Solar

Mike B1026 · Jul 31, 2012

Solar Info

A 40w panel should keep your batteries up daily, fine. If you were only sailing on weekends and had the other 5 days of the week to charge, even a 20w should work.

I think there is some confusion regarding the "30% power boost" quote. I am thinking that you read some info on a "MPPT" type of charge controller. They do have some advantages on larger solar systems but it is doubtful they would help any on a smaller wattage system like a 20w or 40w. In fact their efficiency declines in warmer temperatures. (and they cost more)

Here is a link about MPPT vs PWM controllers:
http://coastalsolarsales.com/News---Info.html

I would buy a "PWM" type of controller. However, there are fake "MPPT" and "PWM" being sold on Ebay. They are actually "shunt type" contollers (dumb switch). I would stay away from unknown brands. Buy a MorningStar or other name brand controller.

PS: Depending on your dual battery setup, there are some specialized controllers to handle them also. (Wired in parallel vs a "A/B/Both battery switch.")

Doug91Mac26S said:
I have a question for the electrical guru's (Walt ).

Okay, I know this topic has been discussed extensively already, but I'm getting close to adding a solar panel and have a couple initial questions.

1) Is a 40W mono-crystalline panel a good choice (MAX Imp 2.29A)?

I have two batts, and want to power my TP10 AH all day, draws .5A - 2.5A, while listening to tunes, GPS, fishfinder. And at the end of the day still have battery power to have a light or two on and the stereo. Maybe I'm asking too much...

2) What's a good charge controller?

I've seen some that say they provide a 30% power boost.

willardj · Jul 31, 2012

A 25a cc is a bit of over kill for a 40w panel. 40w / 12v x .77% = 2.56a out of that panel. A good 10a charger would work fine and save you a bunch of cash.

willardj · Jul 31, 2012

Well its all about how much you want to spend really. If you plan on upgrading later that's a good way to go. When I picked my cc I wanted it a lil bigger so if I decide to upgrade to a 190w or 220w later. With a 25a charger you can upgrade up to 300w( maybe 2-145's) if you so decide later.

willardj · Jul 31, 2012

A shore power charger is a lot different than a solar charger. A solar charger is only going to give you what it has coming in or can convert( MPPT type) but shore power will give you what ever it is rated at.

Mike B1026 · Jul 31, 2012

Doug91Mac26S said:
Thanks Mike! Good info! I think you make a good suggestion to go with a unit that is designed to charge dual batts. And I appreciate the PWM recommendation.

I like the MorningStar SunSaver Duo 25 Amp PWM, with the remote display. The cheapest price I've found so far is $135, but looks like a nice setup. I wonder if the display will show the amount of amps being used.

So do you think a 40W panel could keep up with the kind of usage I described all day, without draining the batteries down?

The 40w works for me. The remote meter is nice. I have mine in the cabin, next to the sink. I can check the charging with just a glance. If you want to go to MorningStar's site, you can download the instructions and read up on it. It has a higher rating than you need but for that 135.00 you are also getting a nice meter that shows the voltage of each battery, the amount on amps the panel is putting out, the amount of amps the panel has put out, even the temperature. (The controller adjust charging to the battery temperature. The meter isn't an "amp gauge" (the amount of discharge) but it does show the voltage of each battery so you know where you are at.

What size are your batteries? Are they the same age, type?

Mike B1026 · Jul 31, 2012

Price

willardj said:
A 25a cc is a bit of over kill for a 40w panel. 40w / 12v x .77% = 2.56a out of that panel. A good 10a charger would work fine and save you a bunch of cash.

Well you could use a 6amp controller too and save a couple of more bucks but that's kind of close. Don't forget for that price he is getting a nice remote meter as well as a temperature correcting controller with a 4 stage charging circuit. Plus if he wants to upgrade down the road...

MrBill_FLL · Jul 31, 2012

12v stereo's can really suck amps. ipods and mp3 players not so much....

what kind of bank do you have now?

willardj · Jul 31, 2012

Agree, Morningstar controller are great controllers that's why I went with there Sunsaver mppt.

Sumner · Jul 31, 2012

Doug91Mac26S said:
I know I have a problem there. The batteries are not the same age. I think when I have the A,B,both switch on both, the older battery drags down the newer one.

So, let me see if I understand. Even though that MorningStar SunSaver Duo 25 Amp PWM, is way more than needed for a 40W panel, it will still be okay?

