Hydrometer Callibration

We, myself, Todd at the High School, and his science class, calibrated my Hydrometers by weighing out a measured volume of Battery Acid, and dividing the mass in grams by the volume in milliliters. We measured 25 ml in this, and got the weight.

Of the four hydrometers, two were defective. A plastic one had a fine crack in the back, and a glass one has fluid in the float. The specific gravity reading is affected how it is done: the battery acid must not go into the bulb, and the rubber tip must stay submerged in the acid while the reading is being done. Then, both the plastic and glass hydrometers gave the same readings.

I had bent a glass hydrometer to be able to read it better, and broke the thermometer hear the tip. A light on a bill cap seems to work best, if there can't be a light in the battery room that will throw a spark and ignite battery room gasses.

Now to measure the specific gravities, and decide which batteries to discard.

Certified Solar Installers make fewer mistakes

Jesse, the Solar Installer Certification Instructor, visited the site, and examined the system. My biggest surprise was that the licensed electricians who installed this system, and the people who trained them, were never certified. That explains why they were unable to plan for and calculate how to expand the system. There are only two certified solar installers in Northern MN. I was lucky to find an electrician with prior experience, since the cabin is in the middle of the wilderness. I had my plate full being assistant then lead General Contractor, Surveyor, Excavator, Mason, and Carpenter. Many talented and hard-working trades people worked with me and together. It is still the biggest challenge for the Owner and General Contractor to get a strong off-the-grid team together sharing the same vision: well driller, electrician, carpenter, architect, plumber, and HVAC professionals all have different goals.

The best news is that Jesse's plastic pointers hydrometer reads about 100 points higher than my two NAPA glass tube with rubber bulb hydrometers, all ignoring temperature compensation. That is the difference between a good battery and a bad one, so for the system of 16 batteries, it is a $12,000 question. Tomorrow I work with the high school's chemistry teacher, Todd, and his students to standardize a hydrometer, so that we know what the true specific gravities are. For lead-acid batteries, open vent, the best test is to apply a load, then to take the specific gravity, then to check the voltage.

Doug's System was installed by the best of Solar Installers in Northern MN: Conservation Technologies. He is also off-the-grid. He has 8 batteries, and at 20 months, had to replace 4. He thinks it is because the Outback charge controller cannot control whether of not an individual battery is overcharged, as it works with groups of 4 for a 24 volt system and 6 volt batteries. Doug's are sealed cell, so he must rely on the voltage to determine the health of the battery. Jesse does not like to do remote diagnosis, but suggested that the long cable length to the set of 4 batteries that has remained good is the reason for making 4 of the batteries go bad so quickly. There is less resistance to the batteries that went bad, since the cables to them were shorter.  Doug will arrange the batteries differently.

Jesse suggested that I get the cables off the floor by building a shelf above the batteries below the inverter on the other side. It won't change the state of charge of the batteries, but will make it easier to take the specific gravities and water the cells.

It was difficult to design my battery room as information was not available. Dairy board works well to protect the wood from battery acid. Grainger has a watering plastic can with a spout you push into the cell.  It stops adding water when the water level is one inch from the top. That saves to much time! Wish I had installed a SunTube for lighting. Because the batteries produce hydrogen gas when charging, I have a PowerVent on the ceiling that exhausts the gas, and can't have a light to switch on. The spark might light the gas. Wish I had a digital hydrometer. I've never seen one that is easy to read. Wish I had a rubber apron. I've wrecked to many clothes. I wear the clothes with holes in them now when I take the Specific Gravities. I always wear plastic glasses over my glasses. Wish they didn't get scratched so easily. Glad I had them on when my hydrometer exploded. Suddenly, the liquid traveled past the markers and up into the rubber bulb and the glass exploded. So now I push the liquid back when it is close to the edge of the bulb. The battery room should be lined in dairy board, then, unless there is something fireproof and acid proof at a reasonable cost.

Ideally the battery room never lets the batteries freeze, at least, never when they are not fully charged. Northern Tool sells the Solar Sheet, and Mother Earth News tells how to build one. It puts warm air into the room when the sun shines, without any fuel other than sunshine. That might have saved my batteries. The one Northern Tool sells comes with a PV panel and fan and thermostat, so it requires no wiring. Just two 5" holes in the wall, and secure the solar thermal panel to the outside of the wall.  A company in MN makes a Solar Furnace that requires electricity, and that the siding be removed where it is installed. I'd like to see Btu comparisons. The Millennial House in Duluth had something like that in 2000, but they refused to release the data. I designed and built my home expecting to install something like that. The foundation walls on the south sides have an extra layer of block, to support the extra weight. So far, I don't know the best way to keep the battery room from freezing, if no one is home.

Solar Installer Instructor Coming to Site Friday.

Hibbing Community Vocational Technical College has certification in solar installation. THe instructor will meet with me Friday to decide what to do with the batteries. We'll go over the logs.

Doug from Isabella, MN also lives off the grid with deep cycle batteries. His got old, he replaced some, and says they do not act like the manufacturer or installer said they would. Mysteries will be explained, or outlined clearly!

The Problem

This winter, my deep cycle batteries froze when the heating system failed. You can see the bulged sides in the photo. A straight edge across the worst battery has a 1/4" gap on either side across the 6" side- they have curved sides now. I have 16 batteries, each is a deep cycle battery, Rolls Surette S460, cabled in four groups of four batteries per group for a 24 volt system. The batteries cannot be fully charged, so it is expensive to have the generator charge them. It is like paying for a full tank of gas, but only getting half the milage out of that fillup.

So I have tried to restore the charge by taking the eight worst to town, and putting then in pairs of 2 on an iota charger to equalize them. I've tried cleaning them out, putting in new battery acid, and equalizing them. One out of four improved with cleaning. The specific gravity readings on each cell were taken over several days. The four best batteries were returned, and have been running the house over the summer. Now I have to figure out what to do. Which batteries do I use? How should they be cabled together? Can I do more to bring any battery back to full charge?

I need to calculate my electrical demand. The heating system is the hardest to figure. One box says it has 40 amps on startup. That can't be true! I hope. I'll see if the library can lend me their watt measuring gizmo. Electrical demand in the summer is almost nothing, as the heating system is not on, the mechanical ventilation system is off, and lights are used very little. I have been practicing not using the electric fridge. Milk needs refrigeration unless it is added to viili, like yogurt. Need the fridge, but with the house running on 4 batteries, it is off now. With winter coming, either the heating system gets turned on, or the water blown out of the pipes and I heat with wood. Can this new configuration of batteries handle the load?

Each battery weighs 125 lbs. The battery room is upstairs in the heated garage. It is really a two person job to get those batteries out of there and into town, and hard to find another person in the middle of the wilderness. I'd rather leave them there. In fact, the Trace 4024 power panel seems to have done a better job of restoring the batteries than taking them to town and putting them on the iota charger did.

Solar panels charge these batteries without generator backup completely in the summer. In November and December, the sun rarely shines. The generator is propane; the price of propane has gone from $0.80 to $2.90 per gallon since I started construction eight years ago. The house could run off the generator, but the cost would not be reasonable, and it is not good for the planet. The batteries can't freeze again; what is there can run a washer, dryer, dish washer, garbage disposal, garage door openers, and 220v well pump in the summer, without the generator. It is a structural insulated panel house (SIP), so is so tight that it has to have a ventilation system running in the winter. Without it, the windows frost over, melt, and rot the window frame. Winter demands more from the batteries and generator. How much more depends on the ability of the generator to fully charge the batteries. When do I say it is time to just not use these batteries anymore? How many batteries do I have now that I want to use? How will I cable them together?