# Newbie Needs Help with Electric Motorcycle Performance



## Amberwolf (May 29, 2009)

ERP said:


> Which was a bit embarrassing since the bike was slow to begin with and I was bragging about all the torque my electric bike would make.


Torque does not equal speed, until you supply it with the proper gear ratio.  What that ratio is depends on your motor's speed and your desired abilities both at a dead stop to start up and at top speed. 

Having a multiple-speed transmission can improve both abilities, at the cost of some lost power (how much power depends on the type of transmission and it's particular design).




> I am currently running 4, 12v 115 Ah marine/RV batteries at 48 volts.


One way to increase speed can be to increase voltage. (instead of using a transmission; so that lower voltages = lower gears, and higher voltages = higher gears). However, you need to know what the max RPM your motor can do, and it is helpful to know it's RPMs per volt, so that you will know how high you can push it before you would be potentially running it faster than it's commutator segments can handle (causing them to come off, kind of like a mini frag grenade between your legs ).





> And a Perm Type 14 DC motor, it looks like the Perm 132 but I bought it on ebay and am not sure exactly what model it is. With the current setup and 3.6:1 gear ratio the bike has a top speed of 44 mph.


Can you type in everything that is on it's labelling into a reply? Photos might be helpful to members familiar with that series (I'm not). 

Three pretty important specs are Max RPM, Max Voltage, and Max Current. Sometimes those aren't all labelled separately, and may have to be determined experimentally, or by calculating them from other specs that *are* labelled. 




> My Amp meter has only shown a peak of 180 Amps during acceleration.


What voltage is across the motor at that time? (assuming max throttle)

What gets hot? Whereever there's heat, there's lost power.

What's the resistance of your wiring, relays/contacts, connections, fuseholders, etc? Including whatever resistances you have from one battery's terminal to the next battery's terminal (not across a battery). 

Do any of those points get hot? Some hotter than others? A non-contact thermometer (even the ones at Harbor Freight would work) can tell you quickly the different temperatures of anything you can see and point it at.

Does the Alltrax have a current limiter? Some controllers limit current draw if the battery falls below a certain voltage, and you might have to change those settings for your pack/etc. 

Otherwise, I suppose it could simply be that the motor requires higher voltage to draw the currents you're after.



> I am planning on adding two more batteries as saddle bags and bumping up to a 72 volt system. But will that make a performance difference or do I need to increase the size of my controller. Or is the motor the problem.


Need to know the motor specs first, before you add more voltage. If the controller can output more amps than you are drawing, then the controller is probably not the limitation. 



> As proof of my electrical ineptitude I purchased two marine battery charges which could each charge 3 batteries at 12 volts. I wanted to mount the charges on the bike and hard wire them in so I could recharge the bike anywhere. The problem was that they each had a common ground for the 3 batteries they charged. Turns out you can not hook up 6 batteries in series and in parallel at the same time. I creates a lot of smoking wires. I had to install two DC solenoids and 4 AC solenoids to make it work. It was a trial by fire but I am really enjoying my commute.


Yeah, that kind of thing happens sometimes if you don't check the internal wiring of things you want to hook up.  Since my projects (heavy bicycle-class) are all built of recycled junk, sometimes I run into some odd things I never thought about before, and I've had a few things I've let the magic smoke out of. 
________
Sizzling_Asian


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## ERP (Jul 1, 2009)

Thanks for the reply. To be more specific I am disappointed with the bikes acceleration, but I am happy with the current top speed. I commute on 35 mph roads so a top speed of 44 mph is fine. My friends 250 cc Nighthawk was quicker to 44 mph than my electric bike.

The Motor does have a small plate on the side that lists some specs.

Perm Motor GmbH
12-72 Volts
P: 1-6,6 Kw S1 100A
P: 10,5 Kw S2 160 A 10 min

I do not know the rpm per volt, but I should be able to calculated it since I know all the other variables, (gear ratio, voltage, tire size, etc). I originally calculated my gear ratio and max speed based on the specs of the PERM 132 motor.

My volt meter shows ~52 volts when fully charged. During full acceleration when the amp meter peaks at 180 amps the voltage drops to 44 volts then climbs up to 47-48 volts once I have reached cruising speed. I am measuring the voltage from before the controller to after the motor.

