Solar Battery Maintainer Selection ??

I keep a remote camp battery topped off with just a 5w panel. No parasitic loads when we are not there, though.

5W panel on the trunk lid works for our 2002 Toyota Spyder, and the same 5W panel behind the windshield on the dashboard is fine for our 93' Ford Ranger pickup.

Shottky diode for isolation, straight to the battery through a fuse tap. No controller.

It's a metal framed polycrystalline from Ebay similar to this one.
http://www.ebay.com/itm/ECO-12v-5W-Solar-Panel-Poly-Crystalline-solar-DIY-system-5Watt-poly-solar-module-/271469095437

Toyota has been sitting for a year (don't ask) - just moved it a few weekends ago - started quickly.

Ranger gets driven 1-2 times a year - starts up great.

DelTran Battery Minder is the hands down favorite for a plug in maintainer. When I saw the DelTran Battery Minder 15 watt solar battery maintainer I asked for one for Christmas. It has a three stage digital controller and while it is about three feet long it fits behind one side of my split windshield and works great. I hard wired mine and have a two wire connector that come out from under my dash and can be tucked back in below the dash while we're on the road.

Google and look at what they have. Many have said it's not big enough but they are all guys who think you should have hundreds of watts, as a battery tender, it is big enough in my opinion. Keeps my batteries topped of with out any problems. It is a battery tender not a charger.

A single starter battery can't be too big - 50 AH maybe - and there is plenty of sun in AZ, so 5W would be adequate if there was no drain. I found 2.5W adequate for my Chevy 1500, outside on the roof, BUT the battery was disconnected.

Now, "inside the windshield" is an interesting question. I didn't notice any difference in performance, other than losses from shading from vehicle frame. But my model is old and new windshield is the cheapest possible. The word is, on newer models there is a coat on the glass that cuts the output more than in half. Also, dust accumulating over a year would cause the output to drop.

Another problem with small solar maintainer under the windshield is that it melts down, literally. Unlike big panels, small chargers have plastic frame and usually a plastic cover at the back. This affects heat dissipation, and it can get VERY hot under windshield. Allegedly, back cover is to keep it "weatherproof" for when used outside, but I wouldn't count too much on that.

You are in a better position in AZ, but in Baja Mex the crocodile connectors of my charger badly corroded in a matter of weeks. Dry area, no rain, 200ft from sea, no salt spray. Very, very poor quality metal.

BFL13 wrote:
Other ideas might include disconnecting the battery so no vampire loads, and you can much reduce self-discharge by having an AGM battery

Due to contractual requirements with the storage facility, disconnecting the battery is not an option :( but switching to an AGM battery certainly is. Thanks!

Golden_HVAC wrote:
10 - 15 watts is more likely needed to keep the battery full, and overcome all the other discharges of the system. *snip* So figure that a 15W panel will only put out about 10W if inside the windshield.

Thanks Fred! Looks like I may need to find a higher wattage panel. As I mentioned, the panel will be mounted outside on the roof (flat, not tilted). Elevation is 5000ft.
This is an older vehicle, and as a result it has very few electronic devices that require constant battery power (e.g. no alarm, no power door locks, no gps, no airbags, etc). The clock in the dash is actually an analog one (remember those?) and I may be able to pull the fuse for the circuit it is in.

-Mark

10 - 15 watts is more likely needed to keep the battery full, and overcome all the other discharges of the system.

I have a hand held isolation meter. It measures the sun watts per square meter for solar system sizing. I was using it one day, and measuring the sun radiation while driving from Boluvard CA to San Diego CA. This dropped me from 3,700' elevation to near sea level in about 1 hour. I was getting 1080 W/square meter at 3,700' and 1040 midway to home. By the time I was in San Diego, it dropped to about 1020 W/Sq M. Inside the windshied of my work van, the reading was only 450 - 870, depending on the area I held the meter. It is tinted towards the top, and that was much less.

So figure that a 15W panel will only put out about 10W if inside the windshield. This will collect about 50 watts per day in sunny conditions, and only about 20-30W in cloudy conditions. This works out to about 2-4 AH daily, or about what the self discharge on a larger AMG battery would be. IT barely takes into account what the radio can draw, or security system, or thing that listens for the remote door unlocker.

Good luck,

Fred.

Other ideas might include disconnecting the battery so no vampire loads, and you can much reduce self-discharge by having an AGM battery AFAIK.