How to Solar Charge an Electric Bicycle

[solbike]

There are four ways to solar charge a lithium ion battery that I know of; please comment if you know of others or better ways. Each has their advantages and disadvantages. A difficulty with solar charging lithium ion batteries for electric bicycles is that the best voltage to use for motor powers from 200W to 500W is 36V. This in nearly exclusively a voltage used for electric bicycles and it's near impossible to find commercially available systems for charging this voltage with care needed to make sure it's suitable for lithium ion chemistry (36V regulators for lead acid batteries can be found, many of these regulators can be set at 12, 24, 36 or 48V).

Here are the methods I can think of with their approximate prices and pros and cons -

1) Get a standard grid connected solar system and then use your charger from the mains power. Approximately $3000 for a 1.5kW system in Australia with current government rebate scheme. Advantages - can charge at any time you like, excess energy fed to grid and you get paid for it. Disadvantages - you need to own a home and have a spare 3K, nothing elegant about it, losses through the system through inverter, AC to DC conversions.

2) Get a 12V 80-100W panel, a 5-10A solar regulator, a 80-120Ah deep cycle lead acid (AGM) battery, an ~300W inverter (modified or true sine wave, both seem to work).Connect all of these items together then connect your regular charger to the inverter. Approximately $1300. Advantages - can charge anytime you like, system can be used for other applications, relatively small, can possibly be put in a trailer for cross county touring. Disadvantages - need an extra storage battery, losses through AC/DC conversions.

3) Get a 36-48V panel. Have an electrician construct a regulator to drop the voltage to float at approximately 42.5V. This is the voltage the regular charger puts out, I've found it to charge batteries fully and not over charge them. I've been using such a system daily for about 4 months. I don't know what the long term damage may be but nothing's exploded yet and range is still fine.If using a 100W panel (48V), then it'll take about 6-26 hours of sun to fully charge a 36V 10Ah battery from dead flat. Approximately $650. Advantages - Quite elegant direct system, can be mounted at work or home and you'll never have to charge from mains if you're in a sunny zone within bombing range of your charging capacity. Disadvantages - When the bike isn't connected the energy created is lost, can't re-charge at night, need to find an electrician to create a step down regulator to match your panel.

4) Get 10W panels (about the largest size you can comfortably attach to a bike) cut specifically to give a closed circuit voltage of ~ 42-43V open circuit voltage of about 50V) - connect this straight to the bike battery. Some Chinese factories will do this if you promise it's just a test sample and you'll by hundreds (of containers full!). Approximately $100. Advantages - small and can be put on a bicycle (see picture), most efficient use of panel energy. Disadvantages - will only allow about 1km travel per hour in the sun, un-regulated system is probably not ideal and could cause battery damage over time (though so far so good).

I've put these methods in a video (it's near the end of the conversion kit video at about 14min into this youtube clip posted here):
http://www.youtube.com/watch?v=N58Jq77-E4k

Matt - Solar Bike - www.solarbike.com.au

[neptronix]

This video contains content from EMI, who has blocked it in your country on copyright grounds.

Damn you, copyrights.

Anyhow i like #2. With a lipo charger, this is easy since most lipo chargers can run off of 10-18v; some even higher than that.
Use a big ol' SLA battery to capture the solar power and run the lipo charger straight off the 12v SLA.

Even better; 3s lipo has a max charged voltage of 12.6v. If you can adjust a solar regulator down by about a volt or volt and a half, you could use lipo as your storage battery. Then you can sidestep the problem of how SLA loses it's lifespan when left below a 50% charge state..

[liveforphysics]

#1 Is the only option that makes sense. Always the most effective use of the solar cells, and they can be making useful energy anytime its sunny, doesn't matter if you happen to be plugged in or riding, or yor lead is full (and lead has a terrible charge storage efficiency), or if your bike isn't facing the sun, and it feeds power everyday to the grid you will be drawing from anywhere you charge in your area.

[Dave Sloan]

Take the money you save with riding an ebike and buy system one - when you think about it - where-ever you plug in you are plugging into your system = the grid - much lighter to carry = 0 kg. Do not buy cheap inverters as they will cost you twice as much in the end through failure and being very inefficient. Cost = 2 x 200 watt panels = 800 dollars with shipping plus 2 x 220 volt inverters - enphase are approx 400 with shipping. Only disadvantage is that you must have enough power to get to the next plug.

[brisbanebikie]

option 5) Sell the military stealth bombers (it is actually a deal in progress), convince them that solar power is the way to go when they are in the middle east with no power. Within a matter of days or weeks their unlimited budget will develop a solar powered charger the size, weight and flexibility of a newspaper that can easily connect to and charge any battery type in 30 mins.

edit: 2007 they were talking about fotovoltaic cells, which are so thin they can be used in paint... so just paint your bike with this and it recharges automatically.. that was 2007... 2011 we still dont have it but the technology is there...


i like this topic...

ive read posts from people here who carry a charger with them in the hope of finding a public socket they can charge for free.... not mentioning any names.. hehe
but this is Definatly a better alternative.

