I have a Concorde RG-35AXC battery and a BatteryMINDer® Model 128CEC2-AA-S5: 12V 8 AMP CONCORDE® Aviation Battery Charger-Maintainer-Desulfator. My plane has the factory installed external power receptacle. I saw on the BatteryMinder website that they sell an APU plug (BatteryMINDer® Accessory: A2GPU-1: Anderson SB-50 To Cessna-style GPU Plug) to connect the BatteryMinder to the aircraft via the external power plug. Looking at the wiring diagram for the external power plug for my aircraft, it shows that the APU plug uses one + pin to energize the external power relay which then connects the second + pin to the aircraft battery.
I typically connect my BatteryMinder to the battery and leave it on until my next flight which could be up to 14 days later. My question is, if I use the BatteryMinder APU plug to connect the BatteryMinder to the aircraft, does the external power relay have a continuous use duty cycle or will it end up burning out due to continuous energize power to the relay?
Battery Minder Connection with APU plug?
0 You Like ThisModel: Bonanza V35A
Aircraft Serial Number: D-8723
Posted 3/20/2023 - 2 months ago
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Replies Sort
When we use the APU plugs for doing maintenance / inspection work the typical load is higher than battery maintenance, and the relays don't take long to get warm. Suggest looking at your relay's specification sheet (from root manufacturer); they would often have helpful information.
Mike
ABS Tech Advisor
Posted 3/21/2023 - 2 months ago
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The FAA suggests adding a battery minder interface kit which attaches to the master relay and not directly to the battery after a couple of aircraft caught on fire due to the wire shorting The kits are available from Aircraft Spruce P/N 11-10835. They can be installed in about 1 hour and will protect the aircraft from a possible short with wire connected directly to the battery.
With this connection you can use your battery minder to play with avionics without affecting any relays.
Bob Ripley
ABS Technical Advisor
Posted 3/21/2023 - 2 months ago
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Recently installed this same kit on my F33A. Works very well and to Bob's point not difficult to install at all.
Posted 3/21/2023 - 2 months ago
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The thermal characteristics of the master relay are different when on the ground vs airborne - no forced convection to draw heat.
Posted 3/21/2023 - 2 months ago
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Thank you all for your various responses. I took Mike Thompson's thoughts and did more investigating.
My aircraft has an external power relay manufactured by White-Rogers, P/N 70-902, which per W-R spec sheet it is a 12V 16ohm coil power contactor with relay contacts rated to 80amps and rated for continuous duty. The relay coil when energized requires 0.75amps.
I then called BatteryMinder Tech Support to see if the external power relay current draw of 0.75amps would affect the performance of the BatteryMinder to charge/desulfate/maintain the battery. Tech Support said there would be no impact to the BatteryMinder unit to perform any of those functions. The unit may indicate "battery under load" but that is being caused by the external power relay not other systems on the aircraft and can be ignored.
Based on this information, I believe the APU style plug connector for the BatteryMinder is a better way to connect the unit to my aircraft than using the BatteryMINDer® Accessory: BM-AIK2A | AIRFRAME INTERFACE KIT FOR USE WITH FAA-CERTIFIED AIRCRAFT as no additional wiring is required under the cowling and will not require open/closing of the cowling saving wear and tear on the camlocs. The only downside could be that the external power relay wears out from continuous service, though it is designed for continuous service, I guess it could wear out of in time with continuous service.
Posted 3/22/2023 - 2 months ago
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I’ve installed a few of those interface kits. Definitely the way to go. Actually prefer now building up my own custom kits with appropriate connectors (usually Anderson) quality aircraft wiring, proper connectors, etc.
If I remember correctly the interface kit and Minder instructions prohibits its use with the master switch in the “on” position.
Don’t forget the requirement for a log book entry if going this route!
Jim