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[DesignerDan]

Since I live in sunny Florida and work 9-5 each day I figured that would be a great opportunity to deploy some solar panels. I looked online and couldn't find any high wattage, fully portable solar panels. So I decided to make my own. The design is pretty simple; two solar arrays, each made up of (10) 13x13" panels. The panels will be incredibly thin (.1 inches in thickness) and will be hinged together so they can fold up. The completed array should fold up small enough to fit in my backpack.

4 cells per panel and 20 panels. Each cell is 3.5 watts. That's a total of 280 watts in direct sunlight. Assuming they will be in direct sunlight for all 8 hours of my work day (which they won't but this is just a rough estimate) that's 2,240 watt hours of power! That's the max value so with the sun not being at the right angle the whole day and the system inefficiencies (dc-dc converter, inverter, charger) I'm going to do a very rough estimate of maybe 1,000 watt hours on average each day. Which isn't bad. On average I'd say I use about 1.5 Kwh to get to work. So my ride home could potentially be 100% sun power.



The fiberglass sheets that the photovoltaic cells will be mounted to:



I have 2.25 out of 20 panels complete so far. It's a time consuming process to make these from scratch:



The stack of cells:



The folding process:



All folded up:



In all honesty, I'm not quite sure if this system will even work. The solar array will be about 20 volts but that value will be fluctuating throughout the day. So the array will plug into a dc-dc converter that will drop it down to 12 volts and keep it constant. The 12 volts will power a standard 12v to 110v ac inverter. The inverter will plug into the Zero's charger. Now I know the charger will "try" to draw 1,300 watts but since the panels can only provide a max of 280 watts, I assume the charger will just operate at 280 watts... I could be wrong though and it might not work at all lol but I don't see why it wouldn't. It's getting it's 110 volts ac so it should be happy and not care about the lack of amps right?

[Doctorbass]

Hello deesignerDan,

Good initiative to solar power your new working zero!
BUt about the cahrger and the hope to have the 280W accepted by your cahrger this is another story. Your charger will try to pull all the current it need to get the CC-CV at the output so the AC voltage input will drop due to the too high current demand and will make the charger to cut.

All these seriee connections ( dc-dc + cahrger etc will make your efficiency to drop significantly so.. what i suggest is to use a BOOST converter DC-DC that will raise yor voltage to the same as the zero is. ( above 100Vdc)

there is some great boost converter on ebay for cheap. you wil need one thst is current limiting at the output.

I think the new zero is 28s lipo so the max voltage is 117.6Volts DC

OR another solution would be to just use a cheap but efficient  250W inverter that accept 24VDC at the input. there is some on ebay too. they should  be able to take 20V input. Then you find the big HV capacitor bank inside ( that'Ms the HV DC stage right before it is pulsated to make it AC with the mosfet) Usually since the cheap inverter are using square wave they usually produce between 115 and 120V DC that is converted in AC so just use the DC output directly. If you push the limit a bit more you could find the trigger wire of the zero that control the current flow of the charger ( it is the white wire on the 2011 and 2012 zero) and to connect it to a relay that activate the inverter or make it to cut when the max voltage is reached on your zero to not overcahrge your battery.

Well alot of possibility

Doc

[trikester]

Doctorbass is correct that the charger will want all or nothing from the input source. I've been wishing from the beginning that the chargers would be made with an adjustable power level so that they could be adjusted to run from a low power source such as a solar panel. At the present time, that is not the case.

I can't even get the 640 W charger in my 2013 FX to run from a 850 W rated gas powered 115 VAC (sine wave) inverter generator. I have been successful in using a 1600 W rated inverter generator to power the 1050 W charger in my 2012 DS.

Trikester

[DesignerDan]

Hello deesignerDan,

Good initiative to solar power your new working zero!
BUt about the cahrger and the hope to have the 280W accepted by your cahrger this is another story. Your charger will try to pull all the current it need to get the CC-CV at the output so the AC voltage input will drop due to the too high current demand and will make the charger to cut.

All these seriee connections ( dc-dc + cahrger etc will make your efficiency to drop significantly so.. what i suggest is to use a BOOST converter DC-DC that will raise yor voltage to the same as the zero is. ( above 100Vdc)

there is some great boost converter on ebay for cheap. you wil need one thst is current limiting at the output.

I think the new zero is 28s lipo so the max voltage is 117.6Volts DC

OR another solution would be to just use a cheap but efficient  250W inverter that accept 24VDC at the input. there is some on ebay too. they should  be able to take 20V input. Then you find the big HV capacitor bank inside ( that'Ms the HV DC stage right before it is pulsated to make it AC with the mosfet) Usually since the cheap inverter are using square wave they usually produce between 115 and 120V DC that is converted in AC so just use the DC output directly. If you push the limit a bit more you could find the trigger wire of the zero that control the current flow of the charger ( it is the white wire on the 2011 and 2012 zero) and to connect it to a relay that activate the inverter or make it to cut when the max voltage is reached on your zero to not overcahrge your battery.

Well alot of possibility

Doc

Darn that was my fear. Could I use lets say a 180 watt charger and have a dc-dc boost bypass the rectifier in the charger so the dc is directly powering the charger? If that would work then I could have cc-cv and not risk over charging. And the charging "shouldn't" cut out unless wattage of the panels drop substantially. But I guess if I used that setup then I would never be using all the available watts...

