Solar charged ebiking!

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Solar charged ebiking!

Postby veloman » Wed Jan 30, 2013 1:00 pm

Here's 75watts of charging my 65v ebike. 1.14amps 5s3p configuration.

Solar mile potential = 20 miles/day

Panels are made up of 5w 0.3amp 17v panels from ebay. The larger module is 10 panels and half the weight of the smaller one which uses heavy glass and aluminum panels. This was about $200 total investment. No charge controller, inverter or any protection, just a straight connection to my controller/battery leads. But I am checking my battery voltage every 20 minutes and not letting it get above 80-90% charged. My battery consists of a 50v 9ah a123 pack and 3s 15ah lipo, for about 62v nominal.
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Re: Solar charged ebiking!

Postby RLD70 » Wed Jan 30, 2013 1:19 pm

Ah I remember using my solar power kit to recharge the bikes batteries and will be able to again when I get them back from my friend that I had store them while I was homeless for awhile. Nothing like charging your batteries while riding the bike 8)
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Re: Solar charged ebiking!

Postby lester12483 » Wed Jan 30, 2013 6:03 pm

Nice job Veloman!
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Re: Solar charged ebiking!

Postby electr0n » Wed Jan 30, 2013 6:27 pm

That is cool. I've been thinking about doing something similar. So you've got 75v at 1.14 amps there? 85 watts for $200 nice. Our power just went out two days ago. It doesn't happen very often but it'd be nice to have some alternative backup like solar panels. I had my nearly 1 kilowatt hour worth of batteries sitting here fully charged wishing I had an inverter to run.

I'd really like to try building a mini wood gasifier to run a small generator. That would be much cheaper than solar panels and not limited by the lack of sun.
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Re: Solar charged ebiking!

Postby veloman » Wed Jan 30, 2013 7:21 pm

That's about right, 75-85watts. The voltage drops to 65v as that's what my battery is, so I'm not sure if I get quite 85watts. 1.14amps is 26% ABOVE their rating. That was in clear sun at near noon here in TX on a January day. (the sun is not directly above).

The large panel mounts on my rear rack in seconds with one bungie cord. So yes, I can charge while riding. It's 5lbs so I barely even notice it's there, and has essential zero aero drag, especially being behind me.

This will pay for itself in food savings in 10 weeks at a food cost of $1 per 250 calories. (compared to pedaling) (bike+battery is already paid for in gas savings). :lol:
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Re: Solar charged ebiking!

Postby mythprod » Wed Jan 30, 2013 9:38 pm

that's awesome, man. Someday I'll get my solar rig going
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Re: Solar charged ebiking!

Postby SamRam » Wed Jan 30, 2013 10:00 pm

electr0n wrote:That is cool. I've been thinking about doing something similar. So you've got 75v at 1.14 amps there? 85 watts for $200 nice. Our power just went out two days ago. It doesn't happen very often but it'd be nice to have some alternative backup like solar panels. I had my nearly 1 kilowatt hour worth of batteries sitting here fully charged wishing I had an inverter to run.

I'd really like to try building a mini wood gasifier to run a small generator. That would be much cheaper than solar panels and not limited by the lack of sun.


I was thinking of building a generator exersize bike for th old a123 cells I have from my last pack
It's 12v now, runs a good 2000W inverter, for power outage bike charge emergency.
Solar is good :-)

Get an inverter my friend! True sine is the best.
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Re: Solar charged ebiking!

Postby veloman » Thu Jan 31, 2013 4:37 am

SamRam wrote:
electr0n wrote:That is cool. I've been thinking about doing something similar. So you've got 75v at 1.14 amps there? 85 watts for $200 nice. Our power just went out two days ago. It doesn't happen very often but it'd be nice to have some alternative backup like solar panels. I had my nearly 1 kilowatt hour worth of batteries sitting here fully charged wishing I had an inverter to run.

I'd really like to try building a mini wood gasifier to run a small generator. That would be much cheaper than solar panels and not limited by the lack of sun.


I was thinking of building a generator exersize bike for th old a123 cells I have from my last pack
It's 12v now, runs a good 2000W inverter, for power outage bike charge emergency.
Solar is good :-)

Get an inverter my friend! True sine is the best.



I did some experimenting with how much human power it would take to charge my bike, using regen. I loaded up a 150lb trailer hooked to the bike. Pushed it up a hill and regen down. With about 5 minutes of work, pushing this load up some small hills, I gained about 4 watt hours back into my battery (according to my CA).

That's the last time I'll do that. I think it's about 4x less efficient to pedal charge an ebike, than to pedal a normal bicycle to go the equivalent distance. Mostly because the conversion of energy back into the battery on the bike is so inefficient. But also due to the losses in friction of 4 tires on the road. That's not to say ebikes are bad at all. I just don't think we should put human energy into charging them. Clearly, solar is much better at charging my bike, assuming you have good sun. In an emergency, a bike generator to power your laptop would be perfectly fine.

