excerpted from the Living Energy Farm November – December, 2016 Newsletter
Nickel Iron Testing
The Nickel-Iron (NiFe) battery testing has been all but miraculous. The marriage of old technologies (NiFe batteries) and new technologies (modern DC LEDs and photovoltaic electricity) is absolutely amazing. We had used lead-acid batteries until we could get the NiFes hooked up. Output from lead-acid batteries is like a river headed for a waterfall. As long as you are at the top, life is good. When the voltage collapses, you’re done.
The NiFes are very different. The NiFes are expensive, bulky, and heavy. Their nominal output (rated in amp-hours) is poor compared to lead-acid. But actual performance could not be more different. Our goal in testing the NiFes is to see how many houses in a village (or how many rooms in a cooperative house) we could light up with LEDs, and how many cell phones we could charge. We had a set of 500 watt panels charging the lead-acid batteries. We didn’t have a charge controller large enough to handle the output of those panels. So we brought a smaller set of PV panels we had been using for irrigation pumps up to the house and tied them to a smaller charge controller and the NiFe batteries. The problem was that we did all that in the early fall. All of our permanently mounted PV panels are up high so they don’t get shaded. But as the sun has fallen toward the horizon this winter, these “new” panels ended up in the shade. By December, the charge meter said we were only putting about 10 amp-hours into the batteries. Converting that to incandescent light-bulbs, we were collecting enough electricity to light up two 60 watt bulbs for one hour. That’s all. I sighed, expecting the NiFes to discharge, and made plans for what to do next. We have been lighting the house and the kitchen, and charging cell phones and personal devices without restriction. And then the miracle. The Nifes didn’t discharge. They discharge current in a whole different way than lead-acid batteries. We have never seen voltages below 12.2 V coming from the NiFes, even with weak input. The LEDs are good down to 9 volts. The discharge current from the NiFes is steady and strong, each decimal down. No waterfall.
Now we have swapped equipment around again, and are now charging the NiFes from a panel on the roof. We have learned a few things. A very modest (100 amp-hour) NiFe set will power a lot of LED’s. A modest PV panel is all that is needed to keep them charged. We still don’t know the maximum output of a 100 amp-hour NiFe set because we are so far away from actually “maxing out” the current system. It is clear that we can support numerous houses in a village with DC LEDs, a couple hundred watts input, and a modest set of NiFe batteries. Somewhere between “numerous” and dozens. We’ll see.
Our DC Economy Continues To Grow
We have been enormously pleased at our ability to do all manner of work with high-voltage, direct-drive DC power. We added two new DC tools this month, electrifying our grain grinder and setting up a compressor with a DC motor. We run these tools when the sun is out — no inverters, no fancy electronics.