intro - solar bike

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joy
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intro - solar bike

New member ... My name is Joy. I bought my electric bike in 2001 with a subsidy from the city of Santa Cruz. Now I live in the foothills of the Sangre de Cristo mountains of Colorado. It's a hybrid road/mountain bike conversion, with a 24v lead-acid battery mounted above the rear wheel. I just ordered my fourth battery!

I live off the grid, using 24v solar. I'd very much like to be able to charge directly off of this, or even better get an on-board panel to increase power and range. I may also get additional batteries to switch over and recharge a few miles away, again to increase range. I am 15 miles back on mostly dirt roads, and must contend with low temps, snow, and wind.

I'm getting closer to the dream of true solar electric transportation. Wish me luck, introduce yourself, and give me ideas.

Cheers,

Joy

reikiman
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Re: intro - solar bike

Hey, welcome...! The mtn's of Colorado are no doubt a lot different than Santa Cruz.

Anyway .. I haven't done anything with a solar panel on a bicycle but off the top of my head - charge controller might be required to avoid overcharging the battery pack - and of course the panels need to produce about 28 volts to properly charge the battery. And living off the grid you must have some experience with the why's of those two statements.

Obviously charging a lead acid battery should to be done by the proper charging algorithm if you're going to safely charge the battery to full. Namely the last section of charging has to be done slowly at low power etc. The charger you're already using does that but of course it requires 120v and in your offgrid home that means running the inverter which is wasteful. Maybe there's a way to directly drive the charger with (?? your house is running on 24 volts?? isn't that an oddball voltage ?? aren't most offgrid homes running at 12 volts ??) the DC house voltage.

The other obviousness is a fully charged 12v nominal SLA is charged at around 14v hence 24v nominal is 28v to charge. The panels need to produce that voltage.

An option might be to rather than treat the on-board panels as enough to fully charge the on-board pack, that the on-board panels are there to give a partial charge (not full charge). e.g. if the on-board panels produced 26-27 volts ... I'd imagine in that case you could hook the panels directly to the pack (via a switch and diode) with no charge controller and it would be fine.

joy
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Re: intro - solar bike

Fridge and water pump are 24v, everything else is on inverters. I guess they are from an RV. In the day it'll charge up to 28 or even 29, at night goes back down to 24. Obviously I only want to recharge the bike when the sun is shining! There ought to be a way to route it to the same kind of plug the charger puts out.

A big enough panel ought to be able to keep the bike going. I can switch the panel from the battery over to the motor, or have the panel assist the battery for extra juice. This can carry me on a fantastic journey.

marylandbob
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Re: intro - solar bike

Charging when at home, parked, is practical, but charging while riding is NOT! Why? at present, a panel of about 6 feet by 6 feet (36 square feet) is needed to capture only 250-350 watts of solar energy, and the output rapidly DECREASES if the panel is not aimed correctly to face the sun, or if shadows or clouds interfere with the sunlight! Masiintaining good sunlight exposure while riding would be very difficult, and the added wind drag and weight will also be a problem!(Most bike size electric motors require at least 250 watts) Even if you used a pair of smaller panels, say 20 watts each, with one on each side, to increase the chance that one of them would be in good sun, about the best it would do is give a very slight boost to your range-maybe 10% on a really GOOD day!---If you are using lead-acid batteries, in both your home and bike, you could charge from the home system by parralleling the bike battery with the home battery during hours of good sunlight, but you should add a "current limiting device" in the lead to your bike battery, and disconnect it during poor sun, or darkness times, to avoid discharging the home or bike battery. A current limiter can be fashioned by connecting a 12 volt, 55 or 60 watt halogen headlamp bulb into the lead to your bike battery. Simply insert it in series with the positive lead to your home battery. When the home battery is near full charge volltage, (27 to 29 volts) and your bike battery is near dead, (20 to 23 volts) connecting for charging will draw current thru the lamp, causing it to glow in relation to the charging current. As the bike battery reaches fully charged, the lamp will dim, and go out. If you leave the charged bike battery connected at night, it will help operate your household load, and will partially discharge, so do not leave it connected when system voltage is below 27.5 volts. Otherwise, there are some very good D.C. to D.C. converters available, with an 18 to 36 volt input, that can be set to provide a 28 volt output of 5 or 10 amperes, to charge your bike antime the home batteries are not completely dead. Many of these converters are about 90% efficient!--Bob

Robert M. Curry

amberwolf
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Re: intro - solar bike

If your solar setup is already designed to charge a lead-acid array, then in theory you could simply parallel your bike's batteries with that array during the day, and then disconnect them once full.

