625ah Battery or 450ah and 400 Solar ?

[colemj]

Yep, $500 for panels, $100 for a regulator, $60 for 8g cable and make the mounts out of junk scrap for free (not really, but I threw it in for a price break).

$660 solar vs. $310 batteries.

If you are going cruising, go with the 450Ah of batteries and 400W of solar over the 625Ah and no solar.

Mark

[colemj]

Originally Posted by engele

Thanks Mark. Unfortunately their aren't a lot of choices for 12v panels, and they are more expensive than the ones that require a MPPT controller. I thought that $1.28w was a good deal. You are right that the panels are more, they just aren't so much more that it ruled the option out. Thanks

There are gobs of choices for nominal 12V panels. Maybe we are getting terms mixed.

Nominal 12V panels will have an open circuit voltage of ~17-19V. They can be controlled with simple pulse width modifying regulators to provide battery charging voltages of ~14.5V.

Higher nominal voltage panels cannot be regulated down easily with PWM controllers (you will throw almost all your money in them away) and are most effective with MPPT controllers.

For 400 watts of nominal 12V panels, you can NOT hook them directly to your batteries. You must use some type of regulating controller between them and your batteries. 400W will require a 25amp controller.

Mark

[engele]

Yeah I was thinking in terms of the entire system $930 all batteries or $1200 for solar and batteries.The difference seems smaller that way. The bottom line is I can't put in the 625ah and also buy solar, but I'd I pass on two of the new batteries I can squeeze in more solar. I think it makes sense. Less weight, panels last longer than batteries, and we need both.

[engele]

I think our current controller is far too small. I did see a deal on the sunelec site for 18.3voc panels. Would those be okay with a basic charge controller? The MPPT controllers I looked at were $600

[colemj]

Yes, 18.3 volt open circuit panels are nominal 12V panels. You will need a 25amp PWM controller for them, but they can be had for $100 or less.

Mark

[Pelagic]

My reasoning goes more towards long term management of batteries and fresh water when at anchor, which is what our controlling needs are when we have found that private piece of paradise and have no schedule to depart.

My AC water maker is large enough to replenish our daily consumption in about 2 hours… 3 on laundry day.

With the Gen on, making water… we bulk up using 2 Victron Chargers in that time period

Knowing that we will eventually get underway, I never worry about charging to 100%, so only Bulk to about 80% State of Charge where the charge rate starts to drop off. (Really when the water tanks are full)

According to Fullriver data, my AGM’s will last the longest if I always keep them above 70%

So my math at anchor is 100%-20% (bulk charge only) =80%

This leaves sizing battery bank to be large enough that you only consume 10% daily, which is what I have done.

It is a large bank, 8 x 240AH fitted on the tank tops port and starboard amidships, but I don’t worry about guest consumption of either power or water.

After 3 years, this balance has worked, no difference in readings and I have not bothered with solar.

The best advice given to me on this Forum was to invest in an intelligent battery monitor

[engele]

Yeah, I have (but have yet to install) a Xantrex battery monitor. Maybe I'll do that this weekend. Doubling the house bank and adding more solar seems to make sense to me. We have been able to get by with 225ah, and if we double that and also increase our loads a bit as well as add solar I can't see how we wouldn't come out okay. Space for batteries and weight is another issue.

[Jim Cate]

G'Day Engele,

Look, it is really pretty simple: no matter how big your battery bank is, you must generate a bit more energy than you take out of the bank (due to chemical and electrical inefficiencies). With a bigger bank, you can go longer without recharging, but then you have a bigger deficit to replace, and it has got to come from somewhere. It will take a lot of engine hours or Honda hours to build up a depleted 600+ Amphour bank.

So, let me add my advice to use the smaller bank and have the big solar array... even if it costs a bit more up front. A good solar system is one of the biggest improvements in the cruising life that we've seen over the years... no maintenance, no fuel, no noise and they really do last a hell of a long time. What's not to like?

Cheers,

Jim

[onestepcsy37]

my boat is about the same size as yours (csy 37) and we use it about the same as you plan to do - living on the hook for months at a time. here's what's been working for us -

1) house bank is four golf cart batteries providing 450 ah - wet cells. we used to have t-105's and they lasted six years but when i went to replace them i decided they were simply too expensive so last year i replaced them with sam's club batteries at $75 each. i also have a size 29 (100 ah) 'starting' battey which is actually a deep cycle wet cell - also from sam's club and about $80.

2) 100 amp alternator on engine. it's a good backup for battery charging but i never use it just for that purpose.