If you want to only start with 40 watts now I'd go with something like this...

http://www.solarblvd.com/Charge-Con...,-12V-Pwm-Charge-Controller/product_info.html

Sunsaver for $25 and then rethink things if you start adding more panels. We used that with a 40 watt panel and it worked fine....

http://purplesagetradingpost.com/sumner/macgregor/outside-22.html

I agree that with only 40 watts a MPPT isn't worth the extra money. I'd put that money into more watts. They can give 'up to' 30% but notice the 'up to' part. Let's say it gives you 20%. 20% of 40 watts is only another 8 watts so that is an expensive 8 watts vs. using the same money for a bigger panel.

Now if your needs go up and you want to maximize things then I'd spend the money on the MPPT. We did have 180 watts (now 200) on the Mac and we run a frig and other items and wanted maximum output since there isn't room for more panels and went with the MPPT...

http://purplesagetradingpost.com/sumner/macgregor2/outside-33.html

.... Even if it only gave us 10% more I'd of spent the money as when you are out on extended trips if you get behind then you aren't catching up without a gen-set or running the outboard (if it puts out). We also went with a MPPT for the Endeavour with 480 watts as we wanted to maximize output there.

Personally I'd drop the duo controller with your setup and put money into 2 batteries that are matched or maybe one newer one that is close to the better one you have and tie them together. You will be a lot more efficient in both charging and use.

If you get new ones think about 2 6 volt golf cart batteries in series. You will get more amp/hrs in the same footprint for about the same money and the use and charging will be more efficient.

I just don't see much point in charging separate batteries with only 40 watts to work with myself. Maybe if you are charging them during the week for a one day sail, but not if you intend to be working the batteries over multiple days. Also for any kind of extended trip 40 watts isn't much. I'd figure about 1/2 that for about 6 hours a day for input considering sun angles and such. 40 helped us on an 18 day trip, but we didn't have the frig then and still ran the gen-set some each day and it is a 60 amp alternator (the batteries never accept that much though).

With 180 watts later and an MPPT controller and out for 7 weeks with a frig and a lot of computer time we only used the gen-set maybe 3-4 hours total,

Sum

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Sumner · Jul 31, 2012

Just something else to add. Here is info on the duo...

http://www.solarblvd.com/Charge-Con...saver-Duo-With-Remote-Meter/product_info.html

...note the part...

When one battery is fully charged, all of the charge current flows to the other battery.

If the one battery never becomes fully charged since you are using it then the second battery might never receive any charge. Also if the charger starts cutting back on the charge once it gets out of the initial 'bulk' charge stage then potential charging power is being wasted since it isn't going to the other battery. I'd check and see if it only sends charge to the second battery once the first is in 'float' stage. If that is the case then a lot of charging potential is not being used. That is one reason that having the batteries tied together is more efficient use of the panel output.

I can see the duo for the purpose it is intended with a start battery and a house batter. With that you use a little electricity out of the start battery starting the outboard. That is quickly replenished and then the charge goes to the house bank.

I don't think that is important with our smaller outboards that can be pull started in necessary. We aren't really using the batteries as start and house. They are primarily house. Put them together and charge and use them together. If one battery is pulling the other down then it is time to replace it.

Good luck,

Sum

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Our Endeavour 37

Our MacGregor 26-S Pages

Our Trips to Utah, Idaho, Canada, Florida

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Ormonddude · Aug 1, 2012

I am sorry but solar Panels should not cost more than four - five dollars a watt all premium panels have a excellent guaranty usually ten - twenty year replacement. Frankly one look at the prices and I would never do business with coastal solar sales contact these guys for a quote http://www.sunelec.com/ tell them EXACTLY your application and a engineer will shoot you a price much more reasonable. I know these guys I live two blocks from the ocean (I live in salt Air) the Hail resistant Panels are the strongest made and I would bet they save you some serious Money!!! over eight dollars a watt is outrageous.

walt · Aug 1, 2012

QUOTE]
If the one battery never becomes fully charged since you are using it then the second battery might never receive any charge.
[/quote]

Its extremely unlikely that the charger works that way since there is no extra cost in the circuit to have it charge the batteries equally when there acceptance was the same and then charge each according to its own acceptance while having to share what is coming in from the panel. This is just software/firmware and I think it’s safe to assume the Morning star guys do a good job.

Doug, Ill throw out another option. Always personal preference but I think the concept of needing a battery switch and two batteries is somewhat obsolete for a boat like we have where its easy to manually start the outboard. What I like a lot better is a single battery that you understand in real time the state of. Two batteries give you a backup but I think you’re more likely to need the backup since it’s harder to know the state of both batteries.

