By Lisa Turner, EAA Lifetime 509911
This piece originally ran in Lisa’s Airworthy column in the August 2020 issue of EAA Sport Aviation magazine.
“I’ll pick you up in front of the post office,” my Uncle Bob said.
I had stayed after school for choir practice and was getting on the late school bus run. It had started to snow — and it was coming down fast. I always felt a surge of excitement seeing snow fall, but I felt a twinge of worry as I got on the bus. Roads were slick, and the air was bitingly cold.
The bus dropped me off. I shivered and wrapped my scarf tighter around my neck as I waited for the ride home. Then I saw the Chevy station wagon come down the road. Bob stopped in front of me and turned the car off.
“I have to run across the street to the store,” he said. “I’ll be right back.”
I got in the car and put my book bag down on the bench seat. The snow quickly covered the windshield. We lived in a rural part of New York, so rural that the little town center, where we were now, consisted of a post office and a general store. That was it.
Bob returned to the car and got in. He turned the key in the ignition. Nothing happened. Perplexed, he tried it again. All was still as the snow swirled outside and clouded the windows.
Bob shook his head and turned to me.
“I’ll go back to the store and see if there’s anyone who could help us out,” he said. “I am guessing that the battery or starter has failed.”
In that moment I thought about how great it would be to know how cars worked. I could simply jump out and magically fix it.
Bob returned several minutes later with the store owner. They popped the hood to the big beast and looked at the battery and the connections. Then, the store owner pulled a hammer out of a small toolbox and smacked the tops of the connections on the battery. I saw them talking. Bob got back in the car and turned the key. The engine fired right up. He smiled and shook his head again, shouting out, “Thanks, Gil!”
As we pulled out onto the road in deep snow, I decided I would learn how to fix cars so I too could pull a hammer out of a toolbox and whack something with it.
I’m sure you have some good battery stories. We all do. When a battery strands us or interrupts our plans, it’s no fun at all.
Rather than delving deeply into battery chemistry or history, I’d like to present practical tips for not getting stranded because of a dead battery. I can’t promise that these tips will prevent battery problems for you, but they should minimize them.
Most of us have lead-acid battery technology in our airplanes. Wet cell, or “flooded,” battery purchases have shifted, for good reason, to sealed boxes where we don’t have to mess with electrolyte levels. The new tech on the block — lithium — is overtaking lead-acid tech on a fast-rising curve.
Lead-acid (“wet cell”) batteries. We’re used to these batteries because they’ve been around forever. At least, it feels that way. Our tractors, trucks, cars, and motorcycles have had this type of battery for years. When you bought a new one, you would fill it with electrolyte and charge it. Maintenance consisted of checking the electrolyte level and keeping it charged.
The aircraft version of the wet cell battery is different from the automotive cousin. The aircraft versions are built lighter and smaller and have a more concentrated electrolyte mix. They are more sensitive to voltage regulation, both under- and over-regulation, than the automotive versions. Wet cell batteries will lose 25 percent of their charge every 30 days at 77 degrees and every 15 days at 95 degrees. Freezing a wet cell battery is likely to kill it.
The only real advantage of the wet cell lead-acid battery is that it usually gives you some warning before dying completely. The disadvantages are multiple, including sulfation and corrosion (where you employ the hammer cure), temperature sensitivity, needing a battery box and venting, and being heavy.
Recombinant gas, valve-regulated lead-acid (VRLA), and absorbed glass mat (AGM) batteries. We commonly call them “sealed” batteries or SLA for sealed lead-acid. These batteries have displaced wet cell as the go-to battery for nearly all of our powered equipment starting requirements. While the chemistry is the same as a wet cell battery (lead-acid), the fact that they are sealed takes a lot of the work out of the maintenance and adds a measure of safety. AGM batteries use a fireproof glass mat separator between the positive and negative plates. The glass mat is saturated with electrolyte, and the mat’s porosity allows the hydrogen and oxygen to recombine. VRLA batteries are designed to recombine the gases generated during the charge-discharge process and to maintain electrolyte throughout the life span of the battery. “Sealed” is actually a misnomer as these batteries do have vents. Sealed batteries are lighter than wet cell and can eliminate the need for a battery box. They give little warning when they fail, but they self-discharge at a third of the rate of wet cell batteries.
Lithium-ion (li-ion) and lithium iron phosphate (LFP) batteries. I know what you are thinking — exploding cellphones. But no, the technology has moved fast on improvements. Now there are a host of safeguards that surround these new batteries to minimize thermal runaways. There are so many advantages to lithium combination technology that there are almost no downsides — except price, which is becoming more reasonable by the year.
Lithium technology batteries won’t corrode, sulfate, freeze, or boil. They are 80 percent lighter than the typical wet cell battery. Self-contained in the accompanying electronics is charging protection, cell balancing, and thermal protection. Charging cycles are 10 times that of lead-acid types. The very few disadvantages include cost, some limits due to FAA approvals, and when one of these batteries dies, it spins in fast. We’ve moved into an electronic glass panel world in newer aircraft, and the lithium batteries are perfect for it. If you own a certified aircraft rather than an experimental, then you’ll need to check with the battery manufacturer and FAA on TSO/STC status. The technology is moving fast, which is a good thing.
