Power: Solar, wind, lights, towed....???

[Grime]

Thanks Bill for the reply.

The batteries are for house loads only. My outboard is rope pull to start. At the moment I don't have a on board way to monitor the usage. That part is in the plans along with moving the panel. It's a long way away from the batteries. I do have a trickle charger for shore power.

Power requirements.

VHF (Have to get a new one as the owner wired it up wrong an burnt the VHF up.)
GPS  (I can use it with 6 AA batteries or put it on an inverter)
Laptop  (Battery included or can use on inverter to charge battery)
Nav Lights
Interior Lights

We do have some LED stickup light in our RV from Wal Mart that work pretty good and cheap. I plan to get some more for the boat cabin. They take 2 AA batteries and I can recharge them when needed.

To me the main thing is the VHF and nav lights. I don't plan on sailing at night, but if I get caught where I can't get back in before dark and have to anchor out I would need the anchor light.

I'll check into the SPDT Center Off switch.

Thanks Shylark for the info. I know one is brand new but not sure of the age of the other. It looks brand new but who knows. The solar panels are cheaper than new batteries so I might just go that way.

Take care
David

[vinegarj]

would i be correct in concluding that the batteries are the "same age"/similar for charging purposes if they are very similar when i test their specific gravity?

also, here's a controller for charging two batteries off of one panel:
http://www.solarpanelstore.com/solar-power.small-charge-controllers.eco-energy.sunsport-10m.info.1.html

but could i run one solar panel through two cheap single battery controllers in order to charge two batteries simultaneously and save a few bucks over the sunsport controller?

??? ??? ???

[skylark]

Grime;

for your situation, you would be best off with the two batteries connected together as a house bank, assuming that they are of similar age/charge capacity.  I have a similar set up with pull start outboard and navlights, cabin lights, vhf, radio and depth sounder as a load.  Two deep discharge marine trolling batteries have always had plenty of charge.  I have a 30W panel.  You can probably get by with a 6W panel if you conserve power and are a weekend user. I have discussed this with a number of sailors who say a 10W panel is adequate, at least for weekend use.

You may want to get a charge controller but with 6W you are right on the edge of not needing one.  See:  http://www.windsun.com/ChargeControls/ChargeCont.htm

If you decide you want one, this one would do a good job: http://store.solar-electric.com/sg-4.html


Vinegar Joe;

After fully charging the batteries, let them sit for a few hours, then measure voltage.  That is one way to compare.  The specific gravity might be another way.  You could also just try them out together.  I think the problem is mainly with batteries that are very different, one new, one very old, for example.  If they are roughly the same you won't lose much.  The issue is that the old battery will "scavenge" voltage from the new battery.  In other words your battery bank is only as good as your worst battery.

Why do you want the batteries charged separately, to keep reserve power to start your motor?  There is another way to achieve that, by connecting your batteries together as a single house bank and using Low Voltage Disconnect.  Take a look at this charge controller:

http://store.solar-electric.com/ss-6l.html

You could connect your house loads to the low voltage disconnect connection and it would shut off your house power if battery voltage fell too far.  You would still have some voltage left to start your engine, which should be connected directly to the battery posts, not through the charge controller.  The website doesn't seem to show what the LVD voltage is, though.  It is probably about 50% discharge which is what the maximum recommended discharge for lead acid batteries.

I have a solar charge controller with LVD but I have never had the battery voltage low enough for it to kick in.

[Grime]

Thanks Skylark for all the information. I should be pretty good shape as I only plan on day sails and maybe some over nights.

[vinegarj]

thanks from me, too, skylark.  not sure i still understand, but i'm getting there.  i have two batteries.  typically, i use only one for everything (starting engine, house electricity) and switch between batteries depending on the day (odd days - battery #1, even days - #2).  i'd like to use a solar panel to keep both batteries always topped up/charged.  it seemed like the easiest way to do this would be to use the sunsport controller that i mentioned.  i think that it's about $100 so the one that you recommended be cheaper.

[Bill NH]

I'd say that with a 6W panel charging two batteries you don't even need a charge controller.  Remember that these devices are primarily designed to work with larger arrays putting out much more current that your 0.5A max.  I'd spend $10-15 on a switch and incorporate it into your routine (for example, draw and charge on Batt 1 , then leave the switch still charging Batt 1 until the next time you go out.  Then switch the whole lot to Batt 2, etc).  Try not to make your system any more complicated (or expensive) than it needs to be.

vinegarj - if you have electric start, does yo0ur outboard also charge the batteries?  If so, how are you controlling where this charge goes at present?

[vinegarj]

my engine charges my batteries.  i try to run it as little as possible and when it is run for long periods then the autopilot is on and draining juice.
no controller to prevent over charging, but it's never been an issue.  i have an analog voltmeter by the nav station and if a battery is getting low then i take action (switch batteries, run engine).

[Grime]

Thanks Bill,
I plan on KISS. I did find today that I had better rewire her. Most of it looks like some kid put it together and doesn't work. The bilge pump was just sitting in the hull with no exit. Not even hooked up.  Boy if that doesn't make since. I guess the guy that owned her figured he would bail her out with a bucket. Funny there isn't one on board. 

[skylark]

Once you get a solar panel and charge controller set up right, you don't have to do anything else, the sun just keeps it charged up.  It is really, really simple in operation and very reliable.

The daily charge for a few hours seems to lengthen the life of the batteries, solar charging and lead acid battery chemistry seem to work well together.

