Where would you place a 72v 25ah battery on this frame?

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B1gD

1 mW
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Dec 20, 2019
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*Rear hub motor
o that would be around 200 18650 batteries placed single depth or double depth.
Would you split the pack? Or keep it as one?
Thanks
 

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20s10p, 25ah. is that a 25r battery? I like 25r but you can get 25ah with 8p of another 18650. im a fan of 25r but am thinking of changing. id go 3 and 4 with 2-20s5p paralleled for range a removable pack at 3 and a single pack at 4, for quick rides unless you need more than 100 amps. 3 is pretty high off the ground. you want your weight low
 
I had a similar problem with my build, and calculated that one standard astm sized brick is about same volume and weight as 45 18650's. One brick =205x90x50mm, 1590g. One 18650 = 65X18X18mm, 45g.
So 200 batteries is about same weight and volume as 5 bricks. Not exact but close enough for trying out different configurations.
 
Thanks guys
Does anyone have a link on joining 2 100 x 18650 battery packs that are physically separated as 20s5p on 3 & 4 as suggested? Is any power lost through doing so?
 
B1gD said:
Thanks guys
Does anyone have a link on joining 2 100 x 18650 battery packs that are physically separated as 20s5p on 3 & 4 as suggested? Is any power lost through doing so?
Click to expand...
I asked the same question about protecting 2 paralleled packs from each other if I wasn't using a bms. I was just using a 2-xt60 plug cable to 1-xt60 plug I soldered together.

ill be using a bms on each pack.

power loss or cell damage, depends on the cells your using and the amps you are using. I run my 25r's at 10 amp max, a 4p pack at 40amps is 10 amps each and when paralleled its 5amps per cell. 8p@40 amps is 5amps a cell. less volt sag when paralleled
 
Are you sure you’d be able to make it small enough to fit in even 2 of those spots? If you can, please let me know, because I’m struggling with figuring out where to fit twice that on a small motorcycle. If it does fit, I’d go for 4 and/or 2, but 2 is less ideal when you factor in how far back the weight will already be with a beefy rear hub.
 
I'd go with a split pack.. But make both of them 20s, and parallel them, instead of split in series. Then you can ride it on one pack for short sprinty trips if you want.
I think you'll find running one pack at the 4 position isn't as great as one would think, too low on the center of gravity isn't great. Def not off the back... That's the worst spot.

This thread has a rundown of my experiences with different battery heights.

https://endless-sphere.com/forums/viewtopic.php?f=3&t=92833
 
And re. that frame shape and mid drive, with the basic Bafang type, theres a welded brace on the front side of the bottom bracket piece the makes it too thick to rotate the motor up at all, so it hangs as low, or lower, than a regular frame.
 
And re. that frame shape and mid drive, paired with the basic Bafang type, theres a welded brace on the front side of the bottom bracket piece the makes it too thick to rotate the motor up at all, so it hangs as low, or lower, than a regular frame.



FYI, that's my shitty low end differently branded version of the bike in question... I just ran backpack battery.... It's a great solution for just riding for fun.
 
#4 if you want to not wheelie all the time if your bike is powerful.
 
Compared to the weight of the rider up there, it doesn't make that much difference between the 3 or 4 position with wheelies. But it does really affect the feel of how sluggish the bike is initiating into turns, and how hard it wants to wind into hard cornering, both of which I found to be way worse with the battery too low during my testing.
And if he's actually going mountain biking, you need to be able to wheelie up over obstacles... So too wheelie resistant is not great unless drag racing.
 
#4 if you dont want to wheelie all the time. Rider is a dynamic load, battery is a static.

I had problems with the power. Hey, my bike flips WAY to easy if it is in any other location. I tried. Plus my battery is about the same weight.


Hey the fastest road going bikes in the world load up the front wheel for traction and to keep capsizing ( aka wheelie) at bay.. Look up GSXR, ZX, CBR, S1000RR, ect... ALL of them are fast (BEST HANDLING MACHINE IN SPEED RACING) and keep the weight low and forward.

