How to Solar Charge an Electric Bicycle

[stanz]

I still like the simplicity of a panel on the bike.

Oh, that's easy!

1) Build a bike with a full fairing.

2) Attach flexible solar panel film to the fairing.

Yes, they do make solar panel film with self-adhesive backing.

[dogman]

Going big with solar can depend a lot on the local tax incentives, and the deal you get with the electric company. Todays headline on the front page, 100kw PV installed and running on the cheese factory in NM. Plans to make it 300kw.

Meanwhile, the big news from Texas, dealing with the exact same El Paso Electric company, People who installed PV on their homes got electric bills that were up to 60% HIGER, than before. ????? It turns out they didn't read their contract too good, and texas state law didn't forbid EPE from sticking it to them. Turns out, the power produced does not go into their house directly. It got metered, and sold to EPE for .05 per kwh. Then they could buy the grid power they actually used for .15 per kwh. Hell of a deal eh? Add to that, they turned on stuff and left it on, thinking they had kwh to burn.

Better deal for New Mexico customers. A few years back, EPE had the same contract in place for NM. I read it, and said, no way no grid tie for me now.

[lcyclist]

A couple of years ago, I scored 2 Sharp panels cheap. I recently built a standalone solar shed in backyard. It is a 250W solar array with 4 Walmart group 31 125AH marine batteries for a 6kWh system. AC power is from a 2000W inverter.

Aside from charging my ebike/power tool batteries; I also use it to run power tools in my shop (saw, drills, etc) and use it to power my lawn mower/hedger. This winter, it will power my outdoor Christmas lights.

The shed is great for charging my lipos as it is isolated from the house.

Here is some pictures of my setup.

Solar shed

solar_shed.jpg (110.7 KiB) Viewed 553 times

inside

inside.jpg (86.89 KiB) Viewed 553 times

[liveforphysics]

Icyclist- I love it! Fantastic setup!

[jbond]

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.

I'd agree that putting cells on the bike makes no sense unless you have a very specific need, like a round the world trip or something.

If you have a boring (!), standard 36v or 48v E-Bike with the typical Li-On battery and charger, then I think plumbing direct into a spare charger makes a certain amount of sense. Switch mode power supplies really don't care what input voltage they have as long as it's above the output voltage. And the charger already knows how to charge LiOn batteries and has suitable cut offs and charging strategies. So applying enough solar cell voltage just after the mains rectification stage should work fine. On the link I pointed to, they'd successfully linked 3 12v solar cells to a standard charger. They had a need to put cells on the bike and mounted them on a trailer but of course, the cells could be stationary on the garage. The point I was trying to make was that for a minimal setup you can do away with the intermediate batteries and inverter or the big cost setup of solar into the grid.

Doing the math on the potential input and output WHr means that a minimal setup might take a very long time to charge your battery. However, if you don't use the bike every day, there might be a sweet spot in there where a couple of days of sunshine are enough to charge the battery for one ride. Even then, one charge of the battery is probably only pennies in electricity cost so you'll never recoup the investment, but you do at least have the feel good factor!

[stanz]

Going big with solar can depend a lot on the local tax incentives, and the deal you get with the electric company. Todays headline on the front page, 100kw PV installed and running on the cheese factory in NM. Plans to make it 300kw.

Meanwhile, the big news from Texas, dealing with the exact same El Paso Electric company, People who installed PV on their homes got electric bills that were up to 60% HIGER, than before. ????? It turns out they didn't read their contract too good, and texas state law didn't forbid EPE from sticking it to them. Turns out, the power produced does not go into their house directly. It got metered, and sold to EPE for .05 per kwh. Then they could buy the grid power they actually used for .15 per kwh. Hell of a deal eh? Add to that, they turned on stuff and left it on, thinking they had kwh to burn.

Better deal for New Mexico customers. A few years back, EPE had the same contract in place for NM. I read it, and said, no way no grid tie for me now.

If you buy power from an investor owned power company in Texas you get net metering, unfortunately EPE is not investor owned.

http://solarpowerrocks.com/texas/

[dogman]

That crappy deal with EPE for the texas customers is in the process of being fixed. Once it got on the local TV news, it suddenly looked like a bad idea for EPE to continue, politically. NM state law made that contract illegal here, so they had to improve the deal for NM customers.

What a great deal it was for those El Paso folks for a while though. All you had to do was spend 20k on a solar panel set up, and it added ten cents a kwh to your bill for every watt it put out. Cool! Now that the situation went on the media, EPE looks like the biggest jackasses on earth. Oh,,,,, that's nothing new. Refer to my comments on needing to use my back up generators several times a year, in a place that has ice storms every 30 years...... I could go on ranting forever.

