72v Build help…

Joined
Oct 2, 2022
Messages
19
Location
Olean NY
So I think I got in over my head. I got talked into a 72v (19.2ah allegedly) UPP battery and a 2000w 45a motor by the sales people assuring me this was the way to go. I built it on a 29” Schwinn Axum bike. I posted on electricbikereview forums and they sent me here. I see the controller on 25a and I do my best to keep the watts to under 1500-2000. Max speed is generally 25-30. I recently hid the wires in a bag as someone suggested for protection and looks but then was told this is a no no. Any advice would be greatly appreciated! I’m wondering if I should try to sell this and get a 52v battery if I can afford it. I’m not worried about longevity over 8-12 months at this point bebaust by then I’ll have a car again and this is my transport for now. My commute is between 3.1-5 miles depending if I’m going to work or the store.
I realize I probably made a mistake but am trying to salvage all I can.323204CC-6CEF-4B7B-B63B-5376266F13DD.jpegD898953A-E286-489F-9514-7D5AF135A670.jpeg57DA17D6-021F-400B-82B2-ED3741B4AD1B.jpeg
 
sweettrade324 said:
So I think I got in over my head. I got talked into a 72v (19.2ah allegedly) UPP battery and a 2000w 45a motor by the sales people assuring me this was the way to go. I built it on a 29” Schwinn Axum bike. I posted on electricbikereview forums and they sent me here. I see the controller on 25a and I do my best to keep the watts to under 1500-2000. Max speed is generally 25-30. I recently hid the wires in a bag as someone suggested for protection and looks but then was told this is a no no. Any advice would be greatly appreciated! I’m wondering if I should try to sell this and get a 52v battery if I can afford it. I’m not worried about longevity over 8-12 months at this point bebaust by then I’ll have a car again and this is my transport for now. My commute is between 3.1-5 miles depending if I’m going to work or the store.
I realize I probably made a mistake but am trying to salvage all I can.323204CC-6CEF-4B7B-B63B-5376266F13DD.jpegD898953A-E286-489F-9514-7D5AF135A670.jpeg57DA17D6-021F-400B-82B2-ED3741B4AD1B.jpeg

Is there something wrong with the bike now, after you hid the wires? Hiding the wires is fine, but putting the controller (the silver box) inside of a bag isn't a good idea, since it needs air flow to keep it cool. If it's still working, then just make sure the controller isn't in the bag, or at least gets some air flow, by keeping the bag open and checking if it gets hot.

EDIT: I see you pics now. Just pull the controller out of the bag and zip tie it in the same place.

Bike looks good/fun. Consider a good suspension seat post if you end up keeping it.
 
The controller will be ok if it gets wet? Thought part of the reason of the bag was to protect it from water and whatnot. I coated the controller in ACF50 to be safe but am worried
 
Your bike looks good. A few changes is all it needs.

Controllers are water resistant, not water proof. I never liked having mine in a place where the wheel will splatter it with water. IMO you would be better off moving it some place where it is harder to get wet like higher up on the frame or maybe behind the seat. In any case, controllers need air flow across them to keep cool.

Also, consider some sort of fenders.

If you wires are all over the place consider shorting them. Or, bundling them up and putting them in a bag. Nothing wrong with putting wires in a bag.

:D :bolt:
 
We thought he might revisit the wiring AWG. And sent him here to a better brain trust of builders.
 
e-beach said:
Also, consider some sort of fenders

If you wires are all over the place consider shorting them. Or, bundling them up and putting them in a bag. Nothing wrong with putting wires in a bag.

:D :bolt:
I have fenders coming tomorrow. I will consider getting a xt60 extension to move the controller (good place to get one?). Excuse the noob question but to short the wires? Would I have to redo all the connectors or could I cut them and splice them?
 
sweettrade324 said:
......Excuse the noob question but to short the wires? Would I have to redo all the connectors or could I cut them and splice them?

To cut sections out of the cables and re-solder and add shrink wrap is fine. Just don't get the splices too wet. Getting new connectors and applying them is the preferred way. New connectors takes a little more skill, but from your build, it looks like you have the chops to do it.

Or simply wrap and enclose your existing cables until in a you gain more confidence in e-bike building.

:D :bolt:
 
sweettrade324 said:
e-beach said:
Also, consider some sort of fenders

If you wires are all over the place consider shorting them. Or, bundling them up and putting them in a bag. Nothing wrong with putting wires in a bag.

:D :bolt:
I have fenders coming tomorrow. I will consider getting a xt60 extension to move the controller (good place to get one?). Excuse the noob question but to short the wires? Would I have to redo all the connectors or could I cut them and splice them?

If you move the battery forward, would you have enough room between it and the seat tube to get it mounted within the triangle? You might not need an extension.
 
[/quote]
I have fenders coming tomorrow. I will consider getting a xt60 extension to move the controller (good place to get one?). Excuse the noob question but to short the wires? Would I have to redo all the connectors or could I cut them and splice them?
[/quote]

If you move the battery forward, would you have enough room between it and the seat tube to get it mounted within the triangle? You might not need an extension.
[/quote]
Unfortunately I do not. It’s too pinched in the front. Good idea though.
 
