Chris Olson

Karen Crane wrote:
Where I am and with the money I havek it is cheaper to stay on the grid.
Is there a way to have both?

Karen, if somebody comes along and claims the cost of solar power can match utility power, they are blowin' smoke and pushing bogus numbers. The one and only thing that makes grid-tied solar power systems cost effective is government subsidies, rebates, tax incentives or FIT (Feed In Tariff) programs.

For anybody with utility power that wants backup power, a small generator that costs less than $1,000 will do more in a power outage than $10,000 worth of solar panels. For anybody that lives off-grid full time, the generator is the most important power producing unit you have - NOT the solar panels, or wind turbines or micro-hydro. The solar panels, wind turbines and hydro generators work at the mercy of Mother Nature. The generator is the one and only thing you can count on. One of the necessary evils of off-grid living is batteries. You need the generator to take care of them for a full-time off-grid home because you can spend $20,000 on solar panels and they still can't take care of your loads and battery bank with 100% reliability.

The fact is that those of us who live off-grid year 'round - and especially up here in the north where we get 200" of snow and it gets to -40 in the winter time - live with VERY expensive power compared to anyone who has utility power. Applying what we have to the everyday needs of someone with grid power is just plain senseless because there is too many pitfalls with solar power (although you'll get a more rosy story from solar installers).

Joe DiMeglio wrote:How about a rack for the batteries made of pallets raised up on two or three "rockers" underneath? A 2X6 on edge, tapered at both ends of the bottom surface and nailed/screwed to the underside of the flat pallet rack would allow you to just put your foot on the corner and rock the batteries a bit each day or two to keep the plates free of stratified elements.

A couple of problems with that:
1.) It won't help
2.) It will only work for a fairly small battery bank.

Addressing number 2 first: Our battery bank weighs 3.08 tons with the cells full of electrolyte. And that's only 16 batteries. It takes two men and a hand cart to move one battery. Our batteries have not been moved since they were installed 7 years ago, and they will not be moved until they are replaced. Putting them on anything but a solid concrete floor would be dangerous beyond belief (and no, it does NOT hurt batteries to set on a concrete floor in your power room).

Addressing number 1: Stirring the electrolyte in tall cell batteries such as ours, and keeping the grids properly desulfated is accomplished by the charging process, not shaking them. And it takes a long time of inactivity to stratify even tall cell batteries. Our batteries get ~70 cycles per year on them (our cycle length between full charges averages about once every 5 days). We have run 2 week long cycles many, many times in the winter and never had any problems at all with stratification. Stratification is not a mysterious thing - the more dense electrolyte settles to the bottom of a tall cell and water collects on top. It is easily dectectable with a hydrometer. But in a real off-grid installation where the batteries are never at rest the battery is undergoing constant chemical reactions, either charging or discharging, and they will never stratify as long as they are active. They will hard sulfate if not properly charged, but that is a different issue.

Vlad Alba wrote:Of course, my charge controller manages how high and such during the day, but I also try to use power during the day rather than the night, so depending on what I use, that cuts into the absorption/float stages. I'm wondering how much is too much, how much is ideal to have a reasonable margin for backup power and battery longevity.

If you are off-grid I would suggest that you quit guessing. You can't tell battery SOC by using voltage. And neither can you properly charge most deep cycle batteries by getting them to 28 volts for a couple hours. Full 100% SOC is reached when the electrolyte gets to 1.265-1.275 SG for flooded lead-acid batteries, so a hydrometer is the ONLY way to know if you are properly charging them. Cronic deficit charging will sulfate them and they'll be dead inside 18 months. And I have never seen a GC-2 that can be properly absorbed at 2.33 VPC.

The first thing to do is find out what your battery manufacturer recommends for Absorb V and for how long, and what they recommend for EQ V. Then charge your batteries according to their recommendation and check the cells with the hydrometer to see where they're at. Do not stop absorbing them until they get to recommended specific gravity. If you have cells that are more than 20 points difference because of sulfation and chronic deficit charging, then EQ the batteries until they "come back". Once you are at full 100% SOC you need one of these:



Properly sync'd, the TriMetric will tell you EXACTLY where your batteries are at with no guessing.

