Solar panel to recharge 2 batteries

[Kelly Hanson East]

Jim - my VW came with a 5W solar panel that is used to keep the Group 24 battery charged while in transit to the dealer.

7 years later, the battery is near end of life, but if I keep it plugged in I can keep enough charge in the battery to start in the winter (0C or so) so even a 5W panel will help out. (I know Im a cheapskate, but I only buy new batteries right before winter)

Quick math - 5W * 12 hours = 60 Watt hours or about 6% of a group 24 capacity

Throwing in a factor of 1/2 for angle loss and 1/2 for cloud cover takes you down to about 15 Watt hours. or 1.5% of your a single battery capacity. You arent going to overcharge that battery, for certain.

I did a little digging into trying to find a reasonable number for lead acid self-discharge rates. People trying to sell you new technologies quote figures like "up to 1% per day charge loss"

More rationale types quote

"This "leakage" or self discharge varies considerably with battery type, age, & temperature. It can range from about 1% to 15% per month."

This works out to 1/2% charge per day at most.

Upshot - a 5W solar charger will keep up with 1 and probably 2 Group 24s okay. In sunny FL, you might get more charge than my conservative 'upstate NY' estimate above too.

[c130king]

I am still getting my small brain around all this electrical mumbo-jumbo...

Is there a problem or potential problem that if I leave a 5W solar trickle charger thing-a-ma-jig hooked up for a long time...say 2-4 months without touching anything...I could overcharge, damage, or "blow up" my batteries in some way?

Thanks,
Jim

(* PS to Hector -- Sorry if I am hijacking your thread. Similar topic and hopefully the info being provided is helpful to you and to others *)

[March]

I am still getting my small brain around all this electrical mumbo-jumbo...

I'm pretty much in the same boat. Rather than use high-falootin' formulae, I rely on hit-and-miss "evidence." I diligently did the math when I refurbished the electrical system when I first got the boat. I started off with a 64 W solar panel for a 2 battery bank which seemed sufficient for my needs (incandescent lights, electronics, a water pump for the fawcet, and -- the biggest hurdle -- a Waeco electrical fridge (50 l). It worked for two years, with brand new batteries, as long as the boat was on the lake, in full sunlight. Over the winter, I would disconnect the panel and the batteries. In spring, I would power-charge the batteries before reattaching the panel.

Year 3: one battery died. Replaced it with a brand new one and the system was again up and running.

Year 4. Replaced both batteries with Optima gels. The system worked for half a season, then one battery died. I was surprised to find out that the Optimas have even LESS warranty than your plain garden-variety WalMart battery that costs much less.

Year 5. Updated the system to a three-bank battery (changed the faulty Optima against a cheaper, regular one, and added another regular one. The only optima I now have is for the engine. Replaced the 2 battery XANTREX distributor with a 3 battery one) and added a second 64W panel, just to be on the safe side. It worked for one season. We'll see how things stand this summer.

To make a long story short. 5 W doesn't seem much of a trickle. Even so, the controller should take care of over-charging. In my system, the Sun Controller cuts off the extra juice once the battery is chock-full, but I wonder verily if you'll ever get to this point. If you add an electrical cooler, you will need something above 50W to keep the system running--barely. (Of course, you always have the option to run the engine and recharge the batteries, but I assume that we all want independence.) I have replaced all interior lights with LED lights. The mast position lights are still original and I use the anchor light every night. I don't use the electronics at anchor. The sink pump is used sparingly. The fridge is kept 24/24 so there is always cold beer and pop. With two photoelectric panels, the system is back to 100% within a sunny morning, and by the end of a cloudy afternoon.

[rwmiller56]

My sits on its trailer in a dry storage yard all winter. There is no AC power available to run the battery charger. Since we still get a fair amount of sunny days here in the winter , I hooked up 2 solar panels and a charge controller to charge the batteries.

