Association Forum - Solar panels & charge controllers on Woot.com $99

Assn Members Area · Join

Home.

Association Forum

Ships Store

Cruising

Racing

Technical Tips

Photo Gallery - New

Boat Search - Updated

Manuals & Brochures

Swap Meet

Links

Officer Flag Line & Staff

Bylaws & Constitution

Members Area

Join the Association

Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.

Association Forum

Username:	Password:
Save Password
Forgot your Password?

All Forums

Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

Solar panels & charge controllers on Woot.com $99

New Topic

Topic Locked

Printer Friendly

Author

Topic

Page: of 3

OLarryR
Master Marine Consultant

Members Avatar

USA
3462 Posts

Response Posted - 02/22/2010 : 16:01:23

Removed my comment. Better off without it.

Edited by - OLarryR on 02/22/2010 22:09:29

TakeFive
Master Marine Consultant

Members Avatar

2272 Posts

Response Posted - 02/22/2010 : 20:31:36

I am aware that the 18w rated capacity of this device is meager, and would never come close to running a refrigerator. But it can help to run my MSI Netbook-based chart plotter. I did the calculations, and that device only draws 12w, so the panel can extend my battery life for light electrical use. I bought this panel just as a starter kit, to get a "free" controller, and to get familiar with the tradeoffs of solar panels. I am not fooling myself into thinking it will do more than it can.

Although I am not an expert at these things, I do know enough to realize that there is no such thing as amps/hour and amps/day. Some review of Physics 102 is needed before doing any more calculations. Amps is a unit of current - and instantaneous flow of electrons that is MULTIPLIED (not divided) by units of time to get capacity. Battery storage capacity is often measured in amp-hours (at a given voltage), its power in watts (for DC current) is volt-amps. Similarly, an 18w solar cell could deliver 1.5 amps at 12 volts if 100% efficient.

Edited by - TakeFive on 02/22/2010 21:13:09

OLarryR
Master Marine Consultant

Members Avatar

USA
3462 Posts

Response Posted - 02/23/2010 : 04:25:24

The Woots site rates the SUNSEI 18 Watt at 1.2 AMPs.
http://www.woot.com/Blog/ViewEntry.aspx?Id=7194

Your posting listing 12 volts, the solar panel would be doubtful to charge a 12 volt battery. The charging rate of a solar panel has to be higher to charge a 12 volt battery. If you were to hook up a voltmeter to the panel, you would find it will charge at a voltage closer to 14 volts. The Kyocera 20 watt panel is also rated at 1.2 AMPs. Perhaps, you have seen somewhere that an 18 watt panel will produce 1.5 AMPs. Okay...maybe that is true. However, if they rated it at 12 volts as you listed, that was probably a 12 volt nominal rating. Most batteries if in good shape will be at around 12.7 -13.4 volts (or thereabouts....my batteries are generally resting at 12.9-13.2 volts) and so a panel that is rated at 1.5 AMPs at 12 volts is likely not to charge a 12 volt battery that has generally a higher voltage. The amps just will not flow to the battery.

By the way, I apologize for not listing amp hours vs amps/hr. Thanks for the correction. But the info I had provided was fairly accurate as to what to expect from a typical 20 watt panel. Thought the info would be helpful for prospective buyers of a panel. For those that already have a panel, well they do not need the info...They already know from experience what the panel puts out in reality...That is if they measuring regularly the watts, amps, volts or have a digital controller readout like on the Morningstar Pro 15M controller.

Edited by - OLarryR on 02/23/2010 04:35:13

tbosch
Navigator

Members Avatar

163 Posts

Response Posted - 02/23/2010 : 10:21:27

I bought one of these panel out over the summer. I'm hoping that it can recharge my single battery system during the 4-5 days I'll be away from the boat during the week. What can I do to verify the ability of the panel to recharge? I plan to do more major electrical upgrades in the future that will go to 2 batteries and shore power. In the mean time I just want to go sail. What can I do with a digital multi-meter to verify that my single battery is fully charged at the beginning of the weekend? How can I tell how much of the battery's capacity was discharged during the weekend? I can do simple voltage measurements but are there other tests that would indicate that the battery was fully charged or not?