If you have two batteries, you are better off connecting them in parallel to make a single house battery bank.  Batteries are damaged slightly each time their amp hours are significantly used.  The rule of thumb is never to use more than 50% of your capacity, or you will risk damage. The closer you can keep your batteries to fully charged, the longer they will last.  If you regularly take one battery down to 50% capacity, it is probably worse on the battery than if you were connect your two batteries in parallel and draw your house bank down 25% with the same load.

If you want to keep a battery reserved just for starting the motor, I would suggest separating the starter battery from the house bank, and charge the house bank only with solar (no engine), while the motor battery could be charged by the motor, and possibly with a separate, small solar panel in the 2W to 4W range. 

[Grime]

Thanks Skylark for all the information. All answers are greatly appreciated as I am still learning what is best and still KISS

I got a charger controller off ebay today. Priced right.

David

[vinegarj]

okay, i ordered a 40 watt panel.  i have a single bank of batteries (two batteries total).  here's a link to what my system will look like:  http://www.boatus.com/boattech/casey/30.htm

so i'll only need one controller between the panel and the two batteries, right?  sorry to be so thick in the brain on this one and thanks in advance.

[CharlieJ]

Here's a link to the charge controller we use with our 32 watt panel. A friend of mine in Florida tested several different controllers in his electronics shop. This one came out the best, and worked the best in hot weather.


http://store.solar-electric.com/ss-10.html

[Tim]

Here is a picture of how I wired Che'



I have the two batteries tied together with one controller like Charlie's

[AdriftAtSea]

David-

You'll probably want to have the batteries separate and connect the solar panel to one at a time. A Six Watt panel is a very small panel and is really only good for battery maintenance, and probably won't recharge the batteries after use to any real degree.   A six watt panel will give you about .3 amps of real output.  A rough estimate for the actual output of the panel for a day would be 1.5 amp-hours (five hours * .3 amps).  If you have a Group 31 wet cell lead-acid battery, you're going to lose about that much per day due to internal losses and self-discharge, since a wet-cell lead acid battery tends to self-discharge at a rate of about .5-1% per day.

The 12.08 Volt charge level you're seeing is most likely a surface charge on the plates, and not the real charge level of the batteries.  If you were to load the battery with a large load to disperse the surface charge, you'd find that the actual voltage of the battery is likely a bit lower.   A fully discharged 12 VDC battery will read about 11.6 VDC. 

To do battery charging with solar panels, you really want to get at least an 80 Watt solar panel.  This will give you about 5-6 amps of current, and about 25 amp-hours per day.  However, you will probably want a charge controller with any solar panel above 40 Watts in size.  With the 80 Watt panel, you could parallel the two batteries and leave them connected to the solar panel, and it is very likely that it would keep the batteries topped off fairly well.  If you're not using a solar panel charge controller, remember to put in a blocking diode in the line coming from the panel, otherwise the panel can discharge the batteries overnight...

:)  YMMV.

I have a 6 watt solar panel and 2 batteries. Is it possible to connect the solar panel to both batteries and only use one battery at a time? That way I always have a fully charged battery. Or should I just connect both batteries together and let the solar panel charge both at the same time? Hope this makes since.

Ebay special on the solar panel. $34.99. Works great. One battery was completely down. I put the panel on the down one Wednesday night and last night I checked the volts and they were sitting at 12.08. So I guess it was worth the few bucks I paid.

Thanks for the advice,
David

[skylark]

okay, i ordered a 40 watt panel.  i have a single bank of batteries (two batteries total).  here's a link to what my system will look like:  http://www.boatus.com/boattech/casey/30.htm

so i'll only need one controller between the panel and the two batteries, right?  sorry to be so thick in the brain on this one and thanks in advance.

Connect battery1 positive to battery2 positive with a red wire.
Connect battery1 negative to battery2 negative with a black wire.

Now you can treat the two batteries as if they were one battery, using one controller. 

Connect the positive connection on the controller to the red wire.
Connect the negative connection on the controller to the black wire.
It doesn't matter where on the wire you make the connections, it could be at either battery terminal or somewhere in between.

Regarding the diodes shown on Casey's website, many solar panels have diodes already installed.  Your specification sheet should tell you if there is a diode.  You do not need two diodes, you just need one. It is probably already mounted in the solar panel.

[vinegarj]

paul...
some questions.
don't most controllers also do the job of the diode?
and if i wire up as you suggested, what becomes of my battery switch (e.g., i would select battery #1 for starting and battery #2 for house juice)?
also what happens if one battery is funky?  for redundancy, won't i be better off to keep the batteries separate? 
help educate this ohm's law reject.

[AdriftAtSea]

Most solar panel charge controllers have the blocking diode function integrated, not always using a diode...but effectively do the same thing. 

If you connect batteries as Skylark suggests, you will only have ONE battery bank. If you want to keep two separate banks, then hook each to one side of the 1/2/Both switch and then get an ACR battery combiner, which will combine the batteries when ever a charging level voltage is detected.

If you connect batteries as Skylark suggest, if one goes bad, it will probably kill the other one.

[Lynx]

The biggest power hogs on my boat has been the Computer and stereo. you may be surprised how you will much you use these when underway or at anchor. And how much you need the sun when you do not have any for a day or 2.

I have 2 - 20W panels. MY solar regulator cannot handle more amps so If I get another one I will need a bigger regulator.

[AdriftAtSea]

Lynx-

I'm kind of surprised that the solar charge controller you have can't handle more than two 20 watt panels.  That's less than 4 amps...

[vinegarj]

adrift...
thanks for the additional info.  for this season, i'm leaning toward keeping the battery arrangement status quo (KISS) and using the panel to only charge the house battery.