The panels are 15W each, for a total of 30W. In direct sunlight, each will produce about 1A (2A total). They are connected in parallel.
The panels:
http://www.amazon.com/gp/product/B0006J ... ss_product

The charge controller can handle up to 8A of current, so there is room to increase the system capacity (add more or larger panels) if I want.
The controller:
http://www.altestore.com/store/Charge-C ... ler/p1539/

I don't have the panels mounted. I just lay them flat on the cockpit seats, and they work fine. This is probably not an optimized position to collect the solar energy (45 degrees to horizontal, and facing south is best), but I wanted to keep the panels low so as not to advertise them, for security reasons.

I have 2 batteries, and I have them connected in parallel to the charge controller battery output.

I built the system with the intent to just charge the batteries, and not to run appliances. However, if I am anchored somewhere, I use the system to top off the batteries, or to run small appliances if the batteries are fully charged.

[c130king]

March and RWMiller,

Both of you guys are mentioning somewhat larger solar charge systems...with controllers. My understanding is that the smaller 5W (or less) systems don't have controllers...they hook directly to the battery.

I found this on Defender: Sunsei SE-500 Solar Power Charger - 7.5 W

The data says it will not overcharge. I think you either plug it into the 12-volt socket or hook direct to a battery. Seems to be weather resistant so I think it can be left connected and sitting somewher on deck while the boat is sitting on the trailer.

Anybody using anything like one of these...not to recharge your batteries so much as to maintain your batteries when the boat is sitting unused?

Thanks,
Jim

[Kelly Hanson East]

Jim- Ill make a call on this, with 99% confidence

I dont think you could harm a single battery with a 5W solar charger hooked up for 4 months, especially if you check the water level and top off (if possible) at the beginning. With two batteries the risk of damage is even less of course.

When you think about it, this is exactly what the car industry is doing with these small solar chargers described above....they are unregulated direct chargers of course.

[Sumner]

....... And if the panel has one set of battery clips can I clip it to one battery and let my Yandina Combiner "share" the charge with second battery?..........Jim

What you guys are forgetting is that we have the Yandina Combiner connecting (combining) the batteries, they are not in parrallel unless it combines them. Here is how it operates from the Yandian Site:

http://www.yandina.com/acrobats/C100Data.pdf

OPERATION
The green “Combined” light will come on some time
after charging has commenced. The time delay depends on
how much current is being delivered to the bank being
charged and its initial state of charge. When the initial bank
reaches 13.3 volts (±1%) the other bank(s) will be placed in
parallel by the Combiner 100. If one bank is very low, the
Combiner 100 may turn off and on a number of times as it
brings it up to voltage. After charging has ceased, the green
light may remain on for quite some additional time if there is
no load on the batteries, due to the “float” voltage above 13.3
volts left over from the charging.

His question was

if the panel has one set of battery clips can I clip it to one battery and let my Yandina Combiner "share" the charge with second battery?..........

The answer is that with a small 5-10 watt solar panel the above will probably not work since the panel will probably never bring the battery it is hooked to up to 13.3 volts. Of course it won't hurt to try and if it does then the combiner will connect the panel to the second battery. The other answer I see is he could by-pass the combiner and hook both batteries in parallel with a second set of leads/clamps off of the solar panel connected to the other leads. Personally I wouldn't attempt this without talking to the tech guys at Yandina. A phone call would quickly answer the question.

The other option I threw out was just get two small panels and hook one to each battery and let the combiner combine them if the voltage ever got above 13.3 volts, but now that isn't necessary as they both have a panel on them. But instead of putting money into that solution I'd go to solarblvd.com (or another site).....

http://www.solarblvd.com/product_info.p ... Panel.html

... and get the 20 watt panel for $75 or the 30 watt for $110 or my choice the 40 watt panel for $135 and the Morningstar Sunguard SG-4 4.5A, 12V Pwm Charge Controller for $25.

http://www.solarblvd.com/product_info.p ... oller.html

Now you would probably put out enough amps and voltage to get the combiner to connect the two batteries and keep both charged and with the charge controller you wouldn't have to worry about overcharging the batteries.