Do the battery meters that are out there simply gauge capacity as the voltage declines? How do they work and what do they actually measure?

Edited by - on

TakeFive
Master Marine Consultant

Members Avatar

2272 Posts

Response Posted - 02/23/2010 : 10:55:18

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by RhythmDoctor
 Similarly, an 18w solar cell could deliver 1.5 amps at 12 volts if 100% efficient.
<hr height="1" noshade id="quote"></blockquote id="quote">
I was not intending to quote the specs of the Sunsei solar cell. I was just showing an illustrative example that 1.5A x 12V = 18W. I did not have time to pull the thing out of the box and look at the specs, and I could not find the Woot site. Obviously it needs to deliver higher volts to provide a positive flux into the battery, and if so the amperage would be proportionally reduced. That is consistent with the numbers that Woot showed (1.2A x 15 V = 18W).

Edited by - TakeFive on 02/23/2010 10:59:04

islander
Master Marine Consultant

Members Avatar

USA
4023 Posts

Response Posted - 02/23/2010 : 12:37:11

<blockquote id="quote">quote:<hr height="1" noshade id="quote">What can I do to verify the ability of the panel to recharge?<hr height="1" noshade id="quote"></blockquote id="quote">A charge controller will tell you if the panel is charging, And when the battery is fully charged. A charge controller should be in the system so the panel wont overcharge the battery. Some have a L.E.D voltage meter (Better) or three L.E.D lights or you can use a simple voltage meter that plugs into a cigarette lighter like this for around $10

OlarryR has a nice photo of his charge controller on the first page of this thread.

Edited by - islander on 02/23/2010 12:54:03

OLarryR
Master Marine Consultant

Members Avatar

USA
3462 Posts

Response Posted - 02/24/2010 : 04:58:34

Todd,

The easiest way to check if a battery is fully charged is if your solar panel controller has an LED or digital readout that indicates the battery is fully charged. While the voltmeters we generally use do not put a load on the battery as one would check a battery at an auto store with their checkers, a voltmeter can be used to check if a battery is fully charged by measuring the voltage across the terminals when the battery is at rest and the solar panel is not charging (ie. during early morning or evening hours). If you do a search on the web for "12 Volt Battery fully charged" or something similar, you will come across a number of sources that will provide the battery voltage and how that relates to percentage fully charged. For example, one source indicates that a flooded battery (one that you add water to it) is 100% charged when the resting voltage is around 12.9-13.2 volts. Other sources may indicate 13.4 volts. 100% fully charged is around that range. 80% around 12.4V, 60% - 12.2V, 50% - 12.1 Volts. Battery voltage should be maintained at 100% and should not go below 12.1 Volts. 40% is around 11.9 Volts and once the resting voltage hits 11.5 Volts or below it indicates the battery is basically fully discharged.

A 5 watt solar panel oftentimes does not need a controller because it charges at such a low rate that the chance of cooking the battery is remote. Water level should still be checked frequently but a 5 watt panel basically will charge a siongle 12 Volt battery about equal to the trickle down rate of a battery which is around .4 AMPs each day in the summer and about .25 AMPs in the winter. Tbhis info can be also be found searching the web but I do not have a handy source for you right now.

A 10 watt or greater solar panel for a single battery will cook off the water and so a controller is then necessary. The benifit of a controller is that it will prevent some discharge back thru the panel which happens to a small extent during the evening hours and a controller will prevent the panel from overcharging a battery. Still, water level should be checked periodically on the battery since some water will evaporate as is the case for all flooded batteries.

