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Old 26-08-2012, 10:23   #1
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Simple Solar For A Simpleton

I've just read the entire Best Solar Panels for the Buck thread and learned a lot, but still have vast chasms where knowledge should be. I didn't want to hijack that thread so...

We have to get solar panels.
The battery bank is like having kids again. We always have to make sure we're home in time to feed the damn things.

The house bank is 10, 6v Trojan 105 batteries hooked up to deliver 12v. I assume that is giving me a 525 amp bank. (separate batteries to crank engine and generator)
At the moment I'm having to run the Onan 4kw generator for 2-3 hours, morning and night, ie 5 - 6 hours a day. That's just crazy.

How much wattage in panels can the system accept?
I read that current in amps must stay below 20% of bank capacity (525amp?), so 105A.
Then I read total wattage gets divided by 3 to get amps, so if I multiplied 105 by 3, I get 315 watts. Is that my limit of solar panels?
That doesn't seem like much.

Should I consider increasing the battery bank too, and by how much?

The idea is to reduce the generator running time as much as possible, and we will be looking at reducing energy consumption later. Refridgeration/freezer setup is gulping most of it, and I will address that in time.

All input, suggestions, total system redsigns etc most welcome.

Vic
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Old 26-08-2012, 17:14   #2
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Re: Simple Solar For A Simpleton

You have a small house bank for such a large boat. You should look to trading out your 105's for something larger like the 6 volt 242 amp batteries, which would more than double you house bank capacity. Even if you can't get ten in, even six new higher amp batteries would given you more house power than you have now. I use the US Battery 125 xc

In you case, any added solar will shorten the use of your generator. The tech geeks will give you the techno babble, but in plain english with an MPPT Controller and four 135 watt panels you should be able to keep up with your refrigertion. I found the cheapest solar panels at Northern Arizona Wind & Sun. Solar controllers are like anchors and everyone has an opinion, mine is Bluesky

You may also want to think about adding insulation around your ice box, which in most older boats was not well thought out and causes the refrigerator to run more often.

Good luck!
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Old 26-08-2012, 17:54   #3
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Re: Simple Solar For A Simpleton

The solar charge controller will adjust the voltage to optimize the charge that goes into the batteries. Watts are amperage draw times volts. A 135 watt panel produces a nominal 17 volts so the panel will produce slightly less than 8 amps at max output. Sounds like you are drawing more than 20 amps per hour out of the batteries. Since you'll only be producing electricity from the panels during daylight hours and max production for only about 4 hours a day on a cloudless day, you'll probably run out of real estate before you get too many panels. 600 watts or more would be minimum to keep your batteries happy. Even with that amount of solar power, you'll be drawing the batteries down to 50% overnight. Think you need to go on a serious amperage diet for the boat to really solve your problems.

More battery capacity wouldn't hurt. Now you've only got 12 hours or so of storage capacity. Personally like to work on at least 48 hours of reserve. That's pretty easy for me cause my usage is under 5 amps.
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Old 26-08-2012, 18:06   #4
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Re: Simple Solar For A Simpleton

It is not about storage at this point.

Imagine a limitless reservoir of power. If you are drawing more power than you are replenishing you will eventually run out of power regardless the size of reservoir.

If you double your storage you will still need to run your generator 4 hours a day or you will just run a defecit until the power runs out.

The storage is reserve to cover the fluctuations in average time between recharging. 2 day reserve? 3 day reserve? This depends on your charging plan.

High latitudes with solar may require a larger reserve to cover bad solar days. A generator is very flexible but requires tankage of fuel. The engine alternator requires running the engine a lot. A shore power inverter/charger needs marinas.

My anecdotal observation around her after reading a lot of threads is that a couple cruising with occasional visitors needs a power plan worked out at around 100 amps a day.

It sounds like you are very thirsty on power.

Sure buy more batteries - and you can also throw away the power plan advice and plan for 200 amps a day - but at some point even a big boat like yours will look more like a floating power station than a cruising boat.

Because you are "thirsty" for power and in a high latitude I would look for a minimum of 3 X 175w of panels run through an MPPT controller. This won't cover your daily needs but should cut down on generator running.
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Old 26-08-2012, 18:20   #5
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Re: Simple Solar For A Simpleton

Solar is great but it can be really hit or miss and is hard to bank on in total. We have two 135 watt Kyoceras that, on a great day, will deliver ~200AH. On a bad day, maybe ~40. Some anchorages (in fact, some of the best around here) have cliffs that really knock out the sun for periods of the day. Some morning cloud cover on top of that, and it can really reduce the effectiveness of your panels.