I have not directly measured the temperature of anything with an IR thermometer, but I have used my hand. At the end of my 5 mile commute the motor is just barely warmer than when I started. I am using 0 gauge wiring and 400 A peak solenoids. The controller is 10-20 F above ambient after my commute even though I am at 100% throttle for most of my commute. Nothing else has a detectable heat increase. This leads me to believe that I am far below the maximum current that the system can handle.

The Alltrax controller can be connected to a computer and is set to 100% current and I set the low voltage shutoff at 35 volts.




Amberwolf said:


> If the controller can output more amps than you are drawing, then the controller is probably not the limitation.


This is what I am unsure about. Is there any way to test this, or do I just need to add two batteries and bring it to 72 volts?

Thanks


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## rillip3 (Jun 19, 2009)

ERP said:


> Thanks for the reply. To be more specific I am disappointed with the bikes acceleration, but I am happy with the current top speed. I commute on 35 mph roads so a top speed of 44 mph is fine. My friends 250 cc Nighthawk was quicker to 44 mph than my electric bike.
> 
> The Motor does have a small plate on the side that lists some specs.
> 
> ...


I'm no genius at reading these things, but doesn't that label indicated 100 A continual 160 max? It looks like the motor might be your bottleneck.


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## PatricioIN (Jun 13, 2008)

I'm wondering if we expect too much from electric motors as compared to the ICE.. I have a similar situation with my EV. While the top speed is fine, and acceleration is acceptable, I did expect the acceleration to be capable of more when I want it to. Perhaps our issues is that we could have put in slightly larger motors?? I have a 1221c Curtis controller rated at 400amp max and I've never seen my ammeter get anywhere near 400. Just over 300amp is the highest I've ever seen. I have 170ah batts.. so you think they'd be capable of putting out 400amps. And my motor is the ADC 8" I've seen in many other EV's.. so you think that would also be capable of pulling 400amps. I've checked all my connections more than once and none are ever a problem. The controller gets hot and certainly the motor..

Anyway, just some ramblings. Again, my acceleration isn't bad, it's just not as quick 0-30 as I expected it to be.


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## rillip3 (Jun 19, 2009)

PatricioIN said:


> I'm wondering if we expect too much from electric motors as compared to the ICE.. I have a similar situation with my EV. While the top speed is fine, and acceleration is acceptable, I did expect the acceleration to be capable of more when I want it to. Perhaps our issues is that we could have put in slightly larger motors?? I have a 1221c Curtis controller rated at 400amp max and I've never seen my ammeter get anywhere near 400. Just over 300amp is the highest I've ever seen. I have 170ah batts.. so you think they'd be capable of putting out 400amps. And my motor is the ADC 8" I've seen in many other EV's.. so you think that would also be capable of pulling 400amps. I've checked all my connections more than once and none are ever a problem. The controller gets hot and certainly the motor..
> 
> Anyway, just some ramblings. Again, my acceleration isn't bad, it's just not as quick 0-30 as I expected it to be.


You sure you're not running into temperature protection? The 1221c Curtis will cut performance based on temperature. The 1231c, which is apparently very similar (they have merged data sheets) has an optional heatsink. You might look into cooling the controller more.


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## PatricioIN (Jun 13, 2008)

rillip3 said:


> You sure you're not running into temperature protection? The 1221c Curtis will cut performance based on temperature. The 1231c, which is apparently very similar (they have merged data sheets) has an optional heatsink. You might look into cooling the controller more.


yes, I'm sure it's not a temp issue


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## ERP (Jul 1, 2009)

From what I have seen of other electric motors their amperage ratings are time limited. The lowest rating is for continuous load, and subsequent higher currents are limited to 30 min, 10 min, 2 min, 30 seconds etc. My motor lists the 160 A current at 10 minutes, so I would assume, it could handle near twice that for the 5-10 seconds I am accelerating up to the speed limit. I am just unsure what is the largest limiting factor in my system, my small 48 volt battery pack (I’m leaning towards this), the controller or the motor.


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## dtbaker (Jan 5, 2008)

so... do you have multiple gears, or not? I have found my ev is pretty slow off the line in 2nd and just cannot draw its full amp load since the rpm is low. MUCH better off the line in 1st.

