Solar Panel Charger

nigelk · 18-07-2006, 05:50 PM

I've got one of those portable solar panel charger things.

It plugs in the cigarette lighter and charges your battery.

I've just checked and in this sunlight, its pushing out 20v.

Will this fry my boat battery or will it be safe to keep it charged up?

Thanks.

1up · 18-07-2006, 06:06 PM

i'm not sure but i think they are sposed to be used with a voltage regulator

jw. · 18-07-2006, 08:17 PM

Yep, if you want to do it properly, you need to use a regulator. You should be able to pick one up for about 15kwid.

glen76 · 18-07-2006, 09:15 PM

anything above 14.5v is bit much for 12v battery!

whats the curent with that 20v though and i presume thats off load??

verytricky · 18-07-2006, 09:54 PM

It really really depents on the WATTAGE and the size of the battery.

For example, a 15w pannel putting out 20v inbright sun onto a 220 ah battery will have zero ill effects.

But a 60w pannel pushing 20v into a 85ah battery will boil the battery....

IMO ( which is based on an electrical enineering degree ) you can be quite safe on anthing under 10w for a standard 85ah car battery. It is always preferable to get a regulator. Typically they run in the £35 range upwards though...

nigelk · 19-07-2006, 08:21 AM

It's something like this

http://cgi.ebay.co.uk/ws/eBayISAPI.d...ADME:B:SS:UK:1

So I guess at 1.5w I should be ok ? Verytricky?

verytricky · 20-07-2006, 12:11 AM

1.5 w should be fine down to about 40ah batteries, provided it does not spike above about 20 volts.

The perfect recharge voltage is supposedly 18 volts

Supposedly a battery is fully charged at 14.5volts

glen76 · 20-07-2006, 06:20 PM

Quote:

Originally posted by verytricky
1.5 w should be fine down to about 40ah batteries, provided it does not spike above about 20 volts.

The perfect recharge voltage is supposedly 18 volts

Supposedly a battery is fully charged at 14.5volts

18V

jus rebuilt my car alternator and regulator and thats capped at 14.5V i though anything over is considered overcharge!

damn u bosch

JamesM · 20-07-2006, 10:39 PM

A poxy little solar panel like that isnt going to hurt a big chunky car battery.

The battery voltage is 12V and the solar panel output voltage is 20V, so if you connect the two together thats a difference of 8 volts. If the interconnecting wire has a resistance of 0.1 ohms then the solar panel would need to drive 80 amps into the battery to maintain its output at 20V. Thats not going to happen!!! Due to its very limited ability to source current (low wattage) what will happen is the output voltage of the panel will collapse to just over that of the car battery and a small amount of current will trickle into the battery from the solar panel. Hence why in the ebay description its called a trickle charger.

You don't need a regulator. If you did they'd build one into the panel, they cost about 20p.

verytricky · 21-07-2006, 12:09 AM

Just to clarify: You dont need a regulator, but in most cases another instalation would!

Also, a regulator *costs* about 20p, but sells for about £35!

JamesM · 21-07-2006, 08:36 AM

You can buy a linear reg from RS for anything from about 80p upto a few £ depending on which one you choose. However thats for 1 from RS in the UK, a factory in China buying then in the tens of thousands won't be paying nearly as much as that hence why I said 20p.

verytricky · 21-07-2006, 08:59 AM

Quote:

A charge controller, or charge regulator is similar to the voltage regulator in your car. It regulates the voltage and current coming from the solar panels going to the battery. Most panels put out 15.5 to 20 volts, so if there is no regulation the batteries will be damaged from overcharging.

Generally, there is no need for a charge controller with the smaller trickle charge panels, such as the 1 to 5 watt panels. A rough rule is that if the panel puts out 1/60th or less per day of the rated battery amp-hour capacity, you don't need one.

I cant find one under £35.

http://store.solar-electric.com/chco.html

http://www.genasun.com/gv.shtml

http://www.solazone.com.au/Regulators.htm

http://www.amazon.com/gp/product/B00...lance&n=228013

JamesM · 21-07-2006, 10:22 AM

We're on different wave lengths, your talking about consumer products I'm talking about one of these.

jw. · 21-07-2006, 10:35 AM

Quote:

Originally posted by verytricky
[B]I cant find one under £35.

http://cgi.ebay.co.uk/16A-LCD-Charge...QQcmdZViewItem

http://cgi.ebay.co.uk/12A-Charge-Con...QQcmdZViewItem

Mr Verytricky, you're looking in the wrong place.

I bought the second one, it was £14.99 a couple of months ago, along with a 64watt panel. It's a multistage charger and works just fine. It arrived from Germany two days later. Quicker service than many UK companies.

A wee voltage regulator like JBD is suggesting will do the job. I use a standard 7812 and 2 diodes on the reference leg to trickle a small gel cell. It regulates to about 13.3v. Three diodes would lift that to about 14v.

verytricky · 21-07-2006, 02:47 PM

I am not looking - I can build my own.

What I am trying to say is that for the 'normal' person who wants to buy a large ( say 60w ) pannel and plug it into their boat or car/truck etc it will cost them £35+ and is required.

For the person who has a 'standard' battery from say 75ah to 90 ah and a 'cheap and nasty' charger ( say 1.5w to 10w ) then there is no requirement to buy/build/ebay a regulator.

Finally: if you are charging with an altenator, producing say 60-80 amps then you would probably set the voltage to around 14.5v - the fully charged load of the battery. If you are charging with a solar panel at around 0.1 amp then you are going to have to step up the voltage to ( perfect? 18 volt ) 20 volts or so to get any actual recharging done..

glen76 · 21-07-2006, 10:20 PM

jbd Agree entirely about 20v as its an off load voltage and the battery will drag it down considerably no doubt!

the little fella in the pic is best used for 1-5A current ranges (big buggers are available but very inefficient and poor regulation) i hope others do not think u can jus clag em on as they run bloody hot and really need a couple of caps in cct for stablity wen pushed!

Another way he Could just run a few diodes in series as they do in cheap torches!

JamesM · 22-07-2006, 12:49 PM

I'd have thought there would be series diodes in there allready as its actually claimed to be a solar powered trickle charger rather than just a solar panel.

JamesM · 22-07-2006, 01:28 PM

Quote:

Originally posted by glen76
the little fella in the pic is best used for 1-5A current ranges (big buggers are available but very inefficient and poor regulation) i hope others do not think u can jus clag em on as they run bloody hot and really need a couple of caps in cct for stablity wen pushed!

I reckon the charge current from that 1.5w panel would be around the 100mA mark so you probably wouldn't even need a heatsink for that lil reg in the picture. In this application the regulator would be there to protect the solar panel from an over current/load situation rather than protecting the battery from an over voltage situation. As I said previously though you dont need it as 100ma almost certainly isn't going to be enough to melt any wires or damage any of the solar panels internal components. You just need a couple of diodes to stop the battery from backfeeding the panel and killing it which it would easily do without them. However its sold as a solar powered charger for 12V car batteries so it should have the diodes built in and if it did need regulation it would have that built in too, but it doesn't so that must tell you something. Just plug it in and go, your battery should be fully charged by September which brings me neatly onto my next point. A £6 1.5w solar powered trickle charger to keep your boat battery topped up, are you for real!!!