I have a question that will show how little I know...

[anoNY42]

I bought a cheap "48v 1000w" kit a few years ago. My controller states on its face that it has a rated current of 11a and a max current of 22a.

Does this mean that the controller is rated to output 500w continuous with only short bursts of 1000w allowed?

Thanks in advance for any help!

 

[fechter]

They're not generally very accurate specs anyway, so some way to measure is best. My translation of that is the current limit is set at 22A but the controller will overheat if you run more than 11A for a long time. Of course, controller cooling plays a huge part in this and if you mount it where it gets good air flow, you can most likely run it at 22A all day with no problems.

 

[Dauntless]

Yeah, these things can work in a vague and general way, but my feeling is the more you ride uphill, etc., the more you endanger this particular controller. Let's call it borderline, the quality of manufacture might prove more important than the specs, how are we mere morals to know?

So here you already have it so you use it and maybe it's fine; if there's a problem you can look for something bigger. Its a bit disappointing, you're right to wonder, but its not a disaster waiting to happen normally.

 

[dogman dan]

Watt ratings of controllers are all over the place.

Most likely, you have a 22 amps controller. This means the controller will limit amps to 22 max. Because of the nature of electric motors, it's very hard to find a situation where the motor demands the full 22 amps for long. So when you start, particularly an uphill start, your motor will demand lots of amps, more than 22, but the controller will limit it to 22 amps. 10 feet down the road, as you get rolling, the motor will start to demand less, and the controller limiting will stop. at cruise speed, say max speed of 25 mph or so,, your motor will only draw about 15 amps continuously, if you are on 48v.

If you put a watt meter on your bike, you will see readings like max amps 24,, that was just briefly till the controller ramped it back to 22.

As you ride, you will see things like 400w going 18-20 mph,, 700w going 25,, 1000w ( 20 amps) going close to 30 mph,, if you reach that.

Don't worry about your controller,, it can handle all it's designed to give. But you can easily kill a weak battery, that is too small. 15 ah or larger is a good idea for a "1000w kit"

 

[anoNY42]

As you ride, you will see things like 400w going 18-20 mph,, 700w going 25,, 1000w ( 20 amps) going close to 30 mph,, if you reach that.

Don't worry about your controller,, it can handle all it's designed to give. But you can easily kill a weak battery, that is too small. 15 ah or larger is a good idea for a "1000w kit"

Yep, the cheap 10ah battery that came with the kit has just recently developed a bad cell that keeps the LVC cutting in after about a 1/4 mile. You are also exactly right that I average about 400w going 20mph, which is where I have the speed limit set. I'm happy with this since I am 220 lbs and I carry my work clothes and lunch and stuff, and the bike is a cheap steel Dback with a suspension fork. It is quite a pain to have to pedal without assistance at that weight.

Thanks a bunch for the responses, folks!