School me on some batteries

[meridian28]

I got my GC2’s through Batteries Plus, cheaper than Sams.

[NorthernMac]

They are group 27!!
12v
Oops

[a64pilot]

Come on guys, a 5 amp fridge, which isn’t a big one, running with a 50% duty cycle, which most actually can’t with people always adding food etc is 60 AH all by itself. 12 hours times 5 amps equals 60 AH
Now as I assume we all will agree that on average a Solar panel on a boat will deliver 1/3 of its rated power in Watts, in Amp hours.
That’s a rule of thumb, don’t get hung up on units not matching, but it’s a pretty good rule of thumb.
So, assuming a 100% charge efficiency, which isn’t possible that takes 180 watts of panels, actually about 200W counting the fact that you have to put in more than you take out.
So that’s 200W of panels just to run a fridge, nothing else.
Now many are going to say BS I do it with a single 100W panel, and to those I’d say no your not, your walking down your battery charge every day and catch up whenever you motor or plug in.

You may not like the numbers but there you are.

Now assuming you want to charge a laptop, run some lights and maybe listen to some music, much less watch a little TV, your going to need more or run your motor some or get a Honda or similar, or have an ice box or do without cold etc.

Now just me, but I think a Honda is a great thing, $1,000 gets you 1800 W or so of power.

[Sailon1]

Don’t forget about installing a compatible charger. I recently installed two 100 amp AGM batteries and bought a 40 W three bank battery charger . The charger required upgrading my wiring to a thicker gauge and purchasing fuses and other odds and ends required for the battery and charger installation. So, just something to keep in mind as far as purchasing and installing a compatible system

[boatpoker]

Originally Posted by a64pilot

I tend to disagree, first 300W isn’t big, and secondly a larger bank means shallower cycling which means a longer life.
It is exactly like having a bank account, yes you can budget to where your money barely meets your needs, but what do you do then when you occasionally need more? It’s not there. But if you have a little excess you don’t come up short.

But do sit down and do a lot of reading on Maine Sails website, you will learn a lot.
Only thing I would say right away is forget about car sized 12V batteries, golf cart batteries are a much better buy.

300Watts is almost 20 square feet. That is huge on a 30' sailboat. I can't imagine such a boat having more power demand than our 38' trawler which manages quite well of 175Watts. I believe it is overkill.

[Stu Jackson]

The Ample Power Primer http://www.amplepower.com/primer/primer.pdf
Sorry, link is gone, Ample Power unfortunately closed. They were so ahead of their time! [May 2019]
The Ample Power Primer is still available on the Wayback Machine at https://web.archive.org/web/20160323...mer/primer.pdf
It remains one of the best...
Many thanks to Bill Murdoch

[Sailing4Jesus]

Originally Posted by NorthernMac

Hey guys,

So looks like I just got a 30’ cutter!, super excited and also a little freaked out

she does need two new 12v batteries, automotive size, I’ll have to look up the exact size, I plan on adding two large removable solar panels, 300w all in, looking to do to do things right the first time, she’ll be doing a mix of shore power liveaboard as well as 30% cruising both in hot and cold areas, what does the hive say for a good battery?


Thanks!

Shipmate,

I am not an Electrical Engineer by any means, however, The Battery on your Boat can be compared to the battery
in one's Pacemaker, i.e., it's failure could cost one his very life. So when considering the purchase of the ship's battery it is this old sailor's opinion that ya just cannot beat the AMG. They are practically maintenance-free, very reliable. and the manufacturers are known to live up to the Guarantee, especially if you purchase Lifeline Batteries.

U.S.Navy Senior Chief, Retired

[a64pilot]

Originally Posted by boatpoker

300Watts is almost 20 square feet. That is huge on a 30' sailboat. I can't imagine such a boat having more power demand than our 38' trawler which manages quite well of 175Watts. I believe it is overkill.

It’s also one single panel measuring 60’” x 45”
If he has davits it would fit there easily.
But it all depends on what he desires to do. I was just trying to say that 300W is by no means a massive bank, not anymore.
And 300W will give you roughly 100 amp hours, max. But probably a lot less due to battery acceptance, unless of course your short cycling your bank.

[daletournier]

Originally Posted by a64pilot

It’s also one single panel measuring 60’” x 45”
If he has davits it would fit there easily.
But it all depends on what he desires to do. I was just trying to say that 300W is by no means a massive bank, not anymore.
And 300W will give you roughly 100 amp hours, max. But probably a lot less due to battery acceptance, unless of course your short cycling your bank.

I had 300w in my 32 footer, it wasnt a problem , I needed every watt.

[Sunsetrider]

Here is a 260W panel on a 25 ft pocket trawler for reference. It feeds 2 GC batteries that keeps my 60 litre fridge/freezer running 24/7 and keeps the batteries up to full charge rain or shine.

[boatpoker]

Originally Posted by a64pilot

It’s also one single panel measuring 60’” x 45”
If he has davits it would fit there easily.
But it all depends on what he desires to do. I was just trying to say that 300W is by no means a massive bank, not anymore.
And 300W will give you roughly 100 amp hours, max. But probably a lot less due to battery acceptance, unless of course your short cycling your bank.

He said "two" panels to make the 300watts. My point it is simply not necessary for the typical systems on a 30 footer.
We run music, refrigerator/freezer and a separate freezer 24/7 on 175Watts.

[boatpoker]

Originally Posted by daletournier

I had 300w in my 32 footer, it wasnt a problem , I needed every watt.Attachment 202543

I use almost half that and have no issue. What you and I need are irrelevant. Why put in a bigger system than is required to cover the needs ? Until the OP has determined his requirements the discussion is moot.

[a64pilot]

You can get to 300W many ways was what so was saying even one single panel. Or six 50W panels if you want and many ways in between

Interesting you can run so much off of 60AH

[Michael Pope]

You know I think ou do get smarter as you get older --- it is just tooo late Golf cart batteries have a life cycle similar to many boats They weigh less and you bu them in pairs.
I am not nearly as embarrassed watching my tiny wife carry a golf cart battery down the dock and she does not bother to batt her lashes at some hunk to carry it like she did with the 12 volt ones. One look at that flat stomach and bulging muscles and you can't stand him . But she makes you be polite and buy him a beer. Ugh! and if you lose your smile she will offer YOUR BOMBAY!! MP

[rbk]

Got our Dekas through Napa (relabelled). Canada’s battery prices are a scam I paid aprox $180 ea ($250cnd) for gc2 6v’s. On the solar topic (probably deserves its own thread) this company out of B.C. Canada developed and released this crazy polymer light bending tech that literally makes things invisible. The part they didn’t touch on i their release is the benefits to solar. Depending on the cost this may make Pv even more viable
HyperStealth Biotechnology Corp.