Living without AC power - Page 3 - Fiberglass RV


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Old 11-28-2009, 05:30 PM   #29
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Our batteries were lead/acid trojans. The engine compartment, although enclosed, was nowhere near sealed off from the rest of the interior of the boat. The boat was 41' long and had a 13.5' beam
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Old 11-28-2009, 05:36 PM   #30
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Hi Judith,

Thanks for the additional detail. Living aboard for 8 years sounds nice

The next time I buy batteries for a boat's house bank, I'm planning to go with 6v golf-cart (lead-acid) batteries in pairs (thinking maybe you had Trojan T-105s). I don't think that my type of usage/charging does well by the AGM's.

I'm not sure with the trailer. If I can justify the weight/placement of two batteries, I'll probably do the same. Otherwise... not sure yet.

I've known a number of people who had lead-acid batteries in non-specifically-vented compartments in the living area of a boat. I'm still not sure I'd recommend it, and I also do still think that most live-aboard boats have a lot more ventilation than a small trailer. I had wind whistling through most of the time (alhough, AGM batteries, and in a compartment somewhat partitioned from the living space but not "sealed" from it).
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Old 11-28-2009, 05:58 PM   #31
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the boat


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Old 11-28-2009, 06:14 PM   #32
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the boat
Let me say WOW!
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Old 11-28-2009, 06:58 PM   #33
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Great photo! Looks like an Out-Island 41. I have a friend with one of those and he really enjoys it for a live-aboard cruiser.

You do get to enjoy some great sunrises/sunsets when living aboard, that's for sure

Raya
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Old 11-29-2009, 01:24 AM   #34
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Peter,

I haven't used the Optima type AGM batteries. Are they more tolerant of constant, slow trickle charging (and concurrent use) than regular AGMs? (It would sure be nice if they were.)

Raya
That was the main reason I bought one. At the time the Optima was the most efficient option for my solar system; now almost 3 years old it keeps on chugging away despite being very deeply discharged a few times while we were in Yellowstone last year. (Which is why I added a second panel.)

One of my experiments this year was to switch off the trailer's converter at the start of this year's camping season. The trailer's battery kept up and charged the whole summer without any charging from a shore connection, even when it was stored in the shade, and it shows no signs of having lost any charge capacity.

Someday when I have a day or two to keep track I'll have to go in and replace some of my trailer's LEDs with traditional incandescent bulbs and calculate the battery's discharge curve at 3 amps. If I start at 12.8-12.9 volts I'm guessing it'll take around 12-15 hours to draw the Optima down to 11.5 volts. That's the value of an experiment: It takes the guess-work out of the equation.
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Old 11-29-2009, 01:53 AM   #35
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Peter, I'm interested in your answer, but I don't completely understand it.

What I understand about AGMs is that they are intolerant of undercharging* (i.e. not being completely recharged in between discharges). Especially that last 10% of float charge. So if one is using them all the time, they never get fully charged with a solar panel (trickle charge) and then they die an early death. It's not so much that they are intolerant of deep discharges, but of constant, nagging lack of being 100% charged.

It sounds like you are charging yours mainly by trickle (solar panel), and they are lasting for years as proven by a load test. One question I have is this: Are you using them regularly? Or do you think that the solar panel is charging them 100% between uses because you are only using the trailer sporadically (once a week or once a month or whatever).

That might make the difference even with regular AGMs

(That AGM vulnerability to chronic undercharging is what has made me eschew them for boats that live on the hook, and typically only charge by solar or wind power and yet are in constant use (hence chronically undercharged).)

Raya

PS: I am with you on experiments: As one of my mentors always said: "If you can't put a number on it, it's Voo-doo" So true!

*actually they are intolerant of overcharging too, but that is less of a problem as long as you have a smart charger.
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Old 11-29-2009, 02:43 AM   #36
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I've never heard that AGM batteries have an inherent problem with being under-charged, but I have read early designs for deep-cycle/starter hybrid AGM batteries heavily favored the "starter" side of being a hybrid and were not good at all good at the deep-cycle end of the spectrum. Later hybrid designs seem to have addressed that flaw. Modern designs, like the Optima, have no problem at lower charge levels.

As for how our system charges, when we had one solar panel we repeatedly discharged the battery to between 11.5 and 12.0 volts and sometimes much lower) at night then charged it back up to 12.6 to 12.7 volts during the day. With our Optima that was never a problem, and now with 105 watts on the roof we get back to 12.8+ volts (leveling at 13.2 volts while trickle-charging at the end of the day) almost every time.
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Old 11-29-2009, 09:37 AM   #37
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You may have mentioned this some other time, but I am interested in knowing what you use battery power for. It seems in the long run, especially if we are going to do solar, I will need to get a meter for the battery to find out exactly what we use and need. But since we haven't even gone on a trip yet and I may want to change our battery during the winter, I am interested in getting a ballpark idea of how big we should go.


Quote:
I've never heard that AGM batteries have an inherent problem with being under-charged, but I have read early designs for deep-cycle/starter hybrid AGM batteries heavily favored the "starter" side of being a hybrid and were not good at all good at the deep-cycle end of the spectrum. Later hybrid designs seem to have addressed that flaw. Modern designs, like the Optima, have no problem at lower charge levels.

