A Couple of Newbie Questions..

These aren't very complete answers, but I'm sure other folks will fill in the gaps:
1) I've experienced no problems rolling backwards at walking speed with my crystalyte 5304 and 72v35a instant-start controller.
2) Regarding freewheeling resistance, I don't believe it matters whether the motor is on the front or the rear. Higher winding count (more torque/amp) hubmotors will "cog" (stick a little at points while freewheeling) a bit more than lower winding count hubmotors. The drag from cogging is barely noticeable on my rear 5304. Hubmotors will built-in freewheel mechanisms, such as the BMC Puma and the (I think) the Heizmanns, should have the least drag. For me, the extra weight is much more of a "drag" while pedaling unpowered than is any cogging effect.
3) No idea.
4) I looked at the revo wheel too, but the specs looked far too under-powered for my desires, (1hp versus 3.5hp)
http://www.revopower.com/the_wheel.html
http://visforvoltage.org/blog-entry/4-xysters-x5-images-and-stats
too complex and likely to break-down, too dirty and too loud. The electrics can be very stealth, allowing access to every place normal bicycles go. I'm very happy I went all-electric. For really long trips, a bike trailer can be rigged with extra batteries or a small generator.

--xyster
moderator

My rides

My take on the questions presented.

• I think the only trouble is the safety factor. If you are rolling backwards with a rear hub motor that has a lot of power to it (say 72 volts) and by accident punch the throttle, you'll probably pull a wheelie and fall on your back. Otherwise, rolling the bike backwards does nothing to damage the motor or batteries unless you are rolling it backwards on purpose and using the throttle for juice to fight the motor and batteries for some odd reason.
  Pedal first controller would solve that "problem" in a way yes.
• Basically the hub motors act like generators when you aren't putting juice to them. But most controllers are setup only allow a little or no current to flow back into the batteries mainly for safety reasons. There are hub motors that freewheel just like the back wheel on your bicycle will when going downhill. In my experience, the slight resistance from the motor is nothing compared to the total weight of the bike as a whole. The weight is what will slow you down, since it will weight 3 or 4 times as much as it did before all the motors and batteries. If you live in a flat area, pushing the heavy bike along will not be an issue. It will be an issue if you come to steep hill because it will be like pedaling your bike with a best friend riding on the back with you.
• They switch on the fly from what I've been told, as long as you are rolling it shouldn't be a problem.
• I would recommend going completely electric. It's quiet (big plus), and less stuff to really worry about. It's as simple (or not really, but appears that way to anyone that just wants it to work) as a motor, speed controller, and batteries. That's about it, only 3 things to really troubleshoot if you should have any issues. I can attest to riding my e-bike over 17,000 miles before I destroyed the motor (by my own stupidity I might add), which means I had to spend another $150 for a new motor, but the controller and batteries are still working just fine.

Yes, you can use whatever source of electricity you wish so long as it will:

1)Provide the voltage you want (voltage is like electricity "pressure"... like water pressure in a pipe. Higher the voltage, higher your top speed, and higher your hill-climbing/acceleration power, which is amperage X voltage) -- wire batteries in series to reach the needed voltage. Most ebike motors can handle "overvolting" of 50-100%. Most controllers will fry if overvolted more than 6 volts, some can withstand an extra 12-24v.

2)Provide the capacity you want for going as long/far as you want(this is total energy -- akin to the volume of "water" in your reservoir, the batteries) -- wire batteries in parallel to reach the needed capacity.

3)Provide the current you need (akin to the width of the electricity's "pipe", the electricity pushed by the voltage through the pipe out of the reservoir. Bigger pipe (more amps) means more power (more "water" passing a point at any time) but unlike voltage, more amps does not equal more speed) -- wire batteries in parallel also so that none is taxed beyond it's "C" or current capability rating. Your batteries must be spec'd to at least provide your controller's "amp" rating, else they'll overheat and die an early death.

4)fit within your weight and size limitations

5)recharge within your desired recharging timeframe. Batteries also have a peak current rating for charging. If exceeded, the batteries will also overheat and die an early death.

6)live as long you wish in both years, and charge/discharge cycles.

7)meet your environmental concerns (cadmium is toxic, and nicad batteries are banned from sale in the EU for example)

Nicad batteries are renowned for their longevity. 8 years or >1000 cycles is nicad's mean-time-to-failure when charged and discharged within current capability specifications.
http://www.batteryuniversity.com is an outstanding source for unbiased battery info.

--xyster
moderator

My rides

hey JDBauman/Knightmb,

i'm fairly new to ebikes too but i think i can answer number 3.i read somewhere in one of Steve Head's posts (techbikes) that you do need to back the throttle right off when changing speeds.maybe one of the more experienced guys can confirm.
I would say read as much as you can - like you i had no clue which kit to buy and i'm only getting my kit tomorrow after loitering around the forums for nearly six months!! lol
it totally depends on how far/fast you need to go in order to know which kit you need to buy - there have been some new developements recently and the choice is vast and a little daunting.
As ever budget will come into play with the lighter batteries costing a lot more than normal.A lot of guys here are very experienced with kit and they would tell you that lithium polymer are the current favourites of choice but cost an arm and a leg!! Motors are more or less the same sort of money but you need to decide if you want dual speed/bottom bracket/uspd - all good at different things.
There is a lot to consider so take your time and ask as much as you need to make sure your happy - it's a shame that the old v site is down as there was a mountain of info on it but this and other forums will help you - personally i would watch all the video you can it's the next best thing to seeing the bikes for yourself - knoxie/xyster/reid all have video to watch here and their setups are different and specced on the site,also there all nice fellas who will answer your questions and generally give you the confidence to build your own - i am just buying my first kit so i will log the build as i go - will give you an idea of how difficult it is as i have no previous experience and im certainly no rocket scientist!!
Best of luck JD!!!

D

For openers, Hubs can be divided into groups:
- brushed (like Heinzmann or some Crystalytes i.e. Sparrow) or brushless (like high power motors - Phoenix)
- geared or ungeared
- freewheel or no freewheel
- front or rear - of course!

1. I think the possible problem that can arise from pushing motors backwards is the generator-effect. If the controller is not powered up, this will drive power back into the controller FETs and this could damage them, as they are not biassed ON. I suppose this 'problem' might arise with any of the motor types. I don't think that many controllers are this sensitive, and I have never heard of any failing this way.

2 & 4. In order to generate power on over-run, you have to forgoe the freewheel. Personally I choose the freewheel, because this offers the best ride under human-power. Given the amount of time the bike is stationary, a solar panel would put more back into the battery than regeneration.

I don't think front or rear makes much difference unless you have a super-power front hub, where traction can be an issue. The biggest weakness of rear hubs is that they only accept screw-on blocks.

all the best

Hi there mr-motorvator,

Nice to see you on the site!

Nick F

(Brighton)

I read the warning about rolling backwards some where else. They thought brushes in a brushed motor took a set in the direction they traveled and backing up eould crack/break the brushes. Many DC motors will run in reverse just by switching battery polarity. Think about all the mobility scooters/wheel chairs and golf carts that drift backwards. I really don't think there is a problem. Jim