[BSDThw]

If it should run efficient you need a MPP (maximum power point) regulator.

http://en.wikipedia.org/wiki/File:Solar-Cell-IV-curve-with-MPP.png 

http://en.wikipedia.org/wiki/Maximum_power_point_tracking

I didn't try to explain I think the wiki links are much better than me

I am curious how it works, my experience of the cells they are like glass and very fragile. Hope your mechanic will work

I would never go from DV to AC and back to DC if there is a possibility of a DC/DC system.

We built solar charger but not for your voltage and normally it is a step down and seldom a step up at battery systems.
My colleague is building one that could be modified to charge a 2012 /74V system but even your voltage of the modules has to be higher than 75V. I was thinking to play with this for mine but in daylight the bike normally not at home so why. And a portable system like yours. I couldn't but it somewhere at the company.

[DesignerDan]

If it should run efficient you need a MPP (maximum power point) regulator.

http://en.wikipedia.org/wiki/File:Solar-Cell-IV-curve-with-MPP.png 

http://en.wikipedia.org/wiki/Maximum_power_point_tracking

I didn't try to explain I think the wiki links are much better than me

I am curious how it works, my experience of the cells they are like glass and very fragile. Hope your mechanic will work

I would never go from DV to AC and back to DC if there is a possibility of a DC/DC system.

We built solar charger but not for your voltage and normally it is a step down and seldom a step up at battery systems.
My colleague is building one that could be modified to charge a 2012 /74V system but even your voltage of the modules has to be higher than 75V. I was thinking to play with this for mine but in daylight the bike normally not at home so why. And a portable system like yours. I couldn't but it somewhere at the company.

The cells break like potato chips. I already accidently broke a few. Those fiberglass sheet are incredibly rigid and the cells are epoxied to those. You have to apply a lot of force to bend the fiberglass to the point where the cells start cracking. But then again, why would I be intentionally bending the panels. lol So I think the strength is enough. I'll just have to be careful folding/unfolding them and transporting them.

Also, do you have any recommendations for what to use to coat the tops of the cells with? I made a test one with an epoxy coat on the top but epoxy dries really shiny and it looks like a lot of light was being reflected. Or should I leave the cells bare? Obviously they wouldn't work if they got wet but if it's raining the sun probably won't be out. The weathering on the surface of the cells would probably greatly reduce their lifespan though...

[BSDThw]

Sorry I am developing the electronic and SW I have no idea what they use to laminate the module, but I know it is a tricky business and not easy to do manually.

I can see and admire you willing to solar charge.

My brain still search what will be a nice way for a charger for you, but I think first it should be sure if mechanic work, before you invest more money.

If it work maybe I can help with charger ideas.

I keep my fingers crossed for your project.
 

[NoiseBoy]

Good on you Dan. I'm in the planning stages of building my own local storage pv array for my amateur radio equipment. Ideally a top sheet of perspex would be good but you could do without and get a specialist silicone based encapsulant. An eBay search should turn some up. You will have to accept that your setup is far from ideal and you will see a loss of efficiency over time.

[trikester]

Offthegrid was showing me how he did a trickle charge from a small solar array on the back of the bike he rode from Florida to CA. He had connected enough cells in series to get up over the battery voltage and fed the DC directly into the battery's external connector. He was actually reluctant to tell people about this, however, because there is no battery management protection against overcharging since the BMS signal to stop charging, when it reaches max V, can't shut down the solar source. He didn't have much concern because his solar array was very small and would have taken a long time to reach overcharge.

If you built a cutoff circuit that could recognize the "stop charging signal" from the BMS and break the connection to the solar panel, it might work that way.

Maybe Offthegrid will weigh in on this subject.

He told me that his solar trickle charge did help him a couple of times to gain a little extra charge when he was going to fall a little  short of the next town.

Trikester

[BSDThw]

That is correct and would work easy
BUT
as I see it correct Dan has complete wavers and a waver has Vo ~600mV and Vmpp ~450mV so hi would need  220 waver to get mpp at 100V that's a lot.

[trikester]

He could also use a DC / DC up converter. That could be where the full charge shut down would take place - when the full charge voltage signal is sent from the BMS, the up converter shuts off and a diode blocks any reverse discharge.

Lots of good stuff to think about. 

Trikester

[protomech]

Bought a Solar Joos recently, 20 Wh battery pack with a 2.6 W solar panel. I typically see 6-10 Wh charged during the day, depending on cloud cover and shading.

Kind of similar at a much smaller scale to what you hope to do. 280 W of panels should be able to charge 600-1000 Wh per day, or 6-10 miles @ 100 Wh/mile. Not a huge gain but a neat project : )

Agree that your best bet is to do DC to DC, use a max power point tracker and install a blocking diode to prevent the battery from discharging into the solar cells.

[Biff]

There are a lot of battery chargers that work from AC or DC.

Example:

http://www.meanwelldirect.co.uk/products/120W-Single-Output-IP65-Rated-LED-Lighting-Power-Supply/HLG-120---A-Series/default.htm

Those chargers have adjustment Pots on them as well to limit the output current.

-ryan

 

[frodus]

You'd be better off leaving the solar at home and having a larger array and go into the grid. I know its nice to go direct but you'd still be offsetting the energy used to charge the bike by what you generate.

Solar to grid is readily available and prices are reasonable.

Just something to think about.

[protomech]

A deployable solar panel would also act as a nice shade for the bike battery.