Solar Charging your Ride

I created this document back in January of 2006, so some of the links may be dated.
I also believe that with the advent of shorai batteries and similar which have 18ah that a solar charging system is unnecessary.
However for those who are interested this is how I did it.

Battery Drain Problems & Solutions

I’m trying to make this as clear as possible, so please don’t be offended if I state things that are obvious to you. It’s not an assault on your intelligence. It’s me being thorough.
I’ve also broken this down into sections, so you can skip anything uninteresting to you.

Definitions:

1. We will primarily be talking in milliamps, or (1/1000ths of an amp) per hour.
2. Batteries for motorcycles are rated in “Amp hours”
3. The stock Yuasa battery, the YTZ12S has a capacity of 11 amp hours.
4. Another Yuasa that fits is the YTZ14S with a capacity of 11.2 amp hours.
5. In a phone conversation with Yuasa, they recommend never more than a 50% discharge to still be able to start the vehicle. This equals 5.5-5.6 amp hours.
6. All figures given below are approximate. YMMV (Your Mileage May Vary.) Its up to you to determine your personal discharge rate, I am using my bike as an extreme example, and letting you know what I am doing about it.
My solutions may be applied in stages based upon your needs.
7. Links to products and pictures will be at the end of the post.

Checking your personal battery drain:

If you would like to check the draw while off of any item connected to your vehicle, first, take out the under seat light bulb so that it doesn’t overload your meter. Then disconnect the item from power. Put the positive lead of your meter on the power and the negative on the positive lead of the item. This should give you the draw. For total draw, disconnect the positive lead to the battery. Take the nut and bolt from the battery positive and put together the stock positive lead and all other leads you had going to the battery positive, and put the bolt thru those leads and screw down the nut for a solid connection of all the leads off the battery. Then take your meter and put the positive lead on the battery and the negative lead on the bolted wires formerly connected to the battery. This will give you your total draw.

Common Battery Drains:

1. Our beloved stock Silverwing can draw around 6 milliamps (ma), for internal needs, like the clock, which requires constant power.
2. According to Yuasa, the battery itself can discharge at a rate of 1% per day even under no load. We can round this up to 5ma
3. If you have any aftermarket devices attached to the bike, such as those that display voltage, temperature, etc, and also have a clock or memory function in it, then you have hooked up the unit to a full time hot. The clock and display demand about another 6ma. Other items and functions may require more.
4. If you have an alarm on your bike, and I think these days everyone should, than unless you have a low-draw alarm like the Scorpio, you are drawing about 25ma.
5. LED’s can draw from 15ma to over 100ma depending upon brightness, with the average LED used for vehicles drawing about 20-25ma. Did you attach one to your alarm? If so, add 25ma to your draw.

Assuming you have all of the above, this alone is a draw of approximately 67ma per hour, or 1.6 amps per 24 hours. Without starting the bike, you drop below the recommended 50% drain limit in less than 3.5 days. A sobering thought!

Showing off your bike?

In addition to all of the above, I have custom LED lighting on my bike, including in the sidelight area above the headlights. 23 LED’s take approximately 25ma and the ones in the sidelights take 35ma. The two switches are lit too, taking another 25ma each. This is a total of 695ma in addition to the 67ma above! These lights are left on at bike nights for approximately 5 hours. This means during a given bike night, I can draw about 3.8amp hours from the battery. At home, these lights are kept off. But I live in a condo. If some kid were to come along at night, and turn on the LED switches, a fully charged battery could drop below 50% in about 7 hours.

Solutions:

In reading thru the archives, I noticed some discussion from a year ago about solar cells being used for keeping the battery charge topped off, and if they were worth it or not. At the time, the discussion was with regard to the inflexible plastic framed cells sold as a complete unit to plug into the cigarette lighter. They were about 15” by 6.5” and nearly 1” thick. They put out a maximum of 100-120ma in bright sunlight. They had limited mounting capability, were easy to steal, took up valuable space, required an accessory socket, and required effort as necessary to set up.

A company called Powerfilm (formerly Iowa Thin Film Technologies) makes FLEXIBLE photovoltaic panels in a variety of sizes. The four I will discuss here are:

PT15-75 Powerfilm WeatherPro TM Series, 15.4V, 50 mA (10.6 x 3.9 inches)
PT15-150 Powerfilm WeatherPro TM Series, 15.4V, 100 mA (10.6 x 6.9 inches)
MPT15-75 Powerfilm Wireless Electronic Series, 15.4V, 50 mA (10 x 3 inches)
MPT15-150 Powerfilm Wireless Electronic Series, 15.4V, 100 mA (10 x 5.9 inches)

Weatherpro series are 1.1mm thick. Wireless Electronic Series is .6mm thick.
Both versions are waterproof.

