Having a front hub motor and a rear hub motor on the same bike ?

[Fergatron]

I currently race around the place on a 2020 Carrera Vengeance E-spec which runs off a Suntour rear hub motor. Although this is fine for me the options for upgrading the current Suntour HESC system are next to none without some serious overhaul. Id love to be able to have a throttle and the range on it is quite poor (flashes low battery after 15 miles even though it states can go up to 40 haha yeah right). My brilliant idea which I am sure has no flaws and will go completely smooth is to install a second kit on to the bike and have a front hub motor and a second battery with controller and display essentially having 2 entire E-bike kits on the one bike. I know its going to weigh a tonne and it may be a little bit ugly but I reckon its the option for me. I hope to mount the second battery on my pannier rack or possibly even the top tube depending on size and cable lengths. The kit id like to install is the Dillinger street legal electric bike kit: https://dillengerelectricbikes.co.uk/collections/e-bike-conversion-kits/products/street-legal-electric-bike-kit-samsung-powered-v2?variant=32803935977604

Would love some feedback and thoughts as to whether this could be a game changer. Double the battery, double the motor, double the fun... I hope

 

[egroover]

that kit was never £1099, so ignore the '£400 saving'

 

[RobN]

see if you can get one large battery made rather than having 2 separate ones if it works?
Sounds like a good plan

 

[Sturmey]

I am running a similar setup at present with a rear yosepower 350w 280rpm with lcd3 and pas only (torque simulation) and 16 ah battery. (36v)
On the front, I have a xf07 240rpm with no lcd or pas with 11 ah battery, fitted to a steel non suspension front fork.(throttle only+ kill switch only extra on handlebars). The motors run independently.
It runs very well and has given good service (other than rim wear) with nearly 21,000Km (twice round the clock) and 900 hours on clock.
It's especially good on hills and against strong winds.
It would be better if the front wheel was a little faster to match the rear motor. (240 >>>280 rpm)
The additional motor and battery adds about 7kg. The front motor seems to balance the bike, so generally the weight is not a huge problem except when you have to lift the bike or get the bike over a stile etc.
In your own case, I would check as to whether the front fork is strong enough to support the motor. Others might advise you on this.

 

[vfr400]

It'll be fine if it's just torque you want. You might get a couple of MPH more from the front motor if you set the speed unlimited. Don't expect to ride everywhere at 20 mph. The Dillenger motor will be on its own after 15 mph, so you'll only get 20 mph downhill, and maybe 18mph on the flat, but you'll be able to hold 15 mph up most hills.

I would have thought that a kit with a rack battery would have been better.

I made several double motor ebikes and one with three motors. It was good to do them as experiments, but I concluded that one powerful rear motor is better than two smaller ones unless you want to do extreme off-road cycling or ride in the snow.

Your motor can give quite a bit more power than what the tiny Suntour (actually Santroll) controller allows. Another option, which is cheaper, nicer looking (neater), more reliable and a lot more convenient would be to replace the controller and battery with a standard Chinese 48V set, which would only cost about £500. You'd get more speed, more power above 15 mph and at least 30% more power for hill-climbing thn you presently have, which is enough for most people, or you can go a bit higher on current to say18 amps, which would give 56% more power.

 

[PC2017]

I have a xf07 240rpm with no lcd or pas

I would be interested in hearing about your experience with this motor as a independent motor. Putting your extra weight and rear motor to one side, what battery voltage are you using? is that a 26" wheel? and any ball park figures for up steep hill speed and top speed with and without pedalling?

 

[sjpt]

I have a xf07 240rpm with no lcd or pas
I would be interested in hearing about your experience with this motor as a independent motor.

We have an XF07 on our tandem. Currently at 3 years/3000 miles without problems. It is slightly underpowered for the tandem (we were warned at the time but there was very little legal choice with 700c wheels when we chose it).

It gives us a big boost on the hills, but we still need low gears and quite a bit of our work. On the rare occasions I ride it solo I notice that it is quite sprightly.