So don't concentrate on some magic number. Just get as many panels as you can because the actual output you see will be all over the map. Regardless, twice as many panels will probably result in twice as much output, even on crap days.
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Old 26-08-2012, 19:33   #6
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Re: Simple Solar For A Simpleton

Quote:
Originally Posted by VirtualVagabond View Post
...
The house bank is 10, 6v Trojan 105 batteries hooked up to deliver 12v. I assume that is giving me a 525 amp bank. (separate batteries to crank engine and generator)
At the moment I'm having to run the Onan 4kw generator for 2-3 hours, morning and night, ie 5 - 6 hours a day. That's just crazy.
...
WOW, that's a lot of run time! I agree that is crazy for a typical cruising boat. What's the amp rating of your battery charger? What is the age/condition of your batteries? Old batteries, or batteries in poor condition, near the end of their service life will absorb charge for a very long time...and never achieve full charge. What are your normal loads in Amp Hours per day?

On both my boat, and at my house, both 12V, I have about 450AH house battery banks. I don't typically need to run the engine/gen driven charging system more than about 1 hour per day depending upon usage. House has a 40A charger and 365W of solar, boat can do max of about 135A from alternators and currently only has about 150W solar, but boat alternator system typically steps down to about 60A within a matter of minutes. In either case I don't typically need to run the genset/engine more that 1-2 hours per day depending upon usage.

Sounds like to me that you have some other energy system issues you should resolve before adding solar.
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Old 27-08-2012, 01:34   #7
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Just for starters. 10-t105's is 5 x 220 ah's which equals 1100 ah's! Sounds to me like you need a lot more current from your charger. We have 10 -t105's, have a large refer and separate freezer using around 200 ah's a day and run our gen at most 1 hour a day. A Xantex freedom 30 puts out 140 amps or our Outback inv/charger puts out 100 amps. We also have 3- 85 watt panels. We're at anchor 99% of the time. Hope that helps.

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Old 27-08-2012, 02:20   #8
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Re: Simple Solar For A Simpleton

You can fit a many solar panels as you like, it will not cause a problem with the batteries.
However if you are running your generator 5-6 hours a day (unless you have a way too small charger) your energy consumption is very high and you will need a lot of panels to make much impact.
In general on a high energy consumption boat power savings are cheaper and easier than adding solar panels and I would reverse the order of your plan.
A detailed energy budget would help. With some more information on production and usage some predictions about how much generator run time would be saved can be made. For example a 300w solar array might cut your generator time by an hour an a half. You can then make an assessment if this is worthwhile.
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Old 27-08-2012, 03:59   #9
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Re: Simple Solar For A Simpleton

Vic,

Solar is so cheap these days, that you just stick on as many panels as will fit on your boat. You should be able to fit on plenty. If you run out of deck real estate, look at an MPPT, but you will generally find that it is cheaper to buy another panel or two than buy an MPPT. Check the maths and $$.

(We produce 100% of our energy from panels, with no generator and no MPPT magic box and a 6A alternator. Two thirds of our panels just go direct to the battery bank thru two breakers in the cockpit, without any sort of controller. No engine battery, just one bank for everything. No need to complicate your life.)

You are using your generator so much, you have another problem somewhere.


Rules of thumb, proven satisfactorily to us from our experience over the last 2 years in the tropics:

Work out your daily Ah usage. Multiply by 4 and install that amount of W in terms of solar panels and about the same in terms of Ah battery capacity. That's it, nothing more to do. Maybe throw your generator overboard or sell it to another cruiser with too few panels and not enough noise in their lives?

Best of luck, mate!
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Old 27-08-2012, 04:08   #10
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Re: Simple Solar For A Simpleton

sounds like you are starting at the wrong end of the equation when working out your power needs.

first replace all domestic and nav lights with led bulbs

,re-engineer your fridge and freezer with thicker insulation,top opening if possible.
replace fan driven or pump driven cooling condensers with a sea water cooled skin fitting type condenser.

replace cabin fans with low draw hella fans,or better get some wind scoops to keep the boat cool.

if you are running a big inverter,get a back up small 250w unit for computers and chargers for every day use ,and only turn on the big inverter when needed.

consider putting in a 24v battery bank for running fridges,inverters etc with a top range high amp smart charger.

if you are going to be spending a lot of time underway a wind gen is essential,as a lot of the time your panels will be in the shadow of the sails on east west passages.
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Old 27-08-2012, 05:20   #11
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Re: Simple Solar For A Simpleton

Quote:
Originally Posted by jeremiason View Post
You have a small house bank for such a large boat. You should look to trading out your 105's for something larger like the 6 volt 242 amp batteries, which would more than double you house bank capacity. Even if you can't get ten in, even six new higher amp batteries would given you more house power than you have now. I use the US Battery 125 xc

In you case, any added solar will shorten the use of your generator. The tech geeks will give you the techno babble, but in plain english with an MPPT Controller and four 135 watt panels you should be able to keep up with your refrigertion. I found the cheapest solar panels at Northern Arizona Wind & Sun. Solar controllers are like anchors and everyone has an opinion, mine is Bluesky

You may also want to think about adding insulation around your ice box, which in most older boats was not well thought out and causes the refrigerator to run more often.

