DC voltage amplifier question

Thread Starter

Csecrist12

Joined Nov 1, 2019
15
As I am new to the electronics world, I have an opportunity at hand. I'm currently building and electric motorcycle that includes the existing transmission. There is a local that is selling a 2.75 hp, treadmill motor that I believe would be a good fit for my application since treadmill motors are used to being turned on for a consistent amount of time (my assumption). Only issue is, it requires a 130v power system and to carry 130v worth of batteries on a motorcycle may be a bit over kill and weigh down the bike significantly. Would it be possibly to have a lower battery voltage run through an amplifier to achieve the desired voltage of the DC motor? Again, I'm still new to dealing with electronics. My apologizes in advanced, sincerely.
 

crutschow

Joined Mar 14, 2008
23,527
You could use a switch-mode power supply (SMPS) to increase the battery voltage to the motor.
Note that the battery current will then increase by the ratio of the output voltage to the battery voltage, so the battery must be sized for that.
 

Thread Starter

Csecrist12

Joined Nov 1, 2019
15
I appreciate the reply. Where would I find the SMPS? What battery size would be needed for sure a setup with this motor? Would supplying the name plate of the motor better help with this question?
 

Thread Starter

Csecrist12

Joined Nov 1, 2019
15
How would this affect the battery drainage? Would this be directly off the controller going into the motor? Would the controller function as normal with the SMPS? I guess, how would I add this into the total build of an electric motorcycle as, obvious, I would have the battery pack, controller to apply different speeds to the motor and the electronics ran off the battery pack (lights, dash, etc.).

Would this be what I'm looking for?
https://www.mouser.com/ProductDetail/MEAN-WELL/ERDN20-48?qs=sGAEpiMZZMvGsmoEFRKS8Fb388U/tE5%2BqZSKj2nw0bbCNCUvvcq0ng==
 

Chris65536

Joined Nov 11, 2019
57
That MEAN WELL converter is really just a redundancy switch, and input and output voltage are the same. But I don't think a SWPS is a great idea for an electric vehicle. It will add weight and reduce efficiency. I also don't think 130V is out of the question for an EV battery. More voltage means less amps, and less copper. I would like to see the data plate from your motor. I thought treadmills were usually 90VDC?
 

Thread Starter

Csecrist12

Joined Nov 1, 2019
15
He has a few motors, but here are the name plates for those. What would you recommend as I'm wanting a 48V system to power everything, controller, lights, motor, but would like to have a 2-3 hp electric motor that I could pick up for fairly cheap rather than a brand new one that's expensive.
 

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Chris65536

Joined Nov 11, 2019
57
He has a few motors, but here are the name plates for those. What would you recommend as I'm wanting a 48V system to power everything, controller, lights, motor, but would like to have a 2-3 hp electric motor that I could pick up for fairly cheap rather than a brand new one that's expensive.
I googled, but couldn't find any DC-DC converters with an output voltage over 48V or power over 1000W. The big ones start to get expensive too. I think your best bet is to get a lower voltage motor, or a higher voltage battery.
 

Thread Starter

Csecrist12

Joined Nov 1, 2019
15
How come the DC to DC converter isn't a good idea? Whats 5 pounds added to the bike with over 300-500 total pounds, a fraction of what the bike weighs.
 

Chris65536

Joined Nov 11, 2019
57
How come the DC to DC converter isn't a good idea? Whats 5 pounds added to the bike with over 300-500 total pounds, a fraction of what the bike weighs.
It could work, but I couldn't find anything that meets your voltage or power requirements. And at 2,000W+, it might weigh more than 5 pounds too. Let us know if you can find anything. I don't know a lot about EV conversions. Maybe they have step-up motor controllers for this purpose?
 

