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Confessions of a Battery Abuser

Anonymous

The night was dark and stormy. The rain pelted the skylights and flooded down the gutters while the wind howled menacingly through the trees and around the house, shaking the windows and chimney. The neighborhood was dark and no lights could be seen for miles around. The few radio stations that were still on the air reported that the utility power was out in the entire southern half of the state.

Fortunately, this home was powered with a photovoltaic renewable energy system with a back-up generator. It had been cloudy for several days preceding the storm and the generator had automatically come on to recharge the batteries the day before. The battery bank was sized to provide four days of cloudy operation.

It was near midnight when, surprisingly, the generator started up again. A quick check of the voltmeter revealed that the batteries were near the bottom of their charge. What! So soon? A question was raised. Was the generator filled with gasoline the day before? No one remembered, and no one wanted to go out and check the fuel gauge in the raging storm.

While everyone was trying to remember whether the generator had been topped up with gas, a quick check was made of the house loads. Was something on that shouldn't be or was there some kind of fault that caused the batteries to be drained so quickly? No, everything appeared normal. There were no new hidden loads and the system ammeter showed that the existing connected loads were drawing only their low, energy-conserving amounts of current.

At this point, the lights dimmed a few times and went out as the generator slowly ran out of fuel and quit. A search with flashlights for the gasoline can found that it was empty. A quick trip to the gas station was aborted when everyone realized that, with the utility electrical outage, there was no power for the gas pumps.

Candles were lit and everyone settled down to try to figure out why the batteries had not kept their charge.

They were, after all, top-of-the-line golf-cart batteries that were only five years old.

Had they run dry and someone forgot to check that water was always over the plates? Well, it seems that that might have happened a couple of times every summer. And during the last year or so, it was getting necessary to check them every three or four weeks to add water. More water was always needed in the upper set of eight batteries on a 24-inch high shelf than was needed in the lower set of eight on the floor.

Did the temperature compensated charge controller work properly? Well, the home-brew charge controller didn't have a temperature compensation device; the voltage set points were adjusted by the seat-of-the-pants method based on the season. The battery charger in the inverter had a temperature sensor, but somehow it had come away from close contact with the batteries. Anyway, it couldn't be too important since only one sensor monitored the temperature of the batteries and they were at two different locations.

Was the temperature too high or too low in the garage where the batteries were mounted? Well, let's see - it must get about 110°F on hot summer days in there and down to about 20°F on cold winter days. Maybe it was a little extreme for batteries that like to stay at 80°F.

Was the three-stage charger working properly? Well, no! This charge controller had only a single set point that held the batteries at that voltage. Did someone remember to lower the set point during the four-week long vacation every summer? Was that really needed? The set point was only a volt or so above the gassing voltage to get those batteries good and stirred up every cycle. But, during the summer vacation, the house loads were reduced to zip, and gee, the batteries sure did need a lot of water when the family returned home.

How about the battery installation? Did every cell get an equal share of current, voltage, temperature? The eight batteries on the floor had a one-foot longer cable than the set on the top shelf. No Z-style plumbing-type wiring was used; after all 2/0 cable was used between cells and those automotive-style posts and clamp-on terminals were plenty hefty. It was also a little cooler all the time near the floor than it was on the shelf.

Were the cable clamps always tight on the terminals and the clamps always tight on the cables? Now, that's an interesting question. At times, when the voltmeter was used to measure the voltage drops in the cable, some cables measured 12 millivolts and some measured 150 millivolts - boy, some of those terminals were warm! Isn't that normal?

When the batteries were equalized every month or so, were the Hydrocap vents removed and the regular battery caps reinstalled? Remove the Hydrocaps every time - heck, there are 48 of them! Maybe they were removed once a year. Anyway, no one wanted all that messy acid dripping out of them.

With nothing more that could be checked that night, everyone went to bed to the sounds of the storm still raging outside.

The next day, the utility managed to restore some power and gasoline could be purchased. The generator was refilled and started to recharge the batteries. The sun came out and the PV array also helped to recharge the batteries.

Measurements on the battery bank, one string at a time, revealed that the eight batteries on the top shelf were totally dead and beyond salvation. The eight batteries on the floor had a little life, very little, and were used to hold the system together until new batteries could be purchased, delivered, and installed. Numerous battery clamps on both the cable end and battery-post end were found to be loose.

Although heavy cables had been used, the slightly longer cable and cooler temperatures for the eight batteries on the floor had given them a longer life. The abuse of the system and lack of proper maintenance had allowed the eight batteries on the top shelf, operating at higher temperatures and higher voltages, to come to the end of their cycle life prematurely.

Proper installation and proper maintenance would have yielded several more years of life from these batteries.

A New Leaf Was Turned Over

A decision was made to replace the nearly dead golf-cart batteries with a new set of batteries that would be installed properly and maintained well.

In a few weeks, a truck delivered a ton of new Trojan L16 batteries (16 at 133 pounds each).

The walls and ceiling of the garage, where the battery bank was installed, were insulated to moderate the seasonal temperature swings. The garage door was also insulated.

The generator was converted to dual-fuel operation (natural gas and gasoline) with propane as a third fuel option. Natural gas pumping stations have back-up generators (run on natural gas - what else?) to deal with power outages. Propane can be stored for a long time.

The old dual-layer shelving was ripped out. A pad of two inches of Styrofoam, wrapped with polyethylene film, was placed on the garage floor to moderate the temperature of the battery bank.

After looking through numerous container catalogs, a trip to the local Walmart yielded some very heavy-duty polyethylene containers. These containers, used as tool boxes in the back of pickup trucks, had lockable lids. With a little modification they were large enough to hold four L-16 batteries complete with Hydrocap vents, and they had plenty of room left over for the wiring. Four of them were set on the insulating pad.

