Ovation battery switching

[r0ckst4r]

In the preflight inspection section of the POH it says to switch the batteries and leave on the battery with the highest voltage.  Well for me it always seems that one battery has a slightly higher voltage than the other.  I know that both batteries are charged during flight but do you guys ever alternate batteries at all despite one having a slightly lower charge?  Does it even matter?  I guess I just feel slightly neglectful flying around on the same battery all the time and never going to the bullpen lol.

[carusoam]

If they seem the same... flip them anyways...

Like anything else... batteries benefit from exercise... some battery brands more than others...

Battery 1, drains continuously while nobody is looking... it is the one that has all of the memory keep alive circuits connected to it... even when all the masters are off...

PP thoughts only, not a mechanic...

Best regards,

-a-

[GeeBee]

As long as they are "in the neighborhood" switch them. You will never see them the same and if both are charged 100% one will always be lower than the other for a variety of reasons.  I used to fly an airplane type with three different batteries, they all varied and all varied from ship to ship.

 

 

[Mark89114]

Supposedly you shouldn’t switch batteries under load as the relay that does it fails prematurely, I would assume do to arcing across contacts.  This from a well known MSC.

 

[GeeBee]

Makes sense

[carusoam]

Relays wear...

Relays get dirty...

But not switching them under load...  

that has the ability to generate a larger dirtier internal spark...

Switching them too slowly also shows limitations in the system...

The system is supposed to close both battery relays/switches before opening the last battery used... taking it off line...

If you test the theory by slowly flipping the switch... it is highly probable that you find a dead spot and the power stop flowing from both...

After that experience, I don’t need to test the system during flight... I am confident that it works if needed... during the pre-flight...

Best regards,

-a-

 

[r0ckst4r]

4 hours ago, Mark89114 said:

Supposedly you shouldn’t switch batteries under load as the relay that does it fails prematurely, I would assume do to arcing across contacts.  This from a well known MSC.

 

Under load as in with Master switch turned on (engine off) during preflight?  So do you just ignore the POH and never check the batteries during preflight?

[GeeBee]

Guess you could turn off the switch, swap batteries then turn it back on.

 

[r0ckst4r]

Flicking the Master switch on and off a couple times to switch the batteries seems like it's not great for the electronics either.

[MIm20c]

Land, taxi, pull mixture, turn off mags and master, switch battery, and exit plane.  Batteries ready to go for the next flight. 

[r0ckst4r]

1 hour ago, MIm20c said:

Land, taxi, pull mixture, turn off mags and master, switch battery, and exit plane.  Batteries ready to go for the next flight. 

That doesn't assess that one of the  batteries hasn't died in the time since the last flight at all though.  Isn't this the whole point of the preflight check in the POH? 

[MIm20c]

8 hours ago, r0ckst4r said:

That doesn't assess that one of the  batteries hasn't died in the time since the last flight at all though.  Isn't this the whole point of the preflight check in the POH? 

In my experience over the last 20 years if you start the plane on battery ___ and fly it for a reasonable amount (like an hour), the battery will be fully charged when you switch to the other (at shutdown). This process of regularly load testing and fully charging both batteries (every other flight) is the only way to test the reserve health. After replacing a ton of trash Gill batteries or half as many Concord you’ll soon be able to predict when the batteries will fail. The only thing this will not test for on every flight is a short etc on the trickle charge circuit. That will be noticed on the following flight load testing (starting). 

[StevenL757]

13 hours ago, r0ckst4r said:

That doesn't assess that one of the  batteries hasn't died in the time since the last flight at all though.  Isn't this the whole point of the preflight check in the POH? 

First, make it a habit to switch batteries before starting the engine every flight.  Second, before turning on the Alt Field, switch batteries again after engine start...but before you switch on the Alt Field.  So, assuming you finished your last flight, say, on BAT2, part of your flow for next flight would be...

• Switch to, and start engine on BAT1
• Stabilize engine, switch briefly to BAT2 to check voltage (~ 8 seconds)
• Switch back to BAT1 and conduct flight

Been using this flow on my two Concordes; both of which have passed 8 years’ service.  Capacities for both are still equal to or better than 84%, and at last annual, were within 2% of each other.  No battery minder present.

This is a safe, expeditious, and effective way to determine the load on both batteries before you bring the rest of your avionics load online as well as the alternator.  The 24v/300 amp switching relays (you have three in the avionics bay) are designed to manage switching of this nature, and are designed to last.

Steve

[Jeff_S]

I routinely switch batteries before every flight, but because I had heard long ago that switching batteries after engine start could result in increase wear and potential failure, I haven't switched them during the startup procedure.  I supposed I could try Steve's process one time to see what happens while on the ground.

Also, earlier in its life (and with the original owner) this plane did have a battery short during climb out which created a great electrical fire smell and prompted the owner to turn off all electrical and eventually do an emergency gear-up landing just to get on the ground as fast as possible.  The shop that had maintained the plane and did the repair after the gear-up said that the only thing really necessary was to just switch the batteries in-flight and everything would have proceeded as normal, but I have to admit, if I smell an electrical fire while in flight I'm going to take extraordinary measures to get on the ground as well.

[StevenL757]

2 hours ago, Jeff_S said:

I routinely switch batteries before every flight, but because I had heard long ago that switching batteries after engine start could result in increase wear and potential failure, I haven't switched them during the startup procedure.  I supposed I could try Steve's process one time to see what happens while on the ground.

