Unregulated Solar Car Battery Charger

[Ducked]

Back in the UK for a few days. Local electronics store Maplins (perhaps a British equivalent to RadioShack) has nominally 1.5W photovoltaic battery chargers for 15 quid.

http://www.maplin.co.uk/p/solar-powered-12v-15w-battery-auto-trickle-charger-l58bf

Since my car sits idle a lot without convenient mains access that might be useful. Insolation can be quite high in Taiwan, plus the car is old low-tech so has little built-in parasitic drain.

Any experience or opinions?

I thought of making one from a junked solar charged sign-lamp a while ago with 2 6V panels in series, but the amperage output was tiny (about 10mA IIRC).

Do these things deteriorate with age?

 

[bullwinkle]

I use four of those, three of them are on 2 battery diesel pickups, one is on the Mercury which generally only gets driven on weekends, they can now sit for indefinite periods without being driven, batteries are always fully charged. I haven't seen any signs of electrolyte boiling off or anything, I just add distilled water a couple times a year.

 

[SwampSurvivor]

I have a few of these on my camper batteries to keep them from going completely flat. And use one on my father's F-350 which sits for months and months at a time. It once sat 6 months and started right up on a 15F night! Was really impressed.

It's not a charger. Just a slight maintainer.

 

[bioburner]

I use a couple for motorcycles with some extra wire and diesel pickup. Easier than running cords to trickle chargers.

 

[meep]

the small ones will not over power the battery. if you want to gain a slight bit more oomph, replace the stock diode in the panel with a schotky diode, which has less voltage drop when flowing.

 

[901Memphis]

Unregulated solar panels can and will over charge any battery no matter the size. You need the proper setup for this.

 

[mk378]

That is about 10 times the panel you are considering. 1.5 watts isn't going to damage anything.

 

[barryh]

I had one of those 1.5W solar panel chargers and the first thing to say is that it only produced the rated output when the panel was square on to the midday sun in the middle of summer. Any thing less than that and it was hopeless. I actually removed the led as that was consuming too much power.

It's true they will produce 18V in a no load open circuit condition butI never saw an excessive voltage when it was hooked up to the battery.

 

[901Memphis]

Originally Posted By: mk378
That is about 10 times the panel you are considering. 1.5 watts isn't going to damage anything.


The issue can still pop up with a fully charged battery hooked up to an unregulated source.

In most cases it would be fine due to the draw of the vehicle computer combined with self discharge bringing it down less than full but still something to monitor and make sure that the voltage doesn't run away on you during the day.

 

[Shannow]

I've got a 2.5W solar panel for giggles...I can't see it doing anything bad...nor anything good.

I can't get it to charge a phone, and it only runs a CPU fan on a fine day, for the few hours that the sun is pretty square.

Set it up as an electrolyser for two weeks (it's summer and it's hot), on a slanted North facing aspect, and would have been lucky to lose 15ml of water, and probably most of that was evaporation.

 

[Ducked]

Mixed opinions then. I've heard elsewhere that output tends to decline with age. OTOH 15 quid isn't a lot of money. Probably depend on how much other junk I'm carrying when I go back. GF is likely to want to use all the 30 kilo allowance and then some.

 

[Ducked]

I didn't get one in the end, but GF got one for her dad. Stopped working (probably as judged by the LED) after a couple of weeks and she's just given it to me to look at.

It produces about 2V in (slightly overcast) sunlight, no detectable amperage. No LED output. The case appears to be plastic-welded so I can't dismantle it without breakage, but there probably won't be an opportunity to return it anyway (the drawback of buying stuff overseas) so that doesn't much matter.

What is likely to go wrong with these, and is any of it fixable?

Badly soldered connections, I suppose. Anything else?

 

[Ducked]

Correction: The broken charger's packaging is branded Astro, so she probably got it in Japan