Leave the masses who worry about petrol prices going up and up...


edit: September 9, 1986, lvin M. Marks "Lumeloid..., could turn 70 to 80 percent of the energy from sunlight they receive into electricity. Most photovoltaic cells are only about 15 percent efficient. The electricity would cost three or four cents per kilowatt hour, as against about 10 cents a kilowatt hour for commercially generated electric power. Most photovoltaic cells produce energy for around $1 per kilowatt hour. "

"The Exxon Corporation recently offered $9 million for Mr. Marks's patents,....But company officials chose not to sell"

- http://www.rexresearch.com/marks2/marks.htm

edited: few times

[liveforphysics]

If you have a grid tied solar setup at home, everywhere you opportunity charge, and everywhere other bikes and EV's charge in your area, they get to use the grid you are supplying.

If you put them on your bicycle, then your solar cells do the least helpful work for the most inconvenience.

[Lock]

I have a fifth option...
http://www.bullfrogpower.com/

I just need to estimate my monthly kWh consumption and for an extra three cents per kWh I'm running 100% wind and solar. This works whether I am charging at home or not, and also works day and night. No initial capital outlay, no extra weight added to the wheels. Equipment maintenance and amortization costs all included.

Tks
Lock

[neptronix]

https://www.bullfrogpower.com/home/onfaq1.cfm#ont3

With Bullfrog Power, you continue to draw electricity from the regional electricity grid, or natural gas from the national natural gas pipeline system—just as you always have—and Bullfrog's generators inject renewable electricity or green natural gas onto the respective energy system to match the amount of electricity or natural gas your home or business uses. No special equipment or wiring is required.

So it's like buying carbon credits ... you hand someone money, they promise they'll do something, but you have no way of verifying that they're actually doing what they're doing.

Oh, they have audits through some 3rd party company.. that they picked..


I'll take the panels please.

[dogman]

Option 2 has some advantages, but only if you get to use some of the power in the house. During the ice storm, or other power outage, a handful of plugs that still work in your house would be real nice. Seperate sytem from the grid plugs in the house. Power goes out, your grid tie solar is shut off.

I ride my bikes a lot, pretty much daily. So about 500 cycles a year x an average charge of a dime. Wow! that's 50 bucks a year of power!

You want to save the planet, buy 50 bucks worth of insulation, caulking, etc and save hundreds of dollars for years and years. Saving the power that runs an ebike is not doing much. There is much lower hanging fruit. Parking the car and riding the ebike is a huge impact. how you charge an ebike is a tiny impact.

Think of it this way, when you don't drive a car, you just bought a huge carbon credit. You know it happened, you did it. The carbon you just didn't use will more than make up for that dimes worth of electricity.

But if you put in a solar collector that runs your TV, or even better air conditioner, then you are doing a significant thing.

[dak664]

Option 2 does have the advantage dogman says, for those who need a backup system anyway. But SLA batteries have poor charge efficiency and need absorption time for maximum life, which has terrible charge efficiency. Replacing that with a LiFePO4 battery would give good charge efficiency and no adsorption time, and still give the backup system. And with two batteries you could swap between bicycle and PV as needed.

24 volt panels generally put out 45 volts open circuit or 36 volts at maximum power, a pretty good fit to a 36 volt battery pack. Depending on temperature and pack size no charge controller may be necessary (or the internal bms will suffice). Below a couple amps a simple PWM buck or boost converter could correct for a larger voltage mismatch. Don't know if those are available are off the shelf though.

[Lock]

So it's like buying carbon credits ... you hand someone money, they promise they'll do something, but you have no way of verifying that they're actually doing what they're doing.
Oh, they have audits through some 3rd party company.. that they picked..

I'll take the panels please.

Hehe... EVery company in the world chooses their own auditors (plus gov auditors etc), in this case Deloitte Touche Tohmatsu Limited.
http://www.deloitte.com/view/en_GX/global/index.htm
To discount this process, ya can dispute EVery set of audited statements published EVerywhere by EVery company etc in the world. Might as well question EVery business professional while yer at it.

LocK

[ebent]

I can think of 2 good reasons to persue this endevour.

1. This is a great science project. It can propel you to the next and next and maybe something practical can be the result.

2. If one intends or is currently in a remote area without electric. Not too many places like that but I know a few.

Maybe there is a third or forth good reason but I can't think of it.

Otherwise Dogman is spot on. Dogman rides a lot and his cost is $50. My cost then is a lot less. If this is a learning opportunity to create something financially effecient and you have the gray matter, you can help us all. If not then plug in.

