Battery Charging "Fix"

[vlittle]

OK, let's face it.  Charging the SV backup battery is a problem.  We have two choices:
1) Fly the aircraft for several hours (I'm over 5 hours and it's still not fully charged).
2) Put a large capacity battery charger on the aircraft battery, turn on the Master Bus and come back in up to 4 hours.

Both of these have problems, especially if you have to charge the battery twice (once to get it fully charged for the battery test; the second to recharge after the battery test).

It's even worse if you have a critical flight coming up.  The logistics of charging this battery is a royal pain.

My suggestion is to provide a separate ground power port for the SkyView system, to be used for powering up the SV or charging the SV battery.  This port does not have to power up the whole panel and the master contactor.

A couple of suggestions are shown in the diagram.  The first (A) is a 'zero drop' port.  The second (B) uses diodes for automatically switching, but suffers from the voltage drop of the diodes which may be an issue for the minimum operating voltage of the SV.

Cheers, Vern

 

[DonFromTX]

I have asked in the past for the same thing. While building this becomes a real problem since we cannot just go fly it to recharge.
I am hoping Dynon gives its blessings for this type addition.

 

[larrynew]

When I installed my avionics and electrical, I kept the battery (PC680) on a trickle charger when everything was off and used an old 2/10 Sears charger when I had power on. Other than leaving the master on once (or twice :, I had no problems with the 2 backup batteries including the new tests and recharging after. If they got a little low, I'd just leave the car charger on for a couple of hours.

 

[dynonsupport]

I'm actually not sure what the question or blessing request here is. What I see is a way to power SkyView without having the master on. No harm in that, and feel free to add it if you really think it's needed. It seems like overkill to deal with the battery in SkyView, which once you are flying is basically a maintenance free system.

The easiest way to deal with all of this is just a good battery charger that can power the whole plane. Anything that has enough current to charge the battery will put you above 12.25V. A good 10 amp charger is only $50 and lets you charge your aircraft battery, run SkyView, and the rest of your panel at any time, instead of something that requires a lot of work and only lets you deal with SkyView. It's what I used when I built my plane.

SkyView requires 12.25V on the master input to charge. This is on purpose. 12.25V or greater means your battery in the plane is being charged, so it's logical to charge our own battery. We assume you don't want us to charge the SkyView battery off your aircraft battery if your alternator is failed (or you just left the master on). So while it makes it a "pain" to charge it, it's for a good reason which is that it doesn't suck your main aircraft battery down.

This does mean that you can't just hook a 12V supply to your plane and have it charge. But that's a good thing, since 12V would actually be draining your aircraft battery as well. 12V on a lead acid battery is only about 25% of charge.

SkyView charges the battery at a rate of about 30 seconds per minute the aircraft is running. So if you had a dead SkyView battery, started the engine, taxied out, and took off after 10 minutes, you'd have about 5 minutes of battery. This is pretty quick overall. If you have flown for 5 hours and the battery is not charged, something is wrong. It should be 90% charged in about 3 hours and the rest in the next ~1 hour.

But, your battery is only dead in normal operation if you just did a battery test right before, which you do once a year. Don't do it before a critical flight, and the screen warns you about this. Seems pretty easy. Your first 25 or 40 hours of flying aren't critical, so go flying for your first 10 hours, do a battery test, then let it charge the next 10. Easy. Why make it more complex?

Another simple fix here is to not hook your battery up while you are building until you are ready to fly. The battery is delivered with a reasonable charge on it. Why drain it why you are building? Why worry about recharging it?

FYI, The Diode method is more of an issue because of the power loss in the diode, not the voltage drop. SkyView turns off at 10V (or switches to battery). Your aircraft battery is basically equally as dead at 10V and 10.7V. But losing 3W in a diode does kind of stink.

We're open to helping out here, but we don't quite see what the issue with the battery is. It shouldn't be dead in any normal operation, and in general it "just works." Let us know if we're missing anything that would be helpful. We've considered a method that would allow you to charge at voltages less than 12.25V with some special key press or menu, but it's not like getting 12.25V is much harder than 12V, and you really don't want to drain your main aircraft battery doing this.

 

[vlittle]

Here's the issue: I'm limited to 7.5 A on my charging circuit and I have an aft battery that's not easily accessible to connect a higher capacity charger. My charging circuit was designed only for light-duty battery charging and not for powering up the panel.

Hence I need a more convenient way of charging the SV battery than flying around for several hours.

So I'm faced with a modification: Either increase the capacity of my charging port on the aircraft (rewiring), add a ground-power plug (heavy, expensive rewiring) or add a dedicated power plug for the SkyView (cheap and easy in my aircraft).

I will still need an external 12V power source, but that's easy.

As for the SV battery not fully charged: It's up to about 11.5 volts. I run it for about 5 minutes on the battery before flight and a typical flight takes an hour. I'm going to give it another hour and see where I get.

Vern