3) solar panel. one kyocera 135 watt which puts out about 7 amps at mid day. figure about 40-50 amps per day. i would like to add a second panel. and now to debunk a myth; you don't have to have a controller at all. i haven't had one ever. my panel is wired straight to the battery bank with an on/off switch. the trick is to use more amps per day than the panel can produce, so you'll have no fear of overcharging. my fridge takes care of that. the panel can just about keep the fridge going so anything else i use guarantee's that i won't overcharge the batteries. the on/off switch allows me to shut the panel down when necessary. if i ever get to add that second panel i'll have to add a controller too.

3) honda 1000 generator and 35 amp 'smart' charger. every couple of days at anchor i have to run the honda for two hours to recharge the batteries. i could have installed an onboard charger but being 'thrifty' i bought a 'smart' automobile charger that starts at 35 amps and tapers off for $70. the boat came with an onboard charger but at 10 amps output it's not worth using.

that's it. a 450 ah battery bank and three independent ways of charging them. i use a digital voltmeter to keep track of battery state (for which i will be denounced on this forum) and i've never run the house down or overcharged it.

our daily usage is under 100 ah per day, the fridge being the biggest single draw. don't forget to include the autopilot when calculating your daily draw. on a long passage you can easily run your bank down without suspecting the source...

[SunDevil]

I have bought from sunelec.com before (even picked up the panels at the warehouse in Phoenix)

I would also vote for the solar panels. But, I would look into making water only during the daytime when it is sunny if possible. You can store fresh water just like it is a battery.

[engele]

Thank you all. The last several comments have basically confirmed what I had started to lean towards. I think I will get the panels, despite the additional cost. At $1.28 per watt it seems like a good buy. I didn't think about the auto pilot at all. I am trying to buy a windvane, but we have davits (which I love), and have not found a used one that will work with them. Our fridge is by far our highest draw. The watermaker being second only because it is run less. I bought a cold holding plate when I built our fridge so that I could cool the plate when I had power and shut it off when I didn't. More solar fits that strategy (and it's a strategy I'll use with the watermaker). 600ah would be great because I would cycle the batteries less, but the added charge capacity should keep a smaller bank up more. I can always run the engine or start up the portable generator if I really need to. Looks like my decision is made!! This one was pretty easy once I saw how much cheaper solar is compared to a few years ago. It used to be $600 for a 125 watt Kyocera.

[noelex 77]

No ifs, no buts, no doubts.

400w of solar will give you more energy to use, and an overall shallower discharge of the battery bank with a longer battery life than the extra 175Ahrs and no solar will give you.

[Play Actor]

Just as another data point, we've been cruising happily for 11 years with 150 watts of solar, 400 watt wind generator, and 450 AH house bank. Our daily consumption is 80 to 100 AH, with most of the load coming from refrigeration. Under normal conditions in the eastern Caribbean, we have to run the engine to charge the batteries anywhere from once a week to once a month.

[colemj]

Originally Posted by onestepcsy37

and now to debunk a myth; you don't have to have a controller at all. i haven't had one ever. my panel is wired straight to the battery bank with an on/off switch. the trick is to use more amps per day than the panel can produce, so you'll have no fear of overcharging. my fridge takes care of that. the panel can just about keep the fridge going so anything else i use guarantee's that i won't overcharge the batteries. the on/off switch allows me to shut the panel down when necessary. if i ever get to add that second panel i'll have to add a controller too.

It is not a myth. Yes, in your situation you don't need a controller, but that is only because you have a smallish panel array and a largish electrical consumption. It is the same as having a large empty water tank and an unwatched trickle of water filling it.

However, the OP is discussing getting an array 3 times larger than yours. He will need a controller, as you admit you would need if adding any more capacity.

The best energy management solution one can do on their boats is to spend money using less electricity rather than generating and storing it. The biggest hog is usually refrigeration. $300 spent building a better box and system will provide more dividends than the same amount in batteries or solar panels. More and better box insulation and mounting a compressor in a cool space with air crossflow will easily give you the equivalent of another solar panel and battery.

Mark

[Maine Sail]

Originally Posted by engele

Yeah I was thinking in terms of the entire system $930 all batteries or $1200 for solar and batteries.The difference seems smaller that way. The bottom line is I can't put in the 625ah and also buy solar, but I'd I pass on two of the new batteries I can squeeze in more solar. I think it makes sense. Less weight, panels last longer than batteries, and we need both.

Have you considered less expensive batteries such as the Deka/East Penn 6V batts sold at Sam's Club under the Duracell brand. The EGC2 model is 230Ah 6V golf cart battery and about $84.00 each.. With these you could do six and solar...

Shallower discharges lead to more cycle life. A bigger bank on the same load with the same energy supply will have shallower discharges than a smaller one.