Depending on the range you need, you might consider a rack of 72 volts with SMALLER lighter batteries than full size. typical 12v motorcycle size for instance would give you the 72 volts of zip, just not for very long.  Or consider Lithium, but then you are talking about some serious money....


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## ERP (Jul 1, 2009)

It is a single speed. I based the gear ratio on a 72 volt setup to get to 62 mph. My rear cog looks like a pizza tray.

Would there be an issue with adding two smaller motorcycle type batteries to my current system to bring it to 72 volts? Or do I need to keep all the batteries the same size and Ah? I like my current lead acid batteries, they are cheap, have a good range and fit well up front. But I am a little worried about fitting two more as saddle bags.


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## Gene (Apr 8, 2009)

It's best to stick with the same type of batteries otherwise you will create an unbalance in the pack which will certainly deteriorate the preformance of your bike. Also charging an unbalanced pack can damage the smaller batteries (overcharging) and undercharge the bigger ones.

What gear ratio are you using? Maybe you could try using a bigger ratio (smaller big chain wheel or bigger small chain wheel, whatever) to improve you top speed and accel, motor will certainly draw more amps to get to the same rpm's.

For my quad conversion i'm using a 14/42 ratio, with an 24V system i get very good acceleration and a top speed of 60kph (about 37 mph). It's the transmission of a superbike, so solid enough to handle 200hp.
First i used the original transmission with a 14/37 ratio, also worked fine but motor drew a lot of amps and heated up (burned the brushes with this ratio), that's why i chose a smaller ratio and now it's much better, you may want to try the opposite.

I'm no expert, just telling what i experienced.


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## Camaro (Jul 29, 2008)

Hey EPR,
I have a bike very similar to yours. Here is a picture. I've been riding it for a few years now. I'm using an Altrax 400amp 48v controller, 8, 20ah B&B sealed lead batteries, for a total of 48V 40ah pack. My gear ratio is about the same as yours, and I get a top speed of 46 mph. 
I've always been happy with my bike's acceleration. I'd say that my 0-30mph time is less than 3 seconds, but I'll have to test it. My friends that drive 1000cc bikes have all been surprised by my bikes acceleration, all though they'd bet me off the line. 
What are your batteries ah rating? As far as getting better performance, you will notice better acceleration and top speed if you up your voltage to 72v, but you might wear out your motor faster.
As I said, I've had my bike for a while now, so I'm ready for new batteries. I'm thinking of Li-batteries, and a new frame. Check out this site. 
http://www.electricmotion.org/
I'll be going with a 72v controller when I do get around to upgrading things.

I hope this helps.


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## dtbaker (Jan 5, 2008)

ERP said:


> It is a single speed.


aha....
well without massive torque via HUGE motor you are going to have predictably slow starts unless you can get a lower gear to start.



ERP said:


> Would there be an issue with adding two smaller motorcycle type batteries to my current system to bring it to 72 volts?


probably highly battery unfriendly... what will happen I think is as the smaller batteries drain, and voltage drops, the whole system will sink to the lowest cell. Mismatched batteries tend to die really fast from what I hear. If you whole system is small 12v then you'll be way lighter, way quicker, but have very limited range.

Hhhmm, I dunno how your motor would like it, but you COULD maybe rig the two small 12v batteries to cut in and out via a contactor, and only use them as 'turbo' for starts, then cut them out.


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## dtbaker (Jan 5, 2008)

Camaro said:


> Hey EPR,
> I have a bike very similar to yours.


the battery packs appear to be the biggest (heaviest) difference.  I would be curious to know the curb weight of both bikes, and the for sure rated torque or max hp of the respective motors.


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## Camaro (Jul 29, 2008)

dtbaker said:


> the battery packs appear to be the biggest (heaviest) difference.  I would be curious to know the curb weight of both bikes, and the for sure rated torque or max hp of the respective motors.


I have an Etek, I bought it 6 years ago for $275. Great deal! 48v*400amps = 19.2 kw or around 25.7 hp according to google, but the Etek is rated for 16hp peak.

I've never weighted my bike, but I'll see if I can over the weekend.


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## ZEVUtah (Apr 10, 2008)

ERP said:


> I am currently running 4, 12v 115 Ah marine/RV batteries at 48 volts. I am using a 300A Alltrax AXE 24-72v controller; although it came with a 250A fuse  And a Perm Type 14 DC motor, it looks like the Perm 132 but I bought it on ebay and am not sure exactly what model it is. With the current setup and 3.6:1 gear ratio the bike has a top speed of 44 mph.