To see how it might behave for you with different batteries/controllers see

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

ebikes.ca

 

[PC2017]

To see how it might behave for you with different batteries/controllers see

Yes the I have dipped my toe in the water that is the ebike.ca sim. I have a vague idea at what I am looking at graph wise, however the controller list and battery drop downs perplex me, I usually select the 48v downtube battery but why there is so many to select when the custom option only has 3 variables and AH has no bearing on performance a part from range. What would a custom inputs for a 48v/14a controller controller look like?

Battery Current Limit (A) assuming 20-25a max continuous (the average low end battery like mine)
Phase Current Limit (A) yep not even gona guess that one

Effective Resistance (Ω) yep no... gives us a hint??

OP - Apologies for hijacking the thread...

 

[vfr400]

Yes the I have dipped my toe in the water that is the ebike.ca sim. I have a vague idea at what I am looking at graph wise, however the controller list and battery drop downs perplex me, I usually select the 48v downtube battery but why there is so many to select when the custom option only has 3 variables and AH has no bearing on performance a part from range. What would a custom inputs for a 48v/14a controller controller look like?

Battery Current Limit (A) assuming 20-25a max continuous (the average low end battery like mine)
Phase Current Limit (A) yep not even gona guess that one

Effective Resistance (Ω) yep no... gives us a hint??

OP - Apologies for hijacking the thread...

The simulator is just a mathematical model based on how a few motors behave. The XF07 predictions won't be accurate. Here's what I found out from MXUS and my own trials:

They make different versions of the motor for different markets.
Mine was nice and quiet and not particularly powerful.
The internal reduction ratio of about 5:1 means that you're not going to get good torque considering its size.
Mine was sort of OK at 36v and 17A. When run at higher current, there was hardly any difference except the motor got warmer.
When I ran at 48v, there was no significant step in performance like you get with other motors, and it got hot on hills.
For reference, I was 100kg at the time and my rides are hilly.


In summary, if you want to run with 20 -25A, you'd be much better of with a Q128H or a Bafang SWX02 or Bafang CST. The Q128C is quite good at 48v too as long as you're not looking for a winch.

 

[StuartsProjects]

For the UK, is an eBike with two 250W motors, street legal ?

 

[flecc]

For the UK, is an eBike with two 250W motors, street legal ?

.
No.

You can have as many motors as you like, but their total rating cannot exceed 250 watts.
.

 

[vfr400]

For the UK, is an eBike with two 250W motors, street legal ?

Strictly speeaking, no because the law refers to "a motor", not "motors". You might get away with it if there were some sort of isolation device that would conclusively prevent both motors from working at the same time. Also,you could probably get away with it if you were using two motor with a total rating of 250.

The honest truth is that nobody is checking. nobody has been prosecuted and nobody has sued anyone, but there's always a first time. The chance of it being you is not very high.

As I said before, you can get a legal Woosh 48v SWX02 kit, which will have enough power for just about anyone. Any more than that seems pointless to me unless you have exceptional circumstances.

 

[Sturmey]

I would be interested in hearing about your experience with this motor as a independent motor. Putting your extra weight and rear motor to one side, what battery voltage are you using? is that a 26" wheel? and any ball park figures for up steep hill speed and top speed with and without pedalling?

Climbing 10% hills at 20km/hr is easily achievable and is consistent with what would be expected with simulator. ( I am about 90Kg, bike 30kg and has 700c wheels).

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

ebikes.ca

Grin technologies (usa)has a discussion on multiple motors below.

Look, dual motors are not the ideal. But I live beside some very steep hills/mountains and this arrangement works well and is very robust. To replace this, I would probably need something like a Bafang BBSHD with some of its disadvantages or some heavy duty hub with at least 65nm rating.

 

[flecc]

Strictly speaking, no because the law refers to "a motor", not "motors".

Not so, the use of the singular has no meaning in this context, it is not limiting law. There are precedents, for example both versions of SRAM's Sparc e-bike motor have two motors. The only thing that matters is the 250 watt legal rating of the cycle, which should be stated as part of the required information on a plate on the cycle, not on motors.

Equally the law refers to "the battery" in the singular, but as we know legal pedelecs sometimes have more than one battery.
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