Solar Panel for Car

I'm looking to get a small Solar Panel to trickle charge my car battery. So far the ones I've seen have been too long and thin, and they would block up my air vents or speakers.
Can anyone recommend any sites in the USA or UK that sell small panels that are about 12x8 inches in size? Was only looking for a panel of around 2-3w maybe 150ma at 15v give or take.
I think size around 12x8, 11x7, 12x7, 10x8 would be the best types of size as this wont block my airbags, speakers or air vents up and it would be able to sit nicely on the dash and connect to the battery.
Thanks for any links,
John

John wrote:

I'm looking to get a small Solar Panel to trickle charge my car battery.

Forget it. All of them are worthless scams. Unless you ger a REALLY big panel that might fit on the rear shelf of a hatchback type car.
Graham

John wrote:

I'm looking to get a small Solar Panel to trickle charge my car battery. So far the ones I've seen have been too long and thin, and they would block up my air vents or speakers.
Can anyone recommend any sites in the USA or UK that sell small panels that are about 12x8 inches in size? Was only looking for a panel of around 2-3w maybe 150ma at 15v give or take.

For how many hours a day ?
It's not going to help your battery any but will relieve your wallet of some money.
Graham

On Sun, 05 Oct 2008 03:52:39 +0100, Eeyore wrote:

John wrote:
I'm looking to get a small Solar Panel to trickle charge my car battery. So far the ones I've seen have been too long and thin, and they would block up my air vents or speakers.
Can anyone recommend any sites in the USA or UK that sell small panels that are about 12x8 inches in size? Was only looking for a panel of around 2-3w maybe 150ma at 15v give or take.
For how many hours a day ?
It's not going to help your battery any but will relieve your wallet of some money.
Graham

Thanks for the input. You reckon its not worth it and they don't make much of a difference?
At the moment I have just bought a new car battery its a special sealed gel type that's for my car and cost �165. Unfortunately I have a lot of electronics on my car that drain the battery while I'm not driving. I have alarm and also the cardkey autosensors amongst other things.
I often don't use my car over the weekend and it takes a few attempts to get started on Monday morning. Even within the week when I am driving each day to work it often doesn't start first time.
At the moment we're going into Winter here in Britain so we wont have as much daylight, maybe 5 to 7 hours max over the next 6 months. In summer a lot more. I think if I only get a small amount of juice to my battery from a small panel it may be the difference between my car starting first time and not starting, and the difference between keeping the battery maintained in top condition and not having to spend more money in another four years to replace the battery, it could last a few years longer than that still.
A small solar panel of maybe 2 or 3 watts may only cost �30 or �35, I guess around $50 USD give or take, and may last 10 years and more. I think if that is something that would work then it would be cheaper for my wallet than the cost of having to replace the battery sooner than I should especially with the type for my car?
What do you think? Still not worth it? Are you generally against anything that is renewable? Because I am not some sort of eco-freak I'm just interested in this to save money not spend it. Are you saying that a small 2 or 3w panel won't help my battery and that I would really need a bigger one? 5w? I guess I could have two small panels on the front dash that connect to my battery, its just the reason I can't have one big one is there's nowhere to put it where it will get a lot of sunlight and wont block up other important stuff.
BTW, I have a small hatchback but it wouldn't be a good idea to put a bigger panel on the parcel shelf because it wouldn't get much sunlight there because my rear window is very small and pretty much vertical.
Thanks for your input,
John

"John" wrote in message

On Sun, 05 Oct 2008 03:52:39 +0100, Eeyore rabbitsfriendsandrelations@hotmail.com> wrote:

