Solar Charger Questions

[craigclu]

I'm putting in a storage building that will not have power available to it in its location.  I was thinking of a deep cell battery (solar charged), 12v lights (very little usage) and some way to keep 3 cycles and a lawn tractor's batteries charged in winter storage.  Has anyone done this or know of good information and equipment sources? 

If the solar charger only charges the deep cycle to something like 13v via a regulator, and the batteries to be maintained are the same, would it self-regulate to a proper level across the system?  It seems that if the deep cycle were initially fully charged that the slight current needed for trickling the stored batteries would be very small?

Anyway, I thought someone in here may have a project like this in their past and save me some mistakes and miscues.

[Wayne Orwig]

I have a 10 watt panel on an out building. I use it to charge a lawn tractor, or motorcycle. I move the connector from one to the other occasionally. I built a regulator so it doesn't cook the batteries.

Since the battery chemistry isn't going to be a good match, I would not parallel the batteries to charge. Though I'm sure that with a low enough voltage it should be fine.

I would install a 12 V bulb of some sort in fine with each battery. That will keep the current down when you initially connect a new battery to your setup, yet will be close enough to a short to get to the peak voltage.

Where will you get the regulator? That is the hard part.

--------------------
Thinking about it, this is what I would do:
Setup the regulator and NO blocking diode at the panel. Then, out of the regulator, have a blocking diode for EACH battery that you are going to charge. So when the sun sets, they are all isolated. The issue still is that a weak or dead battery keeps the whole system from charging.

[oldbike54]

 Simplest might be to use two separate circuits , one for the lights , and one for the MC batteries .

 Dusty

[Triple Jim]

Where will you get the regulator? That is the hard part.

They're readily available and not terribly expensive, known as "solar charge controllers".  Good ones are quite smart, with settings for flooded, AGM, and gel, and even perform an automatic monthly equalization charge.  I have one on an electric boat with 250 watts of solar panel, and it has been flawless for something like eight years.  Mine is a Morningstar brand.

[Wayne Orwig]

For smallish systems, from what I could find, the off the shelf regulators are expensive and have a high parasitic drain.

[Triple Jim]

If craigclu is going to use something like a trolling motor sized deep cycle battery, the parasitic drain of a small commercial charge controller shouldn't be a problem, but I suppose any motorcycle shunt regulator should work OK as a bare bones regulator.  I'm using one like I sell for Kawasaki triples as a charge regulator for a 50 watt panel on the roof of my van.  It's set at 13.8 volts, so it doesn't cause electrolyte loss or other problems.

[Sasquatch Jim]

When I lived up in the Selkirks I had three 55 watt panels going through an automatic controller into
 six deep cycle six volt batteries of 200 amp hours each.  they were wired in a series parallel for twelve volts.
  The input wires were at opposite ends of the double banks so that all the batteries charged at the same rate.
 For the first 2 years I kept a log book with voltages of cell to cell readings of each battery and monthly hydro readings.  The system was flawless.  It powered an Airstream trailer that I lived in for about 5 years.

[Testarossa]

I have one on an electric boat with 250 watts of solar panel, and it has been flawless for something like eight years.  Mine is a Morningstar brand.

This is what I use in the camper van.  Works great. I'm charging two 6-volt deep cycle batteries wired in series for 12v at 250 amp-hours.  That's way more batteries than you'll need.  I should think a 12v deep-cycle marine battery (trolling motor battery) would work fine for what you want to do.

[RinkRat II]

 The system you describe should be pretty straight forward. These guys are great to deal with, including all (my) your stupid questions.http://www.backwoodssolar.com/


    Paul B

[craigclu]

I was scratching my head on this in regard to a simple inverter running some Battery Tenders I already have and when looking up some related specs on the Deltran site, discovered they make simple solar powered versions of their Battery Tenders...  I went from head scratching to forehead flattening.  This might be a simple solution as the controller is built in and the decision would be how to best charge multiple devices via one of these:

http://www.batterytender.com/Solar/15-Watt-Solar-Tender-Charger-With-Built-in-Controller.html

I keep thinking that the minimal draw for battery maintenance could have a single unit easily covering my needs?  They also make a couple of smaller units, I see.

[Wayne Orwig]

I was scratching my head on this in regard to a simple inverter running some Battery Tenders I already have and when looking up some related specs on the Deltran site, discovered they make simple solar powered versions of their Battery Tenders...  I went from head scratching to forehead flattening.  This might be a simple solution as the controller is built in and the decision would be how to best charge multiple devices via one of these:

http://www.batterytender.com/Solar/15-Watt-Solar-Tender-Charger-With-Built-in-Controller.html

I keep thinking that the minimal draw for battery maintenance could have a single unit easily covering my needs?  They also make a couple of smaller units, I see.

The inefficiencies of using inverters from a 12 volts system, to charge 12 volt systems, would be pretty large. It would be killing the main battery, even after all of the secondary batteries are fully charged.

15 watts for $154, that is pretty steep. I have a 10 watt system on my shed for about $25.

[Testarossa]

I bought all my stuff from Backwoods Solar, too.

At today's prices, don't pay more than $2 per watt for a panel, and a good deal would be $1 to $1.50 per watt. Grid-connected systems, including a good inverter, sell for about $2.50 per watt, installed, in most states.

Amazon is selling 10w 12v battery charging systems, including the charge controller, for as little as $40.  They list the Batter Tender charge controller for $23. Add a 10w panel at $15 to $20 and there you are.