Running 24v & 36v on the same controller

[V_Mark]

Is there a controller that will run both a 24v and 36v battery? I have a folder with a Bafang 24v 200w motor that I'd like to get a bit more power from. Here is my original thread about the bike: http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=22324

My wife actually doesn't mind the bike (I never thought I'd ever see her on one!) and while I'd like to upgrade to 36v, I want to keep it 24v compatible for her because I doubt she would actually ride it with the increased power. It came with a 24v battery. I tried running a 36v battery on the stock controller but it didn't seem to like it. I'd like to get a controller that will enable me to connect either my 24v or 36v battery at any given time. I'd like to keep the amps 17 or lower if possible to save the motor & batteries. What are my options?

 

[amberwolf]

You can use a controller rated for 36V on a 24V system, but you need to make sure it doesn't have an LVC or that it is already set low enough for your 24V pack (or you have to alter or defeat it, and then use something else to monitor your pack for LVC).

Often you can use a 24V controller on a 36V system, if all the parts in it are rated high enough to survive it, but there will be less margin for overvoltage (full charge, or spikes, or regen, or other higher-voltage conditions). You'd have to either verify with the controller's manufacturer (or distributor if they are technical enough), or open it up and check for yourself.

 

[dogman dan]

The controllers that used to come with wilderness energy kits had lvc's set low enough to run 24v. I found them so underpowered at 24v that they would shudder on a hill, or start. But they could run at 24v on flat ground once you got pedaled up to 10 mph. If you look at controllers intended to run 24v, the amperage is usually higher. With higher amps, there is enough watts to run the motor well, and it won't balk like mine did at 24v.

So mabye find a 30 amp controller instead of a 20, which has a LVC at least as low as 24v, and you could sucessfully run 24v or 36v.

My solution of course, would be to get a second bike.

Also, those WE controllers were sensorless, and didn't run gearmotors like a bafang well. I'm suprised that your controller didn't run great with 36v. I would have expected it to run fine, or puff smoke. Not run poorly. Could the battery have been inadequate?

 

[V_Mark]

So mabye find a 30 amp controller instead of a 20, which has a LVC at least as low as 24v, and you could sucessfully run 24v or 36v.

My solution of course, would be to get a second bike.

The batteries I'd be using are a 24v10ah Li-ion "little frog" battery and a 36v15ah Ping. Wouldn't a 30 amp controller destroy both batteries? I wish I could get another bike-- unfortunately I already have 4 bikes (3 electric) and live in a high-rise building with assigned bike parking and I'm sure eyebrows would raise if I tried to get a 5th parking spot. I may try it anyway if I get another bike.

I got the folder so I could take it on the train if necessary for my commute. My wife, who I thought would never ride an Ebike, took a liking to it and it's the only one of my bikes that will fit her. She likes using it for assist at 10-15mph, wheras I want to power to work at 23mph.

I'm suprised that your controller didn't run great with 36v. I would have expected it to run fine, or puff smoke. Not run poorly. Could the battery have been inadequate?

You know, that is a possibility. My 36v ping started puffing a few weeks after I tried this. It would cut out randomly on my 22amp controller for another bike; shouldn't the controller for a 200w 24v bafang be less of an issue for it? I have new cells from Ping and will be attempting to fix as soon as I get time. Hoping that the repair job isn't over my head. I've soldered cables before, but not batteries. I now also have a 48v15ah Ping. Would I be crazy to run 48v on this motor?

 

[dogman dan]

True enough, that strategy would only work with a battery up to pulling 30 amps. I just found that partiular dd motor would not run well at 24v 20 amps. It became a pedal first controller with not enough volts to perk up the motor.

You're going the other way, motor and controller designed for 24v more or less. So maybe you would be fine with merely the right battery, and the controller you have. I've not heard of high volt cutoffs, just low volt cutoffs.