John wrote:
I'm looking to get a small Solar Panel to trickle charge my car battery. So far the ones I've seen have been too long and thin, and they would block up my air vents or speakers.
Can anyone recommend any sites in the USA or UK that sell small panels that are about 12x8 inches in size? Was only looking for a panel of around 2-3w maybe 150ma at 15v give or take.
For how many hours a day ?
It's not going to help your battery any but will relieve your wallet of some money.
Graham
Thanks for the input. You reckon its not worth it and they don't make much of a difference?
At the moment I have just bought a new car battery its a special sealed gel type that's for my car and cost �165. Unfortunately I have a lot of electronics on my car that drain the battery while I'm not driving. I have alarm and also the cardkey autosensors amongst other things.
I often don't use my car over the weekend and it takes a few attempts to get started on Monday morning. Even within the week when I am driving each day to work it often doesn't start first time.
At the moment we're going into Winter here in Britain so we wont have as much daylight, maybe 5 to 7 hours max over the next 6 months. In summer a lot more. I think if I only get a small amount of juice to my battery from a small panel it may be the difference between my car starting first time and not starting, and the difference between keeping the battery maintained in top condition and not having to spend more money in another four years to replace the battery, it could last a few years longer than that still.
A small solar panel of maybe 2 or 3 watts may only cost �30 or �35, I guess around $50 USD give or take, and may last 10 years and more. I think if that is something that would work then it would be cheaper for my wallet than the cost of having to replace the battery sooner than I should especially with the type for my car?
What do you think? Still not worth it? Are you generally against anything that is renewable? Because I am not some sort of eco-freak I'm just interested in this to save money not spend it. Are you saying that a small 2 or 3w panel won't help my battery and that I would really need a bigger one? 5w? I guess I could have two small panels on the front dash that connect to my battery, its just the reason I can't have one big one is there's nowhere to put it where it will get a lot of sunlight and wont block up other important stuff.
BTW, I have a small hatchback but it wouldn't be a good idea to put a bigger panel on the parcel shelf because it wouldn't get much sunlight there because my rear window is very small and pretty much vertical.
Thanks for your input,
John

The reason everyone is saying it is a waste of time and money is because the size of panel you are talking about might be able to keep an iPod or your security system LED flashing , the rate of charge recommended for Gel / AGM batteries is 10% of the battery's AH capacity . Being a late model car you could expect that your battery will be at least 80AH , so you need 8 amps to charge it. If the things you have running are drawing it down enough to effect the starting , then it means it must be dropping by around 40% of it's capacity and this is only over the weekend !So around 32AH , Over the weekend the charging you are talking about if there was 8 hours of perfect sunlight everyday would replace 2.4AH in 2 days.
I have standard AA touch batteries rated at 1100ma , your panel suggestion would be lucky to even charge one of them on a good day let alone have any noticeable impact on car battery..
If you were considering something around the 25w mark you might see a more noticeable effect , but then for the cost you would be better off saving that money until you batteries dies and replacing it with a brand new one and still have money left over. You might even want to consider a dual battery system , this would better cater to your concerns.

In spaco writes:
[ snip ]

Why not fix the car so it starts the first time? Are you certain that the car's alternator is working properly?
Or, at least one mfr on this side of the pond makes a "Dual battery" If the main section goes dead, you throw a switch that is built into the battery, and the other section starts your car.

I had one of those two decades ago under the Sears Diehard brand name. It worked fine, and saved my ass when I left the headlights on one time.
BUT, one day, when I turned on the ignition, it went "kaboom". Small explosion, fortunately, with no damage.
I headed to Sears and they swapped in a regular Diehard.
A bit later I checked and found that they had stopped selling them, and there were some indications this was because of some similar events. (This was before the day of easy internet access, so I didn't see any stories).
One of the big battery manufacturers whose name escapes me for the moment had a similar unit, and kept offerring it for a while (but I could never find a store that actually had it or was able to order it with a reasonable delivery time), leading me to suspect they were the supplier and had stopped making it.
If there's anyone selling this product these days, and they've got good quality control, it could be worth it.
Oh, another two suggestions for the original poster:
a: if your battery drain is one of those unwanted things (i.e. a short somewhere) you could hook up a fairly cheap and easy "kill" switch at the battery. These are commonly used for a theft protection device, but would help here as well. On the other hand, this might mean losing all your radio, etc., settings.
b: One of the best $30 investments I made was a "jumper battery". This is a self contained unit ,about half the size of a tissue box, which contains a small rechargable battery and jumper cables. You simply lift it up and hook it to the main bettery, and you've got plenty of power to start up.
In the USofA these range from $20 to $50 or so and are available at automotive supply stores and mass marketers.
Any model above the el-cheapo-basement unit would be fine.