Practically it may not work quite that way, depending on your existing array and the amount of current generated by the array charger vs the current max limit on your bike batteries (printed on the side of each one). Also it will depend on the charge voltage the array charger puts out--if it is for a float charge it may be too low a voltage to properly charge your bike pack, which sees cyclic use and as such is charged at a higher voltage, usually. Again, check the side label of the batteries for that, and the array charger manual (if it's not a DIY).

--
Michael Elliott
Cybernetic Necromancers, Discorporated
Phoenix, AZ
Watch me build an electric-assisted recumbent bike from recycled junk:
http://electricle.blogspot.com

joy
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Re: intro - solar bike

I'll need to extend the range quite a bit, 40% or so over the advertised range of 15 miles, double or more the realistic range of about 10. I sit on a long gentle aluvial fan about 400ft above the valley floor. Work is 4mi, Moffat 15 mi, Villa Grove 16 mi, Saguache 20 mi, Crestone 23 mi. What other ways can you think of to extend the range (besides going on a diet)? Putting on bigger batteries and a bigger motor, maybe on a power trailer? Another way is to buy a second battery and charger(25lb), swap and charge at halfway point, charge at destination, pick up fresh battery at halfway point (or leave it there for next time).

I'll have to run my numbers... I'll have to look at my charger and get th wattage. I know my home panel is rated for 900 watts, realistically gets 600. I had thought about getting fold-up or roll-out panels to carry with me to charge while parked, I guess the crucial factors are weight and dollar cost per watt.

the biggest worry I have about taking sun while moving is dumping and damaging the panels. Here in the San Luis Valley, a high altitude desert, we have the best solar potential in Colorado. The roads go arrow straight, so I'd only need to adjust the tilt here and there. I can think of several schemes to do this.

Or maybe I really do need one of those road-legal golf carts.

amberwolf
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Re: intro - solar bike

I'll need to extend the range quite a bit, 40% or so over the advertised range of 15 miles, double or more the realistic range of about 10. I sit on a long gentle aluvial fan about 400ft above the valley floor. Work is 4mi, Moffat 15 mi, Villa Grove 16 mi, Saguache 20 mi, Crestone 23 mi.

Sounds like you need more than double the range, then, practically. With lead-acid, that's problematic in that it weighs a lot for the energy you get out, and on anything other than flat terrain that matters a lot.

Plus, lead-acid hates cold even more than most chemistries, so you can lose a LOT of capacity when it gets as cold as it does up there. Taking the bicycle (or at least the pack) inside with you will help some, to keep it at "ambient" temperatures aroun 60-70F or more. Insulating the pack well will also help, such as putting it in a styrofoam cooler, then putting some of those blue-ice type of gel packs in there, but warmed up in a pot of hot water rather than frozen. Wrapping it in a fluffy blanket would be better than nothing.

(I have a friend near Durango that has described the conditions she's preparing her cabin for now)

If your motor and controller support regen braking, then using that instead of your regular brakes whenever possible, and "riding" the regen brake on all downhills to control your speed would be a good way to "regain" a few percent of the energy you otherwise simply lose. If they don't support it, it may not be worth changing that to get it, though. The money could be better spent on a different chemistry pack.

Using a pack of one of the Lithium chemistries would help with both the temperature problems and the weight, but will be much more expensive than the lead-acid. The good news is that if you can DIY your packs, I know there are lots of people using RC car/plane/heli LiPo battery packs to run their bikes, and those can be had for pretty cheap for packs that can handle high currents for both charge and discharge, and can be wired up into as large a bike pack as you need.

Disadvantage to them is cost and the amount of DIY you have to do, and the care you need to take with them to prevent pack damage, unless you also buy a good BMS (Battery Management System) to control charge and discharge of the pack, like the modular one at TPPacks.

Headway makes arguably the best current solution for the money, and they're available from EVComponents.com in various sizes. They should also have the chargers for them, but you would want to ask them if you don't see them on the site, as that was the case when I looked a few months ago.

