hill climbing/range

[aseb]

Hi. I have a powabyke, and a few nearby hills that I need to give pedal assistance to get up. I gather these are 200 or 250 Watt, but I've seen 500W and 750W kits that would theoretically be twice or three times as powerful. I have read that these ratings are not peak, so I guess that there may not be twice and three times the power really available for hill climbing.
Anyhow, how improved is hill climbing for the extra power? (I'm not really bothered about top speed). I haven't found anything that gives indication of hill climbing for the different powers- eg hill gradients or relative performance. I realise that many other things will affect performance- weight, motor make/characteristics- but is there an indication of how hill climbing is improved with the extra power.
Finally, would you expect range to decrease for the higher powered motors?

thanks

 

[Pedalo]

You might get an idea of how power translates to hill climbing ability from one of the bike power calculators you find on the web - e.g.

Bike Calculator

Power affects the speed at which you can expect to go up a hill of a given gradient. Therefore gearing is the other factor you need to take into account. Even a relatively low power motor can get you up a steep hill at low speed provided they have sufficient gearing. This is why crank drive systems are unbeatable for hill climbing ability since they make use of the bikes gearing.

 

[aseb]

Wow, interesting! But I'm a utility/neccesity rider and wouldn't have a clue about some of the input figures. I'll have a play to see what I can learn though, love playing with these kinds of toys (but may not input accurate info or interpret correctly!)

You might get an idea of how power translates to hill climbing ability from one of the bike power calculators you find on the web - e.g.

Bike Calculator

Power affects the speed at which you can expect to go up a hill of a given gradient. Therefore gearing is the other factor you need to take into account. Even a relatively low power motor can get you up a steep hill at low speed provided they have sufficient gearing. This is why crank drive systems are unbeatable for hill climbing ability since they make use of the bikes gearing.

 

[flecc]

Not a big improvement if any, since the Powabyke motor is one of the most powerful ever made with a gross peak of about 700 watts.

If yours is one of the heavy SLA battery models it's the weight that limits the climbing, but it will still be one of the best climbers around. You would be shocked at how weak many e-bike models are on hills.
.

 

[aseb]

Not a big improvement if any, since the Powabyke motor is one of the most powerful ever made with a gross peak of about 700 watts.

If yours is one of the heavy SLA battery models it's the weight that limits the climbing, but it will still be one of the best climbers around. You would be shocked at how weak many e-bike models are on hills.
.

Ahhhhh... That explains why it does perform better than I had originally expected. The hills I go up aren't excessively long, but are steep. Would the LiFePO4 battery at 20Ah help? I guess it won't really make any difference, just help me get further before it flattens. I did read somewhere that a newer chemistry battery (can't recall if LiFePO4 or NiMH) will do further than a similar sized Lead battery because of cut out voltages.

I also read that a brushed motor performs better than a brushless at lower speeds, so this would also help with the hill climbing, but what sort of peak powers would the 500W and 750W motors have?

 

[flecc]

Yours is a brush motor already, so nothing to gain there.

You would probably get more range with a large capacity LiFePO4 battery, but they aren't particularly good at delivering the high currents your motor needs at full throttle when climbing at around 7 mph or less, so you could even find a little loss of power then.

Those 500 and 700 watt motors might not have more power, they might just be quoting the actual maximum, rather than the legal nicety of 20 or 250 watts, both of those invariably being only notional power statements to satisfy legal requirements. Virtually no e-bikes are actually that weak.

On the other hand, the 500 and 700 watt ones may have a higher peak, but you'd need to see the power curve charts to be sure, and few publish those. Many of the high power motors are actually direct drive ones, and those don't have very good low speed torque. Therefore, although their power makes for great high speeds, they can be rather poor on hills, especially the steep ones. The best climbing hub motors are the internally geared ones like your present one,the Heinzmann and the higher powered Suzhou Bafang ones.
.
.

 

[aseb]

Yours is a brush motor already, so nothing to gain there.

You would probably get more range with a large capacity LiFePO4 battery, but they aren't particularly good at delivering the high currents your motor needs at full throttle when climbing at around 7 mph or less, so you could even find a little loss of power then.

Those 500 and 700 watt motors might not have more power, they might just be quoting the actual maximum, rather than the legal nicety of 20 or 250 watts, both of those invariably being only notional power statements to satisfy legal requirements. Virtually no e-bikes are actually that weak.

On the other hand, the 500 and 700 watt ones may have a higher peak, but you'd need to see the power curve charts to be sure, and few publish those. Many of the high power motors are actually direct drive ones, and those don't have very good low speed torque. Therefore, although their power makes for great high speeds, they can be rather poor on hills, especially the steep ones. The best climbing hub motors are the internally geared ones like your present one,the Heinzmann and the higher powered Suzhou Bafang ones.
.
.

Thanks again.

I take it there is a restriction on the powerbyke to keep it to 15mph, can this be removed? Although I guess this would only affect max speed rather than power through the rev range.

 

[aseb]

Out of interest who manufactures the powabyke motors? They have a Z with a circle around on the hub, but no name.

 

[flecc]

I've never known the manufacturer of those.

I don't think there's any restriction, the motor's internal gearing is deliberately low to benefit hill climbing so the speed is limited to what the motor runs to on the supply voltage. Many e-bikes are like that. As you say removal of any restriction if there was any present would not affect climb power, only top speed.
.

 

[aseb]

I've never known the manufacturer of those.

I don't think there's any restriction, the motor's internal gearing is deliberately low to benefit hill climbing so the speed is limited to what the motor runs to on the supply voltage. Many e-bikes are like that. As you say removal of any restriction if there was any present would not affect climb power, only top speed.
.

thanks very much, your advice has been very helpful.