Search found 159 matches

by cerewa
Aug 14 2009 1:52pm
Forum: Battery Technology
Topic: laptop battery challenge
Replies: 9
Views: 731

laptop battery challenge

Seems like a lot of the folks on this forum know how to accomplish some pretty awesome stuff with electronics, so I wanted to offer a challenge. I know a number of Haitians who use laptop computers off-the-grid in Haiti. Small solar panels are not particularly expensive, but the cost barrier to gett...
by cerewa
May 10 2009 9:20am
Forum: E-Bike Technical
Topic: 9-speed cassette freehub
Replies: 5
Views: 2170

Re: 9-speed cassette freehub

In order to use your existing shifter, you'd need a 9 speed freewheel. Search google for 9 speed freewheel. Note that your crystalyte wheel with a 9 speed freewheel may be too wide to fit in your frame . With a steel frame, you can just bend to fit if you want; non steel frames (any metal or nonmeta...
by cerewa
Apr 05 2009 8:50am
Forum: Battery Technology
Topic: Need advice on mixing chemistries
Replies: 10
Views: 888

Re: Need advice on mixing chemistries

I purchased 2 new battery packs, 48V/20Ah LiFePO4. Probably I won't use NiCAD anymore, depending on the performance of LiFePO4.
Any experience with LiFePO4?
Just one of those 48V20Ah packs is some serious range. Two packs and you'll be able to go a long, long way.
by cerewa
Mar 27 2009 9:59am
Forum: E-Bike Technical
Topic: Do 5303's make noise?
Replies: 10
Views: 759

Re: Do 5303's make noise?

At anything near 100% of the no-load speed, pulse width modulation is normally not what limits the current to the motor, it's just I=V/R (current equals voltage divided by resistance) because the effective voltage is small (back EMF voltage being nearly as high as battery [forward] voltage). Of cour...
by cerewa
Mar 13 2009 10:47am
Forum: E-Bike Technical
Topic: will a car wiper run a dc ebike motor
Replies: 13
Views: 1692

Re: will a car wiper run a dc ebike motor

I suspect car wiper motors are something like 50 watts at the most. The motor and controller are both designed for that kind of low power use. If you want something that even matches a low power ebike, neither the DC controller nor the motor will be suitable, I suspect.
by cerewa
Mar 04 2009 2:34pm
Forum: E-Bike General Discussion
Topic: System (U, Motor, Controller) Efficiency
Replies: 118
Views: 63846

Re: System (U, Motor, Controller) Efficiency

This is for the commute I used to do. The motor's controller broke and I switched jobs, and these days I commute without a motor. 1. Efficiency (Watt-hours/mile): 6 - 7 watt hours per mile 2. Speed (mph | kph): 16mph (65 minutes each way, 17 miles each way) 3. Gradient (%): lots of hills, 10% of the...
by cerewa
Feb 11 2009 11:20am
Forum: E-Bike Technical
Topic: use 48v 20ah on rc controller
Replies: 8
Views: 829

Re: use 48v 20ah on rc controller

If it breaks we will know why. It apparently has capacitors (and other components, maybe) that are designed for 50 volts (actual volts) max. The ping battery is rated at "48V" but its actual voltage during use starts at about 56 volts and only drops to 48 volts when the battery is nearly 100% discha...
by cerewa
Feb 03 2009 3:47pm
Forum: E-Bike Technical
Topic: Reconfigure Ping LiFePo4 battery?
Replies: 12
Views: 1176

Re: Reconfigure Ping LiFePo4 battery?

cerewa, would that mean that there are only 3, to make up the full 12Ah? When I peeked under the tape, I saw tons of very thin ones, much thiner than real pop tarts... Each cell may be folded over on itself several times. A 48V12Ah pack that's made of 3V4Ah cells must be set up as 16-series x 3-par...
by cerewa
Feb 02 2009 5:13pm
Forum: E-Bike Technical
Topic: Reconfigure Ping LiFePo4 battery?
Replies: 12
Views: 1176

Re: Reconfigure Ping LiFePo4 battery?

to the best of my knowlege, your pack consists of cells that are 4Ah, nominal voltage 3V. (actual operating voltage closer to 3.1V to 3.4V) If that's true, you could set it up as 72V 8Ah provided you had an appropriate BMS or some other way to avoid over-discharging individual cells. The useable C r...
by cerewa
Dec 23 2008 6:09pm
Forum: E-Bike General Discussion
Topic: 7, 8, 9, 10 speed inefficiency
Replies: 13
Views: 1171

Re: 7, 8, 9, 10 speed inefficiency

On an e-bike that you pedal, yeah, 5 speeds should be enough.

E-bikes can keep much more consistent speeds with up-hills, compared to regular bikes. So there's generally no need for ultra-low gears.
by cerewa
Dec 02 2008 5:18pm
Forum: E-Bike Technical
Topic: Odd lengths of wire between batteries.
Replies: 6
Views: 748

Re: Odd lengths of wire between batteries.

If it seems like the long wire is eating more energy than you want it to, all you need is a wire that is fatter than necessary... Like fechter says, the wire will drop the voltage some, (under load only) but not the current. If the total voltage of the pack is dropped too much across the wire then y...
by cerewa
Nov 15 2008 8:22pm
Forum: Battery Technology
Topic: BMS's That are Available NOW
Replies: 40
Views: 5609

Re: BMS's That are Available NOW

What component is used to switch the capacitors?
by cerewa
Nov 05 2008 11:50pm
Forum: E-Bike General Discussion
Topic: experts weigh in: 72v at 10A or 36v at 20A, performance?
Replies: 13
Views: 1821

Re: experts weigh in: 72v at 10A or 36v at 20A, performance?