My Morningstar Pro 15M controller has LEDs to indicate if the battery is fully charged and/or if the solar panel is presently charging the battery. It also has a digital readout that alternates between a direct solar panel load hooked up to the panel (I have none so it reads "0" ), the battery voltage and the amps that the solar panel is presently putting out. When the solar panel is not charging, the solar controller reads the resting battery voltage which on my two batteries is generally between 12.9 and 13.2 volts.

Some fishfinders also have a mode that will provide a digital readout of the battery voltage, though, that's with the fishfinder on but means that you may not have to get out your voltmeter to check battery voltage if you can read it off of your fishfinder.

Sometimes from work, my boat website does not come up so fast, so I cannot easily provide a photo of my controller. But you can access the photos directly going to my website. I went with a digital controller but it was expensive and as I indicated above, you could use your voltmeter or possibly your fishfinder to get a battery voltage reading which will give you an idea of your battery status. I believe the best indicator or better indicator of battery health is using the load testers the auto stores.

Edited by - OLarryR on 02/24/2010 05:03:40

tbosch
Navigator

Members Avatar

163 Posts

Response Posted - 02/24/2010 : 11:54:04

Thanks for the responses. Very helpful!

Larry, I appreciate the info on your web site as well. I'll keep that handy.

Edited by - on

Voyager
Master Marine Consultant

Members Avatar

USA
5368 Posts

Response Posted - 02/25/2010 : 16:36:01

Larry's comments are very helpful and hit the nail on the head.

Don Casey's book "Sailboat Electrics Simplified" has several tables for amount of charge in the battery versus its terminal voltage. You can also measure specific gravity of the battery fluid too, but it correlates with voltage.

Note that all voltages should be taken with the charger disconnected, and the battery has about 2 hours or so to settle down from the charger voltage (around 13.4V)

Fully charged wet cell Group 24-------> 75 to 80 AH--->12.6V
75% charged wet cell Group 24-------> 57 to 60 AH--->12.4V
50% charged wet cell Group 24-------> 38 to 40 AH--->12.2V
25% charged wet cell Group 24-------> 18 to 20 AH--->12.0V --- this battery is in the critical discharge zone
Dead battery---------------------------------------->11.8V --- this battery may not last too long

For gel cell and glass mat batteries, add 0.2V Fully charged, they measure around 12.8V

In practice, you can get 40 AH out of a Marine Group 24 battery, then you must recharge it. Don't discharge it further, or you risk seriously limiting its life.

Casey warns that if you heavily discharge your battery with a water pump, lots of lights or other high current devices, its voltage will read low once you disconnect the devices, then "recover" somewhat and read a higher voltage afterward.

If you look at the charging side of the equation --> using a 1.0 A solar charger, and you assume you can get 1A for 12 hours a day during the summer, it would take about four days to recharge a 1/2 discharged G24 battery. Since one day might be cloudy, you'd need five days to fully recharge.

I have two 18W panels (2A max), and after a few days in summer, my battery comes back up to snuff. I do remove it from the boat from time to time to put it on my home battery charger, to equalize it.

There are several posts about equalizing your batteries on the forum.

Edited by - on

C25OBrien
1st Mate

Members Avatar

USA
44 Posts

Response Posted - 03/02/2010 : 08:15:47

My boat will most likely be on a mooring this season so solar power looks to be my best bet. Has anyone had experience using the MPPT style controller versus standard 3 stage controller? It is my understanding that they can trade volts for amps and vice-a-versa when the panel is generating more or less than 14.4 volts to charge a 12V. Has anyone used these and do you feel the efficiency gained is worth the more expensive price tag of the MPPT controller? I'd rather have a smaller "footprint" on my panel and boost it's efficiency wherever possible.

