Will a bigger motor solve my problems or cause more??

Joined
Aug 20, 2017
Messages
14
HI,

I have a 24v 250 watt system... I have two 10ah li-ion batteries that swap interchangeably. I have been using this rig believe it or not to haul a little trailer with gardening materials (usually trays of small annuals and pots less than 6"). It preforms beautifully unless I demand that it go up hill a bit w/ the throttle engaged beyond the default PAS.

I found a 450w motor with seemingly the same bolt pattern for mounting and specs that should be within the scope of the stock controller/ battery but I am wondering if installing it will help at all????? The guy at the local e bike store says my controller is the limiting factor and that a larger motor will not help. The customer service lady at the scooter parts place says a larger motor will give me a boost. I have a feeling that because both answers come from sales reps rather than mechanics or engineers they may be underinformed.

I guess my question is:

When my bike motor cuts out before the battery is empty and won't be restarted for a few minutes, is it because . . .

A. the controller senses that the battery is being over drawn?

B. the controller senses that the motor or controller is over temp?

C. the motor itself cuts at a certain temp?

D. I am asking outmoded technology to do more than it was ever intended to. Be grateful for the 8mph governor it may slow me down enough to keep me alive in traffic. :roll:

Thanks
 
Welcome to the forum. Lots of possibilities, and probably more info and pictures will be needed to help you sort it out, but my first guess is that the controller has a temp sensor that shuts it down to avoid damage. My earliest setup would do what you describe, no PAS, but when pushing a little too hard up hill would quit and I had to wait several minutes until it cooled a little before it would work again. After it cooled I had to disconnect or switch the power off and then back on to reset the controller.

Even though a battery BMS or a controller low voltage cutoff can shut you down, in my experience there was no wait required before they either reset themselves or I could reset them since the battery voltage increased very quickly once there was no load on it.

Edit: When my motor/controller got too hot and cut out it was mainly because I was just pushing it too hard. The solution was to ease back on the throttle and add more energy to the pedals, which would allow me to get up the same hill a little slower but without over heating anything.
 
Thanks. Your answer is very reasonable.

What information should I post to help whittle this problem down????
 
My first suggestion would be to carefully feel the controller and motor the next time it happens. If it is very hot, i.e., you can't keep your hand on it, then overheating is probably the problem. Don't burn yourself. :D

If it is overheating, then a discussion would be in order as to how to eliminate the problem. If it isn't overheating, then a discussion would be in order to determine what is happening, such as using an inline watt meter.

The additional information needed in most cases would include the battery chemistry and BMS info. The motor specifics including hub motor or mid-motor etc., motor brand, winding, brushed/brushless. Total weight of bike and cargo, and drive wheel size. In other words, anything that helps define the system you have. From your first post I would guess you have a non-hub motor mounted to drive a wheel with a chain or something, maybe even a friction drive, but don't make us guess what the gearing and rpm etc. are, and of course a picture can help us visualize it.
 
What is your battery setup?
Lead Acid Batteries, LiPo, Lithium Ion

I assume you want to keep your battery for some $aving$ so just wondering if you can take 12V and add it to the 24V to make 36V, then you could go to BMS Battery and buy a 500W motor
https://bmsbattery.com/44-36v?id_category=44&n=16

then a controller
https://bmsbattery.com/46-sine-wave?id_category=46&n=16

then the KT Display
https://bmsbattery.com/51-lcdled-display

then some torque arms
https://bmsbattery.com/ebike-parts/450-a-pair-of-ebike-torque-arm-parts.html?search_query=torque+arms&results=86

Cant find the cutoff brake levers but they come in the kit.
 
Thanks again for helping. Here is what I could come up with:

Rassy said:
My first suggestion would be to carefully feel the controller and motor the next time it happens. If it is very hot, i.e., you can't keep your hand on it, then overheating is probably the problem. Don't burn yourself. :D

The motor is def very hot every time the bike conks out. I have not felt the controller cause it is enclosed under the bottom bracket.

If it is overheating, then a discussion would be in order as to how to eliminate the problem. If it isn't overheating, then a discussion would be in order to determine what is happening, such as using an inline watt meter.

The additional information needed in most cases would include the

battery chemistry and BMS - Not sure where to find this info? all I know. Rear tube mount battery (RTMB) lithium Ion battery pack for the IZIP® Skyline men's electric bike. Battery pack rating 24 Volt 10.5 Ah.
Item # CTE-24379


The motor specifics. 250 w non hub mounted to drive rear wheel 9 tooth sprocket 20ish T freewheel

Total weight of bike 52 lbs

and cargo me and stuff mebe 250 ish

, and drive wheel size 26"

. In other words, anything that helps define the system you have. From your first post I would guess you have a non-hub motor mounted to drive a wheel with a chain or something, maybe even a friction drive, but don't make us guess what the gearing and rpm etc. are, and of course a picture can help us visualize it.


eZip
MODEL:
Skyline

ELECTRIC BIKE CLASS:
Throttle on Demand (Class 2)

TOTAL WEIGHT:
52 lbs (23.58 kg)

WHEEL SIZES:
26 in (66.04cm)

Electronic Details
MOTOR TYPE:
Rear-Mounted Geared Motor 9 T sprocket and 20 T Freewheel

MOTOR NOMINAL OUTPUT:
250 watts
BATTERY VOLTAGE:
24 volts
BATTERY AMP HOURS:
10 ah
BATTERY WATT HOURS:
240 wh
BATTERY CHEMISTRY:
Lithium-ion
CHARGE TIME:
6 hours
ESTIMATED MIN RANGE:
15 miles (24 km)
ESTIMATED MAX RANGE:
25 miles (40 km)

TOP SPEED:
15 mph (24 kph)


I hope it helps narrow it down some let me know If there is anything else or somewhere better to look for the info
 
They are perhaps both slightly right.