When you returned from sailing or if needed on a long weekend or longer sail you would know that your batteries were not only going to maintain a charge, but you have enough charging capacity to actually re-charge them from a discharged state.

I would still run the panel size by Yandina and make sure it would be large enough to accomplish what you want to do. Worst case money wise with the 40 watt panel and charge controller would be about a $160 investment plus shipping and some wire and a fuse (around $100 with a 20 watt panel). Once you had a panel that actually did something you would probably be hooked like we are.

Good luck,

Sum

Our Trips to...

Our Mac Pages

Mac Links

[c130king]

Sum,

Good info. Thanks. Those ideas would probably work fine but the kicker is I do not want any "permanently" installed solar panels. I want something that can be relatively easily stored out of the way when out on the boat and then pulled out and hooked up relatively easily when putting the boat away.

I will continue to research.

Thanks again,
Jim

[Sumner]

...the kicker is I do not want any "permanently" installed solar panels. I want something that can be relatively easily stored out of the way when out on the boat and then pulled out and hooked up relatively easily when putting the boat away.....Jim

That 20 watt is only 19.5 x 14 x 1 and weighs only 5 lbs.. I have that small charge controller I gave the link to and it is very small. It could be mounted permanently to the side or below the panel with a a cord off of it with the battery clips. The panel at only 1 inch thick it wouldn't take up much room.

I'd still call their tech guys and see what the smallest wattage/voltage panel would work with the combiner. They have smaller ones than the 20 watt. Getting a single panel to work with the combiner would simplify things for you and I think the charge controller is the way to go. They make the panels more efficient and also handle all of the undercharge/overcharge problems. The panel with controller attached could probably just lay in the cockpit since it does have some weight to it.

You probably want it to recharge the batteries after a sail. If so the larger the panel you could live with the faster the batteries would be back at full charge if you wanted to use the boat again without much time between outings.

c ya,

Sum

[c130king]

Sum,

Do you have this system you are talking about? How much wire comes with a panel? How about the controller? And how do you work in the fuse?

Thanks,
Jim

[Sumner]

Sum,

Do you have this system you are talking about? How much wire comes with a panel? How about the controller? And how do you work in the fuse?

Thanks,
Jim

I'm using the 40 watt panel with that charge controller....



....I have the charge controller mounted in the laz....



..... but in your case I would just mount it right to the panel with a simple bracket underneath, but it can be mounted outside. They just say to mount it so that water can drain from it. I'd bend up a bracket so that it would be under the panel, but with the top of it upright if the panel was laying flat. Most hardware stores sell aluminum in round and flats and the flats would be easy to bend up for the bracket.

I think I added it before, but here is a link to the charge controller and as I mentioned before using one has a lot of benifits....

http://www.solarblvd.com/product_info.p ... oller.html

I'd buy a cheap outside extension cord and use it. Cut off a short hunk for the wire from the panel to the controller and then a longer piece to go from the panel to the battery. Mount a 10 amp in-line fuse (from the auto parts store --either a round or spade/I like the spade). Mount the fuse to the output of the controller and then connect the positive wire going to the battery to it and use shrink tubing on the connections. You might are might not want to use one of the connectors on the end of the extension cord (I used one end). I'd take a hunk of the cord with the female end and attach it permanently to the battery. Then use the male end of the cord from the panel and plug it into the female when you have the panel set up. Use another female off another old cord or just buy one at the hardware store and put it on the male plug on the cord from the panel when you are moving it around so that you don't accidentally short out the plug when it isn't plugged into the female plug at the battery. The extension cord is cheap and will hold up pretty well outside.