Curious on the groups opinion if I have enough with one grin tech v4 torque arm or should invest in a second. It’s a 72v 2000w 45a controller (set to 30). Bike is a Schwinn Axum 29” aluminum mtb. E36B9A36-F7C5-4A7F-9E3C-04F7AE0E1D93.jpeg 4D824CF6-8503-415C-B6B7-F68EF9871DF2.jpeg
 
amazon for quick ship pigtails.
https://www.amazon.com/s?k=xt90+pigtail+10awg&crid=154DVBYII9FRY&sprefix=xt90+pigtails%2Caps%2C104&ref=nb_sb_ss_deep-retrain-0-ops-acceptance_1_13
 
I'm a two-arm Grin guy on ALL hubs. IMO it's a wise move. Especially with your 2000W setup.
 
That 1st torque arm configuration looks pretty dodgy. Look at it carefully and imagine the forces at play. Those metal clamp are not really working at keeping that torque arm from swinging away. They are are keeping it from sliding away.

torque_arm.jpg
 
Comrade said:
That 1st torque arm configuration looks pretty dodgy. Look at it carefully and imagine the forces at play. Those metal clamp are not really working at keeping that torque arm from swinging away. They are are keeping it from sliding away.

torque_arm.jpg
How else could I mount it? Or should I find a different type?
 
I think two just as you have them will be fine.
 
sweettrade324 said:
How else could I mount it? Or should I find a different type?

Unbolt the second part of the torque arm that's under the metal band clamps, and swing the part that's on the axle until it hits the frame? It's tough to see from a 2D picture how well the frame will keep it from spinning in the direction of the red arrows. Might need to get rid of the kickstand.

I would have designed my own. Something like this. Laser metal cutting is so cheap, that you could cut a dozen custom ones for the price of one Grin.

custom_torque_arm.png
 
sweettrade324 said:
Curious on the groups opinion if I have enough with one grin tech v4 torque arm or should invest in a second. It’s a 72v 2000w 45a controller (set to 30). Bike is a Schwinn Axum 29” aluminum mtb.
Do you use regen braking?

Is the TA a tight fit on the axle? Or was it easy to slip onto the axle, maybe some slop?

As mentioned above, take some time and imagine the forces the axle presents to the dropout.

Under forward power, the axle will to try to spin backwards, in the opposite direction of the wheel spinning.

Make sure the TA is fastened and clamped to keep the axle from spinning in that direction.

Under regen the axle will try to spin in the same direction as the wheel forward direction. That is primarily the reason for the second TA, to be fastened and clamped to stop the axle from spinning in the other direction.
 
sweettrade324 said:
Excuse the noob question but to short the wires? Would I have to redo all the connectors or could I cut them and splice them?
Betting that was a typo, probably should have been "shorten" the wires.

It looks like you have gathered and folded up the excessive length wires into the bag? Generally no problem with this. A benefit would be possible easier adaptation for a later swap out to another bike if desired.
 
sweettrade324 said:
So I think I got in over my head. I got talked into a 72v (19.2ah allegedly) UPP battery and a 2000w 45a motor by the sales people assuring me this was the way to go. I built it on a 29” Schwinn Axum bike. I posted on electricbikereview forums and they sent me here. I see the controller on 25a and I do my best to keep the watts to under 1500-2000. Max speed is generally 25-30. I recently hid the wires in a bag as someone suggested for protection and looks but then was told this is a no no. Any advice would be greatly appreciated! I’m wondering if I should try to sell this and get a 52v battery if I can afford it. I’m not worried about longevity over 8-12 months at this point bebaust by then I’ll have a car again and this is my transport for now. My commute is between 3.1-5 miles depending if I’m going to work or the store.
I realize I probably made a mistake but am trying to salvage all I can.


What doesn't work in your system, or what doesn't it do that you want it to do, that you want to change?

If you can tell us that, we can tell you what to do to achieve that.
 
Comrade said:
They are are keeping it from sliding away.

torque_arm.jpg

Not really. If you put the hose clamps in the end of the slots like he did with one of them, it will keep the TA from sliding backwards. It looks like the rear hose clamp won't be able to slide because of where it's placed.

However it never hurts to have two torque arms just in case.
 
tomjasz said:
I'm a two-arm Grin guy on ALL hubs. IMO it's a wise move.

Same here. Its cheap enough, and the consequences are bad enough, that the small amount of extra effort is well worth the added insurance policy..
 
nicobie said:
Not really.

They really are. I didn't say it will slide away. Those stainless clamps will get good bite into that aluminum frame. :lol:
 
999zip999 said:
Yes on two T.A.
What motor is that ? Link.

It’s on Alibaba app this is the best I can do. It seemed the same as a Amazon motor but cheaper… that’s not the actual price bit for the 1500w one. reviews seemed good so we will see.0EC9F812-22B1-4AB2-841D-29EE75CBBA71.png
 
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