…immediately followed by !^&%+()&.

Having not flown my own airplane for nearly 4 weeks, I tried my best to sneak in a 30-minute hop over lunch at the end of the week, knowing that a second consecutive weekend of poor weather was about to blow through. Skipping food didn’t feel like an option today, so a cheap sub went with me to the airport, consumed with one hand while the other hand untied ropes, uncovered cabin, pitot, and fuel vents, unlocked door, and de-plugged the cowl. Finished before doing the fuel sumps.

Grabbed the headset and kneeboard, crawled in, cleared prop, primed, hit the master, turned the key, and…click. Prop moved about an inch at the tip, and that’s it. I’m not going anywhere today.

I knew this battery was getting near the end of it’s useful life (18 months is typical for a firewall-mounted battery in this climate, and this one was installed 6/2009 before a Montana trip, thus it was on borrowed time). It had been cranking somewhat sluggishly the last couple of months. No surprise that after sitting for 2 days short of 4 weeks that it’d be weak. I could have charged it for a bit and tried again, but I was just out of time and needed to get back to the office.

Removed the old battery, stopped by a local shop on my way back to work to get a fresh one, and $195 later, back to work I went. Now my workbench looks like this:

New G-25 Charging Up

So what do I have here?

  • A fresh G-25 filled and on the charger, adjusting electrolyte levels per the activation instructions that accompany it.
  • A meter for testing
  • Acid-proof paint
  • Baking Soda and Water

New aircraft batteries are delivered dry-charged so that they store well, with the accompanying electrolyte delivered in a weak solution in 2 quart bottles.

The startup process is to fill the new battery with electrolyte and equalize the level between all 6 cells (I use a drinking straw and a thumb to make fine adjustments). Install the caps loosely, rock it a little and wait 30 minutes for any trapped air to work out and heat from any reactions to settle, then adjust level again if needed. Electrolyte level will appear low, just leave it that way for now.

Next step is to charge for about an hour at a few amps, making sure the temperature doesn’t rise. As the battery charges, the electrolyte level will rise subtly with the change in specific gravity of the solution.

After this, I’ll usually charge in 1 hour cycles over the course of a day, with a final electrolyte adjustment at the end. You can either check specific gravity, or use stability of the on-charge voltage (12.6+) as an indicator of completeness of the charge. Tighten the caps, and we’re ready to go.

Meanwhile, since the battery activation process takes a little time, this is a good time to clean up the box. Any metal battery box (typically aluminum) is liable to have some corroded spots if a drop or two of electrolyte finds its way down the sides or into the bottom. I use a solution of baking soda and water to wash out the box, followed by clean water. Make sure the water flows through the vent hose OK. The baking soda neutralizes any residual acids and leaves a clean surface free of corrosion salts. If there is any exposed metal, once cleaned, it can be touched up with some acid-proof paint to protect it.

With this done, the new battery can go in. Of course, if you choose to do this as an owner maintenance item (battery replacement and service is listed as preventive maintenance under part 43 appendix A (c)(24)), it does need to be performed under the airframe and battery maintenance instructions, and the work logged before the aircraft can return to service.

With this done, I can take trips over the coming summer with a little less concern of getting stuck. When summer 2012 arrives, I’ll probably need to do this again, of course.

Maybe I can get out this week and fly. 4 weeks of an airplane sitting around is just sad…


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