BBS02 - How many watts do you really need for a MTB?

Alan2000

Alan2000

100 mW
Joined
Feb 25, 2016
Messages
42
Location
Orange County - CA
I recently installed my first electric drive in a bike. I installed a 36v 500w 25A BBS02 in my old mountain bike. It has an 8 speed cassette with 11T-32T. I went with the lower voltage and wattage to keep costs down and looking for longer battery life. I've been playing around reprogramming the controller to get it setup for how I ride and I have cut back the power from 25A to 20A. At 25A it was pulling almost 1000w and I didn't have any problems climbing hills. (I swapped out the Bafang 44T chain ring for a 34T chain ring.) Yet I've seen people say you need at least a 48V 1000w system.

If I want to I can in the future upgrade my BBS02 to 48V 750W for about $100. I'm wondering why I would need the extra power? Currently I can go 26MPH on battery alone with no peddling, which is fast enough for me. If I'm not looking for more top end speed, is there a reason to have something more powerful than 36V 500W?
 
Fat folk need more power (I know :lol: ).
 
You need more power for 30mph as wind resistance is a major factor (It's a logarithmic algorithm past 25mph I believe). As a cyclocross/gravel grinder/commuter I upgraded to a bigger chainring for higher top speed to add leg input for 30+mph whilst maintaining a good cadence. To be honest though, the BBS02 is at its limit at 32mph on a bike that has a slightly upright position. To cruise on power only at 32mph+ you need about 2kw+.
 
If your happy at the speed you are at, change is just going to cost more and achieve little.

Better off considering charging technique, regular maintenance/greasing to prolong part life etc.

(yes thats boring which is why you will start thinking about putting together another bike) :twisted:
 
I'm 165 lbs. I have no interest in going faster. I can do about 30mph if I pedal along but really don't care to go much over 15 most of the time. Purpose of the bike is only to use it off road on dirt trails. I was wondering if I was missing something or if those who say you need 1000W+ 48v are saying that because they want to be able to go fast? I have not tried any crazy steep hills yet, but on the moderate steep hills it has been pretty effortless. I think with the 34T chain ring and 32T cassette I'm still geared a bit high for trails. But if I go any smaller on the chain ring then the cadence probably gets stupid fast when I do want to go faster. I'm not a spring chicken and at my age I keep in mind that when you double speed, you quadruple the impact force. :)

I've read that these conversions are rough on chains. Other than carrying a chain repair tool, or a master link connector, any other chain care advice?
 
Measure the chain periodically for wear and replace it when it shows wear, before it ruins the cogs and chainrings.

With a mid drive the gearing provides high torque, so the need for power is related to speed. In the rough I find I don't want to go fast, so not much power is needed. On pavement up grade is a different story, and that's where I run out of power. Climbing steep grades reduces speed a great deal unless you can tap into more power.

If you have enough speed, and the motor is not getting hot, you are done. No need to upgrade.
 
Hiya. To REDUCE wattage per mile needs, give a google search for "windscreen bicycle" maybe. :wink:
 
Alan B pretty much summed it up. With increased power going through the chain line, chain maintenance becomes important. I switching to a system of three chains per cassette, switching them out for cleaning and reinstallation every couple of weeks (I'm doing 400km per week+ in commuting to minimize cassette and Lekkie ring wear. This is where your money is better off being spent if you are happy with the speed you are going.
 
Alan2000 said:
I've read that these conversions are rough on chains. Other than carrying a chain repair tool, or a master link connector, any other chain care advice?
Click to expand...
Run the chain through a rag after every ride to remove the muck. Then lube it up periodically with a quality lube. Finish Line Dry Teflon Lube is a good one to use.

My chain is on 1700 miles at the moment with no discernible wear.
 
alfantastic said:
Alan2000 said:
I've read that these conversions are rough on chains. Other than carrying a chain repair tool, or a master link connector, any other chain care advice?
Click to expand...
Run the chain through a rag after every ride to remove the muck. Then lube it up periodically with a quality lube. Finish Line Dry Teflon Lube is a good one to use.

My chain is on 1700 miles at the moment with no discernible wear.
Click to expand...

You are measuring that with a chain wear gauge, right? Visual inspection means little.
 
Alan B said:
alfantastic said:
Alan2000 said:
I've read that these conversions are rough on chains. Other than carrying a chain repair tool, or a master link connector, any other chain care advice?
Click to expand...
Run the chain through a rag after every ride to remove the muck. Then lube it up periodically with a quality lube. Finish Line Dry Teflon Lube is a good one to use.

