroBraap]

Perfect!

Can you provide a link and some information / specs etc. for the electric motor you purchased - thanks

This should do it!
View attachment 5133

 

[schwankl]

is it 4s of 5s10p modules?

 

[Rashid510]

*cough* 8p20s

 

[Philip]

Assuming your 18650 cells are 3.6 V & 2.6 amps for each cell I calculate you battery is 20 S (series) & 10 P (parallel)

Maybe it is 18s and 9p, if you assume the 4.0V 2.8Ah batteries.

 

[Mark911]

Ok, @Rishid510 wins! The original Alta (MX) uses Panasonic NCR 18650 BD cells. The data sheet on these cells say 3.6v, 3180ma typical (I measured more like 3150).

The voltage - You know the voltage =72, so 72/3.6 = 20 cells in series, easy.

From the dyno chart 10.5hp = 7.8kw. @90% efficiency 7.8kw = 8.6 kw/72v (nominal voltage) = 120amps (this number will be used later).

P Groups- This is where engineering judgement comes into play, how hard to push the selected cell. Anyone that owns an Alta MX with the Panasonics should be aware that at full load its pulling about 120-130 amps or more depending on conditions. The Alta has 6 cells per P group so that's 120/6 = 20 amp cell. That's like 20/3 = 7C peak! Too much in my mind and one reason the MX has thermal problems at race pace.

What's more reasonable? My engineering judgement said 5C. 5C * 3ah =15 amps per cell. So that's 15/120 (remember the number above) = 8 cells per P group. So we get 8P x 20S

Note, it does make a difference what comes first, the P or S designation. If the pack is made using a bunch of P groups connected in series it's P first. If the pack is made by combining a bunch of series connected cells in parallel its S first. It sounds dumb until you start working out how to keep the cells all balanced and/or try to fuse the thing. BIG difference. Ours is P first, the most common.

 

[Philip]

This game was rigged!!! Either the Alta's 6p 84s A-pack is just a 302V pack (not 350V), or Mark's pack is really an 84V pack (not 72V)!
I quit!!!

 

[Mark911]

This game was rigged!!! Either the Alta's 6p 84s A-pack is just a 302V pack (not 350V), or Mark's pack is really an 84V pack (not 72V)!
I quit!!!

72 nominal! 84 at 4.2v per cell.

 

[Mark911]

Testing . A video example of the hill climb potential (click "testing"). On slope from a dead stop. The incline is much steeper than it looks from this perspective.

 

[snydes]

Ok, @Rishid510 wins! The original Alta (MX) uses Panasonic NCR 18650 BD cells. The data sheet on these cells say 3.6v, 3180ma typical (I measured more like 3150).

Ahhh, that’s where I was going wrong, I thought the calculations would go on rated capacity and not typical. Thanks for the explanation!

 

[Philip]

Mark, why did you choose to go with Panasonic cells and not Sony for this application?

 

[Butch]

Close, but your assumptions about the cell are probably off. The cell you modeled wouldn't be a good candidate for this application. Another clue, think original ALTA cell. Isn't this FUN! Lol.

that was my question... you do this for fun, right? Or is it the big bucks?

 

[Mark911]

Nothing involving dirt bikes is big bucks, it’s a matter of limiting your losses.