Today was the first time I had to unplug my solar panel. I took a trip to a friends place, which used 66wh, and after about 90 minutes I had to unplug because I was at the point of charge voltage that I don't want to pass. I tell ya, compared to 25w of panel, 75w really gets the job done a LOT faster. (3x, duh) :)


I actually do have a 400w/800w sine wave inverter from Harbor Freight. I powered my drill with it off 4 headways. If I went this route to charge, think about the inefficiency of going through an inverter AND a charger! Easily lose half the energy right there. My charger is 70% efficient.
Last edited by veloman on Thu Jan 31, 2013 4:41 am, edited 1 time in total. View post history.
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Re: Solar charged ebiking!

Postby Lebowski » Thu Jan 31, 2013 5:08 am

why doesn't someone build a proper boost converter ? One where you can set the load it should show to the solar
panel such that the panel operates in its most efficient range. I don't know what this is, but I can imagine you want
to load the panel such that the panels output voltage is constant or maybe panels are most efficient if you draw a
constant current from them ? And then at the output of the converter it should provide the typical cc-cv that the
LiPo's like.

Then you could just parallel a bunch of panels, to get something like 24 or 36V out nominal. This goes into the converter,
and then at the output you charge 20s Lipo with it.

Takes a simple 16F processor, two ACS type current sensors, boost converter hardware and some programming.
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Re: Solar charged ebiking!

Postby ddk » Thu Jan 31, 2013 5:41 am

Lebowski wrote:why doesn't someone build a proper boost converter ? One where you can set the load it should show to the solar
panel such that the panel operates in its most efficient range...

What you described is known as an MPPT solar controller.
I use a Blue Sky MPPT 2512ix to charge 12V gel cell batteries which then feed the input of a 1010B+ iCharger. (currently using an eco6 300W charger because the iCharger broke, was replaced and is in-transit back to me)

I can also wire the 2 panels (145W ea) in series (44V oc) for direct connection to my 10S batteries by simply replugging a couple of banana connectors.
The 12V system also feeds my winch and 12V led lighting system for my workshop (still wiring it all up)
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Re: Solar charged ebiking!

Postby amberwolf » Thu Jan 31, 2013 6:22 am

MPPT is what you're talking about, AFAIK. Maximum Power Point Tracking
http://en.wikipedia.org/wiki/Maximum_po ... t_tracking
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Re: Solar charged ebiking!

Postby Diamondback » Fri Feb 01, 2013 8:58 am

im using solar too.... though not for charging the trike!

im doing a long distance self supported ride this may, and i want to be able to keep the phone and bike computer etc charged.

two solar panels, one is 9 watts the other 15 watts. these will be used to charge 2 small (5ah and 6.6ah) batteries during the days ride.
these will in turn be used to charge my usb devices in the evenings.

i realize that ill not get maximum efficiency having the panels facing straight up at the sky all day, but it's the best i can do.

the banner on the rear of the trailer is just for added visibility, and a little in-joke among my friends.
when im pulling the trailer, im about 5m long and 5 wheels !

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Re: Solar charged ebiking!

Postby ddk » Fri Feb 01, 2013 4:18 pm

a 'lil note for those considering solar on-the-go
first a 135W roll-up panel @ $230
nXt is a terribly mis-speced mppt controller that may or may not be what it's supposed to be
LOL- I dunno !
-but I bought three, expecting delivery in mid Feb
:pancake:
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Re: Solar charged ebiking!

Postby dak664 » Fri Feb 01, 2013 5:45 pm

For bulk battery charging, maximizing the charge current is all that counts. A buck-boost MPPT converter can do that over a wide range of voltages, but If the PV output voltage is greater than the battery voltage then it is more simply done just using current feedback into a PWM buck converter. Such a buck converter is basically the old PWM circuit with the addition of a small coil and diode, adding maybe $1 to the parts cost. The specs say input 12-40 volts batteries 12-24 volts but I'd be surprised if the input voltage could be less than the output voltage.

Weight 760 grams, shipping weight 40 pounds! What's up with that?
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Re: Solar charged ebiking!

Postby amberwolf » Fri Feb 01, 2013 6:26 pm

dak664 wrote:Weight 760 grams, shipping weight 40 pounds! What's up with that?

Common way for amazoners and ebayers to make extra money, especially with cheap items. Some of them will give you the real cost/etc when you call them on it, and some say bugger-off. :(
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Re: Solar charged ebiking!

Postby SamTexas » Fri Feb 01, 2013 8:28 pm

ddk wrote:nXt is a terribly mis-speced mppt controller that may or may not be what it's supposed to be
LOL- I dunno !
-but I bought three, expecting delivery in mid Feb

Just bought one. There is one 5-star review, not that it means anything. But for $5.87, what the heck. Thanks for the link.
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Re: Solar charged ebiking!

Postby ddk » Fri Feb 01, 2013 10:39 pm

amberwolf wrote:
dak664 wrote:Weight 760 grams, shipping weight 40 pounds! What's up with that?

Common way for amazoners and ebayers to make extra money, especially with cheap items. Some of them will give you the real cost/etc when you call them on it, and some say bugger-off. :(
in this, uhm, interesting case

shipping is free! and the price is under $6 -or same price as a bad event @ McD's-
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Re: Solar charged ebiking!

