VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #1  
Old 03-02-2017, 01:41 PM
jeffw@sc47's Avatar
jeffw@sc47 jeffw@sc47 is offline
 
Join Date: Aug 2014
Location: Simpsonville, SC (SC47)
Posts: 122
Default RV14 second battery

What is a good location on the firewall for a second battery.

Especially anyone who has mounted a second battery and found that it was the ideal location or found that somewhere else would have been better.
__________________
Jeff Warren
Simpsonville, SC (SC47)
1946 Bellanca Cruisair 14-13-2 (70 YRS OLD 8/15/16)
RV14A (N14ZT), Ser#140195
Empennage 10/11/14 - 6/15/15
SB Wing 7/22/15 - 8/12/16
Rcvd QB Fuse and Finish kits 10/10/16
QB Fuse substantial completion 12/7/16
Finish Kit started 1/11/17
Engine / Prop ordered April 2017
Dues paid 11/11/16 (USA 2/67-2/70)
www.mykitlog.com/jeffw@sc47
Reply With Quote
  #2  
Old 03-02-2017, 03:02 PM
asw20c asw20c is offline
 
Join Date: Jun 2010
Location: Edgewood, NM
Posts: 67
Default

I recently discovered some corrosion on the belly of my Cessna 180 that was later traced back to the battery vent tube a few feet forward on the bottom of the fuselage. Apparently for a reason I still have not determined, the fairly new battery I installed decided to offload some of its electrolyte that discharged through the vent and resulted in the bit of corrosion I found. The reason I tell this story is because my A&P suggested that maybe at some point it was overcharging and boiled off, so it got me to thinking about batteries mounted on the firewall in an environment MUCH hotter than underneath my baggage area. There were some posts here not long ago with people offering temperatures they have recorded in this very area that were hot enough to be a real problem (I would think) for a battery with plastic housing. Are batteries designed to withstand boiling temperatures as can be expected in this area? I get the desirability of mounting batteries there-favorable CG, a lot less heavy cable required, easier access, etc. But what about temperature?
__________________
Empennage Complete Except for Tips
Starting Wings
Reply With Quote
  #3  
Old 03-02-2017, 05:55 PM
JohnInReno's Avatar
JohnInReno JohnInReno is offline
 
Join Date: Jun 2005
Location: Fermley, NV
Posts: 223
Default Batery temp

I think your AP was right to suggest over-charging. This EX900 battery on the firewall of my RV9A shows a max temp of 150 degrees f after one year including Arizona summers. I do not open the oil door to help cool.
__________________
John Morgensen
RV-9A N946PM 400+ hours since 2013
Nevada
Reply With Quote
  #4  
Old 03-02-2017, 07:08 PM
N941WR's Avatar
N941WR N941WR is offline
 
Join Date: Jan 2005
Location: SC
Posts: 10,865
Default

Why do you need a second battery?

Whatever EFIS you pick will have its own backup battery.

If you pick an ignition that can run independently of your aircraft's electrical system, what else do you need?

Jeff, give me a call so we can discuss your options.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
Reply With Quote
  #5  
Old 05-07-2017, 01:16 PM
Cliff Goldstein Cliff Goldstein is offline
 
Join Date: Oct 2014
Location: Boulder, Colorado
Posts: 5
Default 2nd battery

I installed EFII so wanted the redundancy of 2nd battery. Peace of mind.
Mounted second battery inside over the pilot rudder pedals on fire wall.
Just below structural channel with enough tilt clearance to take battery out and still have full rudder pedal travel.
Since I mounted my engine ECU's on inside firewall, I added access panels on both sides of the boot cowl. It then allows easy access to ECU and battery. And if u really wanted to move the rudder pedals, you could do it without standing on ur head.
cliff
Cliff@eclipseseal.com
Reply With Quote
  #6  
Old 05-07-2017, 04:42 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 908
Default

Quote:
Originally Posted by N941WR View Post
Why do you need a second battery?

Whatever EFIS you pick will have its own backup battery.

If you pick an ignition that can run independently of your aircraft's electrical system, what else do you need?

Jeff, give me a call so we can discuss your options.
I have posted on this before. A single PC-680 battery is inadequate for RVs if you plan on any operation other than local VFR. It simply does not have the reserve electrical capacity for IFR work. I'm not a big fan of EFIS backup batteries as I find they typically do not have enough capacity if you really need them, and dead weight for most of their life. There are better power distribution options if you take the step of adding a second battery. If you consider approach, look at the PC-625 battery. It is a little lighter, better AH and CCA ratings than the PC-680, and I find it a better form factor for mounting.

One other point that has been previous discussed. It seems the current PC-680 battery is not as good as it once was.

Carl
Reply With Quote
  #7  
Old 05-07-2017, 05:42 PM
ChiefPilot's Avatar
ChiefPilot ChiefPilot is offline
 
Join Date: Jan 2005
Location: Twin Cities, MN
Posts: 1,365
Default

Quote:
Originally Posted by Carl Froehlich View Post
A single PC-680 battery is inadequate for RVs if you plan on any operation other than local VFR.
Do you find these statements to be just as true?
  • "A non-certified aircraft is inadequate if you plan on any operation other than local VFR."
  • "A single engine aircraft is inadequate if you plan on any operation other than local VFR."
  • "A single pilot aircraft is inadequate if you plan on any operation other than local VFR."
  • "A non-turbine aircraft is inadequate if you plan on any operation other than local VFR."
  • "Flights performed under FAR part 91 are inadequate if you plan on any operation other than local VFR."

