NOTE: Detailed information regarding Concorde RG Series aircraft batteries is documented in the RG Series Owner/Operator Manual (Document 5-0324) and the applicable Component Maintenance Manual (CMM). Supplemental information is provided below in the format of Q&As.

If the battery is able to pass above 90% without a conditioning charge, then you can switch back to original frequency of capacity checks. An example of this would be a turbine starting battery that tested at 88% and 3 months later was tested again and came in at 91%. The next capacity check would be 6 months later. However, if a battery fails the capacity test (i.e., capacity tests below 85%) and a conditioning charge is required to pass, then the increased frequency must continue to be used for the life of the battery. This aspect is covered in Note (2) under the Conditioning Charge Procedure in the applicable CMM.

The recommended torque on hold-down bar fasteners is 10-15 inch-pounds. Note that to ensure the fasteners do not come loose, some type of locking method is required (e.g., safety wire, lock washers self-locking nut plates, etc.). If self-locking nut plates are used, the torque may need to exceed 15 inch-pounds to overcome the nut plate resistance. In this case, do not allow the ends of the hold-down bar to deflect more than 1/8 inch from the center line.

No, as long as both batteries have the same nominal voltage and the charging source is constant voltage (i.e., DC bus or alternator). If the charging source is a constant current charger, then parallel charging should be avoided. Note that the two batteries do not have to have the same capacity rating because each battery will self-regulate the charging current. Also, it may take longer to charge both batteries due to the higher combined capacity rating. For further reading on this subject, see: http://www.aeroelectric.com/articles/bat_iso2.pdf.

The short answer is “No”. Even though a capacity test discharges the battery to 100% depth of discharge (DOD), this procedure does not damage the battery or impact the battery’s service life. Concorde has performed cycle life testing of aircraft batteries to 100% DOD (i.e., same DOD as a capacity test) and the number of cycles to reach end of life far exceeds the number of capacity tests that any battery would experience during its service life. For example, even if a battery was capacity tested every 3 months for 8 years (32 total cycles), there would be minimal loss of capacity due to the capacity testing itself.

As defined in FAA Advisory Circular AC 43.13-2B, an aircraft battery is considered airworthy if it can provide at least 80% of its C1 capacity. This 80% capacity level is typically used by airframe manufacturers as the basis for certifying minimum run time (typically 30 or 60 minutes) when the battery is powering the electrical system during emergency conditions. Concorde’s recommendation for return to service threshold is 85% capacity. The 5% margin provides a buffer to assure that the battery will not fall below the minimum airworthiness condition before the next capacity check. Other battery manufacturers typically use 80% as the threshold for return to service. This threshold provides no buffer and creates a much greater risk that batteries will fall below the minimum airworthiness condition before the next capacity check. Thus, Concorde’s threshold of 85% gives the owner/operator extra assurance that the minimum reserve capacity is available in the case of an emergency condition where battery power is required for safe landing

First, let’s compare the actual capacity check intervals of Concorde and two other manufacturers (Teledyne and Enersys). Capacity check intervals from Concorde Component Maintenance Manuals (CMMs) are summarized in the following table:

Battery Application First Check

Subsequent Checks

Battery @ 91 % or more

Subsequent Checks

Battery @ 85-90%
Starting Turbine Engines(1) 12 months/1000 hours 6 months/500 hours 3 months/250 hours
Starting Piston Engines(1) 12 months/1000 hours 12 months/1000 hours 6 months/500 hours
Emergency Back-up(2) 12 months/1000 hours 12 months/1000 hours 6 months/500 hours

Capacity check intervals from Teledyne CMMs are summarized in the following table:

Battery Application First Check Subsequent Checks
Generic(3) 18 months/1800 hours 9 months/900 hours
Bell Helicopters(4) 11 months/1200 hours 6 months/600 hours
Cessna Mustang & 7243-16T Battery(5) 12 months/900 hours 6 months/450 hours
Embraer Phenom 100/300(6) 12 months 6 months
Gulfstream 280(7) 11 months/1200 hours 6 months/600 hours

Capacity check intervals from Enersys CMM are summarized in the following table:

Battery Application First Check

Subsequent Checks

Battery @ 91 % or more

Subsequent Checks

Battery @ 85-90%
Generic(8) 18 months/4500 hours 6 months/1500 hours 3 months/750 hours
Bell 206(8)
Jetstream 41(8)
Saab 340(8)
12 months/3000 hours 6 months/1500 hours 3 months/750 hours

(1) Concorde Battery Corporation, 5-0171 Rev Q
(2) Concorde Battery Corporation, 5-0167 Rev E
(3) Teledyne Battery Products Q01-1101 Rev. K
(4) Teledyne Battery Products Q01-2001 Rev. C
(5) Teledyne Battery Products Q01-3000 Rev. NC
(6) Teledyne Battery Products Q01-4000 Rev. J
(7) Teledyne Battery Products Q01-2002 Rev. F
(8) EnerSys Energy Products 2602-0018 Rev. 5

As seen in the above tables, the main difference is that Concorde’s first check is at 12 months whereas the other manufacturer’s first check is at 18 months for “generic” applications. However, the other manufacturers modify the first check for specific applications and in all cases, it matches Concorde’s first check very closely (11-12 months). So, the main difference is the first check interval for “generic” applications. The other manufacturers start at 18 months, and then shorten the interval once historical data is available. Concorde starts at 12 months, and then allows the interval to be adjusted up or down once historical data is available. Specifically, Concorde has the following note the CMMs: NOTE: THE CAPACITY CHECK INTERVALS SPECIFIED ABOVE ARE GENERAL RECOMMENDATIONS SUITABLE FOR MOST APPLICATIONS. THE INTERVALS MAY BE ADJUSTED FOR A SPECIFIC AIRCRAFT OR FLEET ONCE THE AVERAGE BATTERY LIFE IS ESTABLISHED. Examples of how to adjust the capacity check intervals are provided in Concorde’s Technical Bulletin 14, Capacity Check Interval Adjustments. A full copy of the Technical Bulletin is available at: https://batterymanagement.concordebattery.com/BatteryDocs/TB14.pdf.

So why doesn’t Concorde change its first check interval to 18 months for “generic” applications? The answer is that Concorde batteries are used in a wide variety of aircraft applications, with unknown duty cycles and operating conditions, some of which may cause the capacity to decline below the minimum airworthiness if the first check was at 18 months. Having the first check at 12 months provides a better guarantee that the battery will stay above the minimum airworthiness condition, even when used in extreme applications.

Concorde has been manufacturing RG Series aircraft batteries for over 30 years, providing excellent performance, reliability and life. Applications include turbine engine starting, APU starting, reciprocation engine stating, and back-up power. Over 150 models are available to choose from and detailed specifications of each model are listed on our website for easy reference. Concorde RG Series aircraft batteries consistently outperform competitors’ products when independent comparisons and surveys are reported. With this long history and wide variety of successful applications, customers are assured that RG Series aircraft batteries have proven themselves over and over again.

RG stands for Recombinant Gas and AGM stands for Absorbed Glass Mat. The AGM is the type of separator used in all RG Series aircraft batteries. The AGM separator allows oxygen gas generated from the positive plates to diffuse through its pores to the negative plates and recombine with electrons to form water. This recombination cycle minimizes outgassing from the batteries so that the electrolyte never needs to be replenished or topped up.

Flooded lead-acid batteries have excess acid in each cell that prevents recombination of gas during charge. The gases generated during charge (hydrogen and oxygen) must be vented from the cell to avoid pressure build-up. This gas generation depletes the electrolyte of water so periodic replenishment of the water is required. AGM batteries have a “starved” electrolyte condition in each cell that allows recombination of gas during charge. Therefore, replenishing the electrolyte with water is not required. Other differences: Flooded batteries emit corrosive acid fumes, are more susceptible to permanent damage when frozen, and have a higher rate of self-discharge compared to AGM batteries.