Two-inch electrical PVC conduit was used between each of the containers and between one container and the power center. The conduits were connected to each end of the containers several inches below the tops of the batteries to prevent hydrogen gas from getting into the conduit and power center. Small holes were drilled in the tops of the containers to allow hydrogen gas to escape.

A call to a cable distributor in the next state placed 100 feet of the flexible 2/0 AWG USE/RHW/RHH cable on order for delivery in a week.

A visit to a local electrical supply house resulted in the purchase of two large, insulated power distribution terminal blocks. These terminal blocks had six large holes capable of connecting up to 250 kcmil cables.

The batteries were placed in the containers, and the distance between all of the terminals was carefully measured. Since the batteries came with type L terminals (posts with two flat sides and a bolt hole), it was decided that copper bar stock would be the cheapest and best way to connect the batteries in series. A metal supply outlet in a nearby city had some copper bar stock in 1/8-inch by one-inch by 12-foot lengths for a reasonable price-cheaper than 2/0 AWG cable and crimp-on terminals.

The Trace 4024 sinewave inverter in the system dictated that two paralleled 2/0 AWG cables be run from the battery bank to the power center. Four equal lengths of cable were cut - two for the positive conductor and two for the negative conductor. At one end of these cables, large lugs were crimped on using a heavy-duty crimper about the size of a large bolt cutter. No solder was used on these crimped terminals, but they were sprayed with an anti-corrosion fluid and covered with heat-shrink tubing. The ends with the terminals were connected to the main battery disconnect switch for the power center - two to the positive terminal and two to the negative terminal.

The other ends of these cables were stripped, run to a location in the center of the battery bank, and then connected to the two large power distribution blocks. From the power distribution blocks, equal lengths of 2/0 cable were run to the ends of the four strings of batteries. Large terminals were crimped on the ends of these cables, and after spraying and covering them with heat shrink tubing, they were attached to the battery terminals.

The copper bar stock (equal in area to 2/0 cable) was cut in nine-inch lengths, drilled for bolts, covered with heat string tubing, and connected between the four batteries in each of the four series strings. All exposed battery posts and terminals and the ends of the copper bars were sprayed with anti-corrosion fluid.

With this wiring configuration, the lengths of cable between the power center and each string of batteries were identical. The positive and negative cables were also equal in length. To further assure that voltages and currents divide equally across the batteries on both charge and discharge cycles, 8 AWG USE type cables were cross connected between the series strings at the 6, 12, and 18-volt levels.

The use of crimp-on terminals was held to a minimum and those that were used, were crimped with a very large, heavy-duty, utility-grade crimper. Terminal blocks were designed to carry several times the current levels required by this system. The use of the proper cables and cable attachment methods kept voltage drops and power losses to an absolute minimum.

Since most batteries are shipped with an initial capacity of only 85% of the design capacity, the batteries were cycled to about 50% state of charge several times and recharged with the generator to bring them to full capacity.

New Hydrocap vents were installed on the batteries. A new Trace C40 charge controller with a three-stage charge control process was installed. The bulk charge voltage was set just above the gassing voltage (28.6 volts at 77°F) at about 29 volts. The float charge voltage was set below gassing at about 26.5 volts. These settings would get the battery up to near full charge every day that sufficient sunlight was available to offset the loads. During long vacations with no loads, the system would keep the batteries fully charged and below the gassing voltage for minimum water usage and long life.

Battery temperature sensors for both the inverter and the charge controller were firmly attached to the side of a battery near the center of the battery bank.

A rubber apron, face shield, rubber gloves, goggles, and old clothes were stored in the garage for use whenever service would required on the battery bank.

A maintenance schedule was set up with a log book. Once a month, the Hydrocap vents would be removed and the original battery caps reinstalled. Either the house loads would be reduced or the generator used to bring every cell in the battery bank to an equal and full charge. This would be done by setting the charge controller or the inverter set points to hold the battery bank at about 29.5-30 volts which would cause the batteries to gently bubble as they generated hydrogen gas. This would stir the electrolyte to avoid stratification and remove any large lead-sulfate crystals that might have formed in the batteries. The batteries would be held at this voltage for three to four hours or until the specific gravity of each cell reached a maximum and was the same for all cells.

Every six months, all of the terminals would be checked for tightness. Voltage drop measurements across all cables and terminals under high charge or discharge currents would be used to identify items that required maintenance. Insulated wrenches would be used to tighten any loose terminals.

In summary, batteries can have very long, productive lives. They must, however, be treated with respect and kindness. A proper and safe installation is an absolute necessity. The correct selection, installation, and adjustment of cables, terminals, and charge controllers will ensure proper operation and long life. Batteries cannot be installed and forgotten in any system. Continued care and feeding is required.

No abuse makes for happy, long-lived batteries with no unexpected blackouts.

Access

Battery Boxes: Packer 45 Storage Chest by Delta Consolidated Industries • PO Box 41209, Raleigh, NC 27629 • UPC 4341990254 • Available at or through Walmart stores.

Insulated Terminal Blocks: Polaris IPLD series by NSI Industries • PO Box 561596, Charlotte, NC 28256 • 800-321-5847

Flexible Cables: Type USE/RHH/RHW • Anixter part number 3BF xxxx • Anixter Brothers • 800-323-8166 (for large quantities) or PV Distributor

Anti-corrosion Fluid: Permatex Battery Terminal Spray • Available from auto parts stores

The Ex Battery Abuser may be contacted at SWTDI/NMSU • POB 30001/Dept. 3 SOLAR • Las Cruces, NM 88003 • 505-646-6105 ^

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