storage battery life

[thirteen]

I would like to get some feedback on maintence free batteries.  What are some of the hidden unknown things about them.  Are they truely maintence free.  It does depend on the types. I will be buying batteries next year for my 24V system.  800 am bank. solar next year and micro hydro in 2 yrs. I keep reading about maintence free batteries but things in real life compared to words are sometimes are two different worlds. I'm just looking for some input.

[mab]

By 'maintenance free' I assume you refer to sealed AGM/gelcel? If so I would avoid them, unless you're getting them very cheap (like ex-UPS batteries).

if you get sealed batteries then you have to stay withing strict charging limits or they will start converting water to gas which then vents and is lost. As they are sealed you cannot easily replace the lost water. The problem with staying withing the charging limits of these batteries (if you are using solar), is that you cannot get the battery fully equalized before the sun goes down and you start discharging again.

With 'flooded/wet' batteries (i.e. not maintenance free), you can 'push them' a bit to fully charge them - and simply top up the water regularly to compensate for that which is lost.

Having said that, it is possible to use sealed batteries - I do use AGMs ATM - but I periodically use grid power to do an overnight equalization. When I buy new batteries I'll be looking at flooded types - unless I get a very good deal on AGM's.

m

[DamonHD]

For my *very small* off-grid system I use gel SLAs and I'm happy with them; I'm on my second round, expanded to over 10x the original capacity.  I make an effort to orient my panels in such a way as to maximise the time over which charging happens and I have a temperature sensor on the batteries to get the best temperature compensation possible, ie to be as kind to the batteries as possible.

Rgds

Damon

[thirteen]

My solar system power will be limeted during the winter months until I get my micro hydro system in. Sound like they do not like abuse as flooded batteries with stamnd it better. It seem to me that I will have a tough time during the winter months when I only get 1 1/2 hrs of sunlight each day at best.  Dec 15 - Feb 15.  I have a mountian that hides the sun during the winter. I could run the panels up the mountian but that would require about 1100 ft of power cable.

[hydrosun]

That 1100 feet of wire could be small if you run at high voltage and then use a mppt controller. Depending on how far the hydro turbine is you may want that mppt controller for the hydro too. On the other hand if the hydro can provide all the power you need in the winter you don't want to put too much into extra wire to the mountain top if you won't need it in two years.
Chris

[thirteen]

The creek sometimes feezes during the winter for it hits -20 / -30 for up to 6 weeks. The hydro will be about 725 ft from the bank. I cannot use the hydro during the mid to late summer mid (Sept.)  just not enough water.  I am not sure but I think I would need a mppt for both the solar and one for the hydro.  Can one mppt work for both  the solar and hydro when they are both supplying power at different voltages?  The more one thing does the more the $$$ go up but if it works. I do not know.
Also anything I build up on the mountian  is carried on your back. The land is steep and rocky and no trails. I throw the 4 in rock back for topsoil. HAHA! I would not be able to bury the power cord but I could put it in condiut.
I will need to get a 400g propane tank and build a trailer for it. They will not come any closer than 6.5 miles to fill it. So I will need to make a trailer to haul it in and out. I plan on coverting one of my generators to propane. I already have a ondemand water heater witch uses propane and I will have an emergency backup old style adiant wall heater in case I get sick and cannot feed my wood stove. I also am cooking with wood. The only power used will be for the frige, the computor desk and some lights and TV system, washing machine. Maybe a toaster.  I do not drink coffee. For any major power use needed I will start my gen set. My domestic water is getting installed and will be a gravity fed system. I may need to put a booster pump in line for my ondemand water heater. I won't be sure until the water system in in place. Hopefully in 4 weeks. I think I will have about 50 feet of fall for the domestic water with a 500 g storage tank. He will need to bring a crawler with a backhoe on the back to get up to the spring water. The land is to steep but the spring comes out of the ground and then goes back in to the ground in about 50 ft. It takes about a minute to fill a 1 gal jug. But it has not changed in 14 years and we have gotton our water there for years. It is just tough to go and get. The flow stays the same year round whether it  is dry or wet and does not freeze but sometimes makes a real big chunk of ice.  290 days and counting.

[Volvo farmer]

I have read it time and again that most batteries do not die, they are murdered. Also, almost everyone murders their first set of RE batteries.  I thought I was smarter than the average RE guy and still only got six years out of a set of Surrette L16s. I was not smarter, I murdered them.

I would recommend something in the T105 golf cart size, in 6V configuration, but it would take 4 strings in parallel for 800 ahr @ 24V, and most experts agree that more parallel strings equals more trouble.

If you could live with 400 ahr or even 600 ahr, you could limit the parallel strings to two or three, and not spend too much money learning about batteries in your first few years.

[thirteen]

Volvo sounds like a good idea. I will have to get my pencil out and figure things for a smaller bank. i never really thought about a smaller bank other than 800 am bk. I was thinking about a couple of 12 v size D batteries for a starter bank. I was also figuring out that I would destroy a battery set. The ones I use now are mismatched and old and tired. They are over 8 years old and i have just a 45 w solar panel charging them. I am up there for four days at a time and my nieghbor tells me that it takes about 2.5 weeks before they show close to a full charge. He drives by every coup[le of days and can see the meter that is on the wall just above the batteries. The four of them usually read 12.5.

[Volvo farmer]

I wonder if we are confusing terms here. You refer to "800 am bank",   I am referring to amp/hours.

No way should you be charging 800 ahr of battery with 45W of solar, you won't even keep up with the self-discharge rate.

Also when you say "D" batteries, do you mean 8D? Two of those would be in the 220 ahr range at 24V. Recommended charging rate for batteries that are cycled regularly are usually around c/10.

So, you would ideally want about 22A of charging rate for two 8D batteries at 24V or about 500 watts of panels. If I were you, I wouldn't purchase any batteries until my charging sources were increased.

[thirteen]

My mistake. The new ones  would be 2 / 8D  batteries, 24v system. I am only up there for four days at a time about every two months. I will retire next May. The batteries I am using are freebies I got several years ago and are barely good enough for the days I use them. they are a couple of old 6v trogens I dug out of and old miners cabin that had been crushed by a mud slide. The others are  just car battereis and there is one that is about the size of a 8D battery but no name just posts. the 45 w solar charges them up and they are normally used for the surflow water pump and a couple of lights at night. I have an old Victor Inverter for power usage another freebie. This makeshift system is 12 v. I will be installing  4 / 230W solar panels next spring I will get them mounted on top of my wood shed. I am going to use or start looking to make an 800 ahr bank.
This 800ahr bank is where I started to figure things out. With the unknowns I needed a starting piont.   Plus I figured it gives me extra hours during the winter when things are not good enough for solar charging. Until I spend a full winter up there my system  would still be in question. I have not been able to moniture the sun year round. That puts things in question as to where they should be put or moved. At times I do go ahead of what I have for I had this planned for me to retire this last year but things did not work out the way i planned them. I have not purchased anything major for the system I wish to put in. I have bought except for some wire and crimp on lugs. The wood shed will have it's battery storage area done this Labor Day weekend. Insulated walls  and big enough to work in. I was going to go with foam blocks but the groung I have is moving and I think the foundation will shift to much so I am going with treated lumber and a footing.