Icylist's solar shed is exactly what I've been thinking of putting up. Just keep hoping to score some panels on the cheap someday. The perfect size for taking a few ebikes, a few power tools, etc off the grid. It doesn't matter what you actually run on the solar power, you are still producing just the right amount to say your bikes are green.

A resident in the condos where I work just put in 2 kw. His next purchase is going to be a plug in prius to replace his current one. So his car will be carbon neutral, and half of his house. Very cool. Nice for him, he's got cash.

[solbike]

If you have a boring (!), standard 36v or 48v E-Bike with the typical Li-On battery and charger, then I think plumbing direct into a spare charger makes a certain amount of sense. Switch mode power supplies really don't care what input voltage they have as long as it's above the output voltage. And the charger already knows how to charge LiOn batteries and has suitable cut offs and charging strategies. So applying enough solar cell voltage just after the mains rectification stage should work fine. On the link I pointed to, they'd successfully linked 3 12v solar cells to a standard charger. They had a need to put cells on the bike and mounted them on a trailer but of course, the cells could be stationary on the garage. The point I was trying to make was that for a minimal setup you can do away with the intermediate batteries and inverter or the big cost setup of solar into the grid.

Yeah, this is a good way for option 3. I thought of this and pulled a charger apart to have a look at it after seeing the youtube clip of someone doing this. I have little electric ability so got someone to make a regulator for me instead of trying it but I think this would be great to use the intelligence of a charger and limit potential bad things happening. I think that there are two levels of protection in any case, one is setting the output voltage to about 42.5 (for a 36V Li battery), when the battery reaches this voltage then no more charge should be able to enter into the battery. The second protection is from the BMS within the battery; hopefully it has intelligence enough to limit overcharge. Once actually, one of the transistors in a basic reg that was made for me blew out and the output voltage went up to the panel's open circuit voltage of 80V. This was plugged straight into the battery and strangely I could not notice any damage to the battery, it charged up just fine and thankfully didn't burst into crazy flames like I saw in one of the videos posted here. I'll try and get an electrician to pull a charger apart for me and show me where to connect the panel voltage and see how that goes. Any takers keen to help out? Send me an address and I'll send a charger out to you and you can fix it for me so I can plug a panel straight into it? jbond perhaps?

[liveforphysics]

Linear regulators eat a bunch of power.

You just want an HVC. I think Gary even sells them for $10usd assembled or something on that order of cheap. Of with 4 resistors and a mosfets you can make your own for $2.

Then you've got the best possible charge efficiency from cells to battery. It also takes up hardly any space, you could have it inline with the wire rather than a separate box.

[HumboldtRc]

Linear regulators eat a bunch of power.

You just want an HVC. I think Gary even sells them for $10usd assembled or something on that order of cheap. Of with 4 resistors and a mosfets you can make your own for $2.

Then you've got the best possible charge efficiency from cells to battery. It also takes up hardly any space, you could have it inline with the wire rather than a separate box.

How would I make a hvc circuit with 4 resistors and a MOSFET ? Any links? Or just a quick explanation... Thanks

Also can you tell me about making server PS's go into a CC mode, like I asked in the PM I sent a few days back...

[brisbanebikie]

"Imagine a world where sunlight can be captured to produce electricity anywhere, on any surface. The makers of thin-film flexible solar cells imagine that world too. But a big problem has been the amount of silicon needed to harvest a little sunshine.

Now, researchers [led by Harry A. Atwater] at Caltech say they’ve designed a device* that gets comparable solar absorption while using just one percent of the silicon per unit area that current solar cells need. The work was published in the journal Nature Materials..."

- http://www.scientificamerican.com/podca ... p-10-02-15

One day the surface area of your helmet will be enough to charge your bike...

[myzter]

Or I think another option is ..
Build a 9V @ 8Amps monocrystalline solar array (18x 6"x6" mono cells)
approx. 70 watts output
- charge two cells from your battery at a time - with a control panel of switches... or use a charge controller

[amberwolf]

One day the surface area of your helmet will be enough to charge your bike...

It already is, if you don't mind spending quite some time doing it, over several days.

But even with 100% conversion of solar radiation to electricity, you still only get about 1KW per square meter of surface area at the ground, assuming no clouds or particulates blocking it, and assuming perpendicular to the rays (so less-equatorial regions get less insolation, and you only get this max at midday).
http://en.wikipedia.org/wiki/Insolation
It's more like a quarter of that on average throughout the day from dawn to dusk, which gives you maybe at best about 6KWh/square meter/day, if you could capture every single bit of energy (which you usually won't...probably less than half that in many places that arent' cloudless deserts, so maybe 3KWh effectively).