If you have problems, well, must be your riding. Many have sucess in the "turns" with the mass and CG lower. GTFO here with that " handles worse"... Where does it reference "MTB"? I see an ebike, not a MTB.


So #4 if you dont want to wheelie all the time.
 
Voltron said:
Compared to the weight of the rider up there, it doesn't make that much difference between the 3 or 4 position with wheelies. But it does really affect the feel of how sluggish the bike is initiating into turns, and how hard it wants to wind into hard cornering, both of which I found to be way worse with the battery too low during my testing.
And if he's actually going mountain biking, you need to be able to wheelie up over obstacles... So too wheelie resistant is not great unless drag racing.
Click to expand...



Baahaha thats some funny shit. "Hard Cornering" "Worse handling with the CG low". Sluggish.

I guess Kawasaki, Honda, Aprilla, BMW, Harley, Buell, Yamaha, Suzuki, MotoGuzzi, Victor, Dukati, all have their best handling road machines cg slung low, in error. Maybe you can go win the MotoGP this year with that idea.
 
Actually, I wrote worse handling with the cg TOO low... But you don't have to come off like a dick because you disagree. It's well established that too low of cg negatively affects handling in s turns, esp on a lightweight platform like a bike. Too high isn't great either obviously...
 
I beleive #3 is to high. For thi rake and trail.

Sorry if I come off like a dick, for disagreeing.

Its just that I feel like you specifically attacked my logic, my experience, and my knowledge, when it was common knowledge you were (attacking) attempting to make note of.

I've flicked the CBR empty and I've flicked the CBR full... Ive launched the Cr250 twenty feet... It does ( final application of moto, ( ie street or off road)) does make a difference.

But if you wheelie uncontrollably, put the pack forward and down. It will help you put the power down.
 
Having an opinion that's relevant to the type of bike the guy was asking about isn't attacking anybody.

And don't get me wrong, I'm as much into weight forward wheelie reduction as anybody...I just like it forward and medium low, not really low. 👍

 
I found this frame that will work with a 72 volt 25 amp hour battery.
 

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I'd make it an upside down U shape and put it at #3 wrapping around the sides and down. #4 can be useful too depending on the physical length of the strings. You have a lot of space at #3, but be careful about getting too much weight concentrated up high, as it can make it very unstable on the kickstand. I had one quite small dual suspension ebike with 440 18650 cells (20s22p) mounted mostly at #3 and #4 as well as on the sides inbetween 3&4 and the bike handled fine despite all that weight. It has 20s8p at 3 20s6p at 4 and 2 strings of 20s2p on each side.

If major chunks of the total pack are already assembled, then take some duct tape and try it out with the pack secured in different locations to see what you like best.
 
Welllllll. I would NOT put 25 ah on that frame. That's a whopper of a battery, and it needs a big ass triangle just for half of it.

If I had to do it on that frame, split pack for sure. 72v 10 ah in each pannier bag or box, and if you must carry the other 5 ah, maybe on the bars to help with wheelies.

For off road riding,, completely different needs for handling. 72v 10 ah at most, in pannier style boxes, one on each side of the frame center. So like two 36v 10 ah packs. Then the bms can ride the top bar. It will make pedaling near impossible, but who cares? this is a bike I rode years ago, on 72v 10 ah lipo. 2812%209c%20dirtbike,%20w%2040%20amp%2072v%20controller..JPG
 
Thanks for the insight guys.

The overall conclusion seems to be 3/4 but as much weight low and to the front as poss

Maybe buying a 29’ or 27.5’ wheel frame then putting 26’ or even 24’ wheels on would give enough space low and forward?
 
Then you'll be getting lots of pedal strikes as the bottom bracket will be closer to the ground. Just wondering, are you actually going to be trail riding, or making a pavement burner?
 
Too many cells, but a combination of #4 and inside the frame

Also do you own that bike? Black diamond is a much better candidate for that kind of build, what you have is the low travel less beefy xc model, teocali

I have almost the same build already completed
 
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