Battery Tips
Know what you have. Exactly what type and model battery do you have? How old is it? Is it the same as the battery specified in your aircraft manual? You’d be surprised at what people use to replace a battery. Yes, in an airplane.
Do you have a folder or a section in your manual for your current battery? If not, it’s a good idea, especially on the experimental side where information accompanying the aircraft is often lacking. Keep the information up to date.
Think twice about propping the airplane or getting a jump-start on a dead battery. Why? Are you confident that all the battery needs is an hour of flying to be back to its dependable self? The alternator will be dumping current into the discharged battery — not the best practice for battery longevity. Why tempt a potential electrical failure in the air? The mags will keep the engine running, but an electrical failure can be confusing. If you don’t absolutely have to be somewhere else fast, it’s better to troubleshoot the battery failure and get it corrected.
Keep batteries charged with the right charger. Following this one single piece of advice can double or even triple your battery’s life span. Wouldn’t that be nice? To do this, you want to cycle the battery — go fly regularly and keep it fully charged when you’re not flying. That’s easy to say and hard to do. If you’re not flying regularly, the battery is easy to forget.
A battery that remains in a depleted state of charge for a long time forms lead sulfate that eventually hardens and crystallizes on the plates to the point that it can’t be converted back into its original components of lead oxide, pure lead and sulfuric acid — no matter how long the battery is left on a charger.
I see a lot of owners who use automotive battery chargers and trickle chargers with their aircraft batteries. This is a mistake that will hasten the replacement day for your battery. Why? Because automotive chargers are designed to charge batteries faster (they are set at a higher output voltage) and are not as finely regulated as are aircraft battery chargers (think over-voltage). Yes, the aircraft chargers are more expensive, but an aviation calibrated smart charger (like the BatteryMINDer) will pay for itself over time by extending the life of your aircraft battery. Aviation float (trickle) chargers are ideal and you can even get one with solar charging.
Lithium (LFP) batteries have a much higher energy density, and they charge quickly. You should use the manufacturer recommended charger for these batteries, which includes a battery management electronics board.
Inspections. Although the annual or condition inspection should include an assessment of battery health along with a load or capacity test, this detail is often overlooked even once a year. Top-quality capacity testers are expensive, so you may not feel like investing in one. Find a shop with a reliable tester and check your battery several times a year. You can also do, or ask your A&P to do, a load test by turning on devices with known draws and seeing how the battery holds up. Cranking the engine or looking at the voltmeter will not reveal much about the battery condition, only that it’s working right now.
Your routine inspections should include a close examination of connections. After checking the posts, follow them to other devices, checking for corrosion, chafing, and loose connections. If you’re using a wet cell battery, check for sulfation and dirt on the posts and clean up with a baking soda/water paste, which will neutralize the acid. Ensure that leads are fully protected so that tools being used in the vicinity won’t short the electrical connections.
Consider a backup battery. Redundancy is a good thing.If you are flying an experimental with an all-electronic panel and dual electronic ignition, a backup battery is more than a good idea. A backup battery should also be installed with your electronic flight instrument system circuit with monitoring electronics. The type and the associated smart electronics will depend on what system you have.
Electronic ignition systems can be non-self-powered (E-Mags) or self-powered (P-Mags), but they both still require a means of energizing the starting circuit.
On certified aircraft, traditional mags still rule, so you have less choice. If you want to upgrade, you can check for applicable STCs from the FAA at www.FAA.gov.
Safety. When you’re working around batteries, especially wet cell lead-acid types, keep the following tips in mind.
- Assume that battery terminals are always “hot.” If they are not covered and a tool makes contact with both terminals at the same time, you will have a short circuit leading to snaps and sparks, possible fire, and possible lead-acid spray, or even an explosion. When working around the battery, make sure you’ve got at least the positive terminal covered with a thick rubber boot.
- Battery acid is highly corrosive, so gloves and safety glasses should be worn any time you are charging or servicing a wet cell battery.
- Remove the battery from the aircraft if you can when you charge it and when you service it. Special connectors are available for float chargers attached to installed batteries.
- If you have a battery box, check drains and vents when you remove the battery. Wear gloves to protect skin and when cleaning the battery case and the box.
The little ones. Don’t forget all the other “little” batteries on your airplane. From the emergency locator transmitter (ELT) to the backup radio, list out everything you have in your aircraft manual and the anticipated replacement dates. Some devices, like the ELT, will have specific requirements. You remember the ELT regulations, right? According to 14 CFR Part 91.207, “Batteries must be replaced after one hour of cumulative use or when 50 percent of their usable life has expired. The expiration date for replacing (or recharging) the batteries must be legibly marked on the outside of the transmitter and entered in the aircraft maintenance record. Must be inspected every 12 calendar months.”
For more resources about aircraft batteries, see www.EAA.org/extras, and may the power be with you — always.
Lisa Turner, EAA Lifetime 509911, is a manufacturing engineer, A&P, EAA technical counselor and flight advisor, and former DAR. She built and flew a Pulsar XP and Kolb Mark III and is researching her next homebuilt project. Lisa’s third book, Dream Take Flight, details her Pulsar flying adventures and life lessons. Write Lisa at Lisa@DreamTakeFlight.com and learn more at https://DreamTakeFlight.com. For more from Lisa, see her Airworthy column each month in EAA Sport Aviation.