This way the panel, controller, fuse and cord would all be one piece and easy to deal with. You could even bolt a handle to the side of the panel. My build page for this is here...

http://purplesagetradingpost.com/sumner ... de-22.html

....now the reason I have the large breaker is that the current from the 63 amp alternator (my on board generator)...

http://purplesagetradingpost.com/sumner ... de-13.html

...goes through that breaker also.

Let me know if there is anything else,

Sum

Our Trips to...

Our Mac Pages

Mac Links

[c130king]

Sum,

You and the other smart guys on this board were right. I emailed Yandina like you recommended and you are right...there would be issues using the combiner.

From: tech@yandina.com [mailto:tech@yandina.com]

Sent: Sunday, March 28, 2010 9:38 PM
To: Jim King
Subject: Re: Question about solar charging with C 100 Combiner

In theory it will work but the problem is 5W Solar Trickle Chargers don't put out 5 Watts. The 5 Watt rating is direct overhead sun at the equator on a new panel on a clear day feeding a low voltage load.

The theoretical maximum output current is less than 1/2 amp. However the average sun compared to mid-day is about 25%. That is further reduced to 12% by the angle to the sun. Factor in cloudy days, higher battery voltage, bird sh~t etc., and your 400 milliamp trickle charger is down to a drip, supplying less than 20 milliamps average. This is barely enough to maintain one battery, let alone two.

Since the Combiner100 requires 130 milliamps when it turns on it would use more than the charger can supply.

I suggest you get a refund on that junk and spend some money on a real one. If you do want to try it, you can disable the Combiner100 by connecting its green lead to any +12 volt supply. This will stop it using any power. You can then jumper the two batteries together with the "BOTH" setting on the switch if you have one, or just clip a lightweight jumper between the positive terminals.

Regards,

Ann-Marie Foster,
tech@yandina.com
-----
On 3/28/2010 4:14 PM, Jim King wrote:
Yandina,

I have two Interstate Group 24 Deep Cycle batteries on my sailboat and they are joined with a Yandina Combiner 100. My question is I would like to hook up a 5W Solar Trickle Charger to keep the batteries topped up when the boat is on the trailer or tied up at the pier for a period of time (no shore power).

Can I hook a 5W Solar Charger to one battery and share the trickle charge using the combiner? Would the combiner keep the batteries separated due to the low power flow from the trickle charger?

I don’t want a bigger “permanent” solar panel system. Hoping to use a smaller system that I can put away when using the boat and only pull out when putting the boat in storage.

Thanks,
James King

So I will probably go with a bigger system and figure out a way to make it "relatively easy" to set-up and remove. Thanks again for the tips and the links.

Cheers,
Jim

[Kelly Hanson East]

Jim - just for laughs I hooked up my 5W panel to my VW battery on a heavy overcast day and measured 6 mA current flow into the battery.

Ill agree with your vendor that this is too little, but Im not sure that the 25% cloud factor is right either...

[School House Steve]

Jim

Here is the solar panel I mounted on my poor mans radar arch. It is a 1500 watt Sunsei with a charge controller. The support was made from an old aluminum camping cot frame mounted to the mast support with CB radio antenna clamps. I have it connected to the two deep cycle house batteries and it does a pretty good job keeping the batteries charged, but with limits. The collector is mounted flat and I live just above the 45 parallel and with the shorter cloudy days last winter I wasn't sure it was even working. Now the days are getting longer and it is charging the batteries again. My hope was it would keep up with the power for the GPS and some other accessories while sailing with the larger deep cycle batteries, but the reality is that I still need to rum the motor some times to keep up with the electrical demand. (GPS, Auto helm, VHF, CB, AM-FM, TV, etc.)

Steve

[The Mutt]

My battery guy told me to use our deep cycle batteries, don't leave them on charge without something draining off a bit regularly, he said deep cycle batteries need use or something happens to the detriment of the battery ... our Engel fridge ticks over on the fridge setting keeping some water chilled while 'Imagine' sits on her trailer.

Glenn