Besides high amperage and high voltage, another factor that could influence whether or not your gears will strip is rider+vehicle weight. If you put a lot of power into the motor and there isn't much resistance then why would the gears get damaged... but if there is a lot of weight to keep the wheel...
by cerewa
Nov 05 2008 9:35am
Forum: E-Bike General Discussion
Topic: Manufacturers/Dealers to Gravitate Towards
Replies: 270
Views: 107922

Re: Manufacturers/Dealers to Gravitate Towards

We recommend sticking to 48V or less and using 30A or lower motor controllers.
Peak power of 1,400 watts is a lot!

Yes, crystalyte 4xx motors can do well over 1400 watts but, assuming you are not looking for an e-motorcycle, 1400 watts should do.
by cerewa
Nov 04 2008 3:38pm
Forum: E-Bike General Discussion
Topic: Motor Bicycling Max Speed
Replies: 6
Views: 1148

Re: Motor Bicycling Max Speed

The 20mph is part of what can get you within the definition of "bicycle" and out of the definition of "motor vehicle". If you're riding a "motor bicycle" (moped) you may need a vehicle registration and liability insurance. Once you have a registered mo-ped, it's probably not legal on bike paths even...
by cerewa
Nov 04 2008 2:43pm
Forum: E-Bike General Discussion
Topic: Extreme efficiency?
Replies: 54
Views: 4626

Re: Extreme efficiency?

The way to make aero efficiency go much higher is to get yourself a full coverage fairing similar to the varna diablo. (There are a number of copies of that fairing, and one or two Varna molds where a person can make his/her own fairing.) http://images.google.com/images?q=varna%20diablo. Energy (per...
by cerewa
Nov 03 2008 3:30pm
Forum: Battery Technology
Topic: Thread for new battery breakthrough PR releases
Replies: 1642
Views: 225845

Re: World’s First Chlorophyll Organic Battery Runs on Any Liquid

it looks likely that they're nonrechargeable, and they may never become rechargeable.

half the "power" may actually refer to half the energy density...
...relative to alkaline nonrechargeable cells maybe?
by cerewa
Nov 02 2008 9:20am
Forum: E-Bike Technical
Topic: Connecting two BLDC motors in series?
Replies: 29
Views: 3069

Re: Connecting two BLDC motors in series?

I see no problem with running two BLDC motors together, but they would need separate controllers at least. The turn radius and tire scrub wouldn't be an issue at all IMO. This is correct. What Papa is missing is the fact that there's very little reason why the motors would want to maintain the same...
by cerewa
Nov 02 2008 8:30am
Forum: E-Bike Technical
Topic: 2 Brushed motors in series will....
Replies: 4
Views: 583

Re: 2 Brushed motors in series will....

Papa, you've got it right. Two in series will get all the amps and half the voltage. So you should expect twice the torque. The only way to know for sure if it'll work well is to try it, though. If you want to, you could also try halving the voltage of your battery (for example if it's four 12v SLA'...
by cerewa
Nov 01 2008 12:41pm
Forum: E-Vehicles General Discussion
Topic: The REAL difference between 30mph and 50mph !
Replies: 22
Views: 6318

Re: The REAL difference between 30mph and 50mph !

I would like to get more info about this "speed record?" The bicycle speed/power calculator http://www.kreuzotter.de/english/espeed.htm says that: 1000 watts gets you about 37 miles per hour on a road bike and 43 miles per hour on a high end timetrial bike. (upright bicycles). According to the calc...
by cerewa
Oct 31 2008 11:58am
Forum: E-Bike Technical
Topic: How to reverse brushless motor, even if it wont.
Replies: 44
Views: 14704

Re: How to reverse brushless motor, even if it wont.

Whether or not the motor has sensors, it MAY be possible to run it off of a sensorless controller, and then switching two of the phase wires will be enough to put it into reverse.
by cerewa
Oct 30 2008 1:25pm
Forum: E-Vehicles General Discussion
Topic: 48V, 93 MPH
Replies: 6
Views: 1406

Re: 48V, 93 MPH

In a speed run like that, the extra weight is not that much of a disadvantage since you have plenty of time to accelerate. And it's flat... The extra weight is an advantage, maybe, in the sense that you do anything you can do to keep the thing going in a straight line with all of its wheels on the ...
by cerewa
Oct 19 2008 9:17pm
Forum: E-Bike Non-hub Motor Drives
Topic: Cyclone Current Draw?
Replies: 4
Views: 1564

Re: Cyclone Current Draw?

run longer wires, (to the front of the tandem) and go light on the throttle. I didn't realize there was no currentlimit in the cyclone controller. I used a 1c-rated 24v10ah battery with my cyclone and never tripped the 20-amps bms current limit. But this is using the motor as assist only, on a light...
by cerewa
Oct 17 2008 7:49am
Forum: E-Vehicles General Discussion
Topic: fwd ice(honda)+ellectric driving rear wheels
Replies: 14
Views: 1902

Re: fwd ice(honda)+ellectric driving rear wheels

I think the increased weight would offset any gain you might see. You would also need something to disconnect the electric drive for the remainder of the pass to prevent any drag on the rear wheels. I saw a honda CRV (i think that's what it was) trying to reverse in snow, and the rear wheels were s...
by cerewa
Oct 10 2008 10:50am
Forum: E-Vehicles General Discussion
Topic: 19 new 100 mile range electric cars announced
Replies: 8
Views: 1320

Re: 19 new 100 mile range electric cars announced

And, for example for the last one, imagine road-side attenaes wirelessly sending electricity/energy to passing cars and each car had a capacitor with enough capacitance to handle the acceleration/hill-climbing needed. Not that the technology exists NOW, but if it emerged, wouldn't that be cool? It ...