Armed with the basic information detailed above, I packed my checkbook and a toothbrush and headed over to Colinton, Alberta to see Ron LaPlace of Photron Canada. We decided on nine Kyocera J43 panels (2.89 amps at 14.8 volts at maximum power point) configured in six panel and three panel subarrays, a Photron Universal Power Enclosure (UPE), a fused General Electric 200 amp source center (with a spring loaded double pole safety disconnect switch), and a Trace SB2012 inverter. The UPE included a six-channel user configurable electronic DC voltage setpoint controller (UPC-6), a blocking diode, two shunts, temperature compensation sensor, and a system analyzer (which measures DC amps in, DC amps out, output circuit setpoints, and battery voltage). The UPC-6 is a neat piece of equipment! It can measure up to three different DC voltages as inputs and actuate up to six different 2 amp relays as corresponding outputs. Each of the six output circuits is fully adjustable which allows the user to configure a multi-function custom control. I set up our UP-6 to control each of our subarrays independently and to alert us to both low and high battery voltage. This still leaves us with two output circuits for future expansion.
I also acquired a used 5,000 watt Yamaha gas power plant, a Cruising Equipment Amp-Hour + meter and a Trace Digital Volt Meter (DVM) for the inverter. The latter two are excellent diagnostic tools—I really don't know how we could accurately analyze our system's performance without them. The Amp-Hour + meter tells us all we need to know about our battery, and then some. Before installing it, we did a lot of guessing. With a $2,100 battery hanging in the balance, the Amp-Hour + meter is well worth every penny it cost. The Trace DVM allows us to monitor power plant Hz, peak volts in, charge rate, and battery voltage—all very valuable information.
GNB recommends starting your test with the battery at full charge and after a minimum of seventy-two hours at a float voltage charge (13.50 to 13.68 for my battery, 13.2 for a flooded lead acid battery). The testing should be done as close as possible to the standard temperature of 25° C (77° F). This is the temperature at which the declared battery capacities are calculated. Obviously, few of us have our houses at 77°. If you do your test at 70°, it will be close enough (at 70° F your battery starts with about 99% of it's capacity). At 60°, however, your battery will only start with about 94% of its capacity, so don't do your test at this low of a temperature. Use the 20 hour rate for your test. For my battery, this is 630 amp-hours divided by 20, which gives a 31.5 amp discharge rate.
Of course you have to turn off your charging sources to do the testing. A resistive load such as an incandescent light or a toaster is the best to use as it is a constant load. An old toaster from the junk store can be easily set up to generate a variable load. Simply cut one side of the wire that leads into the toaster and attach a one foot piece of equivalent size wire to the live side. Now attach an alligator clip to the other end of this new wire. Take the body off the toaster and clip the alligator clip to the toasting coil inside. Plug the toaster in and check the amp draw on your multimeter or Cruising Meter. If the reading is too high or too low, unplug the toaster and move the alligator clip.
Once you find the location on the coil that gives you a current draw equal to the 20 hour rate for your battery, you can start your test. Plug in the toaster and monitor the battery voltage. The test stops when your battery voltage hits 10.5 volts. If your battery voltage drops to 10.5 volts 20 hours after you started your test, your battery has 100 percent capacity. Congratulations—you have treated it lovingly and it is rewarding you with a long and dedicated life. If the 10.5 voltage is achieved prior to 20 hours, the following graph and some simple math will allow you to calculate the battery's capacity.
In my case, if the 10.5 volt level is achieved in 16 hours, here's the math: The Amp-Hour + meter or multimeter will read 504 amp-hours (31.5 amp test load times 16 hour test duration). Dividing this capacity by the 16 hour percent capacity from the graph below, reveals that the true 20 hour rate capacity in amp-hours of my battery is 520 (my test capacity of 504 divided by 0.97 equals 520). If you want to confirm your data, recharge the battery and do the test over with the new 20 hour discharge amperage of 26 amps (newly calculated battery capacity of 520 amp-hours divided by 20 hours). This test capacity should see your battery drop to 10.5 volts in 20 hours if it is correct.
Capacity vs Discharge Rate (GNB 6-75A15 Battery)
Capacity vs Discharge Rate (GNB 6-75A15 Battery)
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You can now recondition your old batteries at home and bring them back to 100 percent of their working condition. This guide will enable you to revive All NiCd batteries regardless of brand and battery volt. It will give you the required information on how to re-energize and revive your NiCd batteries through the RVD process, charging method and charging guidelines.