GC-2 golf cart batteries are quite fragile as far as deep cycle batteries go. They are at the absolute rock-bottom low end for off-grid systems. They can be safely discharged to 80% DoD (20% SOC) as long as they are immediately recharged to 100%. 50% DoD is the normal limit to get best efficiency and longest life. They can be cycled at 20% DoD without hurting them, however energy storage efficiency will suffer and the batteries will cost you more in the long run per kWh of storage. In all cases they must be recharged immediately, and they will last about 4-5 years.

Real off-grid or "solar" batteries can be repeatedly discharged to 80% DoD and withstand PSOC (Partial State of Charge) cycling for many days between full recharges. They typically last 10 years or longer and have low specific gravity electrolyte (1.255-1.265) with very heavy (over 1/4" thick) plates.

Steven Harris wrote:Chris, as an expert on hydrogen, and running a company that publishes the largest amount of books on hydrogen, I can tell you there are NONE, ZERO Charging gasses that you EVER have to worry about no matter what.

This has drifted off-topic pretty far for the OP that wanted an auto-start genset. But frankly I can't believe I am reading the above on a public forum. Even a neophyte knows the dangers of batteries. You have obviously never seen an entire string of batteries that blew due to one battery going into thermal runaway. I have. I hope the folks that read this thread have enough common sense to weed out the nonsense.

There are numerous things in a off-grid power system that can kill or injure you, from improper grounding of equipment, to solar arrays running at lethal voltages of 60VDC or above. Wind turbines are also common for off-grid installations and they are more deadly than high voltage solar arrays. Ours runs at 600 volts input to the coupling inverter and it is not even safe to have the high voltage components of it in the power room



I hate this notion that stuff can be cobbled together or corners cut for an off-grid system, some of which compromise the safety of the people that live with the system. I certainly hope any prospective, or even experienced off-gridders that read this come away with a full realization that you do not put batteries anywhere in the living area of your home. And when you work with them, which is a regular part of off-grid life, that you wear and use the proper safety equipment. And realize that while one sitting in the middle of the floor is relatively safe, when you combine a bunch of them into a bank they become very dangerous, and they need to be treated as such.

For the benefit of the OP looking at putting in an auto-start genset, here is a couple videos I made on the topic some time back. This first one shows how you can use an auto-start/stop system for a peaking generator to power extreme heavy loads in your home without having to buy more inverters and batteries



This second one is a basic overview of automatic generator starting, more specific to a Schneider Electric XW Power System. But Magnum energy systems are similar. Outback is a different animal because Outback does not make an AGS (Automatic Generator Start) for their systems, and they require the use of an expensive aftermarket Atkinson generator controller. But this shows the basics:

Steven Harris wrote:and what you are taking about hydrogen developed in a battery is a mouse fart of hydrogen.

Steve, I have had two FLA batteries explode in my face over the years and blow the tops right off and totally douse me with battery acid - one starting battery in a semi and one Trojan deep cycle that I was hooking up the cables on. I also had a Craftsman claw hammer accidentally fall into a 1,000A DC bus box once and vaporize in front of my face. I still have burn scars from the hammer explosion. I have basically worked around them pretty much all my adult life and am smart enough to wear safety glasses and gloves when working with them.

Again, I don't care if you want to go blind or are not scared of them. But do NOT urge other folks to do things they shouldn't regarding batteries. A 48V battery bank can lay you out on the floor deader than a doornail if you happen to become the path to battery ground and touch a positive lead. A bank of them is deadly dangerous and you treat them with respect.

Well, I'd like to sort of point out that our batteries are inside, nice and warm in the winter and nice and cool in the summer. In a room and case designed specifically for them. Our current bank of batteries has been there for over 7 years. You don't want batteries in the living area of the house. They are dangerous. Our battery bank can deliver 1,600 amps to the bus before any breakers would trip if you were to throw a shorting bar across the bus. They weigh over 400lbs each full of electrolyte and it requires a hand truck to move one. They have to be serviced every 3 months, including filling out a log with the SG and at-rest voltage of each cell, and how many cc of water it takes for each cell.

This is why off-grid folks design a room or building specific to batteries, and usually the associated equipment. We are not cave people or some weirdo "preppers". We live normal and that means if I bring 2 tons worth of batteries in the house I got a wife that stands with her hands on her hips and proclaims that I have a choice - I can live with the batteries or live with her, but she's not living with batteries in her house.

