Final Breakthrough

By , May 19, 2015

The long, drawn out process of installing the new solar panels included one final touch: the addition of a vent fan.

Lead acid batteries “gas” at high charge levels, emitting vaporized sulfuric acid and flammable hydrogen. This is unhealthy to breathe, and potentially explosive, so battery boxes must be properly vented for safety. Even the fine print of the “safer” nickel-iron batteries we’ll soon receive (see Power Shift: A New/Old Battery Bank) recommends venting them for safety.

We built a vent to the outside of the cabin into the battery box when we first moved the “homestead” battery bank inside. We did not, however, install a fan. The vent helped move the bad air inside the box to the outside, but Michelle often complained about the sulfur smell during periods of high wind when the batteries charge well. Our carbon monoxide monitors, installed along with smoke alarms around the cabin, pick up on battery bank gassing. In fact, I routinely use the carbon monoxide alarm upstairs when equalizing the battery bank every 60 days—when it begins shrieking, I know that I’m getting close to a full equalization charge!

When we set in motion our plan to upgrade our power system, I included a vent fan in the orders. The new charge controller that would manage the solar panels’ output includes an auxiliary diversion that manages a vent fan. It turns the fan on when the battery voltage rises to the level where gassing becomes likely, and turns it off again when the voltage drops below gassing levels.

Convenient in theory. But, I had to make it work!

I ordered a 12 volt relay along with the fan. I installed both the fan and relay to the letter of the instructions. I followed the charge controller’s manual for setting up the auxiliary power supply to run the fan. But nothing happened.

I messed around for several days, trying to figure it all out. I called the company that had provided the fan and relay, and got help with testing the relay to ensure it worked. The fan I figured out on my own—I touched the lead wires to a 9V battery, and the thing started up. Test successful!

I traced the problem to the charge controller. Voltmeter tests showed that it didn’t provide power to the relay, even though the settings were correct. I opened up the controller and found printing on the circuit board that showed two different settings for a pair of tiny jumpers.They seemed to be in position to run the fan; the other position seemed designed for a different use.

I called the charge controller’s technical support, and learned that, in fact, those jumpers needed to be moved to the other (i.e. non factory default) setting to run a fan. I pried the jumpers off the contacts and moved them to the second setting. As I pulled the second jumper, I thought to myself: “Do not drop this!” I immediately fumbled it, and I heard it clatter across the floor.

Thankfully, Michelle found it for me, far outside the area I searched for the missing piece. I put it carefully in place and . . . nothing happened.

I decided to trace all the wiring one last time. I quickly discovered that the negative battery contact, which I’d removed several nights ago while installing the breakers, had not been reconnected. I touched it to a negative post in the battery bank, and heard the sweet sound of the vent fan starting up!

This final breakthrough completed the installation. Everything now works as it should, including the vent fan. This feels really, really good.

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