-- _____________________________________________________ Knowledge may be power, but communications is the key dannyb@panix.com [to foil spammers, my address has been double rot-13 encoded]

One other reason that a small solar panel won't serve YOUR purpose is that, if the UK is anything like western Wisconsin in the USA, December and January are alomost TOTAL washouts as far as solar energy goes. This would mean that you'd have at least 2 months where it would be of no value at all. I am not making this up! I have been recording solar input daily here for almost a year now. See: http://www.spaco.org/PV/PVSolar.htm I have a cheap 1 meter square panel and it stores a maxumum of about 150 watt hours on a totally sunny day in summer, facing due south and at the correct vertical angle. On a typical cloudy day, (like this very day so far), I am getting 2 watts at 12.51 volts into a "car battery". Since I left a small (10 watt) load on that battery all day yesterday, the terminal voltage was 12.2 at midnight last night when I removed that load. The terminal voltage will improve during the day today, up to maybe 12.89, by day's end. Remember, this is a 1 meter square panel, capable of supplying up to 30 watts in DIRECT sun.
Why not fix the car so it starts the first time? Are you certain that the car's alternator is working properly?
Or, at least one mfr on this side of the pond makes a "Dual battery" If the main section goes dead, you throw a switch that is built into the battery, and the other section starts your car.
Pete Stanaitis ------------------------------
John wrote:

I'm looking to get a small Solar Panel to trickle charge my car battery. So far the ones I've seen have been too long and thin, and they would block up my air vents or speakers.
Can anyone recommend any sites in the USA or UK that sell small panels that are about 12x8 inches in size? Was only looking for a panel of around 2-3w maybe 150ma at 15v give or take.
I think size around 12x8, 11x7, 12x7, 10x8 would be the best types of size as this wont block my airbags, speakers or air vents up and it would be able to sit nicely on the dash and connect to the battery.
Thanks for any links,
John

Slick wrote:

... the rate of charge recommended for Gel / AGM batteries is 10% of the battery's AH capacity .

That sounds more like a max than a min.

Being a late model car you could expect that your battery will be at least 80AH , so you need 8 amps to charge it.

If a battery takes 3 weeks to self-discharge, we might keep it charged with 80AH/(3x168H) = 160 mA, ie 1.9 watts, on a continuous basis.
Nick

John wrote:

Eeyore wrote: John wrote:
I'm looking to get a small Solar Panel to trickle charge my car battery. So far the ones I've seen have been too long and thin, and they would block up my air vents or speakers.
Can anyone recommend any sites in the USA or UK that sell small panels that are about 12x8 inches in size? Was only looking for a panel of around 2-3w maybe 150ma at 15v give or take.
For how many hours a day ?
It's not going to help your battery any but will relieve your wallet of some money.
Thanks for the input. You reckon its not worth it and they don't make much of a difference?

Absolutely 100% worthless. I know someone who tried one and the battery still went flat from all the electronic loads (like an alarm) on it when not in use.

At the moment I have just bought a new car battery its a special sealed gel type that's for my car and cost �165. Unfortunately I have a lot of electronics on my car that drain the battery while I'm not driving. I have alarm and also the cardkey autosensors amongst other things.

Yes, and a solar cell has NO HOPE of powering those. it'll provide a few tens of Watt-hours a day but it's pathetic.
Graham

spaco wrote:

One other reason that a small solar panel won't serve YOUR purpose is that, if the UK is anything like western Wisconsin in the USA, December and January are alomost TOTAL washouts as far as solar energy goes. This would mean that you'd have at least 2 months where it would be of no value at all.

