popatop75

hell'o! Is there a rule of thumb on how much power ( motor watt ect ) the E bike should have per say so many pounds.. example I weigh 190 whats the smallest size Ebike should I buy?? wife is 250 should she buy a bigger Ebike.. 350 watt motor there will be hills on the route and maybe some sand or soft dirt......thanks david

nfmisso

Hi David;

There is no rule of thumb, but there are some generalizations.
* more speed requires more power
* for a given amount of power; and mid drive will climb better than a hub motor.
* for steady state cruising on the flat, hub and mid drive are about the same.
* for extremely high power (>1500W or so) mid drive systems run into bike chain strength and life issues.
* hub motor perform best between half and full speed - they are not so good at going slow.

One of my ebike is a 500W 36V 13Ah front hub, and the other is 1000W, 48V, 13Ah. Top speed is less than 2 mph different. The 1000W one accelerates much faster, and climbs a LOT better. Range is proportional to the Wh (=Ah x V) of the battery. The 624Wh of the 48V bike (vs 468Wh of the 36V one) is a very noticeable difference. At the end of my 10 mile commute, the 36V bike has noticeably lost a great deal of performance, where as the 48V bike has not - this is not due to the voltage difference, it is due the battery capacity (Wh) difference.

If you are getting a mid-drive ebike; 250W-350W is adequate. If you are getting a hub motor, I'd suggest at least 500W, with 750W to 1000W being preferred. I also suggest a minimum of 50Wh of battery capacity per mile for your longest regular rides. So if you are planning 10 mile rides, get a 500Wh battery (14Ah for 36V, 10½Ah for 48V). This will give some margin in most cases.

qbiker

I have a 750 watt Bafang if I could change anything I would make it half the weight half the power. I spend most of my time on one or two a real bad hill maybe 3. It's a mid drive though like Nigel says big watts is more about speed than hill climbing.

2old

+ with the advice above. I'm 180 and my first conversion, a 350w (36V) front hub, was great but I needed to pedal hard on hills. My wife (120 - pounds, not years) and I have 750w BBS02's that we ride off road in either no assist or level 1 (of five) more than 95% of the time. Also, when either of us has ridden an OEM bike from Haibike, Bulls, Specilized etc we find we are infrequently in higher than eco level. Any of these examples should be adequate for both you and your wife. The next big decisions are how much do you want to spend and DIY or complete. Also, look at the simulator on ebikesca to get an idea of how various factors influence speed, efficiency .....

popatop75

ok

MikeDD

You can never have too much power. My wife's Liberty Trike and my RadMini both have 750 watt motors. We have been on steep hills where we needed the power.