My chain is on 1700 miles at the moment with no discernible wear.
Click to expand...

You are measuring that with a chain wear gauge, right? Visual inspection means little.
Click to expand...
Yeah, with one of these:

ParkTool.jpg
Considering I ride mostly cross country giving the unit plenty of beans, I am surprised that the chain, chainring and cassette are in such good condition. I've heard some BBS02's each drivetrains for breakfast.
 
Alan B said:
You are measuring that with a chain wear gauge, right? Visual inspection means little.
Click to expand...

Before chain checkers were common tools, we mechanics had to be able to suss out a worn chain without them. The usual quick way was to grab the run of chain behind the ring, to pull it snug at the top and bottom of the ring. Then the amount of slack at the front of the ring could be used as an indicator of chain elongation.

A more rigorous method was to measure 12 inches worth of links, pin to pin. Once that length grew to 12-1/16", it was time to replace the chain.
 
Chalo said:
Alan B said:
You are measuring that with a chain wear gauge, right? Visual inspection means little.
Click to expand...

Before chain checkers were common tools, we mechanics had to be able to suss out a worn chain without them. The usual quick way was to grab the run of chain behind the ring, to pull it snug at the top and bottom of the ring. Then the amount of slack at the front of the ring could be used as an indicator of chain elongation.

A more rigorous method was to measure 12 inches worth of links, pin to pin. Once that length grew to 12-1/16", it was time to replace the chain.
Click to expand...
Amazing how a few dollars tool makes life so much easier :D
 
Having done surveys here on es, it seems there are two distinct groups. Most are happy doing about 18mph, while the rest want a motorcycle not assistance. Then you have to look at the setup you have. Many have no gears at all so need a lot of power. Like having a car that was stuck in 5th gear all the time. They can't climb without some energy consumption. While you have a set of gears that can trade speed for climbing ability, as a cyclist would. A horsepower is about 750w and a horse is a lot bigger than we are. An amature level competative cyclist might average 250w for half hours duration, while a pro might peak over 1000w short term. Your 48v 25a near 1250w so with efficiency in mind, your close to a very fit cyclists peak performance. If you can't get round an mtb trials course then something would be wrong. However feed that level of power to a DD hub motor and it is quite poor at climbing. Like any vehicle, gears make a huge difference
 
friendly1uk said:
... Like any vehicle, gears make a huge difference
Click to expand...
Good point. I had a tiny Suzuki Samurai 4x4 that only had around 75HP. I put in lower gears and the top speed was only 65mph. But put her in low gear and it could crawl over anything.
 
Total power needed =
power needed to overcome rolling resistance +
power needed to overcome aerodynamic resistance +
power needed to overcome changes in speed (kinetic energy) +
power needed to overcome changes in elevation (potential energy)


So the main inputs are

How heavy is your all up weight
How fast do you want to go
How steep a hill do you want to climb

with that info you can solve the problem (once you look up the formulas).
 
http://kreuzotter.de/english/espeed.htm

It's a good speed and power calculator. If you want to simulate an e-bike operated without pedaling, set the cadence to 1 rpm. (Pedaling affects aerodynamics, so it has an effect on speed.)
 
More watts = faster arrival time
Its a classic case of each to there own , it comes down to desire and compatibility some people do well with less watts / top speed while others desire more volts and rpm from their rides. 48v systems are not wild systems instead they are punchy. 72 and 100v systems are within reach for most people if they plan well and want the speed which is why we see it so often.
 
It depends where you live and what you carry around too. People that live in fairly flat places really have no concept of a "big hill". Climbing a 10% hill for a few miles is nothing unusual where I live, if I couldn't pull my mid drive into a low gear I'd need substantially more power to even make it where I need to get sometimes, let alone at a decent speed.

Also sometimes I'm carrying a hundred extra pounds of cargo with me up said hill.

My bike works for a living, it's not just a toy I use for exercise and entertainment sometimes.
 
You must log in or register to reply here.

Similar threads

B
Converting a gravel-bike
Replies
6
Views
571
baisikol
B
K
BBS02 vs BBSHD - how much can you alter programming also
Replies
16
Views
1,836
uhmwpolyethylene
U
M
determining the over/under voltage capability of motors?
Replies
0
Views
138
mindgames11
M
inkobl
Valdenaire french postman bicycle TSDZ2B, TSDZ8 or BBS02B ?
Replies
22
Views
1,746
inkobl
inkobl
R
    • Like
Really good article comparing Bafang vs. Tongsheng vs. CYC
Replies
12
Views
10,633
999zip999
999zip999
Back
Top