Correlation between controller watts and maximum amps?

I'm searching for a new controller to replace my current "48V 1000W 22±1A" controller by DMHC but I am having a hard time wrapping my head around the power and amp ratings of different controllers... I know that P=U*I so it made sense to me that my current controller would be a 1000W unit since 48 volts times 22 amps max would equal 1056 watts peak power.

But looking at, for example, these two controllers from RisunMotor just makes me confused:
https://risunmotor.com/24v-36v-48v-...less-dc-controller-regenerative-function.html
https://risunmotor.com/24v-500w-36v...usoidal-controller-regenerative-function.html

The first controller is physically a lot smaller and it is rated for 750W at 48V but with 25±1A max current. Now that 25±1A max current is a lot more than my DMHC controller has but this RisunMotor controller is still only rated for 750W. Shouldn't it be 1200W with that kind of current at 48 volts? And the second controller is physically a lot larger with 3 more mosfets but it can handle only 1 amp max more than the smaller one while being rated 250W higher at 48V. I'm sure there's something I've completely misunderstood so please enlighten me

Power ratings have become marketing gibberish, and in reality what gets to the motor is extremely effected by the battery's current state, and to some degree the wiring within the battery, from the battery to the controller and from the controller to the motor. And the resistance of the motor.

P = V*I

But you don't know the real V or the rel I at any given time without measuring it.

Most markets don't allow more than 750W, so marking the controller for 750W makes it fit the market.

750W may be the continuous rating.

The currents say they are peak values rather than continuous, and so would be higher.

The amount of safety margin in the controller may vary a lot. Some will have good safety margins, others will push them to the limit with increased risk of failure.

The type of mosfets makes a large difference, not just the count. Using more (cheaper) mosfets that each have less power capacity may make ratings lower than you expect.

So the numbers are not always what you expect.

Ok so basically I can't really properly compare the "48V 1000W 22±1A" controller I now have to those two being sold on risunmotor.com based on numbers alone. I would need something like a Cycle Analyst to really see the difference, right? And so the marketed watt ratings don't actually really matter all that much, the real world performance is something else.

The reported continuous rating for the 750W unit is 12A which would only be 576W at 48w whereas its peak power value would be 1200W (48V*25A). My current controller has 10 * LM317T mosfets and its physical size is 125mm*65mm*30mm so it's actually a bit smaller than the 9 mosfet 750W unit at risunmotor.com.

I'd just like to replace my DMHC controller with something that would be equal or slightly higher power but it seems quite impossible to do on paper alone when I don't really even know the real world current draw of my current unit... Are the controllers being sold on risunmotor.com generally any good?

LM317T is a voltage regulator, not a FET.

I would ignore the watt rating and judge by the continuous and peak battery current ratings.

Alan B said:

LM317T is a voltage regulator, not a FET.

I would ignore the watt rating and judge by the continuous and peak battery current ratings.

Click to expand...

Gah, yeah I looked at the wrong component . So yeah actually my DMHC controller also has only 9 FETs, they are of the type S70N08R. Basically this means that it is likely that the "750W" unit on risunmotor.com is able to push more power to the motor than my stock DMHC supposedly "1000W" controller since it, at least on paper, is rated to a higher max current, no? The continuous current rating of the DMHC controller is unknown. I think I'll have to get a Cycle Analyst in any case to measure the actual difference. Thanks for the help!

Couldnt' say if the info you wnat is there, but there've been mentions/etc of the company:
https://endless-sphere.com/forums/search.php?keywords=*risunmotor*&terms=all&author=&sc=1&sf=all&sr=posts&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

that said, why do you want the higher power?

Faster acceleration?

Better hill climbing?

Because that's the main things that will do.

If you want something else, you may not need a higher wattage controller.

I don't really want any significant power increase, I want to keep it at the 1000W legal limit. I just don't want any less power when I change the controller :wink: . So preferably I would want to keep the power level pretty much the same but if something has to change then it would be better if I'd have slightly more power vs less power.

The bike has good enough acceleration and hill climbing as it is. But with that being said, my motor, battery and controller all have always been running quite cool with my current setup. Even after heavy loads the controller and motor only feel lukewarm, the battery never has felt even warm to the touch. So I think that I'd be safe with a controller which would be rated to 25A max versus my current 22A max...

Well, if it all works, then that begs the question of why are you changing the controller at all? :?

Giving all of the details of what and why could help us help you figure out what to get.

Without that, all we can do is guess, which makes it less likely you'll get a useful recommendation, or get what you really want. :/

amberwolf said:

Well, if it all works, then that begs the question of why are you changing the controller at all? :?

Giving all of the details of what and why could help us help you figure out what to get.

Without that, all we can do is guess, which makes it less likely you'll get a useful recommendation, or get what you really want. :/

Click to expand...

Yeah sorry I did not tell why I want to replace it, the reason why I want to change the controller is that the stock DMHC unit has some issues and a serious lack of features and documentation. One of the issues is that the speed limiting feature does not work (it's buggy and unusable), the bundled LCD only shows very basic information and it has only a few settings and most of them don't seem to do anything. And the lack of documentation does not help, I have tried to request proper manuals from both the ebike seller and straight from the manufacturer but to no avail. I only have the basic manual which does not go into the settings details.

The LCD3 and LCD6 displays which would work with these controllers from risunmotor.com seem to be packed with features and settings which I'd love to have. They seem to be well used and tested and they have good documentation, with my current setup I am completely in the dark and I can't limit the speed to legal limits.

If you're potentially looking at the Cycle Analyst end of the market, take a look at the controller Grin Cycles also makes. They're supposed to be a lot better than the typical Chinese controllers.