Advertise on Bikeforums.net



User Tag List

Results 1 to 7 of 7
  1. #1
    Member rick kimura's Avatar
    Join Date
    Mar 2015
    Location
    gold coast australia
    My Bikes
    repco MTB 26" + sram 2 speed automatix hub , road king cruiser 26" + lifepo4 48v x 12ah + 200w motor
    Posts
    35
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Big & small motors vs big & small batteries

    Ive been thinking about this recently and haven't come to any real conclusions , so im all ears to peoples opinions here . Its got to do with small and larger motors with batteries .
    my first kit is the 200w motor I now have , it came with a 36v 9ah li-ion bottle type battery . It gave me around 40kms @30kph (20mph)
    I then bought a 350w elifeQ100 motor and built another bike thinking it would go faster (which it did) , though using my 36v battery it only travelled HALF of that distance . The motor , though it went faster , i was disappointed about the battery running out of steam after 10 kms . I then heard on the forum that a more powerful battery can be used to power the 200w providing the controller caps are up for the task . Pulling the controller apart I soon found out it was ,,, so i went and got the (lifepo4) 48v x 12ah battery . Now to my amazement , not only am I getting over TWICE the original distance (80kms +) ,,, but it goes almost 15kms faster (40-45kph or nearly 30mph )

    So im wondering,,, why would you buy a bigger Watt motor and use a 36v battery , when a small watt motor with a bigger battery will do it better ? Im not real cluey on technical issues here , so this is what I have found in my short experience playing with motors and batteries .
    This is where technical knowledge comes in handy i suppose i need ?

    rick
    repco 26" 1995 with sram 2 speed hub
    cruiser 26" 1982 "the cruiser by road king"

  2. #2
    Senior Member chas58's Avatar
    Join Date
    Jul 2010
    Posts
    1,233
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Hey Rick,

    Your motor “size” (aka power) does not make much of a difference. The power is not determined by the motor. The power is determined by the Volts (battery) X amps (controller). The battery and controller determines your speed, power, and thus range.

    a “350 watt” motor may have a 36v battery * 15 amp controller giving 540 watts max power (your Q100), and typically 10 amps at a steady state (360 watts), while a 200 watt motor typically lowers the power by using a 24v battery.

    If you use the same controller & battery for your 200 watt and the 350 watt motor, you would get the same range. But I assume you used a different controller, giving you more amps, more power, and less range.

    The Q100 is a nice motor (I have 3). If you got the 200rpm version, you can run it at 48v and have a motor that runs at 260rpm (200*48/36). Of course if you over volt a motor you will have to be more careful about having the motor or controller overheat (i.e. it may burn up on hills or other places where sustained high power is needed at lower speeds).

    Any more questions?

  3. #3
    Senior Member
    Join Date
    Feb 2013
    Location
    Midwest USA
    Posts
    51
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by rick kimura View Post
    Ive been thinking about this recently and haven't come to any real conclusions , so im all ears to peoples opinions here . Its got to do with small and larger motors with batteries .
    my first kit is the 200w motor I now have , it came with a 36v 9ah li-ion bottle type battery . It gave me around 40kms @30kph (20mph)
    I then bought a 350w elifeQ100 motor and built another bike thinking it would go faster (which it did) , though using my 36v battery it only travelled HALF of that distance . The motor , though it went faster , i was disappointed about the battery running out of steam after 10 kms . I then heard on the forum that a more powerful battery can be used to power the 200w providing the controller caps are up for the task . Pulling the controller apart I soon found out it was ,,, so i went and got the (lifepo4) 48v x 12ah battery . Now to my amazement , not only am I getting over TWICE the original distance (80kms +) ,,, but it goes almost 15kms faster (40-45kph or nearly 30mph )

    So im wondering,,, why would you buy a bigger Watt motor and use a 36v battery , when a small watt motor with a bigger battery will do it better ? Im not real cluey on technical issues here , so this is what I have found in my short experience playing with motors and batteries .
    This is where technical knowledge comes in handy i suppose i need ?

    rick
    The faster you go, the more power you need to reach and maintain this speed. As you go faster, -all- types of drag increase. What this means is the amount of resistance you encounter as you go faster, for example as you go faster through the air drag increases, a lot. Most of the it takes to keep you going at a higher speed is spent fighting the drag you encounter from air.

    There is a lot to electric bicycle motors, many different approaches.

    Direct drive hub motors have no gears inside, no clutch (don't freewheel) and are large and heavy because they spin at a 1:1 ratio. They need a very high pole count to achieve a reasonable level of efficiency during from stop acceleration and hill climbing. Due to their larger surface area though, direct drive hub motors will often have a significantly higher thermal capacity. What does this mean? It applies directly to your question, your limit is how much power you can put through the motor without burning the motor. The higher the thermal limit, the more you can do with it, very simple. So why would someone want a higher thermal capacity motor? The rider weighs more, they carry heavy loads, they climb mountains, they like to accelerate really fast or go really fast and so on.

    Your motors are geared hub motors. Geared hub motors have planetary gears that turn the motor a certain number of times for every 1 revolution of the motor. Maybe your Q100 has a reduction ratio of something like 8:1, this yields certain advantages and disadvantages. The summary of this is you can make a much smaller and lighter motor, while not necessarily having the same capacity, can achieve a lot for it's size. The down side to geared hub motors is the gears themselves. They aren't anywhere near as quiet as direct drive, they can wear out and break. The gears themselves provide some friction as well, so lets say you hypothetically had two identical motors, one was direct drive and one was geared, you would get more propulsion from the direct drive motor at it's peak efficiency compared to the geared motor simply because the drag from the gears wasn't present.