Not to case-build for my suggestion, but my BAT1 relay failed on the ground about 3 years ago when I flipped the master on.  I contacted Kissling US, who in turn contacted their HQ in Germany.  As expected, they firmly stood by the product, insisting my airplane caused the failure, and requested I send the bad relay for analysis.

About three weeks later and a few Q&A sessions with them, they sent a note of their findings which essentially said "our relay failed", apologized profusely and said it was a "very rare failure".  In parallel, they sent a note to my local distributor (where I purchase them) directing them to replace it at no cost.  Their conclusion was switching batteries like I described would not, and did not, cause the failure in question.  I'm grateful they covered the cost of a new one...I pay $435 apiece for them through my distributor.  Mooney charges well-north of $1200 for the same relay.  Both parts come from the same people and are PMA'd.  The kicker was that my "bad" relay was almost 15 years old at the time.

For those who care about background reading...  https://www.kissling.us/fileadmin/produkte/Catalog_us/Catalog_sheet_26_300L_us.pdf

 

[GeeBee]

At least in my airplane, switching batteries after power up will result in some boxes, usually nav/comm 1 or 2 not returning back on line with the G1000. Do not know why, but I would suspect the G1000 has some "recognition" issues after it is powered up and a box gets interrupted. 

 

[r0ckst4r]

7 hours ago, StevenL757 said:

First, make it a habit to switch batteries before starting the engine every flight.  Second, before turning on the Alt Field, switch batteries again after engine start...but before you switch on the Alt Field.  So, assuming you finished your last flight, say, on BAT2, part of your flow for next flight would be...

• Switch to, and start engine on BAT1
• Stabilize engine, switch briefly to BAT2 to check voltage (~ 8 seconds)
• Switch back to BAT1 and conduct flight

Been using this flow on my two Concordes; both of which have passed 8 years’ service.  Capacities for both are still equal to or better than 84%, and at last annual, were within 2% of each other.  No battery minder present.

This is a safe, expeditious, and effective way to determine the load on both batteries before you bring the rest of your avionics load online as well as the alternator.  The 24v/300 amp switching relays (you have three in the avionics bay) are designed to manage switching of this nature, and are designed to last.

Steve

In the POH the first time it says to switch batteries is in the pre-flight prior to engine start and prior to powering up avionics or turning on the Alt field switch to check voltage.  So this would be in line with what you are saying here.  It also appears again in the prior to takeoff section where the engine is on, Alt field in on, and avionics is on and tells you to switch the batteries to ensure that they are both showing positive charge (>26.5v).    So from what I am gathering here is that the first check with only the master switch on is ok but the second check during run up should be omitted?  The only difference between your method and the POH (pre-flight check) is that the engine is on when you do it however with the Alt field switch off it should not matter if the engine  is running or not.  Does that follow?

[carusoam]

One alternator or two?

Are we checking the batteries, or the alternators, or the switches/wires in between..?

I only have one alternator with two batteries... testing before start adequately covers all of my bases...

The way the battery relays are set-up... there shouldn’t be a drop out when switching between batteries... by design...  if you flip the battery selector switch slowly enough, you can get it to mis behave... if it behaves as designed... the batteries are both momentarily connected at the same time before the first one drops off line...

PP thoughts only...

Best regards,

-a-

[StevenL757]

9 minutes ago, r0ckst4r said:

So from what I am gathering here is that the first check with only the master switch on is ok but the second check during run up should be omitted?  The only difference between your method and the POH (pre-flight check) is that the engine is on when you do it however with the Alt field switch off it should not matter if the engine  is running or not.  Does that follow?

I do follow.  Although the "second check" you describe during run-up isn't in my checklist, it really doesn't prove anything.  You've already demonstrated before this point that both batteries have ample voltage, and that the battery not used during the previous flight has enough cranking amps to start the engine.  In all practicality, your "second check" can be omitted.  As @carusoam states, alternators are a different story...assuming you have the 100-amp primary and the 20-amp backup.

What does your specific cockpit checklist say?

Edited April 13, 2020 by StevenL757
Added context

[r0ckst4r]

[StevenL757]

Right, but I don't see the "second check" like you described.

Simply put...if you do this procedure one time, and each battery checks ok, just remember to fly on the battery "opposite" the one on your most-recent flight.  Over the long-term (assuming you fly regularly and for roughly an hour), your batteries will stay conditioned and charged somewhat evenly.

[buddy]

I always switch batteries after every shut down.

[VetRepp]

+1 form switching after shutdown.

I've found on my G1000, that switching while engine running can play havoc with the MFD/PFD displays briefly (which doesn't seem good for them or at least bothers me more so I don't) 

[r0ckst4r]

2 hours ago, StevenL757 said:

Right, but I don't see the "second check" like you described.

Simply put...if you do this procedure one time, and each battery checks ok, just remember to fly on the battery "opposite" the one on your most-recent flight.  Over the long-term (assuming you fly regularly and for roughly an hour), your batteries will stay conditioned and charged somewhat evenly.

Actually that was my mistake.  The second check I described was something else.  Yes, I have one alternator.  So it would seem that if you follow the POH segment I posted above but instead of keeping on the battery with the highest voltage as described just switch it once which will check both voltages and also switch to the battery not used last flight.  Does that fall under having  a load on the battery or is that more when the engine is on and the alternator is charging?

[GeeBee]

Battery 1 east bound, battery 2 westbound.