500W kits .....36V or 48V ?

freddofrog

Pedelecer
Jan 6, 2012
64
14
East Midlands
As I intend to be building something that's not restricted to 15 mph, I thought that I'd ask the question in this section of the forum.

I already have a 250W Izip with a 36V battery, and although the battery is now 3 years old, I have always looked after it and it still seems to have a good % of its original A-h

I want to convert a standard mountain bike and I'm thinking of getting a 500W kit, but I don't know whether to get 36V or 48V. I am leaning towards the 36V, but mainly because of the 36V battery that I have.

What are the advantages of 48V on a 500W kit ?
 
D

Deleted member 4366

Guest
Your 36v battery wouldn't be able to supply enough power even when it was new. You will send it to an early grave if you connect it to a 500w controller -that's if the BMS doesn't trip.

My advice is to get one of those 48v 09 bottle batteries with the included 20A sinewave controllers. It goes nicely with the 260 rpm 48v 500w BPM or the 36v 201 rpm Q128H.
 
D

Deleted member 4366

Guest
If you run a 36v motor at 48v, it goes 33% faster, so a 201 rpm one becomes 260 rpm. The Q128H is lighter than the BPM. It's smaller, but spins faster internally and has a greater reduction ratio, so it still makes high torque. I'm just waiting for one to come from BMSBattery. Then I'll be able to tell you exactly how it performs.

The 260 rpm 36v BPM at 30 amps with a 36v battery will perform the same as a 260 rpm 48v one at about 23 amps with a 48v battery. When you increase the voltage, the torque and speed both increase more or less in proportion, so you have to be aware of what exactly the speed of your motor isvat any given voltage. If you make your motor go too fast for its power, it will run inefficiently. A 250w motor is OK up to about 20 mph, 500w up to 25 mph and 1000w for 30mph. It's not an exact dcience though because there's do many other variables.
 
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freddofrog

Pedelecer
Jan 6, 2012
64
14
East Midlands
I'm a bit confused, possibly by what I mean as a "kit"

From what you're saying, for top speed, a 500W 36V motor with a 48V battery and appropriate controller will go faster (for obvious reasons), but some "kits" come with a battery, and some without.

If I buy a 500W kit that has a 48V motor and includes a 48V battery and appropriate controller, why would this be any better than a 500W kit that has a 36V motor and includes a 36V battery and appropriate controller ?
 

freddofrog

Pedelecer
Jan 6, 2012
64
14
East Midlands
The 260 rpm 36v BPM at 30 amps with a 36v battery will perform the same as a 260 rpm 48v one at about 23 amps with a 48v battery. When you increase the voltage, the torque and speed both increase more or less in proportion, so you have to be aware of what exactly the speed of your motor isvat any given voltage. If you make your motor go too fast for its power, it will run inefficiently. A 250w motor is OK up to about 20 mph, 500w up to 25 mph and 1000w for 30mph. It's not an exact dcience though because there's do many other variables.
ahhh that answers my question quite nicely in the second paragraph above which you added in #4 while I was typing #5 LOL
 
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appyarry

Pedelecer
Mar 16, 2015
40
13
66
Lyminge, Kent
Does this mean I would be better buying a 36 V motor but running 48V with a good controller and ensuring I only run the motor at the peak efficiency (RPM) rather than buy a 48 volt motor and battery.
Sorry if it is a silly question, I'm not up to speed with all the permutations, yet :)
Ta,
 
D

Deleted member 4366

Guest
You get more power with 48v, but you have to be mindful of the speed. A 36v motor will spin 33% faster at 48v, but you can lose torque and efficiency if you make a motor spin too fast for its power, which not only wastes battery, but it can overheat your motor.
 

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