Author Topic: 5 watt solar panel  (Read 4555 times)

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johnnym

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5 watt solar panel
« on: January 27, 2017, 10:54:10 AM »
I got this little 5 watt solar panel but it came with no terminals or wires. Where do I get the wires to use this? Are these mc4 connectors? Would this be able to charge a 12v battery? I am new at this so any help would be appreciated.

Ungrounded Lightning Rod

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Re: 5 watt solar panel
« Reply #1 on: January 27, 2017, 01:16:50 PM »
I can't make out the connector.

18V open-circuit is about right for charging a 12V battery.  That gives you a margin for things like the voltage dropping if the panel gets hot.  A panel that is loaded acts close to a constant-current source limited by the amount of illumination on the least-illuminated cell (or parallel rank of cells in big panels).  The energy lost due to the voltage of the load being lower than the panel's open-circuit voltage appears as heat in the panel.  In an unconnected panel just sitting in the sun ALL the absorbed energy appears as heat there, so this smaller amount is not an issue.

Face-on to high noon sun it should be able to drive about a quarter amp into a 12v battery with a direct connection (or through a back-leakage blocking diode.)  You could probably get away with hooking it up directly.

Figure an average of something like 5 solar-hours per day (temperate zone) if the panel is facing south and tilted to the latitude or the sun's noonday angle for the season.  That gives you, at a max, 1 1/4 amp-hours per day.  A small automotive battery is in the ballpark of 45 amp-hours, so that's not enough to charge it very effectively.  If you discharged it to 50% it would take nearly three weeks to bring it back to full charge.  That's long enough for some sulfation to occur.  (A deep-cycle battery's capacity tends to run in the 90 amp-hour range, so while it's got more power and is better at surviving deep discharges, a 50% discharge would take over a month of sunny days to recover.)  So if the panel is the only source of charging you need to use the battery only for a small loads for a short time, or expect its life to be shortened.p

Having said that:  This is exactly the way I ran our first sailboat's system:  The outboard auxiliary was only used for getting in and out of dock and perhaps navigating a channel or getting out of some difficult situation (like dodging a freighter).  A deep-cycle battery provided power for a VHF radio, navigation lights, and cabin lights.  A weekend day outing or out-overnight-back trip to another marina would partially discharge the battery.  A flexy solar panel provided a similar amount of charge and have it back to full power within a couple weeks.  Had to replace the battery every couple years, and keep it topped off with water regularly (see next paragraph).

On the other hand, a five-watt panel should be dandy for keeping a battery from dying in, say, a vehicle that is not used for months at a time.  The panel will cover any trickle loads (like the clock or the auto computers in sleep mode), drive the battery to full charge and then a slight overcharge, keeping it equalized and dissipating any extra energy by electrolyzing the water.  Checking/refilling the battery every few months to keep it from uncovering the plates is a lot better than replacing the battery when you go to use the vehicle again.  (Switching out the caps for ones with a catalyst to recombine the gasses is even better.)  With only five watts you don't have to worry about it boiling the battery dry over a sunny fortnght.

OperaHouse

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Re: 5 watt solar panel
« Reply #2 on: January 27, 2017, 02:08:35 PM »
I don't see any connectors, so pop the cover off and you will likely see screw connectors.  If outside you will want to have a watertight connection and these generally have 1/2 inch knockouts.  You could drill a small hole in one of the knockouts and just pass a wire through if you seal it with silicone  or hot melt glue.  MC4 connectors take an odd size wire and are kinda expensive for such a small panel.  That panel is too small to need a controller.   What is your target battery?  A small ebay $1 buck converter would with this small panel for other rechargeable batteries.

tanner0441

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Re: 5 watt solar panel
« Reply #3 on: January 27, 2017, 04:19:55 PM »
Hi

I use a 5 W solar panel to keep my 12 V torch, but it only has a 12 V 12Ah gell  battery in it and it is on charge 24 hours a day unless it is being used. I don't use a charge controller but I have a single blocking diode

A 40 plus Ah flooded lead acid car battery on the other hand is unlikely charge with only 5W as the maximum output under optimum conditions. Anything with a car battery in it and I would aim for a minimum of 40W that is only 3 A under ideal conditions.

Brian

DamonHD

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Re: 5 watt solar panel
« Reply #4 on: January 28, 2017, 01:12:58 AM »
Note that 1.5W PV units are sold as trickle chargers for cars, eg:

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

Rgds

Damon

george65

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Re: 5 watt solar panel
« Reply #5 on: January 28, 2017, 03:03:40 AM »
Note that 1.5W PV units are sold as trickle chargers for cars, eg:

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

Rgds

Damon

And are just another useless and completely ineffective accessory amount the million or so in the automotive world.
At best, they may slow the discharge of your battery down a fraction.... or speed it up if they were really crappy and didn't have a diode in them to prevent reverse flow of the power. 1.5W wouldn't even cover the drain of the electrical system for the computer, radio and other things in a modern car and I'd guarantee the internal self discharge of the battery would be higher as well.