Since you have two batteries, I would go with two 6 volt golf cart batteries in series.

Get a charge monitor such as the Victron http://www.victronenergy.com/battery-monitors/bmv-600s%20and%20bmv-602s/ for about $150. This tells you both current and voltage but it also tells you a nice little additional thing and that is accumulated current - i.e. amp hours. For example, if you ran all your electronics during the day and had some solar putting something back in, the charge monitor would be keeping track of all current in or out of the battery and at the end of the day you could see exactly how many net amp hours you had used.

Also, on boats this size, you’re probably never going to be out for more than week. So you also can size charging needs so that at the end of the week, your batteries are about empty (i.e., down 50%). As an example, if you have 100 amp hours available and are using 20 amp hours per day but only replenishing 10, your net is to use 10 amp hours per day and you can go for 10 days before your battery is down 50%. At the end of 10 days when your boat is in the drive way, plug it in to recharge with the house AC. Having the charge monitor helps here since you can tell exactly where you are for the net usage at any time.

For your needs (which will be similar to mine if I get an auto pilot), the pilot will use say 10 amp hours per day (1.5 amps * 6 hours). If your stereo is less than 10 years old, it will likely use about 1.5 amps on average so if on 5 hours, that is another 7.5 amp hours. Add in a few amp hours for LED lights etc and you’re at about 20 amp hours per day usage.

With two six volt batteries, you have about 100 amp hours available. At 20 am hours per day usage, you don’t even need any solar panel at all if you don’t stay out longer than 5 days.

Lets say you went with a 30 watt panel which would put out somewhere between say 7 to 10 amp hours per day (we will use 7 here), your net use is now 20 - 7 = 13 amp hours.

At 13 amp hours per day and with 100 available, you can now stay out 7.7 days instead of 5 before your battery is down 50%. Once again, the charge monitor is nice to be able to do this sort of thing since you can be confident that you know exactly the state of your battery.

The choice for 40 watts is not bad but might end up being more than you really need. The above pretty much describes exactly what I have in my boat and I have a 40 watt but am also going to have something like a 10 watt - both panels easilly removable (nice to sail without the panel) and interchangeable.

FYI, my charge controller is PWM and a max of 10 amps (more than I will ever need) but also has this programable output that can turn on an anchor light - for some hours or all night. It uses the solar panel of course to sense when its night. I used this to control an anchor light when my boat was on a mooring.

Sumner · Aug 1, 2012

walt said:
If the one battery never becomes fully charged since you are using it then the second battery might never receive any charge.

Click to expand

Its extremely unlikely that the charger works that way since there is no extra cost in the circuit to have it charge the batteries equally when there acceptance was the same and then charge each according to its own acceptance while having to share what is coming in from the panel. This is just software/firmware and I think it’s safe to assume the Morning star guys do a good job...

The thing is Walt according to their literature in the link I posted the second battery doesn't receive a charge until the first is fully charged. From the sales literature...

Two Battery Charging Solar charge current is shared between the two batteries based on a user selectable priority. When one battery is fully
charged, all of the charge current flows to the other battery.

I agree that it shouldn't work that way, but they say it does. I think that actually they just have a combiner circuit in the charger that is like...

http://www.defender.com/product.jsp?path=-1|328|51495|299265&id=750182

...the combiner we bought for the Endeavour like in the link above. Their charger is meant to work with a starter and house battery. I don't see it being a good charger for Doug's application,

Sum

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Our Endeavour 37

Our MacGregor 26-S Pages

Our Trips to Utah, Idaho, Canada, Florida

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walt · Aug 1, 2012

If you’re going by this

Two Battery Charging Solar charge current is shared between the two batteries based on a user selectable priority. When one battery is fully
charged, all of the charge current flows to the other battery.

I’m not sure how you interpret that to mean that the second battery does not receive any charge until the first one is full. It just says that once one battery is full, all the charge goes to the second battery. It does not say the second battery won’t receive any charge until the first one is full. Maybe I’m missing something?

That circuit is likely very simple - just an electronic switch from each battery to the solar panel input. The algorithm likely measures each battery voltage and controls each switch independently. If it sensed one battery was lower than the other, it could simply keep one switch on longer than the other (i.e., pulse width modulate). Given that this is a simple problem, I have a hard time believing that the engineering team would allow a situation where one battery never got charged at all.

It also sounds like there is some user selection control – that is input to the algorithm and gives options on how the two batteries are charged.