Cj Verde wrote:I'm off grid too, but my battery bank is inside in the utility room vented outside.

That's pretty standard in cold climates. In warmer climates in the mid to southern states I've seen many off-grid installations with a separate battery house that's not heated or insulated. Usually just a small wooden shed where the batteries are. If we had it to do over we would not have our power room built onto the house. We would put the equipment and batteries in a separate utility building and bury the necessary ductwork to the building from the house to heat it in the winter. Our XW inverter is mounted on the wall in the power room and on the other side of the wall is the kitchen. The XW's have a big torroid transformer in them that sounds about like a 100kVA three-phase utility transformer and at full load the noise from the transformer is plainly audible in the kitchen thru the wall.

There's probably lots of things off-grid folks would change if they had it to do over.

Steve,

Steve, the main problem is that we have a quite large battery bank weighing over 2 tons and batteries give off arsine and stibine which are the two toxic gases that make them stink when being absorbed. We have many thousands of dollars worth of equipment in the power room that we do not want corroded, nor do we want metal hydride gases accumulating in the battery case and power room. So we pressure vent (as opposed to vacuum venting) the battery case to the outside, as is standard procedure with any large battery bank.

Also, large batteries enclosed in a case like ours are can very quickly accumulate explosive levels of hydrogen gas within minutes during absorb stage. It only takes a little over 4% by volume to make the mixture explosive. If you do not want to vent your battery case for your off-grid home, or want to charge batteries in free-air in your battery or power room, that's your business. But we prefer to keep our power room clean, free of fumes, cobwebs, moisture, etc..

Cj Verde wrote:You store 21 cords but how much do you burn? We burn 2 1/2 cords for our 2400 sq ft home - no back up heat but I get cranky if the downstairs is less than 65°. It's R38 on 6 sides and has good passive solar features.

It greatly depends on ambient temp. We keep our thermostat set at 68F and last winter when it never got above -20F for 6 weeks and was at -38 to -40 for many nights, we went thru a little over 6 face cord in the house. Most of it gets burned heating my shop, as I keep it at 65F all winter and keep some diesel equipment in there that I use in the woods when I'm logging in the middle of winter. When the snow gets too deep to drive the Dodge Cummins into the woods to pre-heat the log skidder to get it started, I bring it home and keep it in the shop and drive it back out to the woods when I go logging. And I got other stuff coming in and out of there all winter so the big overhead doors get opened a lot during the day. It's not unusual to burn 10-11 face cord in the shop during a winter. You bring a 15 ton log skidder into the shop that's been out in -20F temperatures all day and it takes a LONG time to heat up that mass of steel. It can be at 65F in there and it's about like standing by a giant refrigerator when that cold hunk of steel comes in the shop.

Edit:
Oh, I should mention too that us off-gridders expend a lot of energy keeping certain things warm in the winter that "normal" folks don't have to worry about. Primary is our battery bank. Our power room is not heated but it is on the north end of the house. It provides a dead air space "buffer" between the living area and the outside and we try to keep it above freezing in there for the equipment to prevent condensation. Our battery bank is in an insulated case in the power room and we blow air from the basement into the battery case that is in turn directly vented to the outside. The battery case airflow is 210 CFM 24/7 all winter. That's a huge "leak" directly to the outside but it is necessary for batteries in cold weather, both for venting charging gases and to keep them above 60F.

Since the catalyst on our wood furnace gives off tremendous heat with the stack temp at 600-700F it is normally quite a bit warmer in the basement than the upstairs. So we leave one basement window open all winter, even in extreme cold weather, to provide fresh combustion air for the furnace. We don't like living in a "tight" house. My grandpa always said a drafty house is a healthy house in the winter. Houses that are too tight and don't exchange the air often enough having people living in them that are sick all the time. Neither me nor my wife has even had a common cold in over 12 years. We attribute that to the fact that we don't seal our house up tight in the winter and it exchanges all the air in the house at least twice a day with fresh. Since our heating fuel is basically free, except for the work of putting it up, we have never bothered with heat recovery air exchangers. We do it the old fashioned way with windows.