Precisely true.
Graham

nicksanspam@ece.villanova.edu wrote:

Slick wrote:
... the rate of charge recommended for Gel / AGM batteries is 10% of the battery's AH capacity .
That sounds more like a max than a min.
Being a late model car you could expect that your battery will be at least 80AH , so you need 8 amps to charge it.
If a battery takes 3 weeks to self-discharge, we might keep it charged with 80AH/(3x168H) = 160 mA, ie 1.9 watts, on a continuous basis.

Which is ~ 45Wh per day. With maybe 2 hours eqivalent peak sunlight in winter that would require a 25W panel (allowing some margin).
@ a typical 15% efficiency a 1 metre square panel only provides 150W so you'd need a 0.17 m^2 panel. Say 1 foot by 2 feet and it must be in direct sunlight ! No guarantee of that so maybe a 2 foot sq panel would do.
BUT, with heavy loads on it, I bet his battery won't last 3 weeks either. Increase the numbers accordingly.
Graham

On Mon, 06 Oct 2008 00:31:52 +0100, Eeyore wrote:

spaco wrote:
One other reason that a small solar panel won't serve YOUR purpose is that, if the UK is anything like western Wisconsin in the USA, December and January are alomost TOTAL washouts as far as solar energy goes. This would mean that you'd have at least 2 months where it would be of no value at all.
Precisely true.
Graham

Ive got essentially the OPs problem. A car thats only used on weekends and sits idle in the garage for the rest of the week. Battery goes flat over the week. Simple cheap fix is a small mains operated battery charger available from any car parts shop, mine cost me $15. Put a cigarette lighter plug on the charger and just leave it pluuged into the car socket when not using the car. Batterys always fully charged when needed. Much cheaper than a solar panel.

In John writes:

Would such a device give enough juice though if in this socket when I am starting up the car? Because I'm sure the socket will become active when I hit the start button and try start the car up.

Not enough to start the car right then and there, but if you could leave it hooked up for 10 minutes or so you'd probably be pleasantly suprised.
-- _____________________________________________________ Knowledge may be power, but communications is the key dannyb@panix.com [to foil spammers, my address has been double rot-13 encoded]

On Sun, 5 Oct 2008 22:48:01 +0800, "Slick" wrote:

The reason everyone is saying it is a waste of time and money is because the size of panel you are talking about might be able to keep an iPod or your security system LED flashing , the rate of charge recommended for Gel / AGM batteries is 10% of the battery's AH capacity . Being a late model car you could expect that your battery will be at least 80AH , so you need 8 amps to charge it.

Apologies but I've not had time to read all the responses yet, but just to quickly confirm my battery is only an 48amp 12v gel type battery in my car. It is just for a small 1.6 litre engine petrol hatch.
Thanks for all the help and advice,
John

On Sun, 5 Oct 2008 22:48:01 +0800, "Slick" wrote:

The reason everyone is saying it is a waste of time and money is because the size of panel you are talking about might be able to keep an iPod or your security system LED flashing , the rate of charge recommended for Gel / AGM batteries is 10% of the battery's AH capacity . Being a late model car you could expect that your battery will be at least 80AH , so you need 8 amps to charge it.

So 48 amp battery 4.8 amps to charge.

If the things you have running are drawing it down enough to effect the starting , then it means it must be dropping by around 40% of it's capacity and this is only over the weekend !So around 32AH ,

If it lost 32 amps I don't think it would start at all ;) it would only have 16left.

Over the weekend the charging you are talking about if there was 8 hours of perfect sunlight everyday would replace 2.4AH in 2 days.
I have standard AA touch batteries rated at 1100ma , your panel suggestion would be lucky to even charge one of them on a good day let alone have any noticeable impact on car battery..

okay, taken onboard.

If you were considering something around the 25w mark you might see a more

Would 15w do for 48 amp battery? I am guessing the 25w was for 80amp?
John