During storage, charging, or discharging, RG Series batteries will release a small amount of hydrogen gas. The hydrogen gas must be diluted to prevent the possibility of ignition and/or explosion. Because the rate of hydrogen emission is very low, only minimal airflow is needed to dilute the hydrogen to safe levels. Most aircraft battery compartments have sufficient natural airflow that a separate air ventilation system is unnecessary. When the natural airflow is not sufficient, RG Series batteries are available with vent tubes for connection to air ventilation systems. Contact Concorde if further assistance is needed to determine the airflow requirements.

The rate of self-discharge of RG Series batteries is only 2-3% per month at room temperature. Maintenance charging is only recommended if your aircraft does not accumulate many flight hours per month, flies short legs that do not allow the battery to fully recharge, or has a parasitic load when the master power switch is turned off. In these cases, the battery should be periodically boost charged in accordance with the CMM. Alternatively, an approved maintenance charger may be used for supplemental charging. When a maintenance charger is used, 24/7 charging is not normally recommended and may actually reduce the battery’s life. A weekly or a monthly charge for 24-48 hours is normally sufficient when using a maintenance charger.

For more information please review Technical Bulletin 15.

Maintenance chargers should include a 3-stage charging profile that includes a bulk stage (current limited), absorb stage, and float stage. The recommended voltage settings at room temperature are 14.125 ± 0.125 (28.25 ± 0.25V for 24-volt batteries) in bulk and absorb stages and 13.2-13.4V (26.4-26.8V for 24-volt batteries) in float stage. These voltage settings should be compensated for using a temperature coefficient of -0.024V/°C (-0.048V/°C for 24-volt batteries). Concorde has tested various models of maintenance chargers and recommends the use of BatteryMinder S5 models (i.e., 128CEC1-AA-S5 for 12-volt batteries and 244CEC1-AA-S5 for 24-volt batteries). If other makes/models are contemplated, contact Concorde for our recommendation.

RG Series aircraft batteries contain a pressure relief valve (PRV) that prevents excessive pressure buildup when the battery is being charged, and automatically reseals once the pressure is released. A slight bulge in the battery container (convex end walls) can appear when the internal pressure is above the surrounding atmospheric pressure but not enough to open the PRV. Alternatively, the end walls can flex inward (concave end walls) when the internal pressure is less than surrounding atmospheric pressure. Both of these conditions are normal and do not affect the battery’s operation.

Battery life depends on how often and how long you fly, ground ambient and operational temperatures, and the duty cycle it performs when doing its intended function. An approximate range is 1-5 years for batteries used to start turbine engine, 3-6 years for batteries used to start reciprocating engines, and 5-15 years for emergency back-up batteries.

Concorde has a mature manufacturing process and has made no changes that would adversely affect the life of the battery. There are many factors that affect the battery life. Some questions to ask are as follows: Are you flying your aircraft more frequently or less frequently? Have the ambient temperature conditions been higher or colder due to a change of location? Are the storage temperature conditions different? Are you keeping battery fully charged when not flying? Have you checked your voltage regulator to make sure they are set correctly? Do you have a parasitic load (drain) that is discharging your battery when the aircraft is not in use? Did you leave the master switch on too long such that the battery became deeply discharged? Have you made any changes or upgrades to your aircraft?

Refer to the applicable CMM for instructions for continued airworthiness. In addition, if the engine starting becomes sluggish even with a fully charged battery, and the starter checks out OK, it is probably time to replace the battery.

Do a conditioning charge in accordance with the CMM listed on Concorde’s website that applies to your battery. Typically, the applicable CMM is Document No. 5-0171. This conditioning charge may restore your battery capacity. If it doesn't, then you will have to replace your battery.

Recharge the battery as soon as possible to prevent permanent sulfation. If it has only been deeply discharged for 24 hours or less, do a normal constant potential charge per the CMM and the battery will not need a capacity test. If it has been longer than 24 hours, check the open circuit voltage (OCV). If the OCV is 20 volts or higher (10 volts or higher for a 12-volt battery), do a conditioning charger per the CMM, followed by a capacity test. If the OCV is less than 20 volts (10 volts for a 12-volt battery), do a deep discharge recovery per the CMM, followed by a capacity test.