Postby amberwolf » Fri Feb 01, 2013 10:52 pm

Well that's a pretty good deal then. :)
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Re: Solar charged ebiking!

Postby SamTexas » Fri Feb 01, 2013 11:00 pm

amberwolf wrote:Well that's a pretty good deal then. :)

Don't count on it. I just saw a few really bad reviews about it. Apparently it's fake and it does not work at all. But I will know for sure in about 2 weeks.
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Re: Solar charged ebiking!

Postby ddk » Fri Feb 01, 2013 11:15 pm

dak664 wrote:
For bulk battery charging, maximizing the charge current is all that counts. A buck-boost MPPT converter can do that over a wide range of voltages, but If the PV output voltage is greater than the battery voltage then it is more simply done just using current feedback into a PWM buck converter. Such a buck converter is basically the old PWM circuit with the addition of a small coil and diode, adding maybe $1 to the parts cost. The specs say input 12-40 volts batteries 12-24 volts but I'd be surprised if the input voltage could be less than the output voltage.

Weight 760 grams, shipping weight 40 pounds! What's up with that?

shippings free and it's 5.87 or sumtin'


The real advantage, as I see it, with an MPPT controller is it's ability extract real power from my panels on cloudy/foggy days.
When the panels are barely generating 15V (nominal 19v-22V) the MPPT is happily sending most the available power into the batteries.
Makes the MPPT's relatively large investment worth it. (cheaper than a couple more 150W panels, anyway... and takes no space on the roof)

-and of course, if these cheapies are MPPT converters all the better (for my wallet) (said the cheapskate)
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Re: Solar charged ebiking!

Postby veloman » Fri Feb 01, 2013 11:29 pm

I got 365watt hours from the sun today. Full charge of what I used yesterday. After the sun went down I wanted to top off my a123 pack with the charger. After about 4 minutes it started flickering on/off, then gave up the ghost. Dead. Fuse looks fine. Everything inside looks fine, nothing loose. There was a little dust/hair/cob webs, but nothing much.

I'm reading this thread and trying to figure out if I can fix it.
http://www.endless-sphere.com/forums/vi ... 9&start=30


Good thing my solar panels are working great! And lots of sun in the forecast. I am going to trying putting two other chargers in series to see if that will charge my battery.
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Re: Solar charged ebiking!

Postby mdd0127 » Fri Feb 01, 2013 11:42 pm

Cool setup!

I've never charged my bike with grid power.
I've got 585 watts of panel with a crappy pwm charge controller getting 350 watts out of them, charging an 880ah 12v battery bank that feeds the Hyperion1420i.
I need an MPPT controller asap!
Turn it OFF!!!

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Re: Solar charged ebiking!

Postby John in CR » Fri Feb 01, 2013 11:43 pm

I hope you guys aren't connecting those charge controllers to lithium batteries. Those are meant for lead, and that auto sensing stuff sounds like a near 100% overcharge rate for lithium. Good quality and high accuracy is require to directly charge our ebikes, and it's expensive. Sure it might be easy for an electron guru like Lebowski, but I can't emulate the Dude, so I'm just going with direct panel output with an HVC to cutoff the charge. That circuit is so cheap that I can stagger the HVCs so my solar charger emulates CC/CV charging which is important, since I'm gearing up for any range of charging from slow to fast with multiple panels to parallel. I've looked at cell output curves and done lot's of measurements with actual panels and different pack voltages. The 30% gain those MPPT controllers always claim includes "up to", and it's just a sales pitch play on wording, and the bigger gains occur when panel output is very low, so the overall gain in watt-hours is nothing close to 30%. All it takes is sizing your series string of solar cells properly so the battery voltage puts the load right in the sweet spot of cell output. It also helps that the percentage variance in voltage of our bike packs is a lot smaller than a lead battery, especially lifepo4.

The panels themselves are now the cheap part of the system, so instead of trying to capture every stray electron you can, it's far cheaper to add more series cells.

Other than 3 cloudy days I've been 100% solar powered for transportation since Dec 16th, and that's using just a fraction of the solar cells I have. My goal is to have a backpack full of folding panels, so I can go riding in the mountains on cloudless days without a care about battery capacity, because in the 9am to 2pm time frame I can stop and add a high powered charge to my batteries. No more tethered to an electrical socket for me. :mrgreen:

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Re: Solar charged ebiking!

Postby mdd0127 » Sat Feb 02, 2013 12:00 am

John in CR has a great point!
I'd definitely recommend running the solar charge controller to an intermediate battery bank and using a proper balancing charger for lipo.
Turn it OFF!!!

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Re: Solar charged ebiking!

Postby veloman » Sat Feb 02, 2013 12:01 am

John, what do you recommend to use for a HVC? Right now I like to stop at 66.5v, but will be changing my booster pack to 7s headways, so more like 78v. That's 5v under 3.65v/cell, or 3.4v/cell end.

Why the need for CC/CV?
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