Good luck!
Thanks Tom,
Do you know if 6v 242 amp batteries are a universal size or if they're unique to US Battery. We won't be back in US waters for a long time and I don't really want to install something that is only available here.
The 105 Trojans are only about 18 months old. Is it not possible to add a few more of them?

Vic
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Old 27-08-2012, 05:51   #12
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Re: Simple Solar For A Simpleton

Quote:
Originally Posted by VirtualVagabond View Post
Should I consider increasing the battery bank too, and by how much?

The idea is to reduce the generator running time as much as possible, and we will be looking at reducing energy consumption later. Refridgeration/freezer setup is gulping most of it, and I will address that in time.

All input, suggestions, total system redsigns etc most welcome.

Vic

Vic

Just what is is your daily amp-hr load and what percentage of battery state of charge have you been trying to mantain?

Both panel sizing and battery capacity is going to be based on your daily loads. There's no upper limit to the panels, just a lower limit of what will recharge your batteries.

I feel I'm a power hog, but if I'll willing to not recharge the batteries above 90-95% I can recharge with my engine in 1.5 hours/day. So your generator run time really has me confused as that's a lot of power.
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Old 27-08-2012, 06:01   #13
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Re: Simple Solar For A Simpleton

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The solar charge controller will adjust the voltage to optimize the charge that goes into the batteries. Watts are amperage draw times volts. A 135 watt panel produces a nominal 17 volts so the panel will produce slightly less than 8 amps at max output. Sounds like you are drawing more than 20 amps per hour out of the batteries. Since you'll only be producing electricity from the panels during daylight hours and max production for only about 4 hours a day on a cloudless day, you'll probably run out of real estate before you get too many panels. 600 watts or more would be minimum to keep your batteries happy. Even with that amount of solar power, you'll be drawing the batteries down to 50% overnight. Think you need to go on a serious amperage diet for the boat to really solve your problems.

More battery capacity wouldn't hurt. Now you've only got 12 hours or so of storage capacity. Personally like to work on at least 48 hours of reserve. That's pretty easy for me cause my usage is under 5 amps.
I do anticipate having to up the battery bank a bit as part of the process. The Trojans are only about 18 months old so I don't really want to toss them out if I can maybe add 4 more.
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Old 27-08-2012, 07:51   #14
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Re: Simple Solar For A Simpleton

[QUOTE=Ex-Calif;1022324]It is not about storage at this point.

Imagine a limitless reservoir of power. If you are drawing more power than you are replenishing you will eventually run out of power regardless the size of reservoir. I get your point, even though your definition of 'limitless' may need reconsidering

If you double your storage you will still need to run your generator 4 hours a day or you will just run a defecit until the power runs out.

The storage is reserve to cover the fluctuations in average time between recharging. 2 day reserve? 3 day reserve? This depends on your charging plan.

High latitudes with solar may require a larger reserve to cover bad solar days. A generator is very flexible but requires tankage of fuel. The engine alternator requires running the engine a lot. A shore power inverter/charger needs marinas.

My anecdotal observation around her after reading a lot of threads is that a couple cruising with occasional visitors needs a power plan worked out at around 100 amps a day.

It sounds like you are very thirsty on power.
Very. And it is something we have to address. I borrowed a meter for a spot check on the neg from the battery bank and at that point, mid morning, we were drawing 14.2 amps. That's an indication we're using 340 amps withought lights, which are already LEDs and underway we'd have auto pilot and chartplotter going too.
We have a top load fridge with 2 cooling units in it, but only one is cooling, the other is left over from a previous system.
There is also an Isotherm fridge/freezer. It's Italian and I need to get on to them to see what it draws because the manual on board is only for a fridge unit without a freezer.

I was replacing the oil cooler on the engine on the weekend and found that the Balmar alternator was pretty warm. Something is not right there. It must be drawing current from somewhere so that's next on the hit list.


Sure buy more batteries - and you can also throw away the power plan advice and plan for 200 amps a day - but at some point even a big boat like yours will look more like a floating power station than a cruising boat.
Not pretty. I can take 2 good size panels on the davits and another 2 on the hard top doghouse/rigid bimini, so out of sight.

Because you are "thirsty" for power and in a high latitude I would look for a minimum of 3 X 175w of panels run through an MPPT controller. This won't cover your daily needs but should cut down on generator running.[/QUOTE]

Thanks Ex-Cal...
This is the main objective and the kind of thing we have in mind.
Vic
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Old 27-08-2012, 07:54   #15
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Re: Simple Solar For A Simpleton

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Solar is great but it can be really hit or miss and is hard to bank on in total. We have two 135 watt Kyoceras that, on a great day, will deliver ~200AH. On a bad day, maybe ~40. Some anchorages (in fact, some of the best around here) have cliffs that really knock out the sun for periods of the day. Some morning cloud cover on top of that, and it can really reduce the effectiveness of your panels.

So don't concentrate on some magic number. Just get as many panels as you can because the actual output you see will be all over the map. Regardless, twice as many panels will probably result in twice as much output, even on crap days.
Kind of my philosophy... with the genny making up the shortfalls.
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