    Geared hub motors have the potential to yield advantages in acceleration and hill climbing, due to their reduction ratios they have a higher efficiency at slower speeds. The idea that I am talking about is efficiency curve. Electric motor efficiency is directly tied to it's RPM. This subject is extremely broad and many variables go into, ideas like KV, winding, wheel size, voltage, laminations and so on are all probably wildly beyond the scope of your question, but they are subjects that are directly correlated.

    Beyond direct drive and geared, there is side or left side drive, mid drive, and friction drive methods for transmitting power from the motor to the wheel. All of these routes have pros and cons.

    Side drive is a bit more simple, but not as visually appealing.

    Friction drives are pretty simple themselves, but wear down tires faster, and sometimes even slip or fail to transmit power to the wheel.

    Mid drive is pretty popular in it's variations. Mid drive allows you to use your bicycle chain and gears to transmit power. I won't go into the down sides of this approach, the main benefit is that you can keep the motor in a pretty ideal point in it's efficiency curve, where this is of most benefit involves really intense levels of acceleration or hill climbing. A lot of motors will turn most of it's power into heat during really slow sharp climbs, but being able to shift into the right gear will allow the motor to turn many times while still keeping the bike at a reasonable speed and allowing the motor to stay in a fairly ideal level of efficiency.

    Personally, I place the highest value on a motor much like yours for electric bicycles. I am working on new designs for a motor like the Q100 and Q75. I think there is a pretty substantial amount of room for improvement on these types of motors which will largely eliminate their down sides and provide a pretty intense amount of value. Small, lightweight, stealthy, really great. Not everyone can get by with a Q100, but really many of those people are probably riding lightweight electric motorcycles in disguise.

  4. #4
    Member rick kimura's Avatar
    Join Date
    Mar 2015
    Location
    gold coast australia
    My Bikes
    repco MTB 26" + sram 2 speed automatix hub , road king cruiser 26" + lifepo4 48v x 12ah + 200w motor
    Posts
    35
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    WP_20150309_005.jpgWP_20150309_002.jpgChas ,,, yes I used a different controller . I was impressed with how the Q100 motor performed but it flattened the battery in no time . What you say makes sense ,,, I should have used the controller that came with the battery on the 200w .

    Sheeeeeesh !,,, if id known that I probably be using it now with the new battery ,,,and getting even better performance . Possibilities are endless .
    Yes , they are a nice motor . I may invest in another later on down the track . Heres a photo I took after the build .
    repco 26" 1995 with sram 2 speed hub
    cruiser 26" 1982 "the cruiser by road king"

  5. #5
    Senior Member chas58's Avatar
    Join Date
    Jul 2010
    Posts
    1,233
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    That is a cool looking bike!

    FYI, I get about 24 miles on a Q100 at 23mph and 36v10ah. But, I do a lot of pedaling, so I'm not sure what the motor will do on its own.

    According to this site: Motor Simulator - Tools, it should go about 22 miles, so I'm not too far off. 10km doesn't sound right at all. I would expect at least 20km minimum, but more likely 30km on that motor/battery for ya.

  6. #6
    Member rick kimura's Avatar
    Join Date
    Mar 2015
    Location
    gold coast australia
    My Bikes
    repco MTB 26" + sram 2 speed automatix hub , road king cruiser 26" + lifepo4 48v x 12ah + 200w motor
    Posts
    35
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Bowlofsalad
    Great reading & thks for the detailed information , I hadn't thought about direct drive ,,, I gather they would wind out a lot more than a geared motor . I can see your point regarding the geared motor getting damaged easier as when I first started using it I would let it pull me from a stop position ,,,,, . It didn't take me long to figure out it doesn't like that ! so now I kick off ,,, pedal a bit ,,,then gently apply throttle .
    Many different approaches like you say ,, ill file this for future ref ,,,!
    rick
    Last edited by rick kimura; 06-03-15 at 12:31 AM.
    repco 26" 1995 with sram 2 speed hub
    cruiser 26" 1982 "the cruiser by road king"

  7. #7
    Member rick kimura's Avatar
    Join Date
    Mar 2015
    Location
    gold coast australia
    My Bikes
    repco MTB 26" + sram 2 speed automatix hub , road king cruiser 26" + lifepo4 48v x 12ah + 200w motor
    Posts
    35
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    WP_20150309_004.jpg
    Quote Originally Posted by chas58 View Post
    That is a cool looking bike!

    FYI, I get about 24 miles on a Q100 at 23mph and 36v10ah. But, I do a lot of pedaling, so I'm not sure what the motor will do on its own.

    According to this site: Motor Simulator - Tools, it should go about 22 miles, so I'm not too far off. 10km doesn't sound right at all. I would expect at least 20km minimum, but more likely 30km on that motor/battery for ya.
    Thanks chas ,,,,,,
    Last edited by rick kimura; 06-03-15 at 12:40 AM.
    repco 26" 1995 with sram 2 speed hub
    cruiser 26" 1982 "the cruiser by road king"

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •