Living without AC power

[Raya]

Yes, that's true. AGM and gel-cell batteries off-gas less than traditional lead-acid batteries. To the point where it's like they don't offgas at all.

They cost more, and are more finicky about charging though, as a trade-off, so you just have to decide what will work best for you.

When they were still a fairly new thing, I bought 6 of them for a sailboat's house bank, plus a smart charger/regulator, etc. Ka-ching! Later, after doing some research (that was not available when I bought), it turns out that the absolutely worst type of charging for them is the constant slow trickle of solar panels and wind chargers. Guess what I had? Yep. Oopsie.

They much prefer the sort of charging that a power boat or a tied-to-the-dock boat gives them. That is, drain to 50%, then charge up all at once right to the top, then drain, then charge, etc. Exactly the opposite from a typical boat out sailing, constantly using the battery (still only down to 50%) and constantly charging at a trickle (solar panels, etc.).

Of course with a trailer that goes to a home base during the week, you will be giving it the kind of charge it likes (but they still like a smart charger and good regulation).

Lead-acid batteries are happier with the constant slow trickle of a solar panel, and are not as fussy about having smart chargers and regulators, etc. You can charge them with just a basic charger.

As with all of this sort of stuff, which one is best? It depends! To my mind you just have to weigh your situation against what each type of battery has to offer (and what it taketh away).

Raya

PS: Donna, that style of battery box for a lead-acid battery in the trailer looks nifty.

[peterh]

The Optima spiral cell batteries mentioned by Darwin & Yvon are great batteries. They're a specialized type of absorbed glass matt (AGM) battery that packs the "glass matt" and lead plates into nested cylinders. They're particularly good for applications like off-road vehicles that bang the battery around a whole lot and for applications like solar-power systems where you want to capture the absolute maximum amount of electricity generated from the solar panels with the absolute minimum amount of loss. (Something you don't need to worry about if you're charging from your tow vehicle or a plug-in charger.)

Their downsides, however, are that they are very expensive and aren't as "energy dense" as a regular AGM battery. If you compare Optima and standard AGM batteries of the same physical size, the Optima will store fewer amp hours -- about 1/3 less -- than the same-sized AGM battery. Putting that in real terms, I have a 55 Amp-hour Optima battery that cost me $180 US a few years ago when I had a single 55-watt solar panel and wanted to squeeze every possible watt out of my daily charging cycle. Now I have two panels and don't have to worry quite so much about capturing every single watt I could buy a standard AGM battery that's the same physical size and would hold 80 Amp-hours for $130.

Beyond differences in their vibration resistance, charging efficiency, and energy density Optima Spiral Cell AGM batteries and standard AGM batteries are pretty much the same. They out-gas the same, they last the same number of years or charging cycles, they maintain the same voltages when they're fully charged, and so on.

[Raya]

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

[Amy M]

Well, I'm obviously no expert, but after doing some googling it seems that AGM and gelled are quite different but that all types of AGM are able to be fully charged with solar.

http://www.windsun.com/Batteries/Battery_FAQ.htm

http://www.exploroz.com/Forum/Topic/20258/...ent_charge.aspx

I am intrigued, especially after looking at the trailer tongue and feeling doubtful that I could fit the current battery out there. Is it possible that my tongue is so much smaller than other people's? (That's a strange question, isn't it?)

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

[Judith Kennedy]

We had four 240AH batteries on our sailboat that we lived aboard for eight years. They didn't have any type vent and just lived in the engine room with no special seals or battery boxes.

We never worried about or had any issue with gassing even though we charged the bank twice a day with a diesel generator. We used about 200 to 250AH each day.

Therefore I question whether a sealed battery box is even nessisary. However, when equalizing, Some venelation would probably be in order.

[Raya]

Hi Amy,

AGM and gel batteries are different, but people often talk about them at the same time because they are both "similar" in that they don't outgas as much as lead-acid batteries, and have other similar characteristics. They also came into being around the same time (as compared to lead-acid, which have been around 'forever').

Solar panels have no problems charging either AGM or gel batteries, that is true. But people seem to be finding, from experience, that AGM batteries don't really "like" to be charged and used at a constant trickle (especially when they never get their last 10% of "float" charge in), and so this shortens their lifespan. Given how much they cost, this is not a happy thing.

Look at it this way: Say batteries were people, and it took 1,000 calories a day to keep them alive and happy. The lead-acid people would be (relatively) happy eating steadily, all day long, just one small bite at a time. They could also get by on only 900 calories, for long periods of time.

The AGM people, on the other hand, would not be as happy with this, but would rather stop working and sit down to eat. They would like just one meal a day, all 1,000 calories in one shot, till they were totally full. Then they are happy to go work again, until it's time to sit down for the next 1,000 calorie meal. They especially would hate to go back to work after only having eaten 900 calories (and in the Battery family, that last 10% of the calories takes the longest to eat).

The AGM people would still survive on the lead-acid people's way, but they would not thrive, nor would they live as long.

On the other hand, the lead-acid people do just fine eating the AGM way. They are not only cheaper but less fussy. On the other hand, they outgas

Again, there is nothing wrong with AGM batteries. They are a great technology, and although they (and their preferred chargers) cost more, they have definite advantages. But they also have their weaknesses. So it just depends on what you want, and how you are going to use them.

Raya

PS: It was pointed out to me that all of these batteries have lead and acid, and that the ones I was referring to should really be properly called "flooded cell" batteries. That's correct and I hope I haven't confused anyone. By "lead-acid" I really did mean "flooded cell."

[Frederick L. Simson]

We had four 240AH batteries on our sailboat that we lived aboard for eight years. They didn't have any type vent [b]and just lived in the engine room with no special seals or battery boxes.

But I'll bet that the engine room wasn't part of the main salon or one of the staterooms. Having the battery open under a bench inside the trailer is like having it right in the room with you. That's why it should be in a compartment that is sealed away from the main living space and vented to the outside, just like the back of the absorption refrigerator should be sealed away from the main living space and vented to the outside.

[Raya]

I wonder what type of batteries Judith had - she didn't specify. Granted, it's nice to have a battery box for any type of battery. But an un-vented AGM battery in the living compartment is different (and less of an issue) than an un-vented lead-acid battery.

You're right to point that out though, Frederick, as she didn't make that clear.

Also, most live-aboard boats would have more volume and more passive ventilation than most of our eggs. Sometimes the engine room is fairly sealed off from the living space; other times, not so much. It really does need more detail before one (Judith, not Frederick) can make a definitive statement like that, in my opinion.

Raya

[Judith Kennedy]

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

[Raya]

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).

[Judith Kennedy]

the boat

[brian m.]

the boat

Let me say WOW!

[Raya]

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

[peterh]

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.

[Raya]

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.

[peterh]

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.

[Amy M]

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.

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.

[peterh]

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.

[Raya]

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

[Judith Kennedy]

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.