alswiseowl

hi there,
just wondering if anyone knows how remote controll(helicopters) batteries go on ebikes
there light small and sell them in 12v packs in the shop for about $100
any one here have experience using these lightweight small batteries on there ebike
thanks

unime

The largest RC Li-poly pack I have seen is 10Ah at 22.2V - sufficient charge, but not enough voltage for ebike use in my estimation. You'll have to double up (or more) on packs to make a battery. Then you'll have to decide whether to add a battery management system, or run the pack without protection (and use a separate balancing circuit when charging).

The good thing about RC Li-polys is very high power capability and low weight, but the cost is typically very high. ThunderPower and Traxxas packs sell for about $2.7/Wh, though I've seen discount brands of lower power (e.g. 8C discharge rating) Li-polys selling for $1.7/Wh.

For comparison, the industrial strength Li-ion commuter pack (18650 cells, I believe) for my Optibike, complete with charger, BMS, and aluminum enclosure, sells for somewhere around $2/Wh. Other lithium batteries are likely to cost less, but the Optibike pack is rated and runs at 80% capacity for longer life.

I had an opportunity to talk with the battery supplier to Optibike the other day. He told me they originally used Li-poly batteries, but had high failure rates. Some of the failures were due to the expansion and contraction of Li-Poly cells in use and issues related to packaging them, but I do not know whether other factors played a role.

If you choose to go with Li-polys, be sure to package them in a way that will minimize harm if they explode. This is standard advice for RC use - for example, I charge them in a metal can placed on a heat resistant surface.

Optimaman

I'm using RC lipolys. Right now, I'm doing 20s1p or 10s2p of the 10,000 mah Maxamps cells. At one point, they were only 37 bucks each but now they're asking 100 bucks each so it's not worth it (740 bucks vs. 2000 bucks). I already have the balancers and chargers so that wasn't the issue for me. It works very well. The limiting factor is my controller now whereas before when using lead acid, the limiting factor was the batteries.

alswiseowl

thanks for the info guys,

alswiseowl

i have also seen slofly.com electric bike build from r.c parts.
just wondering how easy it would be to adjust a twist type throttle,+using a large r.c heli motor with a sprocket,running it thru the bicycles gears...any one have info or links to where i could learn from.
i currently own a 36v 30amp 400watt electric hub(front drive)i have been very happy with it,except for the weight,its heavy.+when it comes to big hills(you know)..

so i was at my local r.c shop the other day & noticed this motor about half the size of a coke can,light as a feather+ could produce more than 4500watt.i thought this would be perfect for a cyclone type set up.the motor was brushless,selling at $150aus...
but the only thing stopping me from building it is the throttle issue...
the guy said finding a twist type throttle or making one could be a bit tricky..

does anyone know how to adjuct a thist type throttle so it runs conpatibly with r.c parts..

once again thanks on the battery advice...

unime

No biggie, use a controller that takes analog input like this, or build (or modify) a servo eliminator to work with a standard throttle.

Much harder to get this right. Start with the 78 pages of discussion here and let us know what your plans are.

Fabricating efficient high ratio RPM reduction, freewheel cranks, mounting bracket, protecting the tight tolerance motor from the elements while ensuring massive air flow for cooling, protecting the chain or belt line so it doesn't eat you alive, and matching a controller to work efficiently over the full RPM range the motor is capable of are all challenges to be overcome, and you're only worried about the twist throttle?

alswiseowl

unime,gees you really have opened my mind up..& down + turned it around.

now after what you have just mentioned,looks like its time for plan b or c
plan b: is building luc123 type of ebike..(i imagine you know of) ..whats your thoughts on this build.

or plan c:at tncscooters.com they sell a 36v 450watt motor with a rpm reduction on it..
so i plan on buying one of these motors(even though its a brushed motor)+i can get cyclone freewheel cranks for $55.00(even though ive heard they are cheap quality..and put it on to my bicycle.
i still plan on using r.c batterys,i just need a pic of some set up in 36v or 48v packs
so what are your thoughts on nickel based batteries..
also does using a bms for the lipos prevent them from overcharging/blowing up..
thank your your time
alex.

unime

If I had a good solution along these lines, I wouldn't have spent a ridiculous amount of money on my Optibike. I find it genuinely hard to make mechanical systems like this that function well the first time, and I am certainly not alone. My sense is that this is a big project.

By the way, there's nothing terribly wrong with brushed motors. According to wikipedia: "Under high mechanical loads, BLDC motors and high-quality brushed motors are comparable in efficiency." Despite this fact, brushless motors tend to be built for very high efficiency (with thinner stator laminations, tighter tolerances, etc.), allowing them to run cooler and thus be smaller and lighter for the same power output (sometimes significantly so).

NiMH work well in my RC car, not so well for RC airplanes, and I didn't even bother with electric helis until outrunner Li-poly drives were available. Nickel is a big step up from lead, which some people use successfully in electric vehicles. The decision is yours.

A LiPo charger will prevent over charging, but I suspect the BMS will prevent charging above max voltage. As for blowing up, It should help, but naked LiPos can be physically damaged pretty easily...

alswiseowl

ok thanks for the information unime.
really my aim is to reduce the weight of an electric bike..+ a increase of power would be great..
but i bet not half as great as the optibike,gees that looks like a sweet ride & looks superb to say the least....im jelous.
so does the optibike motor use the bicycles gears...
once again nice ride umine

unime

Yes - it has a normal 9 speed rear cluster with a fixed front chainwheel.

The motor and reduction gearing fit inside the bottom bracket, and both the motor and pedals freewheel. It is an elegant solution, but good luck to anyone who tries to duplicate the motorized bottom bracket at home - they'll need it!

alswiseowl

hey there,
would you be able to post some pics of your battery set up...
+ pics of any important factors about the set up...
see i plan on using r.c batteries for my ebike,but the guy at the r.c shop thinks i shouldnt...
but i know thru the net that there is people out there like your self that can...i just need your help
im thinking of using nimh,just because they are a bit safer...
i just dont know how to set this up safely,so i need somewhere to learn from..
i would like to make a 36v 30amp nimh pack,is this possible
hope to hear from you soon...


alex