The Weatherpro series also has a UV protection coating, and border that you can screw or rivet into, so mounting preferences may help you in your decision as to which version is best for you. The disadvantage to it is that the coating approximates Teflon. This means that you will have a hard (but not impossible) time mounting it with an adhesive.

The non-Weatherpro version can be attached using adhesive without a problem, but it has no real borders for mounting. In fact, they can be pressed against the inside of glass with adhesive on the front. To do this, Powerfilm recommends Avery-Dennison adhesive 3035 or 1126.

Making the Weatherpro series capable of accepting adhesive:

To attach the Weatherpro series with an adhesive, there are three ways to do it.

1. A process called “Corona Etching”, which uses a plasma laser to abrade the surface without changing opacity. This is what Powerfilm called it. I couldn’t find anyone in my area who even knew what I was talking about.
2. The company recommends using a Fluoropolymer Pre-Bonding Etchant which is $50 a pint. I elected to go with this and test it out.
3. Do nothing special and apply with double sided stick tape and/or silicone on the back, or the Avery-Dennison adhesive 3035 or 1126 on the front. When I used method 2, I had a very small amount of etchant (1 pint) so I only applied it to the outer half-inch frame of each piece. The installer decided to cut the frame off when mounting to the bike, and it seems to be holding quite well. We used the A/D 1126 double sided adhesive plastic sheet for the windscreen, with no problems yet. So choose this method at your own risk.

Using Method #2

The process is a bit like developing photographs, with an echant bath, alcohol bath, and distilled water bath. They also recommended a slightly acidic water bath, but I declined to deal with that.
Ideally, go to the office store and pick up one of those folder holders that attach to the wall…the kind you usually see on the door of examination rooms in a doctor’s office. This is sealed deep and wide, but thin…large enough for the power film with a very small amount of surface area exposed to air. Use this for your etchant bath. Then pick up disposable baking pans for the alcohol and distilled water bath, all of which should be available at the local market or drug store. If you have an extremely small amount of etchant, or very few panels that you can do quickly, a baking pan will work for the etchant too, but the etchant loses strength as it is exposed to oxygen, so do what is best for your situation.
Prepare everything in advance, and it goes pretty smoothly. You should be able to do all the panels I did, within 5 minutes. I was very worried at the outset that the process might reduce the opacity of the Weatherpro coating, but there was no visible difference. I purchased the smallest amount they sold. If I had to do it over again and do the same number of panels, I would have gotten the next size up. Also, use this stuff in a VERY WELL VENTILATED AREA!.
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Diodes:

You will also need a diode for each panel. This is connected between the positive lead of the panel, and the positive lead of the battery. Without the diode, in low light conditions, the panels may actually DRAW 5-10ma of power depending upon size. The recommended diode is 1N5817, which I am told has an equivalent, NTE585.

Placement:

I have found 4 places on my Silverwing to mount these panels, giving me a total maximum of 250ma of power. In addition, I could have added another panel (100ma) to the top of my Givi case, but if I wanted to mount a rack later on, it would interfere, and it would also require a disconnect for case removal. I wanted my install to be permanent and maintenance free.
While it does not mitigate all of my power needs, it is a balance between compensation for consumption, keeping the battery fully charged, and aesthetics. According to Yuasa, there is no chance that this level of unregulated constant charge can hurt the battery. I use the 100ma version behind my windshield, and 50ma versions elsewhere, as shown in pictures.

Power Conversion:

Keep in mind that the ratings for these panels are maximum conversion capability in bright sunlight. You will notice that my panels do not point directly into the sun. That is because rarely do we have these conditions. These panels convert any type of light into power (think solar calculators that work indoors). Also if you put the panel behind a tinted windscreen, you can lose about 10% of your capability. The adhesive on the front cuts down another ½ %. I thought about putting the photovoltaic panel on the outside of the windscreen, but I didn’t want to risk road debris damaging it. Personally I think if you routinely get 70% of the claim you are doing fantastic. I recommend that you consider your power needs and to the extent possible put on double what you need. This way at 50% capability, you are still covered. That’s just my opinion.

Links:
For pictures of my bike with its new photovoltaic panels, check out my album liked to in my sig.

http://www.kingsolar.com/catalog/mfg/powerfilm/index.html

http://www.siliconsolar.com/shop/catalog/Flexible-Solar-Panels-7v-12v-05-1292-p-16164.html

http://www.powerfilmsolar.com/

http://www.actontech.com/fluor1.htm

I hope someone can use this. Good luck all.
Dan