Batteries are often crippled from the outset-that may be a bit of hyperbole, but it may be other causes than the battery maker responsible for problems with short lived or early failed batteries, especially with flooded cells. Look at the battery maker requirements for activation of a dry-charged battery as well as elements that an owner can do to adversely affect battery life significantly, and the failure rate and relatively short service life may be not so surprising, as I’ll elaborate below. You may find things you didn’t realize and how important they are.
As an owner you can control some of the variables, though, to get much better, more reliable and longer lived battery-not a battery that can just start your plane in warm weather, but more importantly, keep the avionics systems running with an alternator failure.
Being chemical beasts, and especially the flooded variety, are susceptible to a host of injuries that shorten their useful life. They are very temperature and voltage dependent for all aspects of function and storage as well as charging requirements.
AVweb Polls
Results of two owner polls of over 1200 owners confirm a very high level of failures in short term use as well as reduced expected service life of flooded cells as well as sealed batteries in the case of Gill.Concorde was much less so, but Concorde sells 99 percent sealed batteries, so making one on one comparisons may not be entirely fair.
Flooded batteries typically last in the area between two and three years-and three years may be pushing it for some flooded batteries that are expected to have a 30-minute reserve or emergency capacity still functional. You can get more from a sealed battery providing it’s taken care of as well as periodically checked by load testing it in some way.
We all have heard of the guy with the five-year-old Gill he brags about, but the reality is this battery likely was kept in a moderate climate such as Southern California, where starting is easy on the battery, and which minimizes temperature change wear and tear on the battery. Also, the battery is likely not to come anywhere near passing a capacity test at that age.
Batteries in this condition are nothing to brag about. They will start the plane fine usually in warm weather, but have nowhere near the safe emergency capacity they should have.
Abused From the Outset
Even the battery retailer may not be properly taking care of batteries waiting to be sold (such as storage temperatures, which we have no control over other than buy from high turnover firms with good reputations, and note the date of manufacture for your new battery.
Other issues that affect battery life are rough transportation, which can damage plates, especially on flooded batteries shipped dry charged. Improper storage temperatures of sealed batteries can be harmful if it goes on for months, and they are not topped off periodically.
There are battery manufacturer charts for the sealed battery that give proper voltages for being in placed in service from storage. Be sure your new battery falls close to this chart or it may have had improper storage conditions, such as high temperatures.
It’s generally a good idea to give a top off charge to a new sealed battery unless the voltage is nearly at full peak charge- specific limits are in the manuals. If the voltage is too low e.g. below 25.5 for a 28 volt system, Gill wants to be called before further action.
Also, a flooded battery that has had the acid added to should be charged within 8 hours, and not simply be allowed to sit uncharged, which is very bad for the battery.
The points I’m trying to make is there are a lot of variables that affect battery life besides the maker, with the owner or servicing shop being the center of potential inadvertent damage during the initializing and then improperly maintaining a flooded battery. Every aspect of proper maintenance can be found in both battery maker manuals. We do admit to sometimes being confused by the Gill manual, but you can wade through it, as is has good info that is critical to the proper life of your battery.
Proper Battery Activation
This is primarily a Gill issue since 99 percent of Concorde sales are sealed batteries, and really a big deal. These recommendations are contained in the Gill maintenance manual. The first one is using the proper electrolyte, not automotive electrolyte, which has a different specific gravity. Auto electrolyte will permanently decrease the rating.
Next comes the proper activation charge after acid is added, and Gill says “must”-the initial charge is to be with a properly controlled constant current charger, which will maximally charge the battery to its rated capacity. This is a 24- hour charge. Thereafter, constant voltage chargers may be used (the aircraft charging system is a constant voltage charger.) For sealed batteries, a constant voltage charger is OK from the initial charge.
Unfortunately, the expensive constant current charger is often ignored-especially by individuals installing the battery since all they have for a charger is the much more common constant voltage design. So right off the bat an owner may reduce the capacity and service life by not using the required charger. These cost several hundred dollars in sophisticated form, and Gill sells them. Trickle chargers of any type are not acceptable for the activation charge of a flooded battery
Another important rate, especially on the activation process is using the proper current rating for the charge, and is only in the 2-4 amp range for optimal charge. How many dry charged batteries are plunked on the shop counter with a huge constant voltage charger putting out excessive amps while the battery gets hotter and hotter. The limit is about 110 degrees case temperature before plate damage starts.
Once a dry charge battery is activated it should be placed in service. If not, it will need periodic recharging, and its service life calculation has been started.
