Oh boy
jherre1,
Anything that has to be made in a "clean" room and costs $18 is suspect. A solar module @ that cost will likely fail under normal environmental conditions. That said, it may survive just fine on the dash. In the rain? After getting cooked? Not likely. All modules are NOT created equal.
The rating of 1.8W/125mA @14.4VDC is STC, or standard test conditions, of 77ºF & irradiance of 1000W/sq. meter. Temp. up performance down and visa versa. 800W/sq. meter is average ground level irradiance. About 80% of STC. And about 80% of light passes thru glass. .80×.80= .64= 64%×1.8W=1.15W not considering the refraction of the glass or the angle of incidence from perpendicular to the rays of the sun.
Sh*t, what the hell uses only 1 Watt. Yer battery.
My tablet is a 24W load to charge. Cell is 6W.
Not really.
That panel would be lucky to put out as much juice, in full sunlight, as a battery self- discharges... ...especially when it's inside, on your dash.
You'd probably want about a square foot of cells to start really making a difference- and then, a controller would be a good idea to make sure it didn't overcharge when it's bright and sunny.
The boat and RV guys have some nice setups that seem to work. They're a LOT bigger.
But it won't hurt, at least. t
Add a fuse to that.
Self-discharge is 3%-20%/month, dependent upon conditions. Likely 4-5%. So, with a batt that has about 125A@20hr rate of storage, like yer cruiser batt. 5%=6.25A@12.5V=78.125W/28days=2.8W/day. So, if the dinky module gets 3hrs of direct sun on the dash he can stave off self-discharge and nothing else.
This is what a battery
maintainer is. It is not a
charger. It will only charge the smallest of batts.
Not meant to keep batts in
top shape, tapage. A maintainer/charger or a larger solar set-up is required.
About 2.5% of batt capacity is the base
charge rate. Meaning enough charge to bring voltage up in a meaningful time period and eliminate the possibility of sulfation.
2.5%@125A=3.125A@14.4VDC=45Watts×1.25(irradiance correction)=56.25Watts to actually make the batt gas enough for health.
To give a good charge a 10% rate is it.
10%@125A=12.5A@14.4VDC=180Watts
This is only looking at power generation from the stand point of what a battery needs as far as charge rate. Not based on power
usage dynamics. EVERY system is custom to some point.
Paul4560, this type of set-up is fine to plug into the lighter assuming the wiring for the circuit is in good shape. Backfeeding power is a perfectly acceptable practice. The fuse and therefore the wire are the limiting factors.
SteveH, the vast majority of modules are built with blocking diodes to stop to reverse flow of energy from the batts out the module. But, alas, some are not.
Below is a link to the charge controller I recommend, in my business, for automotive purposes:
http://www.morningstarcorp.com/en/sun-saver-duo
Built for up to 25Amps or >300Watts. Charges 2 separate batts @ 50%/50% or 90%/10%. Perfect for Start/House battery systems. Made by Morningstar in the US. About as reliable as it gets. Around a $100 shipped. Comes with a digital meter for a $60 upgrade. Temp sensors are also recommended.
Good modules, as in solid and well built with good power characteristics are about $45-$170 for 5W-55W. And $200-375 for 70W-150W. Plus shipping. 12V modules by definition are smaller than todays standard modules and don't benefit from the economies of scale quite as much. The bigger, the cheaper per watt. The bigger ones are all >24VDC.
Btw, electrician and solar installer here.
C
