Battery dead?

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supertrooper2002

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supertrooper2002
I have a 172RG with a Gill-243 battery in it that's ~2 yrs old. The last 2 times I went to start it the meter read 20-22v and it couldn't turn the prop. I had a friend give me a charge and it ran fine. Couple of questions.
-Is this battery dead?
-Is this a maintenance issues (ie top off fluid, get a battery tender, etc)?
 
Gill's suck. Where/how are you measuring voltage? At the battery with a multimeter?

What's the environment the plane is kept in? Hot? Cold? Hangar? What's the health of the charging system? Cables, alternator, connections, ground?
 
How often is it flying and for how long? What's the voltage at when running? When was the last time the battery was serviced? The battery could be OK but just needs charging and servicing, it could have a cell that is going bad, etc, it's hard to say. I would suggest getting it serviced and capacity checked IAW the CMM for the battery to give you an idea what kind of shape it's in.
 
Ryan Klems wrote above:
"I would suggest getting it serviced and capacity checked IAW the CMM for the battery to give you an idea what kind of shape it's in."

Do this for a good result, or rely on the advice of SGOTI, the choice is yours...

-Skip
 
supertrooper2002 said:
I have a 172RG with a Gill-243 battery in it that's ~2 yrs old. The last 2 times I went to start it the meter read 20-22v and it couldn't turn the prop. I had a friend give me a charge and it ran fine. Couple of questions.
-Is this battery dead?
-Is this a maintenance issues (ie top off fluid, get a battery tender, etc)?
Click to expand...
Hard to say if the battery needs replaced because you don’t include enough information.

Like how often you check the electrolyte levels and service the battery. This needs to be done about every 80 hours. If a cell has plates exposed, usually the cell closest the positive terminal on a G243, you are on borrowed time. Hopefully your friend checked this before he charged it.
 
supertrooper2002 said:
-Is this battery dead?
-Is this a maintenance issues (ie top off fluid, get a battery tender, etc)?
Click to expand...
Unless you have someone perform some basic troubleshooting, like voltage drops, resistance checks, etc, and review those results its anyone's guess what it could be.
 
supertrooper2002 said:
I have a 172RG with a Gill-243 battery in it that's ~2 yrs old. The last 2 times I went to start it the meter read 20-22v and it couldn't turn the prop. I had a friend give me a charge and it ran fine. Couple of questions.
-Is this battery dead?
-Is this a maintenance issues (ie top off fluid, get a battery tender, etc)?
Click to expand...
Follow this Skytec troubleshooting guide to see where the problem actually is

Aircraft Starter Performance Issues | Sky-Tec

Basic aircraft starter testing is the place to start when your parts aren’t performing as well as they should.
skytec.aero skytec.aero
 
Agree with the others. Don't get out the parts shotgun just yet. Have the battery charged and load tested. Have the charging system tested to see if in fact the alternator and regulator are working correctly. Low battery voltage does tend to indicate a battery concern but it may just be that it's not being recharged in flight. It could be a faulty connection or maybe (?) a faulty starter. Gotta do some troubleshooting ...
 
Racerx said:
Gill's suck. Where/how are you measuring voltage? At the battery with a multimeter?

What's the environment the plane is kept in? Hot? Cold? Hangar? What's the health of the charging system? Cables, alternator, connections, ground?
Click to expand...
- Voltage is just from the dashboard gauge (Davtron gauge - not at the battery)
- Plane spent the winter in a non-climate controlled hangar so it got very cold (ie 10-15F for a couple weeks in Jan & Feb)
 
Ryan Klems said:
How often is it flying and for how long? What's the voltage at when running? When was the last time the battery was serviced? The battery could be OK but just needs charging and servicing, it could have a cell that is going bad, etc, it's hard to say. I would suggest getting it serviced and capacity checked IAW the CMM for the battery to give you an idea what kind of shape it's in.
Click to expand...
- Hasn't flown since November 2025 but has been started 1-2x / month
- Not sure on volts when running - probably 24-28 range
- Battery was serviced August / September 2025 (more fluid added)
 
That's a long time to be sitting and not flown.
Starting it on the ground and not flying it is surely not doing the battery and engine any favors.
IMO if it sits that much then put a battery charger on it for day or two at a time instead starting it and not flying it.
I have the same battery and mine last 5-6 years, but I fly a lot.
 
If you have the misfortune to be outside, do this:

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Buy BatteryMINDer SCC1224-20 Solar Battery Charger Maintainer Desulfator with 20W Solar Panel 12V/24V Dual Voltage for All Lead-Acid Batteries: Battery Chargers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com

Solar panel on the glareshield, cabling out the left door seal and wiring through the oil door.
Likely your battery is all sulfated up. And this is cheap considering that your battery is a $700 model. Yeowch!

Battery backed up sump pumps all live on desulfator/chargers. That should tell you something.
(I have a 2014 Concord AXC-35 that lives on a VDC desulfator in the garage. Last year it cranked the bejeesus out of an Arrow which had a neglected battery!).
 
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supertrooper2002 said:
- Hasn't flown since November 2025 but has been started 1-2x / month
- Not sure on volts when running - probably 24-28 range
- Battery was serviced August / September 2025 (more fluid added)
Click to expand...
My guess is that this is the problem. Starting it isn't the same as flying it for long periods of time, to give the alternator time to throw some juice back into the battery. If it were me, I'd charge it up to full capacity and then load check IAW Gill's procedures. If it load checks OK, I'd put a maintainer on it to keep it topped off between starts.
 
supertrooper2002 said:
- Hasn't flown since November 2025 but has been started 1-2x / month
Click to expand...
If you keep that up you'll be buying a new engine. The corrosion from ground runs is terrible.
supertrooper2002 said:
- Battery was serviced August / September 2025 (more fluid added)
Click to expand...
Topping up the electrolyte must be done in accordance with the battery owner's manual. If you fill it to the split ring while it's just sitting on the bench or in the airplane, it will be overfilled. That electrolyte expands considerably due to heat and bubbles in it, and it will overflow and end up "low" again. Keeping adding water while losing acid and you eventually have a truly dead battery.

The battery is supposed to be topped up while it is on charge and actively bubbling. I never topped it to more than halfway between the plates and split ring if it wasn't on charge.
 
Medium sits without a tender of some type is borderline abusive behavior, in my book. Did we talk temps yet? Like engine oil temp when trying to crank? I don’t need to leave a tender on 24/7, but could. I mostly just do a ‘top off’ every 6-8 weeks or so.
 
20-22V (10-11V in 12 V format) is a completely discharged battery. If it stays in that state for long, it will become irreversibly sulfated. Get a Concorde AGM battery and don't look back. AGM batteries have low self discharge rates compared to flooded batteries. My Concordes will go 4 months without charging in winter with no issues. If you must, get a proper smart battery tender, but I've never used one with AGM batteries. I gave up on Gill batteries decades ago.
 
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I'm using a Concorde RG-35A, an AGM battery like @chemgeek recommends. https://batterymanagement.concordebattery.com/BatteryDocs/Brochures/RG-35A.pdf When I did my engine overhaul last year, the battery was out of the plane from Nov 2024 until June 2025. I kept the battery on a shelf with a BatteryMinder connected. https://www.aircraftspruce.com/catalog/elpages/batteryminder_11-19244.php

When I put the battery back into the plane, it worked fine. I've put about 50 hours on it since with no issues.

Were I you, I'd get a BatteryMinder. If a load test shows your battery is still okay, continue with it for now but keep it on the BatteryMinder between flights. When the time comes to replace the battery, switch to a Concorde. Continue using the BatteryMinder whenever practical for a little extra insurance.
 
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