Battery Life Stealers
There are a whole host of factors, and they’re nothing exotic. They include improper voltage settings. Some voltage regulators auto adjust for the temperature, while others don’t. Your manual will tell you, but self-adjusting voltage regulators will be over .5 volt higher in cold winter weather, such as 14.8 volts.
Many batteries are stored in the tail so they don’t have the engine to keep them warm. Such remote mount batteries need to have special attention paid to them getting the proper charge for the temperatures, including possible excess current loss in the long cable runs. The charts are in the battery maintenance manual.
Overcharging shortens the life of both sealed and flooded batteries. With the flooded you can add water if you catch it, but with sealed, overcharging results in the irreversible loss of electrolyte. Again the limits are in the manuals, but around 14.8 and 29.6 charge volts is about the practical limit for charging in 80F, whether it’s via a battery charger or the charging system.
This varies to a degree based on battery air temperature. All standard references to voltages with batteries are at 80 F. Again, proper charge rates change with temps and can vary up to a full degree on a 12 volt system, depending on the OAT of the battery. When a battery is undercharged for the temperature condition the battery develops sulfation, which a desulfating charger may or may not help, depending on the severity and length of time of sulfation.
One more issue on the battery charger is trickle or maintenance charges. It varies for flooded to sealed so check the manual. Gill has what we consider pretty high trickle voltage limits for flooded batteries- more than we have seen recommended by others, as much as 13.8 volts. If you trickle charge that high we recommend frequent checking of electrolyte, because we think such a rate is excessive and it will use electrolyte.
For a sealed battery it’s more like 13.4, but check your manual. As soon as a flooded battery’s plates are exposed to air from loss of electrolyte, the capacity for that section of plates is lost or reduced. Gill also says on-the-shelf charging must be done from 65 to 80F (or have a temperature compensated charger).
If you operate in a hot climate, that reduces life. Anything over 100F is considered life shortening for a battery.
The Forgotten Master Switch
Many have forgotten the master switch on and run the battery absolutely flat-down to or below 10 volts, and it may have remained there for some time. Both of these issues are very damaging to the battery, generally resulting in permanent capacity and battery life loss. Gill says any battery in this discharged state over 15 days is a “gonner” if the temps were in the 30 to 80F range. Always recharge quickly.The longer you wait and the deeper the discharge the greater irreversible sulfation starts.
There is a specific procedure for trying to recover such a badly discharged battery. Once again it results in the need to use a constant current charger-or Gill’s special combo constant current constant voltage charger. The Gill manual has all the details, levels and diagrams of the charge profile.
Capacity Checks
Both Gill and Concorde are about the same for these checks but verify the current status requirements from the latest applicable manual, as they have changed over the years. Typically, the capacity test is done at the end of year one and thereafter every 6 months, plus or minus one month. This is to verify the battery still has the capacity to run emergency avionics with a charging system failure for a period of 30 minutes. The battery passes if it meets 80 percent of the one-hour rating of the battery.
While this test may be ignored by many, not doing some form of capacity test periodically (more as the battery ages) should be limited to VFR fliers who stay in the pattern and carry a good handheld radio in our view. See the previous article for sample (but unofficial load tests).
Jump Starts
The simple answer is both Concorde, Gill and LPM say don’t do it with a dead battery since for the period of one to 3 hours, even a battery in good shape will not sustain avionics with an alternator failure and therefore is technically not airworthy.
Get the battery charged properly. Also, you may have no idea why the battery went flat. Further investigation of the airplane may be prudent as well to verify the cause.
Sample Good and Bad Battery
Old 24-volt Flooded Gill Battery
1. Resting voltage after long flight: 25 volts
2. Check with landing light load (10 amps, 250 watts) for 2 minutes.
3. With load, battery was at 20.8 volts.
4. Immediately after load removal: 23 volts.
5. After a 2-hour recovery, voltage was 23.8 volts.
The battery failed to start the plane reliably.
New Concorde AGM; same test.
1. After one-hour rest from initial charge: 26.1 volts.
2. Check with landing light 250 (10 amps) watts for 2 minutes.
3. With load in place: 24.8 volts.
4. After removing load: 25.6 volts.
5. After a 2 hour recovery: 25.9 volts.
The differences don’t seem all that mcuch, but in the battery world they are significant.
If you start record keeping with a new battery, you can track changes and easily tell when the battery is getting weak.
This article originally appeared in the November 2012 issue of Light Plane MaintenanceMagazine.
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