[stanz]

Option #1 is the only one that makes sense.

edit: September 9, 1986, lvin M. Marks "Lumeloid..., could turn 70 to 80 percent of the energy from sunlight they receive into electricity. Most photovoltaic cells are only about 15 percent efficient. The electricity would cost three or four cents per kilowatt hour, as against about 10 cents a kilowatt hour for commercially generated electric power. Most photovoltaic cells produce energy for around $1 per kilowatt hour.

The theory sounds good but they still haven't delivered anything out of the lab. You'd think with how hot solar is right now they would have at least shown a prototype running at high efficiency.

Here in the USA commercial solar installations are profitable in 2-3 years due to government subsidies even with today's solar cell technologies.

[jbond]

Another option. Get 3 12v trickle chargers designed for a car. Wire them in series to get ~36v. Then get a spare 36v battery charger for your 36v E-Bike. Open it up and apply the solar 36v out to the rectified side of the 4 diode rectifier on the 240v input side of the charger.

[liveforphysics]

Another option. Get 3 12v trickle chargers designed for a car. Wire them in series to get ~36v. Then get a spare 36v battery charger for your 36v E-Bike. Open it up and apply the solar 36v out to the rectified side of the 4 diode rectifier on the 240v input side of the charger.

Just curious, are you retarded by chance?

[grindz145]

Another option. Get 3 12v trickle chargers designed for a car. Wire them in series to get ~36v. Then get a spare 36v battery charger for your 36v E-Bike. Open it up and apply the solar 36v out to the rectified side of the 4 diode rectifier on the 240v input side of the charger.

Just curious, are you retarded by chance?

dood! Harsh......

...yammer yammer...

#1, unless you trek deep into the wilderness and still need to charge up....

[jbond]

Another option. Get 3 12v trickle chargers designed for a car. Wire them in series to get ~36v. Then get a spare 36v battery charger for your 36v E-Bike. Open it up and apply the solar 36v out to the rectified side of the 4 diode rectifier on the 240v input side of the charger.

Just curious, are you retarded by chance?

OK. tell me why it won't work. Then go and look at this. viewtopic.php?f=6&t=13091&p=193922&hilit=solarbike#p193922

[heathyoung]

I'd be looking at a decent panel size and voltage - at least 2, 180's or 250's - coupled with a proper MPPT setup and DC:DC converter to get your float voltages right, you would be losing the least amount of power in conversion losses.

[liveforphysics]

AC power comes in, gets rectified to DC, filtered with a cap, then switched at 50-500khz, run through a step down transformer, rectified again, and then sent to a regulation stage (linear or switching), then filtered, and sent to the pack.

Just hook the cells to the battery if you wanted to do it that way. (and either select the right panel voltage, or use a simple $5 HVC circuit to open a relay when they are topped off) But again, cells on the bicycle itself in no way make any sense, likely the most wasteful application you could use the cells for.

Grid-tie at home in a permanent installation. From sunrise to sunset, you can have your cells supplying energy in the most efficient way. You'r cells will always be creating the most useful energy possible, doesn't matter if you're riding, or parked your bike at a bad angle to the sun, or brought your bike inside, and you don't have to waste extra energy and liability dragging around solar cells (which is semi-retarded in it's own right).

[Gordo]

https://www.bullfrogpower.com/home/onfaq1.cfm#ont3

With Bullfrog Power, you continue to draw electricity from the regional electricity grid, or natural gas from the national natural gas pipeline system—just as you always have—and Bullfrog's generators inject renewable electricity or green natural gas onto the respective energy system to match the amount of electricity or natural gas your home or business uses. No special equipment or wiring is required.

So it's like buying carbon credits ... you hand someone money, they promise they'll do something, but you have no way of verifying that they're actually doing what they're doing.

Oh, they have audits through some 3rd party company.. that they picked..


I'll take the panels please.

Are there really enough stupid people on the planet to support this GREEN BS?
+1 on the panels.

[Lock]

Are there really enough stupid people on the planet to support this GREEN BS?
+1 on the panels.

Hehe... didn't realize it was that complicated. I'm just buying electrons from somebuddy elses grid-tied panels, wind gen, etc... or are grid-tied panels also "BS"?
Lock

[John in CR]

Charge controllers are available with almost any desired output voltage (to the battery) and a wide variety of wide range input voltages. While previous posters are correct about overall economic efficiency and grid tie, our bikes are low power enough that solar charging is feasible in some cases. Once I figure out how to DIY some panels for my bike I expect to only rarely need to plug it in to charge. Of course I'm in the tropics and at altitude, so it's just not the same sun. Plus my rides are typically just short blasts with multiple trips per day, so I can park my bike with the panel(s) at good angles to the sun. Paying only 50cents/watt for the solar cells is what puts it in the realm of making sense, especially once I do a trike with a roof or body.

