Battery dead - replacement?

[08EscapeHybrid]

I have a few solar battery chargers for vehicles that don't get driven on a daily basis, and since I bought them I haven't had to replace a battery or jump start a vehicle. $20 @ Harbor Freight. Just plug it into the cigarette lighter, and leave the panel on the dash.

[RedylC94]

Originally Posted by 08EscapeHybrid

... $20 @ Harbor Freight. Just plug it into the cigarette lighter, and leave the panel on the dash.

Last winter, I bought one of those from Harbor Freight for even less on sale. It does work, BUT you'd be shocked how tiny its practical output power is even on a sunny day, compared to the claimed 1.5W. It might do that under ideal conditions. I measured up to about 1.1W in February with it outside the car directly facing the sun near noon. Inside a car, you can't realistically keep it oriented perfectly, the windshield stops a fraction of the light, and output drops a lot when it gets hot---which it will on the dash in the sun in a closed car, even in cool weather. The instructions warn that the housing may melt if you're not careful.

[08EscapeHybrid]

Yeah, I'm aware its not optimal, but on a vehicle that's not driven much, it will maintain a battery if its parked with a full charge. My 1 ton van will fire right up after not being driven for almost a year. Same with my 81 Buick. I do make a point of parking the vehicles facing south before leaving them with the solar panel though.

[EVuser]

Solar maintainer. Works great on a good battery and good solar angle. They just don't do so well in the garage with the doors closed or in darker northern latitudes in the winter.

I use a 20 watt flex panel in my dodge van. Can park it in the shade facing north and provide a few watts. Requires a charge controller or it will destroy the battery in full sun.

You have to remember that the rating on panels is almost always going to be open voltage so without a mppt controller the wattage will be less than rated. A good battery will allow the PV to track at a higher voltage for a win win.

Those really small panels can not over come the charging resistance on a really weak Pba battery.

Sure wish I could get my neighbor to use them on his battery killing /RV. The Pba floodies even disconnected self discharge on a schedule that far exceeds his charging plan.

[RedylC94]

Following up ... I just rechecked the output, and could not duplicate my aforementioned February result. In direct full sun near noon, I measured only about 30mA (roughly 0.4W) maximum, which soon dropped under 20mA as it warmed up in the sun. Still lower through glass. About 4mA in shade.

Do you leave it on the dash in the summer?

[08EscapeHybrid]

Yeah, I leave mine on the dash always.

[EVuser]

Originally Posted by RedylC94

Following up ... I just rechecked the output, and could not duplicate my aforementioned February result. In direct full sun near noon, I measured only about 30mA (roughly 0.4W) maximum, which soon dropped under 20mA as it warmed up in the sun. Still lower through glass. About 4mA in shade.

Do you leave it on the dash in the summer?

Really low cost panel could be low quality. Perhaps it has degraded. Dash under glass is a pretty hot spot and PV output drops with heat which you verified.

[RedylC94]

Unlike 08EscapeHybrid, I've never left mine on the dash except for a few minutes on a cool (about 40°F) day. It's apparently the same model he has, purchased February of this year.

Open-circuit voltage is over 20V, even in shade.

[08EscapeHybrid]

All I care is I don't have to get jumper cables out when I go to start one of the rarely used vehicles in my fleet. I have solar panels for the 81 Buick, 98 GMC K1500, and the 2000 GMC Savanna 3500. Any of these vehicles can go months between uses.