If the open circuit voltage (OCV) is below 25.0 volts (below 12.5 volts for a 12-volt battery), a capacity test should be performed to see if it is still good. Refer to the Storage section of the CMM (pages 1501 -1502). Note: If the OCV is 25.0 volts or higher (12.5 volts or higher for a 12-volt battery), the capacity test is optional.

The Ipp and Ipr rating is listed on Concorde’s website for all engine starting batteries. Ipp is discharge current at time = 0.3 seconds when a battery is discharged at half of the nominal voltage (6 volts for a 12-volts battery and 12 volts for a 24-volt battery) Similarly, Ipr is discharge current at time = 15 seconds when a battery is discharged at half of the nominal voltage.

Cold cranking amps (CCA) is a rating for automotive batteries. The CCA rating is the current a battery can supply for 30 seconds at -18°C with a minimum voltage of 7.2 volts for a 12 volt battery and 14.4 volts for a 24 volt battery. Aircraft batteries do not have a CCA rating but instead are rated in terms of Ipp and Ipr. See FAQ "What Are The IPP and IPR Ratings of my Battery" for an explanation of these ratings.

Each and every Concorde aircraft battery is capacity tested at the factory to verify it will deliver at least 100% of its nameplate rating. If the battery is capacity tested after receipt, there are several reasons it may deliver less than 100% of its nameplate rating: a) It was not fully charged prior to discharge test, b) it was in storage long enough that it became sulfated, c) the discharge current or cutoff voltage as not correct. If your battery tests below 100% when new, repeat the capacity test in accordance with the CMM. If it still delivers less than 100% of its nameplate rating, contact Concorde for assistance.

In brief, batteries used for starting reciprocating engines or for emergency standby have a 6-month full and a 24-month prorated warranty. Batteries used for starting turbine engines have a 6-month full and a 12-month prorated warranty. The detailed warranty terms are provided on our website. Here is the link: Click Here.

Instructions for making a warranty claim are provided on our website. Here is the link: Click Here.

D8565 Series aircraft batteries used in military aircraft should be serviced in accordance with NAVAIR 17-15BAD-1 (US Navy and Army) or the applicable USAF Technical Order.

A Supplemental Type Certificate (STC) is an FAA approval to modify the aircraft from its original design. A STC is required when the modification results in a major change that impacts weight, balance, structure, reliability, operational characteristics or any other airworthiness factor. In general, an STC, PMA, Filed Approval or other installation approval is required to install a battery model that is different than what is listed in the Illustrated Parts List of an aircraft.

Some STCs held by Concorde are supplied at a reasonable cost whereas others are free of charge. For those that are free of charge you may request the STC paperwork and Letter Of Authorization for your aircraft through This email address is being protected from spambots. You need JavaScript enabled to view it.. STCs available to purchase may be procured through your preferred Distributor. To expedite the issuance, please be sure to provide the aircraft registration details to your distributor at the time of purchase.

Follow the procedure given in Technical Bulletin #10 (Click Here )

When a battery is marked with TSO authorization that means it complies with the Minimum Operational Performance Standard (MOPS) of the TSO specifications. TSO specifications are independent of the battery's intended installation on an aircraft. A PMA'd battery is approved for installation into a specific aircraft model.

Visit the Concorde website using this link: www.concordebattery.com . You can search by aircraft type and model. You can also search by specification. This allows you to determine if the battery you have selected will meet the technical specifications defined by the aircraft manufacturer.

Boost charge the battery per the applicable CMM. In most cases, the voltage will recover to the normal range. If it doesn't, then contact your distributor for a replacement battery.

This happens to all lead acid batteries. The active materials on the plates convert from lead and lead dioxide to lead sulfate whenever a battery is discharged. The battery starts to discharge as soon as you turn on the battery master switch for preflight operations before starting the engine. It can also be the result of a parasitic load (drain). The depth of discharge and time are the main enemies here. The deeper the discharge and the longer the battery stays in a discharged state, the more resistive the lead sulfate crystals become. Over time, it becomes harder and harder to convert the lead sulfate crystals back to lead and lead dioxide. A conditioning charge can help reverse this process, but may not work if the battery has been discharged too deeply for too long. As a rule of thumb, the battery should be recharged within 24 hours if the depth of discharge is greater than 80%.


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