Toobuilder
Well Known Member
I?ve been looking at various schemes to provide backup power to my electrically dependent airplane. I?ve considered everything from airliner style dual busses so I can press on with 100% capability in a failure, to dual alternators with somewhat reduced capability, and considering my mission, have settled on a simple backup battery that handles ONLY my engine needs for an hour or so. I?m not here to debate risk posture, so let?s try keep that in check.
I am exploring the technical drawbacks of mixing battery chemistry on the same buss however. My thinking is that I?m going to run the airplane with a single alternator and battery just like we?ve been doing for decades. However, I?d like to add a smallish Li-Ion (or other suitable chemistry) battery in reserve to power the fuel pumps, ignition and engine CPU if the ship?s main system goes Tango Uniform. Think of this as a scaled up EFIS backup battery. I?d rather not have the various auto isolation methods taking care of tending the battery though ? I want a stone reliable toggle switch that connects the battery to the engine buss through a single circuit. I?m not opposed to charging the battery once a month on the ground and keeping the backup strictly isolated from the ship?s main buss, but I think it would be beneficial to have a ?charge? position on the toggle so that when skies are blue and all is well, I can use the ship to keep the backup topped off. Most of the time the switch would be in a ?NORM? position ? backup battery completely disconnected.
I am only considering the more recent, exotic chemistry because this battery will be 100% dead weight until an emergency so I want it to be as small as possible while meeting the power requirements. I have only scratched the surface of the various battery offerings and know only that some of these batteries have different charging requirements WRT input voltage and amperage.
So long story comes down to a simple, broad question: Is anybody running mixed battery chemistry on a common buss, and what are the cautions/concerns/mitigating actions?
I am exploring the technical drawbacks of mixing battery chemistry on the same buss however. My thinking is that I?m going to run the airplane with a single alternator and battery just like we?ve been doing for decades. However, I?d like to add a smallish Li-Ion (or other suitable chemistry) battery in reserve to power the fuel pumps, ignition and engine CPU if the ship?s main system goes Tango Uniform. Think of this as a scaled up EFIS backup battery. I?d rather not have the various auto isolation methods taking care of tending the battery though ? I want a stone reliable toggle switch that connects the battery to the engine buss through a single circuit. I?m not opposed to charging the battery once a month on the ground and keeping the backup strictly isolated from the ship?s main buss, but I think it would be beneficial to have a ?charge? position on the toggle so that when skies are blue and all is well, I can use the ship to keep the backup topped off. Most of the time the switch would be in a ?NORM? position ? backup battery completely disconnected.
I am only considering the more recent, exotic chemistry because this battery will be 100% dead weight until an emergency so I want it to be as small as possible while meeting the power requirements. I have only scratched the surface of the various battery offerings and know only that some of these batteries have different charging requirements WRT input voltage and amperage.
So long story comes down to a simple, broad question: Is anybody running mixed battery chemistry on a common buss, and what are the cautions/concerns/mitigating actions?