quick question

[Noobster]

http://cgi.ebay.com/48V-600W-brushl...ViewItemQQptZScooters?_trksid=p3286.m20.l1116
This is a 48v 30 amp brushless controller and says 600-800 watts. Well 48 X 30 = 1440. Even factoring in battery sag why is it rated so low? Is it just that inefficient? And just one more question I'm looking for a 48v 1000w brushless controller for cheap, any ideas/leads?

 

[Almasi]

http://cgi.ebay.com/48V-600W-brushl...ViewItemQQptZScooters?_trksid=p3286.m20.l1116
This is a 48v 30 amp brushless controller and says 600-800 watts. Well 48 X 30 = 1440. Even factoring in battery sag why is it rated so low? Is it just that inefficient? And just one more question I'm looking for a 48v 1000w brushless controller for cheap, any ideas/leads?

Maybe it's 30 Amp Phase current ??? (I would be surprised..but you never know)

Or maybe the 30 Amp is Peak rating ...

 

[dogman dan]

Amp ratings are a grey area, and I'm not so sure they all measure them the same. My experience with two WE controllers, one brushed and one brushless, is that the rated amps is a peak, but the controller may pull even more than that in a spike before it cuts off. So a 30 amp, would be able to pull 30 amps continuously on a steep enough hill. It may do that also, briefly, getting up to full speed. Once at full speed, they will pull a lot less amps, just like your car uses less gas once you stop accelerating and go into cruising mode. My controllers use aproximately half the rated amps when cruising on flat ground, and the average is slightly higher than half the rated amperage. So a 1500 watt controller will tend to use an average of 800 in typical use. Unless you are looking to climb a super steep hill, pull a trailer, or need super fast starts, 30 amps is enough for most hubmotors except the 5300 series clyte. Speed is from more volts, if speed is what you need. Amps is nice, but hard on the batteries, so unless you need it, like for a dirtbike or a motorcycle conversion, 30 amps is a good choice of controller for getting the max lifespan out of your batteries.

 

[fechter]

Yes, the watt ratings are somewhat confusing. The true rating is based on heating more than anything else.

The motor in the ad says 600-800w. From this you can assume it will survive 600-800w continuously (>1hr) without overheating and self-destructing.

It can run at 1440 watts or higher when you are taking off from a dead stop or climbing a steep hill. The motor can run at this level for a short time before overheating. Normally the motor only spends a small percentage of time above it's continuous rating, so it does OK. If you keep increasing the power, you will reach a point where it fails due to overheating.

My 600w BMC motor can survive close to 5000 watts for about 30 seconds with forced-air cooling. Most motors can run about twice their continuous rating for about a minute (varies widely).

The ratings posted in some ads may be wildly inaccurate or exaggerated, but in general I've found them to be pretty close, at least for the continuous ratings.

 

[Noobster]

Thanks fetcher but I was speaking of brushless controllers not motors. I'm already aware of the motors peak curretnt/time and sustained current limits. My question was about this controller, If it's like what the guy who posted just before fetcher said and controllers are rated similarly to motors and the 600-800watt rating is what the controller can continuously provide I'm sold on it as that means that it has the 1440 watt max, which is plenty for accelerating. Is what I just said an accurate assumption? Thanks. Ryan.

 

[dogman dan]

Makes sense to me. My WE controllers run at around 700-800 watts on flat ground. But 35a x36v =1260 watts before it cuts out. But of course, for legal purposes, they call this stuff 600 watt to stay within federal ebike limits. The dang thing goes slightly faster than 20 mph too.

If you want real watts while cruising, at 48v you need a 50 amp or larger controller, but then you open a can of worms with what battery can stand that that I can afford? Lots of folks want the power for speed, so more volts is then the answer.