I understand when you're coming from - risk identification and mitigation to suit one's own level of risk acceptance is something that I don't think enough RV builders perform either. But to make a statement that a configuration used by many, if not most, RVs is inadequate for flights performed by many, if not most, RVs doesn't pass the sniff test.
__________________
Brad Benson, Maplewood MN.
RV-6A N164BL, Flying since Nov 2012!
If you're not making mistakes, you're probably not making anything
Reply With Quote
  #8  
Old 05-07-2017, 07:00 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 908
Default

Quote:
Originally Posted by ChiefPilot View Post
Do you find these statements to be just as true?
  • "A non-certified aircraft is inadequate if you plan on any operation other than local VFR."
  • "A single engine aircraft is inadequate if you plan on any operation other than local VFR."
  • "A single pilot aircraft is inadequate if you plan on any operation other than local VFR."
  • "A non-turbine aircraft is inadequate if you plan on any operation other than local VFR."
  • "Flights performed under FAR part 91 are inadequate if you plan on any operation other than local VFR."

I understand when you're coming from - risk identification and mitigation to suit one's own level of risk acceptance is something that I don't think enough RV builders perform either. But to make a statement that a configuration used by many, if not most, RVs is inadequate for flights performed by many, if not most, RVs doesn't pass the sniff test.
Ok - I'll bite.

Time has marched on. Most people building RVs for IFR operations are doing electric dependent panels. Reserve electrical capacity defines how long you can maintain those panels while IFR when any element in the power distribution chain fails (you pick you failed competent - the basic 1960 Cessna power distribution that many emulate has many more single failure modes than just the simple alternator failure).

Do a test. Sit in the plane with the panel up and engine off. How long does your EFIS, XPDR, GPS navigator, comm, autopilot and such stay on line? Now do the same test and simulate your master solenoid failing by opening the master switch. Do you have anything left running? If so, how long?

I design for maintaining a full panel after any single electrical power distribution component failure. In the worst case, this results in single battery with no alternator operation - a reserve of about 90 minutes if you shed non-vital loads. If both batteries are available I have about the same electrical endurance as I do fuel. That is my risk tolerance. Add to that the straight forward approach to get that level of performance and the design decision is easy.

I've installed dual PC-625 batteries setups in four RVs, operating over 15 years. The design has proven its worth to me and the other RV owners.

On the RV-10 I even added a standby alternator as further mitigation as the power hungry panel ate away at some of my reserve capacity. It is diode isolated to prevent a single fault from taking it out as well. I offer that just adding a standby alternator to a standard single battery install protects from one fault only, a loss of primary alternator.

Carl
Reply With Quote
  #9  
Old 05-07-2017, 07:16 PM
ChiefPilot's Avatar
ChiefPilot ChiefPilot is offline
 
Join Date: Jan 2005
Location: Twin Cities, MN
Posts: 1,365
Default

Quote:
Originally Posted by Carl Froehlich View Post
Ok - I'll bite.
Well, actually, I do know I have 42 minutes of reserve juice should the alternator fail. This compares somewhat better than the electrical analysis spreadsheet I built for the design would suggest (I designed for 30 mins), so I'm happy. And I specifically chose to not worry about the master relay failing, because it's typical failure mode is failing "on" when it fails during operation as identified via FMEA. But all that is kind of beside the point.

The main point of my post was that your opinion was posted as fact - which is most certainly is not; it's an opinion and should probably be clearly called out as such. A well reasoned opinion, with thoughtfulness and analysis to be sure, but an opinion nonetheless that doesn't apply to many (if not the overwhelming majority) of RVs that have a single PC-680 as shown on the plans and which are flown on more than just local VFR missions daily. I think are probably more risk averse than most - nothing wrong with that - but the operational history of the RV fleet hasn't demonstrated that planes flying other-than-local-VFR missions are falling out of the sky due to electrical failure either.
__________________
Brad Benson, Maplewood MN.
RV-6A N164BL, Flying since Nov 2012!
If you're not making mistakes, you're probably not making anything

Last edited by ChiefPilot : 05-07-2017 at 07:20 PM.
Reply With Quote
  #10  
Old 05-08-2017, 08:31 AM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 908
Default

[quote=ChiefPilot;1171480]Well, actually, I do know I have 42 minutes of reserve juice should the alternator fail. /QUOTE]

Not to beat a dead horse, but I note that unless the single failure you list happens at just the right time during your IFR flight, you have less electrical reserve than the required minimum fuel reserve.

It does not require a lot of money or weight to build a more robust power system that can maintain panel operation after something fails. Considering the trend to EFIS backup batteries such an approach may even save some weight and money.

My point is not to argue risk tolerance. If there is little cost to mitigating potential failures, why not just do it?

Carl
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 02:53 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.