The first thing I would change is the gearing. For my bike with a pmg-132 motor a 5 : 1 ratio worked best. The motor sprockets are fairly cheap to buy and every bike is different. I am also using 72 volts instead of 48. The sprockets on my Ninja are 14 and 72 tooth.

http://www.evalbum.com/1414

I recently changed to Odyssey batteries and performance has improved over the floodies.

Cheers,
Kyle


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## ithinkidontknow (May 14, 2009)

This thread really made me think about another thing I have been worrying about as I start building;

Is it possible that the batteries have too low of a discharge rate and so it is impossible for them to even feed enough energy to the controller? Maybe someone who knows more about battery technology could help me wrap my head around what seems like a pretty substantial issue.

Anyway, I just figured that it was at least possible that this is a cause of people's performance issues.


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## dtbaker (Jan 5, 2008)

ithinkidontknow said:


> Is it possible that the batteries have too low of a discharge rate and so it is impossible for them to even feed enough energy to the controller?


I doubt thats the problem.  Li batteries maybe since if you go over 10C for very long they get hot enough to be a problem from what I hear. Floodies would probably melt the terminal off if the controller allowed.

My guess is internal limits from the controller, too small a motor, or most likely too tall a gear for the gross weight to get it going very fast.


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## Camaro (Jul 29, 2008)

I think another limit is the "300 amp" cut off switch that most of us use. That switch is rated at 300 amps, but only 12 volts. The watt rating is only 3.6kw but our controls running at 48v at 300amps need 14.4kw. I just replaced it with an Anderson style connector and I get much better acceleration.


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## ithinkidontknow (May 14, 2009)

Camaro said:


> I think another limit is the "300 amp" cut off switch that most of us use. That switch is rated at 300 amps, but only 12 volts. The watt rating is only 3.6kw but our controls running at 48v at 300amps need 14.4kw. I just replaced it with an Anderson style connector and I get much better acceleration.


Wouldn't the switch just burn up and not work rather than limit the flow to the motor? Maybe I misunderstood but it doesn't sound like this would be a problem if the switch is still working.


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## Camaro (Jul 29, 2008)

ithinkidontknow said:


> Wouldn't the switch just burn up and not work rather than limit the flow to the motor? Maybe I misunderstood but it doesn't sound like this would be a problem if the switch is still working.


Not necessarily, it's acting as a resistor. Resisters limit current but don't burn up.


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## ithinkidontknow (May 14, 2009)

Camaro said:


> Not necessarily, it's acting as a resistor. Resisters limit current but don't burn up.


So you are saying that if you go past that current limit the resistance increases but otherwise it is not noticeable? I wouldn't think that this cutoff switch would be variable resistance. This does not make any sense to me.


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## Camaro (Jul 29, 2008)

ithinkidontknow said:


> So you are saying that if you go past that current limit the resistance increases but otherwise it is not noticeable? I wouldn't think that this cutoff switch would be variable resistance. This does not make any sense to me.


No, that's not what I'm saying; the resistance is always there. It's always noticeable. Think of it like water flowing through a pipe. I this case the smallest section of "pipe" would be the switch. It will only let a certain amount of current through it.


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## speedboats (Jan 10, 2009)

While I'm just a beginner, I did some simple math.

P=VI
P=48*180
p=8.6kW

How much power does the standard bike have?

While using the RV LA's, what are their CCA's? (Should be on the label). This is the maximum amps the batt can give at any 1 time. RV batts tend to be deep cycle, so aren't generally built for high current draw as that of a start battery (which aren't designed to be deep cycled)

Problem seems to be trying to draw more wattage from the battery. Perhaps it's available and getting bottled somewhere else (resistance load)


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## ithinkidontknow (May 14, 2009)

Camaro said:


> No, that's not what I'm saying; the resistance is always there. It's always noticeable. Think of it like water flowing through a pipe. I this case the smallest section of "pipe" would be the switch. It will only let a certain amount of current through it.


If the resistance is always there, why is this only a problem if the current and voltage are high? Wouldn't the resistance be constant if this is just acting as a resistor? And in this case it makes no sense that higher current would make the switch start being resistant to the flow.


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