Real wheel conversion with aluminium frame

[stefandeml]

Hello everyone,

I'm thinking of converting my gravel bike with a bafang 500w real wheel motor.
Looking the mount on the real wheel let me start wondering if this conversion is really sustainable.
Do you guys have experience with attaching a 500w (45Nm) motor on those aluminium break-outs?
Aluminium is quite soft as material so I fear that those mounts might wear out quite quickly.

Thanks!
Stefan

 

[Scruffydroid]

It'll be fine. I converted my ally with a 1500w rear hub motor.

 

[sjpt]

You'd probably be better off with a nominal 250w one to keep it legal. Most have torque ratings higher than 45Nm anyway. Either way you should be fine with torque arms.

e.g. https://wooshbikes.co.uk/?hubkits#swx02-48v-kit claims 60Nm

 

[stefandeml]

Thank you a lot!

A quick follow up question:
do you know if a small 48v 6ah battery (like this one) can be used to power the 500W motor?
The battery is specified with a 500W power rating .. so in theory should be good..

 

[Nealh]

Thank you a lot!

A quick follow up question:
do you know if a small 48v 6ah battery (like this one) can be used to power the 500W motor?
The battery is specified with a 500W power rating .. so in theory should be good..

It's not whether the battery can power it because it can. The question should be asked is, can the battery continuous current rating provide more power for the max current draw of the controller.

The battery in the link is only 15a continuous rated, ignore the red herring of 45a max instantaneous current. For a battery ideally one needs a continuous current rating that is higher then the controller rating.

 

[stefandeml]

It's not whether the battery can power it because it can. The question should be asked is, can the battery continuous current rating provide more power for the max current draw of the controller.

The battery in the link is only 15a continuous rated, ignore the red herring of 45a max instantaneous current. For a battery ideally one needs a continuous current rating that is higher then the controller rating.

Thanks.
I'm looking into this kit.
500/48 => 11Amps should be the controller draw, but maybe you guys know more?
13s2p seams to really be on the lower end of the spectrum, so I might go with a 13s3p package to be safe.

A quick OT question:
how the hell can some 13s3p battery packages like this come with 100Ah rating?
Anyone has a link to a thread here in forum with some recommendations for legit sellers?

 

[Nealh]

Controller rating with that kit is 18a +/- 1a so one needs a battery ideally with a 20 - 25a continuous rating.

One has to be wary of china battery claims of 100ah, they will be false and misleading. Buy cheap one could be buying twice if not 100% sure of the product.
For 13s3p the max for 18650 cells is 10.4ah and for 21700 max is currently 15ah.

 

[stefandeml]

Controller rating with that kit is 18a +/- 1a so one needs a battery ideally with a 20 - 25a continuous rating.

One has to be wary of china battery claims of 100ah, they will be false and misleading. Buy cheap one could be buying twice if not 100% sure of the product.
For 13s3p the max for 18650 cells is 10.4ah and for 21700 max is currently 15ah.

Okay, thank you very much.
But that would mean one needs at least a 13s4p (or even better 13s5p) battery for that motor?

 

[Benjahmin]

Ignore the motor rating, it is meaning less in this context, the motor will take what the controller gives to it, providing the battery is capable of delivering it.
So look to the controller maximum current, this is what the battery needs to supply.
So, as said, if controller is rated 18A (which will be the maximum, continuous will be lower), you need a battery capable of 20-15A continuous so as to not stress the cells and cause voltage sag - so shortening the life of the battery.
The Ah rating is the capacity of the battery. Don't confuse the two.

 

[Nealh]

Okay, thank you very much.
But that would mean one needs at least a 13s4p (or even better 13s5p) battery for that motor?

No.
You can run it on 13s1p or 13s2p if the chosen cell is right, so a LG 3000mah 20a Hg2 or a Sony vtc5/6 would have enough power.
I run a 12s2p in a Ali drinks bottle using HG2, for up to 30 miles on low power.

A motor rating as said is a bit meaningless for geared hubs, the important bits are the controller current rating and a battery that can output above the controller rating so cell config or cell choice is important.
If one used a 21700 cell of 3000/4000mah with a 40a rating it would supply enough power but not for many miles.

 

[Nealh]

Hello everyone,

I'm thinking of converting my gravel bike with a bafang 500w real wheel motor.
Looking the mount on the real wheel let me start wondering if this conversion is really sustainable.
Do you guys have experience with attaching a 500w (45Nm) motor on those aluminium break-outs?
Aluminium is quite soft as material so I fear that those mounts might wear out quite quickly.

Thanks!
Stefan

Have torque arms been fitted ?