As for how our system charges, when we had one solar panel we repeatedly discharged the battery to between 11.5 and 12.0 volts and sometimes much lower) at night then charged it back up to 12.6 to 12.7 volts during the day. With our Optima that was never a problem, and now with 105 watts on the roof we get back to 12.8+ volts (leveling at 13.2 volts while trickle-charging at the end of the day) almost every time.
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Old 11-29-2009, 01:43 PM   #38
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That's a good point. Our Scamp 5er is a "big" trailer (by Fiberglass standards), and we have quite a few lights, 13 inside and a porch light. They're generally not all on at the same time (why waste energy lighting the loft when you're not up there?), but when they are all on they burn less energy (30w/2.5 Amps) than just two incandescent bulbs (up to 36 watts, 3 Amps). If you light your trailer with Incandescent bulbs, that's where your major energy use is going to be. SO LEDs are a huge energy saver. The down side is those LEDs cost us a lot of money -- more on that later.

The other things we have that consume power include the furnace (2.8 Amps, when it's heating), water pump (4.2 Amps when it's pumping), a small 12v HDTV/Radio/DVD player (0.25 Amps to 1.6 Amps, depending on whether we're using just the radio or the full DVD player & TV), various electronics that need occasional charging, and a "200 watt" Inverter (that actually can only maintain 120 watts) for those occasions when we need 110v power. We have a few other items that pull down 12v power, like an Amps/volts meter and some setup equipment, but these draw minimal or no power once we're set up.

We have some 110v AC appliances, like a microwave, coffee maker, and toaster, which only get power when we have hookups. (Our inverter doesn't put out any where near the power we'd need.) Most of these we can happily live without, but we chose a coffee maker that has a thermal carafe that keeps coffee hot for two hours and a top that opens wide so we can pour water boiled on our stovetop through the basket. Works really, really well.

When we're dry camping our major power draw is our furnace. On the furnace can easily pull down 10 to 20 Amp-hours a day, sometimes more. Meanwhile, a 50-watt solar panel produces just 18 Amp-hours of battery power during the early spring and late Fall months if we park the panel in the sun, which is why we added a second solar panel.

As for a meter, we do have a meter that displays both voltage and amps, but the Amps meter is really only useful for testing whether the solar panels are connected and producing power, something the LED on my charge controller already tells me. The rest of the time I just look at the volts to figure out how well charged or deeply discharged the battery is.
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Old 11-29-2009, 02:00 PM   #39
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Amy,

I don't mean to answer for Peter, and I'm sure he will have good "real world" info because he has used these systems in an egg. But I'm going to suggest a way that you can calculate based on your trailer and your electrical usage. It's still a good idea to make up your own power usage calcs, because you will never be exactly the same as anyone else, and also it helps you to understand how it all works, and what it means when you turn on a light, or fire up the laptop.

Basically, each electrical item that exists has a set amount of power it draws when it's on. So you look at each of your electrical items (or their manuals), and you can see exactly what it draws. If it says, say, 2 amps, that means two amps for every hour you are running it.

So you get a list going (because this will be different for everyone). Something like this:

Kitchen light -----------------2 amps
Refrigerator (if on 12v) ---- 14 amps
Laptop (with 12v adapter) - 16 amps
Reading lights----------------1 amps (each)
Fan--------------------------- 2 amps

And so on.

Then you figure how many hours per day you are likely to use each of these. You have to guess, of course. When in doubt, round up. Now multiply to get the total number of amps per day.

So:

Kitchen light, 1 hour = 2 amps
Refrigerator, will run on propane = 0 amps
Laptop, 2 hours = 32 amps
Reading lights 2 of them x 4 hours =8 amps
Fan, 8 hours = 16 amps

So, your total number is 58 amps for a 24 hour period. Aren't you glad you have a furnace with no fan, and a propane refrigerator?

Now let's say you round up to 65 amps. (And now you know why people get LED lights, because they draw next to nothing. Also something like a Hella marine fan will draw .5 amp.)

You don't want to draw your battery down by more than 50%, because that will kill it much sooner, so you want to keep that in mind when sizing your battery. Of course if you have constant solar power going back in, that's also a factor (you can figure out about how much they put back in, too). Or, with no solar, but if you plan to go out for two days and not charge witha charger until you get back, then you will be using 130 amps. For that you would want about 260 amps in your battery bank.

You can see there are variables on what battery size you need, depending on your recharging methods, but what you do know is that you need to "give back" 65 amps per day, somehow, and at some point in time. If you had a 1300 amp bank of batteries (not practical! I'm just saying), you could go 10 days without giving any back. etc.

Sometimes appliances list watts not amps, but you can easily convert.

Amps = Watts divided by Volts (use 12 for 12-volt items).

For figuring in a solar panel it gets a bit more complicated, because although they will have a certain power rating, of course you aren't getting power from them when it is dark or very cloudy (or reduced power input). So it becomes a game of estimation and trial and measurement. But if you are figuring for a system with a 110 volt charger putting power back in (like when you get home), of course you can be more precise.

If you're doing trips on just weekends, it would probably make sense to start with a good battery bank and a charger to plug in when you get home during the week, and then add solar later. But solar is nice to have, absolutely

When I lived on a boat we had a 360 amp house bank of batteries, one solar panel of about 150 watts, and a wind generator. That was nice but it would be a bit hard to cram that all in to a 13-foot Boler. We still had to be parsimonious with our power usage.

Raya
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Old 11-29-2009, 02:05 PM   #40
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I put a push button switch on my meter so that it only draws current when being read. Saving those microamps any way I can.
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