Edited by - on

PCP777
Master Marine Consultant

Members Avatar

USA
1225 Posts

Response Posted - 03/07/2010 : 08:36:37

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by RhythmDoctor
 <blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by tbosch
 Dang! I just received my new solar panel and the glass is shattered. What a bummer! I've got an email into Woot. It will be interesting to see what happens next. I doubt they have a replacement since they get fixed quantities and sell them until they are gone. Hopefully I'll at least get a refund. I sent them a photo showing the cracked plastic end cap and the shattered glass.
<hr height="1" noshade id="quote"></blockquote id="quote">
I just checked the tracking # on mine. Says it's supposed to arrive today. Fat chance with 18" of fresh snow, and still falling!

You should save your packing materials and contact the shipper. Chances are they will be responsible, and you'll get faster response dealing with them directly than trying to work through the Woot-bots.
<hr height="1" noshade id="quote"></blockquote id="quote">

I got mine and just noticed it did NOT come with the charge controller. Did you get one? Did it arrive separately?

Edited by - on

tbosch
Navigator

Members Avatar

163 Posts

Response Posted - 03/08/2010 : 10:33:59

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by PCP777
 

I got mine and just noticed it did NOT come with the charge controller. Did you get one? Did it arrive separately?
<hr height="1" noshade id="quote"></blockquote id="quote">

My shipment contained both a panel and a charge controller in a single box. The panel and the controller were packaged separately within.

Edited by - on

PCP777
Master Marine Consultant

Members Avatar

USA
1225 Posts

Response Posted - 03/08/2010 : 13:12:37

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by tbosch
 <blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by PCP777
 

I got mine and just noticed it did NOT come with the charge controller. Did you get one? Did it arrive separately?
<hr height="1" noshade id="quote"></blockquote id="quote">

My shipment contained both a panel and a charge controller in a single box. The panel and the controller were packaged separately within.
<hr height="1" noshade id="quote"></blockquote id="quote">

<s>Interesting. I did not receive the charge controller.</s>

Thank you!! I found it, way in the back of the box.

Edited by - PCP777 on 03/08/2010 13:16:41

Voyager
Master Marine Consultant

Members Avatar

USA
5368 Posts

Response Posted - 03/08/2010 : 19:52:17

So as things sometimes go - one of my two solar panels failed this week. Last week it was working, this week it isn't.

First year, an internal connection between the aluminum conductor sticking out of the glass panel and the positive electrical lead had broken.

At the time, I was able to re-solder the connection (don't ask me how I got tin, lead, copper and aluminum to "solder" - suffice it to say it's still holding fine).

I checked the other lead. It appeared to be physically connected, the reverse diode tested out fine and all the leads had continuity.

So now I assume the connection inside the glass may have blown. With the tarp on the boat and the very low humidity in the air (dew point this week was -3 degrees F), a random static charge could very well have built up and arced out a tiny connection in the panel. This weekend as I was working under the tarp, I received continuous static "shocks" as I moved around.

I went back to Amazon to check on an 18W (18V@1A) panel and they're around $80. With shipping, it ought to be about $100.

Edited by - on

islander
Master Marine Consultant

Members Avatar

USA
4023 Posts

Response Posted - 03/09/2010 : 10:49:25

Bruce, Isn't it baffling that something that doesn't move and has no moving parts can just stop working. I would take the frame and glass off and put a solder gun to all the connections/strips between the cells, enough to remelt the solder. Could be just a hairline crack somewhere. Nothing to lose if your going to toss it anyway.

Edited by - on

Voyager
Master Marine Consultant

Members Avatar

USA
5368 Posts

Response Posted - 03/09/2010 : 19:56:39

Scott,
While I originally thought it might have been static electricity, the real killer this time of year is thermal expansion and contraction.

When it's 60 degree air temp during the day, and maybe the black plastic got up to 80 degrees in the sun, then at night it's about 30 (and just add a little water/ice), that can put your sensitive electronics out of whack in a hurry.

I have a 2000W heat gun, maybe I should run that around the connections and see what happens!

Edited by - Voyager on 03/09/2010 19:57:52

Page: of 3

Topic

New Topic

Topic Locked

Printer Friendly

Jump To:

Association Forum

Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.