Steep hills that strain the hub motor

[Learning Curve]

I am wondering if I need to be careful not to damage the hub motor or controller on my ebike by pushing myself and the motor to go as far as we can, up some of the steeper sections of the many hills in my area.

The bike was sold to me as having a 350 watt brushless hub motor. The bike was made in China by a company called Wuxing and I see a bike they sell that looks almost identical to mine that has 250 watt hub motor. Which makes me wonder if the hub motor in my bike is 350 or 250 watt. The controller on my bike is 15 amp. Will the 15 amp controller protect my hub motor from getting damaged on a steep hill, or do I need to get off and walk it up the sections where I notice the power is no longer sufficient and the bike is going slower and slower and I am peddling with all my might?

Or maybe I should get off and walk it up the steep hills before it gets to the point of substantially slowing down?

I have just set it up with a new 15 amp hour 36 volt battery, and did not realize I might damage the hub motor by riding it hard up a steep hill... But it is nice to be able to use the motor for as much assistance as possible!

Some advice on how to maintain the health of this type of hub motor in area with lots of substantial hills, would be appreciated!

 

[wesnewell]

A 36V battery will charge to about 42V, so 42V x 15A means you are pushing 630W into the controller. And that's fine for even a 250W motor as long as you don't do it for more than a few minutes. When you hear the motor bogging down, pedal harder and release the throttle to the point the motor sounds more normal.

 

[Racer_X]

When you hear the motor bogging down, pedal harder and release the throttle to the point the motor sounds more normal.

Perfect advice, melted the nylon gears on a geared hub motor like yours pushing it to 1000w (48v 20a) when I let it bog down going up a steep hill.
It is less likely to happen to you since you run 36v 15a but it can still happen.

 

[dogman dan]

A general rule of thumb is do what you can to keep moving faster up the steepest hills. Somewhere around 12 mph, you better start pedaling hard as you can, below 10 mph, you are heating that motor up fast. It drops in efficiency a lot when a load slows it down that much.

BTW 5 mph on the flat is fine, or riding slower up hills with less throttle. Especially if less throttle will still get you a decent speed with you pedaling hard. I mean that when full throttle can only do 10 mph, you are really heating the motor. No problem for the controller, it actually likes full throttle best.

So do you need to get off and push, or ride up without the motor if you slow to 10 mph, pedaling all you can? Not if the hill is short. Half a mile running inefficient won't fry that motor. But too slow up a really long hill will do er, in about 2-3 miles nonstop. So if you need to get up steep grades that long, be careful to keep your speed up, 13-15 mph ideal on the steeper hills.

If you get your motor so hot you cannot hold your hand on the cover at all, STOP. It's way hotter in the center of the motor.

If you have rolling hills, the motor gets some rest going down, and some cooling, but the center of a hot motor takes forever to cool. Tossing cold water on the hub helps some, but mostly it just gives you something to do during the wait to cool.

 

[d8veh]

Rather than struggle up the hills, you can modify the controller to give more current. It's not good to let your motor struggle because it will be heating up all the time and could overheat. Whatever you do, don't let it stall completely because that can damage the controller.

I've had a few bikes with 250w motors that struggled on hills. After increasing the current, the additional torque kept the motors spinning faster, so they didn't go into the danger zone. Plus, it's a lot easier for the rider - no more puffing!. The modification involves adding some solder to about 25% to 30% of the shunt in the controller. I've never had a controller or motor fail by doing it, and I must have done about thirty in total. Don't be greedy and go past 30% though. Some controllers come from the factory with this procedure already done too. If most cases, the shunt sits behind the end-plate like this one, so it's very easy to do.

Before


After:

 

[Learning Curve]

Thanks so much for all the great information! The advice about easing off on the throttle and letting my legs take more of the load makes excellent sense.