I was playing with a 15W panel run through a PWM controller on a 20Ah battery a couple of months back and that barely did anything to charge it back up.

I have been playing with a cheap PWM controller that seems to work fine off a domestic 250W, 37V panel charging 2x 12V lead acid batteries.  I'm wondering if I can put the controllers in series with teh output so I can charge 12V batteries in mowers, tractors etc.
I already tried charging a 12V battery through the controller and blew the ship out of it. Clearly they don't like the high to low conversion but are happy with the high to high setup.
Other than that, I may have to try and find a 24>12V reducer that will handle a decent amperage and run them off that.

johnnym

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Re: 5 watt solar panel
« Reply #6 on: January 28, 2017, 02:41:25 PM »
Ok, thank you for replying everybody. Some of what you are talking about is going over my head. Keep in mind I have little knowledge with this stuff. It is like trying to explain algebra to a 5 year old. I know what 2 + 2 equals but when you add some x's and y's I get lost :-[ So a charge controller isn't necessary for this size panel? I do have a charge controller. I have a blocking diode. The charge controller was originally for a wind turbine that I have but have yet to put up due to my lack of knowledge about all of this stuff.

johnnym

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Re: 5 watt solar panel
« Reply #7 on: January 28, 2017, 02:44:22 PM »
charge controller and diode

OperaHouse

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Re: 5 watt solar panel
« Reply #8 on: January 28, 2017, 04:22:13 PM »
That controller would be pretty much useless. It looks like those designed for wind that shunt the battery with an external load when the set voltage is exceeded.  With the display, it probably consumes about as much as the panel produces  for much of the day.  The diode while oversize will work, the right size diode only costs a dime.

Mary B

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Re: 5 watt solar panel
« Reply #9 on: January 28, 2017, 06:35:02 PM »
24 to 12 volt DC-DC converters are readily available on Amazon. I use a Samlex SDC-30 to run my ham gear https://www.amazon.com/Samlex-America-SDC30-Amp-Converter/dp/B0054MXPRE

dnix71

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Re: 5 watt solar panel
« Reply #10 on: January 28, 2017, 08:29:52 PM »
I would be careful with a 5 watt unit. I put one on a full size car battery without a charge controller and it went way overvoltage quickly. I bought the panel from Harbor Freight, it isn't fancy.

george65 complained the 1.5w units are worthless. I disagree. Car makers use those to keep batteries fresh when shipping cars on top of ships to a foreign market. 1.5 watts without a controller is safe and effective. It won't recharge a dead battery, but it won't overcharge a good one either. There used to be surplus units on sale on eBay that were takeouts from VW.

johnnym

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Re: 5 watt solar panel
« Reply #11 on: January 30, 2017, 03:07:24 PM »
This is a picture of the junction box opened. What size terminals would this need?

Johann

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Re: 5 watt solar panel
« Reply #12 on: January 30, 2017, 03:43:10 PM »
charge controller and diode

I used one like that for about 2-3 month when my MPPT charge controller croaked when I turned it it into a test. I hooked up a relay to it so it can handle more power.

It is not like an expensive charge controller, but more like an cheap controller.

You can use it as N.o or N.C contacts, You can set the upper voltage and lower voltage. You also can set the on time and /or the off time  etc etc.

Well, let me just paste the operation modes
Operating modes:

P-1: Timer ( 1-999 S / 1-999 Min)

P-2: Delay timer ( 1-999 S / 1-999 Min)

P-3: Voltage control relay ( control the load on/off)

P-4: Voltage control Timer- A (close first)

P-5: Voltage control Timer- B (release first)

P-6: Voltage range control relay

P-7: Voltage range control Timer

P-8: Set display shut

I was satisfied when running the test and it keeped the batteries charged. I did not use it as dump controller, but as a controller to interrupt the power going to the battery. That relay must have turned on and off thousands of times to keep the voltage where I set it.

For an emergency it may be ok and using for such a small panel it may work also.




OperaHouse

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Re: 5 watt solar panel
« Reply #13 on: January 30, 2017, 04:25:54 PM »
A viable solution with a larger panel, but that will likely take at least 120ma to run if only used as dump.  That is half of what the panel could put out.

johnnym

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Re: 5 watt solar panel
« Reply #14 on: January 30, 2017, 05:35:25 PM »
Can anyone tell what type of terminals this would use? I am pretty sure it is a ring shaped one to fit under the screw but what size?

Thanks

george65

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Re: 5 watt solar panel
« Reply #15 on: January 30, 2017, 10:16:58 PM »
As far as I know the crimp terminals are all standard sizes and I'd suggest it would be the smallest ones that would fit the screws. You can use the forked type as well, they don't have to be the rings.
Other than that it's just the wire size they accept that is different and the panel being so low in power, just get whatever fits the wire you have or buy it to match.

Terminals aren't expensive so if you do somehow get them wrong, they will only be a couple of bux for a packet you can put away and no doubt find a use for later.

johnnym

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Re: 5 watt solar panel
« Reply #16 on: January 31, 2017, 04:29:04 AM »
Cool, thank you everyone. I am going to test this thing out now. Will update on the results.