Ping also seems to make good packs, but you will need a pack at least two or three times as large as you would expect based on the Ah rating, as his (and other duct-tape prismatic) packs aren't rated at a C high enough to safely pull the amount of power you'll need for hills. That's going to get expensive, large, and heavy, compared to the cylindrical high-C cell type of pack Headway makes.

There are a lot of resellers of various bike packs to "avoid", based on people's varied experiences, and there is at least one list of them over on Endless Sphere forums. Might be one here, too.

What other ways can you think of to extend the range (besides going on a diet)? Putting on bigger batteries and a bigger motor, maybe on a power trailer? Another way is to buy a second battery and charger(25lb), swap and charge at halfway point, charge at destination, pick up fresh battery at halfway point (or leave it there for next time).

Any of those is a possibility, except a bigger motor probably won't change your range, just make it easier on it when you take hills. :) If your motor is a hub motor, changing over to a motor running thru the bike drivetrain *would* probably extend your range, because you could shift gears to help keep it in it's more efficient "fast" but less-loaded speed regions.

If you had a trike, or a sidecar, you probably wouldn't spill the bike, and could put a small panel for a trickle charge on there with little effect to the way you ride, except for the extra weight. That extra weight is the problem--on hills it is likely that you won't get enough power back from the panel during the whole ride to make up for having had to accelerate it's extra mass. You could do the math to figure that out, but I don't know what formulas you'd use.

There are several ways to make a sidecar from the back end of a second bike, including a tilting sidecar with basket between it and the bike built by Tho X. Bui here in AZ. If interested, I'll dig up some links if you don't find him on google.

--
Michael Elliott
Cybernetic Necromancers, Discorporated
Phoenix, AZ
Watch me build an electric-assisted recumbent bike from recycled junk:
http://electricle.blogspot.com

reikiman
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Re: intro - solar bike

+1 on getting lithium-iron-phosphate batteries. With my year-old pingbattery 36v15ah battery pack I can do 15 miles or more quite easily, and the thing weighs 1/3rd the weight of an equivalent SLA pack. I've never ridden further than 20 miles at a go and stopped because my butt was sore not because the battery pack wore out.

Amp-hours = range. A more powerful motor could decrease your range because you might end up hitting the throttle for extra power and use up the ah's more quickly. The way to increase range is to increase the ah's on board. And with the lithium-iron-phosphate batteries the energy/weight ratio makes it feasible to put more ah's on board than if you're using SLA.

joy
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Re: intro - solar bike

It looks like the cheapest way across the valley would be the battery swap...

Given the high cost of panels, Lithium is a step I'd like to take before solar... Please tell me more about the RC battery solution as my friend is an RC car dude and a patient DIY guy.

I thought of the "power trailer" as a way to carry big batteries or panels. I was worried a heavy load might burn out the motor, thus the larger motor. (A previous attempt to pull a trailer up a hill blew my batter pack).

An ultralight solar trailer would pull lots of watts, but panels would be expensive. Still, it would allow me to move about the landscape without needing a power outlet. Or, stop to charge in the sun and ride on at night. A 180 watt ultralight panel, 30 by 60 inches, weighs only 1.2 kg. It also costs nearly twice as much as the bike!

joy
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Re: intro - solar bike

Also my ultimate plan "A"... Getting in great shape and using leg power only to get across the big flat. Prevailing winds are an issue here.

evolvegreen
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Re: intro - solar bike

Hello Joy My name is Lorena and I think with a little more info I could help you. I guess your bike needs ac for the charge?? If that is the case you might be able to by pass that and just charge what is needed ie 6 volt or 12 volt DC right to the battery.

joy
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Re: intro - solar bike

The battery charger has 24v 1.2/2 amp output. The battery itself is a 24v 7-12 amp sealed lead acid battery.

evolvegreen
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Re: intro - solar bike

So at home you have a 12 volt solar system? If this is the case all you need to do is put 2 solar panels in parallel and connect to a 24 volt charge controller 10 amp then connect to your bike batteries to charge. This should work for you, The 24 volt controller 10 amp is only about $45. You could probable pick that up close to home. I hope this helps. Ensure the amps on your 2 panels are ok for the controller.

joy
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Re: intro - solar bike

It's a 24v system at home. Right now, I'm charging via AC, so some power is wasted. I'll see how long it'll take to charge, soon enough for a ride in the afternoon!

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