What's the surface area of a helmet? SWAG of 0.25m-sq? (remember that very little of it is perpendicular to the rays at any one time, and that's the only really effective part, reducing the effective area a lot--I think really it'd be more like 0.1m-sq or less, effectively).

So at best you get 0.25 x 3KWh...about 750Wh. Sounds like a lot? But that's over perhaps 12 hours...are you riding with your helmet in the sun for 12 hours? Probably not.

If you have a stationary panel setup that is that same surface area, with a suntracker, that stores all of that power in a spare battery for the bike, which you swap out as needed, well, yes it would be effective.

But on the helmet itself, probably not.

[bigisland]

I just went off grid moving to Hawaii. I needed to upgrade the existing system here on the property I bought, really rebuild it, and If you can do your own install you will save a lot of the expense and with the federal tax credit of 30% off every thing I bought I am happy with it. One thing I am happily surprised with is my 2350 watt array ( Solar World 235W. USA made) puts out 500 watts with clouds over head. Seeing this simple equipment
supply me with all my electric is really nice. I think where ever I go now after seeing it work I would allways be looking to harvest some sun !!!!

[Kurt]

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 any time 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.

$1300 is way over the price for this setup..

$614 total to your door

$200 for a 100ah agm
http://www.ebay.com.au/itm/Deep-Cycle-Battery-12V-95Ah-20hr-AGM-marine-caravan-/330571322485?pt=Caravan_Parts_Accessories&hash=item4cf7961475

$269 for a 120w solar panel
http://www.ebay.com.au/itm/Mono-Solar-Panel-Home-Power-Generator-Battery-120W-/270743759432?pt=AU_Solar&hash=item3f0995ea48

$76 digital solar charge regulator
http://www.ebay.com.au/itm/LCD-display-20A-Solar-Charger-Regulator-12V-24V-panel-/120730619509?pt=AU_Solar&hash=item1c1c1b0e75

$69 300-600w inverter
http://www.ebay.com.au/itm/Pure-Sine-Wave-300W-600W-Max-12V-240V-Power-Inverter-/270621485870?pt=LH_DefaultDomain_15&hash=item3f024c2b2e


I run a 1500w system on the roof of my house feeding into the grid.I also have a 120w panel,100amp agm and inverter on my camper van. They both have there advantages. I like how I can charge my ebike up when we are camping and if the power is out we still have backup 240v.The solar on the house just 1/2 my electricity bill.

Kurt.

[stanz]

"Imagine a world where sunlight can be captured to produce electricity anywhere, on any surface. The makers of thin-film flexible solar cells imagine that world too. But a big problem has been the amount of silicon needed to harvest a little sunshine.

Now, researchers [led by Harry A. Atwater] at Caltech say they’ve designed a device* that gets comparable solar absorption while using just one percent of the silicon per unit area that current solar cells need. The work was published in the journal Nature Materials..."

- http://www.scientificamerican.com/podca ... p-10-02-15

One day the surface area of your helmet will be enough to charge your bike...

No actual solar cells have been produced from the new microwires, yet. But "if you can't absorb light efficiently, then you certainly can't convert it to electricity efficiently," notes Caltech chemist Nate Lewis, who was also involved in the research. The silicon blades show enough light absorption to make them "interesting candidates from which to make solar cells."

[auraslip]

These guys use solar to charge their electric lawn tools. Seems like a good idea for my lawn care bike. How much power could I make with a 3" x 5" solar panel? Enough to charge up a 250Whr battery pack in two hours?

It'd still be simpler to use customers power outlets, but 90% of the older houses in the area don't have outdoor power.

[REdiculous]

How much power could I make with a 3" x 5" solar panel? Enough to charge up a 250Whr battery pack in two hours?

Not much. I highly doubt it.

This is roughly 3" x 5" and it takes 7-9 hours to charge its little 1600mAh internal battery...guessing the battery is 3.5v or so..not 48v.

[amberwolf]

How much power could I make with a 3" x 5" solar panel? Enough to charge up a 250Whr battery pack in two hours?

I don't think it could be even close.

Just to give the basic math (although my numbers may be off some, they shouldn't be by that much--if it is, please correct me, as me and math don't get along all that well. ),

How much actual insolation do you get there? At a guess, probably less than 200W/square meter average during the day, possibly a lot less. At midday it'll be significantly more, maybe two or three times that.

What percentage of area is 3"x5" vs 1 square meter? 15 square inches...which is about 0.01 square meters.

0.01 x 200W is 2W.

Even if you got the full 1KW/square meter at noon, you'll still only get about 10W out of that.

Oh, and that doesn't cover the efficiency of the panel. Let's be generous and call it 20%. So you get about 2W in the last example, and about 0.4W in the first one.