Mary B

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Re: 5 watt solar panel
« Reply #17 on: January 31, 2017, 05:59:05 PM »
Get a variety kit of terminals, usually about $20 with a crimp tool that will work sorta.

Johann

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Re: 5 watt solar panel
« Reply #18 on: February 01, 2017, 07:38:14 PM »
A viable solution with a larger panel, but that will likely take at least 120ma to run if only used as dump.  That is half of what the panel could put out.

It says, with the display turned off ( you can turn the display off with this unit) it uses 6 ma, but it does not say how much it would use with the display turned on.

The build-in relay can handle 10 amps and can handle 1 million switches.

richhagen

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Re: 5 watt solar panel
« Reply #19 on: February 02, 2017, 12:36:06 PM »
You can actually do some useful stuff with a 5 watt panel.  We used similar panels to build simple lighting systems to provide evening light inside of huts with no electrical service in the northern Philippines.   Coupled with a simple charge controller and a 7 amp hour battery such as those used in alarm systems works well for such a purpose, or a light in a shed which is only used occassionally.   For ones I have here I replaced the batteries with a small ultracapacitor bank (a bit pricey) and the things are basically maintenance free for years and years.  Keep in mind that you are not going to have major power from 5 Watts, for me in Chicago in the winter I may see less than three Watt hours on dark over cast days from one of these, and that is provided it is not covered with snow.  As for the wiring, in our case we just popped off the back and used the screws to attach either tinned wire directly, or crimped and soldered on ring or spade terminals.  I suspect that over many years there would be corrosion inside the junction box from condensation and such and if you are in a marine environment you might need to seal over your connections with with epoxy, silicon, or some other coating as the box is not environmentally sealed, but I personally, have not seen issues with that yet on these types of junction boxes. 
A Joule saved is a Joule made!

richhagen

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Re: 5 watt solar panel
« Reply #20 on: February 02, 2017, 01:03:40 PM »
I thought I might have a photo of the inside of the junction box on one of these.  Since the maximum current is generally less than a half an amp, practically any crimp terminal you find that would fit the screw would be able to handle that. 

panel wired to roof of a hut.

the first light put in.  (I am pretty sure we tacked up the wiring a bit after this)

Provides a few hours of light, enough to eat dinner by without using a kerosene lamp. 
A Joule saved is a Joule made!

george65

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Re: 5 watt solar panel
« Reply #21 on: February 03, 2017, 01:25:46 AM »

I can see how that one light would really be something to the living situation like that.
Very evident the soot coating everything from what I presumed was just the fire but Obviously the kero lamps as well.

My nephew is working on a lighting project in Cambodia.
They are developing a power distribution system basically. If a hut has a panel and battery which hits charge, the excess is diverted to a neighbour for battery charging or lighting. A lot of the Villagers there use car batterys for Lighting and Radios. Usualy these batterys are taken from Vehicles that will no longer start and charged in town.  The people in town have a small horizontal  Yanmar/ Changfa type Diesel driving a car or truck alternator with no control on it. The batteries are thought to be charged when they boil so you can Imagine the capacity they have left. You super caps would probably outdo them by a long shot.

A lot of these people earn less in a year than a westerner makes in a few days so even a small panel, battery and light is a big investment. In the long term though, it's a BIG saving on kero.  My nephew is working with small panels so I suggested buying used panels here and sending them over. I suggested 250W panels and he laughed how a couple of those would light a whole Village. Trouble is the postal/ transport system over there is a shambles and he reckons the only organise thing there is the Corruption that would have anything valuable dissapear the minute it hit the distribution point. It's a difficult and expensive exercise getting things into the place.

It's amazing how something so simple that so many take for granted could be such a huge  improvement in quality of life ( and health) to others.

Johann

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Re: 5 watt solar panel
« Reply #22 on: February 03, 2017, 07:52:33 PM »
What country is that and where is over there?

Bruce S

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Re: 5 watt solar panel
« Reply #23 on: February 05, 2017, 12:13:17 PM »
Rich;
Those pics bring back the memories!
I should post right next to yours the one of the 80+ YO lady whose house we lit up. She passed us going up the rocks with 40+ lbs of rice on her back. AND the light was the first one she and her husband ever had her entire life!

george65;
You are correct, mostly. the suet on the walls and ceiling are from the kero lights. IF memory serves me right, there was a hut lost to a kero fire before we arrived.
The packs Rich, the 1/2 dozen porters and I carried up the mountain each weighed in at 60+lbs each. We had to porter in everything.
The 5 watt panels are more than enough for an individuals hut, but if there's more than one light , the school had 3 , then a 17 watt was way better. Rich merely couple 7Ah batteries and used a $5 charge controller.

Johann;
The place that Rich is talking about is the Luzan/Banaue region of the Philippines. look up UNESCO rice fields of the
Philippines. That's basically where we were at.

PS>>>> This is a link to the post(s) http://www.fieldlines.com/index.php/topic,145384.msg987904.html#msg987904
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