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Touring Motor Gliders Association (TMGA)
Gfeldman

skyview battery backup replacement

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Gfeldman

Hi Phoenix pilots,

As I have mentioned in a previous post the backup battery in my Skyview was failing. The backup battery is meant to serve as a power source for the Skyview during startup. Because it was weak or non-existent current spikes on startup caused the Skyview to startup and shut down a number of times. Today I had a Dynon Avionics technician replace the backup which was almost 6 years old.

The backup battery is not attached to the Skyview unit itself but rather it is anchored to the firewall and at least in my plane not very accessible. It took two individuals to remove and replace it.

So my question is how to keep the backup battery charged when the plane is not being used. Can I leave the Skyview on while trickle charging the main batteries from the charging socket near my panel? Is it ok to leave the Skyview on overnight? Will the chargers supply enough current so that the main batteries themselves won't be discharged over this time?

This problem is not confined to our group but extends to all Dynon Skyview users. I've read some posts but am not sure which are reliable and applicable to our setup.

George Feldman

N33GF

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mikeschumann

The Skyview Backup Battery only charges when the power feeding the Skyview System is > 12.25V.  This ensures that the backup battery only charges when the engine is running, or if you have a battery charger attached to your plane.  Note:  Only the Skyview system can charge the backup battery, so the Skyview system needs to be on for charging to take place.  It takes up to 4 hours to fully charge a completely drained backup battery.  The Skyview Display draws about 3 amps (without the Transponder, Radio, Intercomm, or AP running) when it is turned on, so you need a charger with greater capacity than that if you intend to keep your Skyview system on when the engine is not running.

I have not had any problem with the backup battery discharging when the Skyview system is turned off, even if I don't fly the airplane for a couple of months.  Nor have I had any issues with my main batteries discharging, as long as I have the main battery selector switch turned off, so there is no leakage current.

When you are flying, if your backup battery is low, you will see a warning message on your Skyview Display.  This will eventually go away when the battery is charged while you are flying.  You shouldn't have any need for any special battery charger to try to keep this battery charged.

If you are seeing your main Skyview system startup and shutdown a number of times without explanation, this may not be due to a failing backup battery, but due to a failing EFIS circuit breaker that is partially tripping under load.

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Gfeldman

Thanks Mike.

I plan to test the system with the new backup battery after charging by doing a normal startup routine ie turning on the Skyview before starting the engine. If this doesn't work then the circuit breaker will be inspected.

Interestingly after reading blogs on the Skyview backup in other aircraft I learned that it is generally thought that the backup battery life is about 5-6years.

This is abnormally short for lithium batteries which power the backup. It has been mentioned that this could be due to the fact that the 2 LiPo batteries in series are never balanced

during charging. One suggestion for an improvement would be to include a balancing plug accessible by the pilot to independently check battery voltage and to balance the cells at least yearly. I fly rc model e-gliders and sport planes powered by lithium batteries and always balance the cells during charge. Cheap LiPo ballancers are available and could be used

periodically on the Phoenix.

Tx for your help.

George

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mikeschumann

I haven't had any issues with the backup battery in my 4 year old Phoenix.  I'm just curious;  When you tested your old battery, how long did the Skyview system run before you ran out of power?

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Gfeldman

Mike,

I had not tested my backup battery. The first signs of failure were 2 indicators: 1) On engine shutdown the little notice from Dynon saying that the Skyview would shut down in 60 or so seconds was entirely missing- the Skyview shut down as soon as I turned off its switch.2) As I mentioned when the Skyview was turned on before engine start there were a number of quirky responses from it on engine ignition.

George

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mikeschumann

If the Skyview immediately shut down on power loss, that would definitely raise big questions about the backup battery.  Was there any warning messages about the backup battery being low when the Skyview system was running?

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Gfeldman

Hi Mike

i saw a low voltage warning after the quirky behaviour of the dynon- I could have missed earlier warnings.

george

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