To me light, durable, and cheap panels are the hold back, not the electronics.

[solbike]

If I had enough money to buy a house and then a bit spare then of course the best option would be to have a grid connected system. Second to that, I like the 36-48V panel regulated down to 42.5V and then directly hooked up to the bike battery. Even though I'll never recover the expense of it all (about $350 all up for me direct from factories) I figure that things aren't always about the money and it's just nice to get some system working. This system actually is pretty good in a few respects as well that weren't mentioned earlier. There are no AC/DC conversion losses and in most cases if you can situate it at work then you are actually getting most of the energy out of it. My uni let me set one up there and I travel 9km to work and 9km back and never have to use my mains power. It's not really the saving from mains power (which is less than 5 cents per day) but it's the feeling of riding on solar energy, the convenience of not having to take my bike or battery inside my house at night to charge up again and also just because we can!

This is the 100W direct solar charging setup I put up at my uni (it actually takes a bit longer to charge than mentioned here but in summer in Perth it's constantly pumping out the electrons):
http://www.solarbike.com.au/solar_success.php

Incidentally, for those wishing to maximise things. I've been playing around a little with testing panels that have a different open circuit voltage. These "48V" panels I bought have an output voltage of around 80V, when I regulate/drop this down to 42.5V I seem to be losing a lot of energy as the maximum current I've been able to measure going into my battery is 1.5Amp (though usually it's about .6-1A). This equates to a max of about 64W - so only really about 64% efficient - though I've been getting these panels from only a mid-range factory in China as they are the only ones that'll do me custom things in low volumes so it was probably never the specified 100W in the first place. When testing with 80W panels that have an open circuit voltage of 54V, I can get a very similar charging rate. Meaning to me that the extra voltage is indeed lost. This could be a factor attributed to regulator design but I believe for a really good "direct" solar charging system then it's best to have the panel at a voltage that will give above about 45V all through the day but not too much in excess as this will be potentially wasted.

[dogman]

I agree, the cost of the panels is what makes other ways of spending money to be green a better way to go. For example, change to led light bulbs, get a more efficient fridge, insulate, or more efficient AC or Heater for the house.

But again, if you have other reasons to desire solar energy that make the setup make economic or practical sense, then the tiny bit you use on the bike won't hurt. I'm thinking of course, of places where there is no power, or you'd have to listen to generators running to have some.

Nothing at all wrong with going grid tie, if you are going big. I'd only want to be off grid with a very small size PV setup.

Personally I'm getting tempted to set up an off grid 200W panel. Then run my TV on the lead acid battery bank. Stupidly expensive per KWH, but I get a back up power plug for those too frequent outages without dragging out the generator from the garage. At least the TV will still work during outages, as well as a charger for batteries. It would get me more power daily than I'll ever use on the bike, thus making the claim possible that my ebike fleet is completely carbon neutral. So what if I still plug the bike into the grid, if I took the TV off it? What matters is that I'm using that much less grid power, not that I actually plug the bike into the actual solar panel.

Soon as the house payment is gone, I want to power the whole house 80% solar. With grid tie. About 7 years from now.

Ya posted while I typed my post. Cool setup on the roof of the school. I'm fuzzy on one thing though, does the pole you plug into ever cut the amps when you are charged? or does it just keep feeding 42v at whatever amps the panel is producing at the moment? I thought that kind of trickle charging once charged was bad for lithium, so that is why the chargers either shut off entirely, or in the case of lead acid chargers, cut the amps to near zero.

[stanz]

I agree, the cost of the panels is what makes other ways of spending money to be green a better way to go. For example, change to led light bulbs, get a more efficient fridge, insulate, or more efficient AC or Heater for the house.

In today's dollars a solar panel installation would be a better financial deal than switching to LED bulbs. LEDs are more efficient incertain applications when you look at lumens/watt but at a much higher cost. I can buy a 12 watt CFL at Home Depot for less than $1 in CT due to incentives. A 60W LED replacement at Amazon, cheaper than Home Depot, is $28.20. The LED bulb consumes less power but it will take many years of average use you pay for the $27.20 difference.

Edit: I just took a closer look at the Amazon LED bulb that is a 60W "replacement" ... it only puts out 300 lumens, that's less than a 40W incandescent!

Solar installations get you a 30% tax break from the feds and in some states up to $2 per installed watt back from your government. I have a college buddy that installs solar systems in NY state and due to all the grants/tax breaks the installations are making money in about 2.5 years. That's a great investment.

I'm trying to do a solar installation on my home and at work. Not because I'm a "green" person but because it makes fiscal sense. Power costs aren't coming down, solar is a good hedge against future costs.

Insulation is also a great investment since our local gas company will pay 75% of the cost up to $2,000.