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Thermal Runaway in AGM Batteries : Skip's Corner

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Can AGM Batteries Suffer Thermal Runaway like Lithium Ion Batteries?

 

 

The Question –

Can AGM Batteries suffer thermal runaway like Lithium Ion Batteries: Are they safe?

 

The Answer –

Does everyone know that when our RG series batteries are subject to the destructive overcharge test that they do NOT thermally runaway?

They get HOT about 260F, the electrolyte boils, the water turns to steam and the excessive internal pressure opens the vent valves releasing the steam (H20) NO ACID is expelled.  This continues for about 10 minutes and as soon as the battery runs out of water the charge current stops and the battery starts to cool down to ambient.

 

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Annunciator light functionality - NiCads : Skip's Corner

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Annunciator light functionality - NiCads

 

 

The Question –

Working on King Air 300 FA-85 with RG380E/44 installed. Have minor issue with Batt charge annunciator and can not locate wiring changes made when ACFT went from NiCad to Lead acid. If you could assist or point me in direction who could please do. Thanks for your time.

 

The Answer –

The CONCORDE King Air STC has the option of taking one of the battery charging cable shunt sensing lead off if the charge light is a nuisance to the operator.

But, it is a great system and the light comes on as long as at least 7 to 10 amps are charging the battery. Normally, with a healthy battery the light goes out before takeoff. IF THE CHARGING SYSTEM IS SET PER THE BEECH MM AT 28 TO 28.5 DCV.

Most of the NiCad's are 20 cell and the charging system is set upwards of 29DCV which is too high for our 24V batteries and the charge light stays on for a long time .

The reason we like to leave the charge light system functional is that it is a CURRENT SENSING SYSTEM And if the light comes on during flight, the pilot merely disconnects the battery that is just showing signs of an internal short , but fully charged and if later the generating system fails, the charged battery can be put back on line to support the load requirements.

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Arcing Conditions : Skips Corner

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Arcing Conditions

 

 

The Question –

We have an RG380E/44 battery, S/N: 40450578 that has slight arcing on the negative battery terminal from a loose connection at the connector. We have replaced the aircraft connector but I cannot find any information in the CMM, (5-0171, Rev P), regarding how to repair this condition. Can you advise on how to repair so that I have manufacturers data/recommendations for repair and return to service please?

 

The Answer –

The battery terminal pins are .375 or 3/8” in diameter. Make sure you remove any copper deposits from the plug socket terminals so the pins will have maximum contact with the airframe plug sockets.

Make a go-no-go gage from a 3/8 drill rod or bolt that you can use to check ALL YOUR AIRFRAME PLUG SOCKETS. There needs to be enough tension on each socket, so that the 3/8” diameter gage will not slip out when the airframe plug is inverted.

The battery terminal pins are silver plated, protect them from corrosion using ACF-50 in the plug sockets.

 

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Voltage Regulator Overcharging : Skip's Corner

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Voltage Regulator Overcharging

 

 

The Question –

If a voltage regulator is set to 14.1 , how does it not overcharge a 12V battery on a long trip, or when the battery is back fully charged, does the regulator continue to attempt to pump 14.1 into the battery? Would that not eventually dry out the matts?

 

The Answer –

No, first the battery is not fully charged after an engine start or worse if the airplane has been inactive. It will take about 3.5 hours to fully charge the battery, then 14.1 IS NOT OVERCHARGING IT, merely charging it normal at RT, too low at cold temperatures and too high or overcharging it at 100F or higher, look in the O/O manual for recommended charging voltages at temperature.

If the recommended charging voltage at the battery temperature is exceeded then yes, the vent valves will allow water to be consumed and the battery will dry out, but this rarely ever happens.

 

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Amp Meter/Volt Meter Oscillation : Skip's Corner

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Amp Meter/Volt Meter Oscillation

 

 

The Question –

Battery SN 40858991 was installed 4/4/17 @ 3159.69 hrs, removed 4/16/17 @ 3162.86 hrs. Induced amp meter and Volt meter oscillation. (And panel lights) Old battery worked perfect when re installed. Why?