Even if you had 100% efficiency and full power of 10W, it'd still take you 25 hours (at noontime power levels) to charge the 250Wh pack. Realistically, that'd probably take several days to do, if it was out charging from dawn to dusk.

This is assuming you get 100% efficiency of the panel output into the pack, which isnt' the case either.

[auraslip]

errr.... 5 feet by 3 feet...... over the top of my trailer. I was out in the sun all day...I'm a little baked

5'x3' = 15 square feet = 1.3935456 square meters.

1.3935456 x 200w = 278w

20% = 55.7w

And with the efficiency of the chargers and batteries? Yeah.... Not to hot!

Are you sure about the 200w per m^2? Seems like it should be higher in the summer time....

[myzter]

5 feet by 3 feet

Well if U had a slightly larger panel
63" x 38"
that would fit about 60x 6.25"x6.25" / 3.8 - 4watt solar cells
off the 'bay for around $150

The 1st question I would be asking myself how high current 8A or 16A ??

[REdiculous]

With 2 of these kits you'd get 75w max from a 3' x 5' setup and you'd have a spare 1' x 3' (15w) panel...for $360-ish.

[amberwolf]

errr.... 5 feet by 3 feet...... over the top of my trailer. I was out in the sun all day...I'm a little baked
5'x3' = 15 square feet = 1.3935456 square meters.

That's a lot more reasonable size for charging expectations.


1.3935456 x 200w = 278w
20% = 55.7w
And with the efficiency of the chargers and batteries? Yeah.... Not to hot!
That's the problem...and that 20% is probably beyond what you would actually get by quite a bit.

Are you sure about the 200w per m^2? Seems like it should be higher in the summer time....[/quote]
It's a guesstimate. 1KW per m^2 is generally what you'd get on a perfect day with the sun absolutely perpendicular overhead, both in latitude and longitude. 200W is a guess as to what you would get as an average over the whole sunrise-sunset period, since you'll get almost nothing at the start and end, and the most in the middle.

Since you're not going to have the sun right overhead at your latitude, it won't quite be 1KW; not sure exactly but at a guess 800W at noon in the summer (lots less in winter?). (there are insolation charts on the web all over at solar places that will tell you about what you get in different locations)

So if you did your charging at noon, you'd get a lot more out of them than later in the day, assuming you don't have a sun-tracker or other way to keep your panel aimed perpendicular to the sun as the spot on Earth you're occupying rotates toward and away from it. But remember: there is more scatter in the atmosphere at any time other than noon (well, at zenith), so even with a tracker it won't get as much at any other time, and it gets worse faster as it gets closer to sunset (or better the farther from dawn).


Then it also depends on which panels you get, as each has some limit to the current draw out of them, AFAIK.

Plus, you have to convert their output to wall-AC power to run your chargers (unless you are using a 12V panel and a 12V powered RC charger--this is probably a lot more efficient for your purposes, at a guess).

Oh, and I forgot about this: The extra weight of the panels is going to eat into your range on the bike, unless you also use them to recharge that (and I don't think you'd have enough spare power from them to make a dent in the power usage there, after what the lawn tools use up). Depending on how you mount the panels, they will also cause more drag, especially at higher speeds 15MPH and up, using yet more power.

[dogman]

Real world, what you get out of a solar panel is a lot less. Typically a 3x5 foot silicone panel is in the 150-200 watt range. Check your local area for average insolation. It should be 6 hrs or less. Of course it's longer in summer, but hot panels put out less power than cool ones.

Chances are, a good ballpark number would be around 100-150 watts, perhaps more if you keep moving the panel every 20 min or so. So a couple hours to fill a 300wh battery would be about your absolute max. Repointing the panel will help a lot with the average insolation, a fixed panel is pointed wrong all but about two hours of the day.

Ideally you'd have customers willing to pay a huge premium for the "green mow". If that works out, carry one panel for show, but do the bulk of your real charging at a fixed charge station at home. Keep hunting for cheap used panels, and even better, find an organization willing to support your green mow buisiness. Maybe a Texas enviromental group could help you with a fund for the panels. A grant would be cool, but even a local fund raiser like a carwash or fancy dinner, or whatever could get you a few bucks from each of the local eco minded folks. Belive it or not, you might even get $$ from the local electric company. Put out press releases about your green mow, get on TV, etc. Work it baby!

[auraslip]

Awwww yeahhhhh

Well, the local bike co-op has got some solar panels courtesy of a local plant that makes them. I might be able to get some after we get done building a solar lighting system for the co-op shop.

It's funny that you say I should get a panel just for show. The link I posted above probably doesn't actually charge their power tools with solar..... at least not on the go.