Overvolting a currie from 24v to 36v

[Jeff Winder]

Hello,
I'm new to the forum, so 'Yes' I did search before posting and making a new thread.
I want to up the voltage on my currie bike. I have a currie eZip Trailz. SLA 24v @ 10ah ,Brushed motor controller (standard setup).

After searching on the web and in other forums, It appears that some currie owners can run 36v without changing the controller, while other cannot...
On my controller is printed the following: DC Brushed Motor Controller
Model No 24v 35A
Control Voltage 1-4v
Drawing No: JC08CN04RMB
2008 03 20

Anyone know if this controller will handle a 36v 10ah batt???? I would really like to know before spending $290.00 + for a Ping LiFePo4.

My backup plan is to do the following:
I do have a variable power supply that is adjustable up to 50v at 3amps, so if I do not hear back from anyone, I will hook up the supply to the terminals and test to see what the upper voltage limit is that I can use to supply my system. So, worse case scenario, I should be able to at least go up a few volts over the standard 24v without changing the controller.


Thanks,
Jeff
Cincinnati, OH

 

[moondog]

Hi , You could also add another battery and see.

The motor on my bike at 24V gets a little warm and that's it. Controller too.

That's good.

Using 36v can make the motor hot.

If the electric motor or controller gets hot that is not good because that heat is wasted battery energy and it can ruin the motor.

 

[safe]

If I have to I'll start pulling out all the charts to explain this more fully, but the short answer is that it's current that actually does most of the damage. Now with brushed motors there is the issue about maximum rpm too... the more you increase the voltage the faster the motor spins and that causes arching across the brush / commutator interface which wears the brushes faster.

Going from 24 volts / 30 amps to 36 volts / 20 amps (or 10 amps) should be fine.

The big problems come about when people increase the voltage, but leave the current limit the same. The effect isn't bad at high rpm, but at low rpm you get a doubling of heat. Low rpm (hills) become the thing that destroys the motor when you overvolt. But with a lower current limit it slows the heating.

I bought one of those ebay Currie motors that are rated as 1.4 hp and I'm running mine at 48 volts / 20 amps (roughly, not sure exactly) and it runs really cool.

If you blow up your stock motor you ought to buy the ebay motor with the Neodymium magnets. That motor is incredibly well built by comparison to stock.

 

[moondog]

They make a 24v and 36v version of that motor, both rated at 450w.

They are not the same. If they are both 450W then the 36V motor would flow less current than the 24V motor.

A 24V motor is designed to work best at 24V.

A 36V motor is designed to work best at 36V.

You can make holes in the 24V motor , put a fan on it for cooling, rewind it or just buy a 36 v motor.

 

[moondog]

This battery

http://cgi.ebay.com/36V-10AH-LiFePO...tem&pt=LH_DefaultDomain_0&hash=item335c7e6ea9

says "Fit 36V Motor Wattage: 200 Watts to 400 Watts, 300 Watts suggested".

That is where Ping says it works best.

Putting that battery pack on the Currie 24V would be asking the battery and motor to work out of their suggested range.

 

[Jeff Winder]

Success...

Ok,
Just hooked up my variable power supply to the bike, and was able to run it up to 36/38 volts without any problem. See attached photos. All I did was connect the supply to the terminals , lift the rear tire and throttle it up. The meter in the picture is showing no amps as I couldn't operate both the camera and experiment at the same time.

The initial throttle pegged the amp meter, then backed down and showed a steady 2.5a load at full throttle. Oh course, not much load with it freewheeling, but I am now confident that the Ping 36v LifePo4 will work.

Jeff

 

[moondog]

A lot of info here. http://endless-sphere.com/forums/viewtopic.php?f=6&t=3249

The meter won't peg, the high current will cause the battery pack to cut off to help save it from damage.

Ping has a good rep for building battery packs. That is something considering how easily people ignore his suggestions for their use.

I have worked in electronics repair for over 25 years now.

The best designed tv's are the ones that don't need a lot of big heatsinks and fans

The worst designed tv's are the ones with a lot of big heatsinks and fans. They get hot and break down more.

Keep this in mind. If your motor, controller, wires and batteries don't get hot then you have a motorized bike that is designed to put your power on the tire and not waste it by making things hot.

 

[safe]

No Load speed doesn't tell you anything about current draw under load.

The controller current limit is your best way to control heat. Lower current limits tend to produce cooler running motors that are more efficient, but they lack the low end torque. High currents allow more low end torque, but this produces a lot of heat and lowers efficiency.

In most cases when you simultaneously increase voltage and lower the current limit you get the best of both worlds. The increased voltage produces more power at higher rpm, but the lowered current tends to still do well in torque because the controllers operate in such a way that the actual current the motor "sees" is larger than the battery current. This concept is somewhat bizarre to people outside of the electric world, but the formula goes:

Total Power = Battery Current * Battery Voltage

"Current Multiplication" = Battery Voltage / Throttle (duty cycle)

...so you might have a situation like:

1 / 50% (throttle) = 2

...which means that there are times when the lower the throttle setting you have (less than 100%) the HIGHER the current you get.

--------------------------

If you aren't confused then you are probably lying, but the technical stuff on this is more complex than you probably realize. The "bottom line" is that the rated settings work well because they are conservative, but there is a whole world of "tuning" that you can do that allows you to achieve optimizations for whatever you want.

The conservative settings are usually pretty good.

-------------------------

In general if you increase voltage you should reduce the current limit if you want to retain a conservative heat profile. And too much voltage can be too much because it increases motor rpm excessively.

 

[moondog]

I have a couple of evg mini ebikes. I studied the history of them.

They used these batteries first.

http://www.encyclopedia.com/doc/1G1-91933744.html

Then went to sla then to NiMH ? Mine have the NiMH batteries.


Then back to sla ? http://www.nycewheels.com/ebike-mini-sla-conversion.html

Batteries confused them too and they had some top people at that company.

They both have http://www.heinzmannusa.com/how_it_works.html

brushed motors that say 24V on them and use 36V battery packs but they do have 20" wheels.

ebike history : http://blog.bradrourke.com/2009/02/16/electric-bicycles-their-time-never-came/

quote:

That brings with it a host of issues. We had to create VIN numbers, meet Department of Transportation regulations, which included having headlights that were as powerful as car headlights, and riders had to wear motorcycle helmets and typically get special motorcycle licenses in order to ride the things. We’re talking bikes with little motors, here, and all this rigmarole just about killed the idea before it started.

But that was my job. The helmet and license thing. Me and a colleague, transportation consultant Ryan Snyder, went around to state capitals trying to get the laws changed in order to allow people to actually ride these things. Ryan had more success than I did with his states, but together we were able to get the law changed in California and I went on to get the law changed in Oregon and Washington states. W00t! The basic idea was simple: we created a new “class” of vehicle called the “electric assisted bicycle.” This new class of vehicle could be ridden without a special license, only on streets (not sidewalks), and anyone under 16 had to wear a helmet — but a bike helmet, not a motorcycle helmet.

============================================================================

Currie went with sla and sold them at Walmart. They are still in business.

 

[Jeff Winder]

Ping Battery box

Just finished up my ping battery box. Fits the currie bike just like the factory battery.

The photos show the box without the front and back mounted.

Now just waiting for the Ping Batt !!

Jeff