Thread Starter

Csecrist12

Joined Nov 1, 2019
15
It could work, but I couldn't find anything that meets your voltage or power requirements. And at 2,000W+, it might weigh more than 5 pounds too. Let us know if you can find anything. I don't know a lot about EV conversions. Maybe they have step-up motor controllers for this purpose?
I'm not too familiar with most of this as of yet, but was just curious if it was possible to use such motors that I have attached prior and match it with a 48V system and if so, how do I do so and what advantages and drawbacks would I be looking at?
 

drc_567

Joined Dec 29, 2008
735
In order to obtain 2.75 hp from a 12 volt battery, you would have to get approximately 156 DC amps ( There are about 750 or so watts per each horsepower. )... continuously from that 12 volt battery. A current drain of that magnitude would empty a 500 AH battery completely in about 3 hours ... in practical use, maybe less than 1 hour, depending on the specific battery type.
A big question is how much storage battery capacity are you able to carry on your electric bike? ... One 12 volt battery does not seem like it would carry you very far, operating at 2.75 hp. ... That is, assuming there was a practical method of going from the 12 volt battery voltage to the 100 volt or so motor voltage.
Would it be possible to go to a 24 volt system, using two 12 volt batteries in series?
 

Thread Starter

Csecrist12

Joined Nov 1, 2019
15
In order to obtain 2.75 hp from a 12 volt battery, you would have to get approximately 156 DC amps ( There are about 750 or so watts per each horsepower. )... continuously from that 12 volt battery. A current drain of that magnitude would empty a 500 AH battery completely in about 3 hours ... in practical use, maybe less than 1 hour, depending on the specific battery type.
A big question is how much storage battery capacity are you able to carry on your electric bike? ... One 12 volt battery does not seem like it would carry you very far, operating at 2.75 hp. ... That is, assuming there was a practical method of going from the 12 volt battery voltage to the 100 volt or so motor voltage.
Would it be possible to go to a 24 volt system, using two 12 volt batteries in series?
I greatly appreciate your response and reality outlook on this project. I'm wanting to have a 48V Lithium system with this bike. I have the controller and batteries picked out (to the best of knowledge).
Controller: https://www.aliexpress.com/item/32892087061.html
Battery Pack: https://solargeni.com/headway-38120s-hp-lifepo4-battery-cell-holder-straps-diy-powerwall-ham-radio-car-audio-battery-competition-ebike-solargeni-westhattechguy-hometechpower-home-tech-power-lithium-li-ion-charger-bms-3s-4s-6s-7s-12s-8s-16s-15s-13s-20s-series-parallel

I cant remember the configuration of the batteries, I berlieve a 15s4p would give me 48V with 40AH if I'm not mistaken.
 

drc_567

Joined Dec 29, 2008
735
With only 40 AH of battery energy storage, it does not seem practical to use the 2.75 hp motor. A fractional hp motor, if you can find one, would at least allow some modest distance to be traveled, although at limited speed.
 

Chris65536

Joined Nov 11, 2019
57
I cant remember the configuration of the batteries, I berlieve a 15s4p would give me 48V with 40AH if I'm not mistaken.
That battery sounds good, but that controller is for a brushless motor. I believe that means the commutator function is in the controller, and it won't work with a regular DC motor. I am not positive though.
 

Thread Starter

Csecrist12

Joined Nov 1, 2019
15
With only 40 AH of battery energy storage, it does not seem practical to use the 2.75 hp motor. A fractional hp motor, if you can find one, would at least allow some modest distance to be traveled, although at limited speed.
What battery system would you recommend for such motor? Or simply put, for the application. What motor would be recommended for such an application with a transmission included?

I have attached my testing setup I currently have. If you know anything about motors, I just attached a small electric razor dirt bike motor onto the crank shaft by the cam chain while taking out the pistons so there isn't much friction.

Thoughts?
 

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drc_567

Joined Dec 29, 2008
735
... Looking at possible motors, besides operating voltage, the wattage or horsepower number is important. The greater the watts, the faster the battery is drained. ... It seems like 40 AH is not really enough. Even a fractional Hp motor would not provide much travel distance. You really need something like 400 AH.
 

Thread Starter

Csecrist12

Joined Nov 1, 2019
15
... Looking at possible motors, besides operating voltage, the wattage or horsepower number is important. The greater the watts, the faster the battery is drained. ... It seems like 40 AH is not really enough. Even a fractional Hp motor would not provide much travel distance. You really need something like 400 AH.
What battery set up would you recommend that would work with a controller on this setup? Basically if we can determine the battery setup, match a motor and controller to that and it's a matter of putting the components together.
 
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