The International Cessna^® 170 Association

To all,
Spent a couple of hours on a saturday recently with the Gill Battery rep in a class. He drove down to Yuma, AZ for problems with a battery charger and ended up giving us a class on Gill Batteries and I thought I'd pass on some of that infomation:
Aircraft batteries 12V at rest (10-24hrs after last charge) should be 12.5V min to 13.0V max
Specific gravity 1.275- 1.300 Cell Voltage 2.1666V
Charge 14.1V-14.3V (For what it's worth, 85C only charges at 13.6V)
Gill batteries can be charged up to 10amps with no adverse effects.
I recently bought a new electronic charger at Wally World for $27.88 It charges 6 &12V batteries at 2-4-6 amps. Made by Schaumberg.
After flying and resting the battery for 14 hours my battery read 12.35V. Hooked up new charger and after it completes charging (gives you that indication on the front using led's) and resting 12hrs until next day. Battery voltage was 12.65V
The reason to give you all the specifics is this. Aircraft batteries sulfinate if below 12.5V at rest. Sulfination costs you in battery life. Mine seem to last appx 2 years. The Gill rep reports batteries lasting 5-6 years. At $100+ bucks per battery, I'm gonna tweak my mechanicial voltage regulator up to 14.1-14.3V at cruise.
More info can be found at:
http://gillbatteries.com/maintenance.cfm Go down to Technical guides then click on Dry Charged batteries. Check temperature chart on page 7 table 2. Also info on other aircraft batteries.
Very usefull information.
Good luck and don't forget what your feet are for.

Float chargers can be used to keep batteries charged over long periods of rest.

So-called "pulse" chargers are promoted as being especially helpful in maintaining and restoring batteries that suffer from sulphation.

I'm gonna tweak my mechanicial voltage regulator up to 14.1-14.3V at cruise.

Exactly what I do with my C-140 and 35amp Gill. I hook up a voltage meter under the dash to check my adjustment while in cruise. (0-200A Cont., Ford 60amp alternator, mechanical VR that I always wondered what would cross reference as it is made by Ford/Delco -Cessna PNC611001-0102)

This week during my annual my battery showed only 36% during a capacity test. I recharged in voltage mode, then repeated the load test. 54%. Repeat. 63%. Then I recharged using constant 2A for 9 hours. By the end the charger output was 16.1V, the battery was bubbling, and all cells were up to 1.275 SG. After charging I did another capacity test, and the result was 91%! Never throw a battery away until you've tried the constant current charge, also known as an "equalization" charge.

I have been charging, desulphating, equalizing, checking, and servicing my brother's Gill battery for over 12 years. It has shown no signs of weakness until this year. I told him it's time for a new one

What's your process for equalization? I ran 8 hours at 2A on an 18AH battery, which is less than some recommendations I've read, but when all the cells hit SG 1.275 I figured that was good enough. Gill recommends 10-12 hours at 3A, but I was afraid to cook the battery. Maybe I could have gotten better than 91%.

How do you desulphate? Is your process something you do annually or as-needed?

DaveF wrote:What's your process for equalization? I ran 8 hours at 2A on an 18AH battery, which is less than some recommendations I've read, but when all the cells hit SG 1.275 I figured that was good enough. Gill recommends 10-12 hours at 3A, but I was afraid to cook the battery. Maybe I could have gotten better than 91%.

How do you desulphate? Is your process something you do annually or as-needed?

We pay attention to the amp and volt meters frequently, and the battery water level "every now and then".
In the winter, we remove the battery and take it home when it gets really cold or when it will be a while between flights.
The first time the battery comes out for a week or so each winter is when I take it home and go to work on it.
This is what I do:
Clean the case and caps.
Make sure the plates are covered with water, no need to top off yet.
Give the battery a normal charge.
Let it sit for a day.
Make sure the plates are covered with water, no need to top off yet.
Check the battery voltage and write down the value for future reference.
Check the SG and write down each cell's value for future reference.
Do a load test. Write down the reading for future reference.
Give the battery another normal charge.
Make sure the plates are covered with water, no need to top off yet.
Give the battery an equalization charge. A charger with this option will charge at around 16 volts and limited amps for a few hours.
Let the battery sit for a day.
Make sure the plates are covered with water, no need to top off yet.
Connect the battery to the desulfator for a few days to a week, depending on available down time. Look in on the battery each day to check that the plates are still covered.
Give the battery a normal charge.
Let it sit for a day.
Check the SG and look for improved and more equal readings, compared to the previous ckeck.
Do a load test and look for and improved reading, compared to the previous check.
Make sure the plates are covered with water, top off to proper level if needed.
Give the battery another normal charge.
Let it sit for a few hours, and check the SG again.
Clean the case and caps again.
The battery is good for another year.

The above is not advice from an expert. It's just a description of how I have been treating the battery in my brother's 170A for the last 12 years.
It seems like a lot to do, but it takes only a few minutes each time I visit the battery. After the first 4 or 5 years, it became a fun challenge to see just how long it would last.
This year it showed its first signs of diminished capacity to crank the engine in cooler weather. I figured he got his money's worth from this battery, and advised him to get a new one. I would hate to have it fail in the air, or leave him stranded somewhere. (I don't think he would want to hand prop it.)
If you see anything in the above process that may have been bad for the battery, feel free to point it out. Maybe we can get 15 years out of the next one.

Except for the desulfator, that looks a lot like what I did. How long and what current do you use for the equalization?

You guys have me wondering. Does being in a "Hot" climate affect battery life? My current battery has been in use since '98' and I had one in the other plane that lasted over 10 years after I patched a crack in one cell (as directed by a fellow who rebuilt batteries). No special maintenance other than cleaning and adding water as needed during routine maintenance. So why do others have such short battery life? Around here we seldom see tempatures above 80 F and then for only a few hours at a time. So that is why I am wondering if temperature has a effect on battery life.

High temperature is definitely bad for batteries. The self-discharge rate is higher and all the unwanted internal chemical reactions occur faster. I know guys in Tucson who are happy to get three years out of a battery.