 

The Answer –

This is the old-style magnetic coil relay voltage regulator that is not fast enough to dampen the overvoltage charging that happens with an RG battery that has lower internal resistance than a flooded battery that has fewer plates per cell.

The older voltage regulator recognizes the battery is going OVER the CP limit and shuts the generator or alternator off, but the battery not being fully charged voltage starts to drop below the normal charging voltage , then the voltage regulator senses it, and the magnetic coil relay contacts close and the fast charge starts again until the battery goes over voltage again.

These events are rapid within seconds, but all electrics either go off and on, or lights flicker as the ammeter is fluctuating from charge to discharge and back and forth.

Two ways to fix the problem - replace the old voltage regulator or alternator control unit with a solid state, or go back to using an old fashioned flooded electrolyte battery.

 

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Short Duty Cycles : Skip's Corner

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Short Duty Cycles

 

 

The Question –

Do short duty cycles have an effect on battery longevity?

 

The Answer -

I will attempt to explain why ANY aircraft battery is NOT designed to perform satisfactorily with short durations of being recharged between the high rate of current of discharge (capacity) required to make a successful turbine engine starts.

Think of the storage battery as being like a bucket of water. With an open top that is full (charged capacity) that you can dump or spill as much as you want rapidly (loss of capacity) BUT you only have a limited volume of water capacity to refill the empty bucket because of your resupplying water filling pipe or hose, so you cannot replenish the capacity lost that you had quickly dumped for some reasonable time before the bucket is full (capacity) again.

Storage batteries are something like this, they can release high rates of power to crank a turbine engine from its static or stopped condition to the starter/generator that is also not moving and because it takes hundreds of amperes to overcome this stalled condition to get all the rotating components moving (at least ten percent of the capacity is used to motor the engine) to draw the cool air into the compressor section BEFORE the compressed air is introduced to the combustion section where fuel is ignited and the fire and super-heated air impinges on the turbine to provide enough energy to have the turbine drive the compressor so the electric starter motor than can be shut off.

Usually aircraft turbine starting batteries have enough stored energy (capacity) to make three successful starts before their capacity is drained to the point of causing a hot or aborted start

A storage battery in a poor state of charge (SOC) or health (worn out below the minimum airworthiness requirement) will and do cause hot starts the ruin the turbine engine, IF the battery DOES NOT HAVE ENOUGH CAPACITY to keep the starter motor turning the engine , driving the compressor and forcing the hot air back to drive the turbine until the turbine can drive the compressor, then the engine stalls and the hot air and flames are allowed to back-up into the aluminum compressor section causing EXPENSIVE engine overhauls or replacements

My first suggestion would be to modify your 350/355’s with the Canadian Airbus Helicopter STC to install our 28Ah P/N RG-390E in the tail boom.

Second install a spare battery, I believe Airbus Helicopters has a SB for dual batteries, If not AIRLIFT in Norway does.

Third, carry a start stick by STARTPAC .

 

 

 

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Bulging Batteries : Skip's Corner

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Bulging Batteries

  

The Question –

Is a sealed battery airworthy if it is bulging?

 

The Answer –

Yes, this is normal when the internal gas pressure is higher than the outside atmospheric pressure, it’s a GOOD sign as each cell pressure relief valve is not leaking.

The cell pressure relief valves remain closed normally but do burp occasionally to relieve excess internal pressure while in service. The recombinant gas battery requires a positive internal pressure to operate normally.

The case will go concave if the aircraft makes a rapid descent from a high altitude.

ALL rechargeable batteries of any type are called “secondary” and ALL have pressure relief valves to prevent the battery case from rupturing or bursting due to high gas pressure that may be caused by overcharging with higher than recommended voltage from either internal or external power. Sometimes this happens to batteries that are shipped in a charged state that are of normal shape at the time of shipment and are subject to either higher or lower atmospheric pressure during transit.

See Page 9 of Document Number 5-0324 “ CONCORDE RG SERIES AIRCRAFT BATTERY OWNER/OPERATOR MANUAL “ packed with each battery.

 

 

 

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