Today's Message Index:
----------------------
1. 05:55 AM - battery selection (Larry Bowen)
2. 10:40 AM - Battery choice par deaux (Stan Loer)
Message 1
INDEX | Back to Main INDEX |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | battery selection |
Thanks for the input Carl. You've got me thinking. I was mostly focused
on endurance, I have to admit.
I'm also using a VP-X which accommodates management of a second battery.
So I may decide to take advantage of that.
Klaus is the one that prompted me to consider one alt, one bat. His
website talks about the endurance of your main battery being enough to get
you home.
There are many single points of failure. Some of them are best addressed
by ongoing inspection and maintenance. Belt and suspenders vs simplicity..
.
I changed my LSI mount to allow for some more ventilation. Thanks for the
input.
--
Larry Bowen
Larry@BowenAero.com
http://BowenAero.com
On Fri, Jan 27, 2012 at 5:15 PM, Carl Froehlich <carl.froehlich@verizon.net
>
wrote:
>
> In a single alternator, single battery install the battery is primary and
the alternator charges the battery, it is not a backup to the battery. I
few thoughts:
>
> 1. Look at where your alternator connects to your battery. I offer
that there are at least two points in the system where a single post
failing (loose, melted, shorted) takes down your entire electrical system.
Not long ago a twin engine plane (two alternators and two batteries) had a
total loss of electrical power when the common post on the master relay
failed.
>
> 2. Look at the single post for ground on your battery. Again a
single failure will lead to total loss of power.
>
> 3. Many alternator installs do not run well without a battery
floating on them for reference (source) voltage. Some do, some don=92t.
>
> 4. For a simple example your master relay fails open. Unless you
have dedicated auxiliary feeds from the battery you have lost all power.
>
>
> I suspect many dual battery installs have only increase capacity to
offer, not added redundancy. Again the objective is to not have a single
failure bring down all your power. It is the system that counts, not the
individual components.
>
>
> The most reliable electrical component in your plane is the battery.
This is why I have two batteries feeding independent master relays and
dedicated smaller relays for the panel, and a single alternator. The odds
of an alternator failing (I had two go south in my 8A over the last 9
years) is way higher than a battery failing in flight. Now if you crank a
battery(s) into the dirt and then take off hoping the alternator will
charge it (before the alternator craps out), you are just asking for
trouble.
>
>
> For a dual Lightspeed install some sort of battery backup for the
ignition is mandatory. The simple Panasonic battery with the diode
isolation as illustrated in Klaus=92 manual is the bare minimum. It will a
t
least let you land at the closest runway instead of an engine out landing
in a field. For an all electric panel, redundant power is mandatory as
well.
>
>
> BTW ' I took a look at your website link. So you know, the Lightspeed
ignition box generates some heat. As you have them mounted back to back
you might want to give Klaus a call to see if this reduction in heat
transfer surface is a problem or not. In my 8A I had them mounted aft of
the fire wall on spacers to allow air to get at the back of the box. I
also had insulation on the cabin side of the firewall to isolate engine
heat.
>
> Carl
>
>
> From: owner-rv8-list-server@matronics.com [mailto:
owner-rv8-list-server@matronics.com] On Behalf Of Larry Bowen
> Sent: Friday, January 27, 2012 3:57 PM
>
> To: rv8-list@matronics.com
> Subject: Re: RV8-List: battery selection
>
>
> I'm already committed to the dual LSI. PMags were still wet behind the
ears when I made the decision.
>
>
> Alternator is primary, main battery is backup. How is that not
practical? Educate me.
>
> --
> Larry Bowen
> Larry@BowenAero.com
> http://BowenAero.com
>
>
> On Fri, Jan 27, 2012 at 3:33 PM, Carl Froehlich <
carl.froehlich@verizon.net> wrote:
>
> No backup battery on a LightSpeed ignition install is not practical.
>
> For no a backup battery system (or one with a back up battery) a dual
P-Mags install is a better approach. If you want, I can tell you the name
of the person I gave my dual Lightspeeds to when I yanked them off my 8A
(replaced with P-Mags). You can get them real cheap.
>
> Carl
>
>
> From: owner-rv8-list-server@matronics.com [mailto:
owner-rv8-list-server@matronics.com] On Behalf Of Larry Bowen
> Sent: Friday, January 27, 2012 3:03 PM
> To: rv8-list@matronics.com
> Subject: Re: RV8-List: battery selection
>
>
> Can't help you on the battery, I've only used the 680.
>
>
> I'll have all glass and dual LSI in the RV-7, and I'm actually
considering one alt and one battery. Crazy, or just practical? TBD...
>
>
> In the RV-8, I put my Pointer ELT under the VS. No added structure
needed and helped a little with fwd CG.
>
>
> Cheers,
>
> --
> Larry Bowen
> Larry@BowenAero.com
> http://BowenAero.com
>
> On Fri, Jan 27, 2012 at 2:26 PM, Stan Loer <stazel@cpros.com> wrote:
>
> Has anyone installed the Odyssey PC625 battery? I know that the PC680 is
more common, but I'm looking at a dual installation with one battery
forward and the other aft. The 625 is slightly smaller and lighter than
the 680. My 8 will be all electric, no steam gauges, and set up for
day/night VFR, so a dual battery installation makes more sense to me than a
back-up alternator. Seems to me that dual paralleled PC625 batteries
should provide plenty of get-home power in case of an alternator failure,
even at night, but my electrical expertise is limited and I'll take all the
help I can get.
>
>
> While I'm at it, a question re ELT mount locations. I've seen several
mounted on the "hat shelf". This is tempting as it's very
>
> convenient, but the shelf is kinda flimsy. Beef it up? I'm also
looking at possibly mounting it on brackets off the side of the aft battery
box. More complex, but maybe a better choice.
>
>
> et="_blank">http://www.matronics.com/Navigator?RV8-List
>
> tp://forums.matronics.com
>
> _blank">http://www.matronics.com/contribution
>
>
> http://www.matronics.com/Navigator?RV8-List
>
> http://forums.matronics.com
>
> http://www.matronics.com/contribution
>
>
> et="_blank">http://www.matronics.com/Navigator?RV8-List
>
> tp://forums.matronics.com
>
> _blank">http://www.matronics.com/contribution
>
>
> http://www.matronics.com/Navigator?RV8-List
>
> http://forums.matronics.com
>
> http://www.matronics.com/contribution
>
>
===========
===========
===========
===========
>
--
--
Larry Bowen
Larry@BowenAero.com
http://BowenAero.com
Message 2
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Battery choice par deaux |
Thanks much for the feedback. It's great to have a pool of expertise to
tap into for us novice builders. Not to belabor the point, but just to
add some specifics not included in my last post: I'll be installing at
least one P-Mag and one E-Mag. Maybe dual P-Mags. Circuit protection
will be through a VPX-Sport. Each battery will feed its own "always
hot" battery bus which will supply the mags and at least the radio. The
Dynon Skyview installation will include the back-up battery option. I
want to be able to turn off both battery master switches and still have
get home power in the unlikely event of a contactor failure. May not
however, be night legal depending on how much complexity I'm willing to
add with back-up circuits.
Stan Loer
RV-8 very slow QB
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|