Dogman Dan, I had read comments about being careful not to slow down past 10 mph on hills, elsewhere in the forum, but as it takes me about 40 minutes to go the 5 miles into town, I don't think I normally go faster than 10 miles an hour! So it is hard for me to judge by that. (Part of that time, maybe 10 minutes is walking up the steepest hills, but even downhill I use the brakes and only go a moderate speed. We have narrow windy somewhat unpredictable roads and I like to feel I can safely stop if need be) But using full throttle going up a steep hill, I generally hear the motor drop in pitch and loose it's power, to a degree I know it is bogging down. Good to know I can also check this out by putting my hand on it to feel if it is warm or hot, and that easing off the throttle will take the strain off the motor. The hills here are rolling and usually do not go up for more than 1/2 a mile before a flat stretch, or they change and then go downhill. And only some sections less than 500 feet long, are steep enough to be difficult. So hopefully my previous bad riding habits have not already damaged the motor.

If I have been straining the motor by riding incorrectly, would the damage be slowly accumulating or is it something that either melts something so that component no longer works, or does no damage at all?

And interesting suggestion about modifying the controller! At this point, I would not attempt this myself but my son has the right type of soldering tools and he could do something like this someday...Or someday I could just get another controller that allows more amps. Is 20 amps about the max I should consider with the battery and lower watt motor I have?

Is there any way to tell if my motor is 250 or 350 watt? All the writing on the bike is in Chinese and I never got any instructions with the bike.



I suspect this may be my first ebike, but not the last, and as I learn more, someday I may decide to try to put one together that is more suited to my exact needs!

 

[d8veh]

That's quite a big motor, so 20A should be no problem. Any damage to the motor is normally from overheating, so would happen one time rather than accumulating. You should try that shunt mod. It'll make your riding much easier at no cost.

 

[dogman dan]

I think there is no question the motor is not limited to 250 or 350 w. Motors that size can easily take 800w, or about 20 amps of 36v.

And you may well have peak watts much higher than 350 now. 15 amps controller would give you 500w or so. If you can walk up this hill in 10 min, you are very unlikely to heat your motor enough to damage it on that hill. It will be heating up fast, but you should be up it in 5-6 min, at 10 mph. So not enough time to really overheat. It won't progressively damage it either.

Ride up the hill, pedal what you can to keep speed up to what you can do, then touch the motor and see if it got really hot. It might take a few min after you top out for the heat to migrate to the cover. Pretty warm is still ok, even if your hand is pretty tender for touching hot stuff. But if it's getting really hot to the touch, then you need more power to climb that hill a bit faster.

Not sure what as fast as the motor goes is, but 12 mph would be good up that hill.

 

[Voltron]

And if it is getting that hot, be sure to check your connectors and such on the way to the motor..it's really easy to get localized hot spots as corrosion builds over time or old connectors get wiggly when pumping the steady amps for hill climbing.
Re the 250/350 thing, manufacturer wattage ratings are all over the place, so don't get too hung up on them, it's a very rough estimate of what you can reliably put to the motor....but if you go doing shunt mods, REALLY feel check your system a lot, and maybe have a second controller ready to go ahead of time. When you get addicted to your Ebike it sucks waiting for parts after hot rodding goes bad.

 

[dogman dan]

He's got a 15 amps controller, so around 500w at least. It should get him up steep hills good enough without damage, given the short length of the hills.

No need to hot rod.

Just pedal hard as you can, and give it full throttle up those fairly short hills.

 

[Learning Curve]

Thanks to everyone for reducing some of the mystery about the wattage of my hub motor, and how to keep it healthy, and I am relived to know I have not damaged it by riding it too hard up the hills.

The motor measures 19 cm across the circular part outer rim to outer rim, or about 15 cm across the inner core, by about 9 cm wide . If there is a correlation between the motor size and it's power it does seem beefier than many hub motors I have seen. There is some stickers put on the bike by Canadian manufacturers saying the bike does not exceed 500 watts, which was confusing if the motor was 350 watts but with the explanations given about the watts only being general ball park, now makes sense.

In Canada ebikes must be under 500 watts to be legal.

But I doubt anyone would care or check on the island where I live, and someday, when I get more skilled and have access to a higher output soldering iron, (like when my more skilled son visits) I may get a more powerful controller or hot rod the controller as suggested.

I would appreciate more power on the hills, and the world probably needs more large old ladies on hot rodded ebikes...

 

[d8veh]

The 500w is the rated power, not the maximum power from the battery, so you can go as high as you like on curren and still be legal because it doesn't affect the rating, which is done by the manufacturer.