Its true going to the bigger motor alone shouldn't meaningfully draw more power or accelerate harder. If your issue was motor overtemp it could help a lot. If your primary issue is controller overtemp, you will likely notice no difference in performance from bigger motor and a bigger controller would help.

For that stock iZip, the OEM motor is so tiny it might help to upgrade or at least re-gear it to trade some topend speed for hill climbing.
 
Let's assume that you have a controller that gives a maximum of 14 amps. That's what's limiting your power: 14 x 24 = 336w maximum from the battery, which is around 250w max output power. Your battery can probably go as high as 20 amps and your present motor most likely can also handle that. An easy way to get that extra power is to adjust the maximum current that your controller allows by soldering it's shunt. The shunt is a a bit of thick wire, like a staple, in the controller. You add a blob of solder to it to increase the current. Roughly speaking, the percentage of its length that you solder gives the same percentage increase in current. A good starting point is about 20%. You shouldn't go higher than 30% otherwise you can get over-heating of the controller. This modification costs nothing and gives up to 30% increase in power and torque for climbing.

A bigger motor won't give you any more power without changing the controller and/or battery.

I had a 24v bike (Cyclamatic), which came with a 12 amp controller. I fitted a 44v battery and a 22 amp controller, which completely transformed it. The power being fed to the motor went up from 288w to 968w, so over three times as much. The speed changed from 15 mph with the wind behind me to 31 mph in any conditions. On my 14% test hill, it previously could only go up a few meters before it stalled out. After the modifications, it would storm up without even pedalling.

There's always plenty you can do to improve power, but we need to know what you have.
 
Those low power systems don't like power upgrades. You upgrade one component and the others soon start to fail. I agree that you should limit yourself to 30% power increase, that can be done with controller mod or replacement. Heat is a problem right now, but could be better if the bike doesn't stall uphill. Nothing is worse than stalling a motor because then, all the power that you feed it is transformed into heat. When you feed it enough power to get it moving, it will produce less heat. This is also true of controllers, for most of the heat produced in a controller is a consequence of current limiting. That does happen when the power demand from the motor is much higher than current limit setting.

Your best torque improvement solution is in gear reduction, because you'd be making the work easier for the motor. A higher reduction ratio, combined with a moderate increase of power, is the key to a better performance without the heat. This is a simple mechanic tuning: changing a gear and fitting the matching spacing.
 
I agree the controller is likely the limiting factor to getting more power right now. However, if you upgrade the controller, you may kill the battery and the motor.. But there are ways to avoid that without too much expense.

Since you have 2 batteries, stop swapping them out. instead, run them in parallel. this will give you twice the amp limit on the output, and will be easier on the batteries over all.

With a more powerful controller in place, Put a BBQ temp probe on the motor and monitor it. If it gets too hot on the hills, try changing out the gearing on it. There are smaller motor cogs and larger wheel sprockets available that will give you more torque up the hills.

If you can't get the heat down in the motor, or if the speed is too low after re-gearing it for the hill, then consider going to a bigger motor.
 
Thanks everyone for your advice. I realize that I forgot to include controller info. It is a 20 amp 24v PAS/TAG controller. The sales people claim that it can handle up to 480w motor. Does that sound right?
 
Bigger motor will have more copper, and more magnet in it, and will pull harder, if that is what you need. Even with the same controller, it will be power hungry for longer, to the controller. So it will pull harder on the controller each start up, then back off as rpm increases.

But it sounds like your real problem is the battery sags under the load, dropping in voltage before fully empty under load. Once the battery is not full, the load drops your voltage too low for the system to run I think. Increasing the load with more controller, or motor, would make that worse.

IMO,, you can upgrade the motor, but you need to upgrade the battery first. After that upgrade, the bigger motor might help, since you might be able to climb the hills faster. Faster turning motor on those hills will mean it runs cooler.

Bottom line, you are pushing that type of kit very hard. Because of the towing, you might consider a very big upgrade, to a 1000w mid drive system. Lotta money though, and you can buy a ton of those replacement motors cheap. Or replace the whole thing with a 36v version of the same type.
 
Hi,

Not sure if this is how to do this but thought I would breathe new life into old thread.

Thanks again for all your help w this problem . . . I did what was suggested and got a more powerful mid drive kit for another bike.

Now I have a 2 52v batteries and I was hoping to use one on the old ezip (specs below). Is there a controller I could buy that would accommodate or should I just wire it up and see what happens??

eZip
MODEL:
Skyline

ELECTRIC BIKE CLASS:
Throttle on Demand (Class 2)

TOTAL WEIGHT:
52 lbs (23.58 kg)

WHEEL SIZES:
26 in (66.04cm)

Electronic Details
MOTOR TYPE:
Rear-Mounted Geared Motor 9 T sprocket and 20 T Freewheel

MOTOR NOMINAL OUTPUT:
250 watts
BATTERY VOLTAGE:
24 volts
BATTERY AMP HOURS:
10 ah
BATTERY WATT HOURS:
240 wh
BATTERY CHEMISTRY:
Lithium-ion
CHARGE TIME:
6 hours
ESTIMATED MIN RANGE:
15 miles (24 km)
ESTIMATED MAX RANGE:
25 miles (40 km)

TOP SPEED:
15 mph (24 kph)
 
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