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RV10 primary elec sys wiring
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airknot



Joined: 12 Aug 2020
Posts: 11
Location: Europe

PostPosted: Tue Aug 18, 2020 11:05 pm    Post subject: Re: RV10 primary elec sys wiring Reply with quote

OK, got it. 1st thing I noticed is that you didn't totalize current for
[/quote]
the various phases of flight. Even without looking there, your 'typical'
consumption for everything is only 36 A. I'd look at cruise, with pitot
heat and boost pump included for worst case numbers. Re-examine what
you've included for each phase of flight. ex: Looks like you show 1 A
for the flap motor, for all phases of flight. Also, look carefully at
recommended circuit protection values for each device. ex: Even though
the flap motor may only consume 5 A, IIRC, the docs for it recommend
closer to 15 A for circuit protection due to startup surge.

I suspect that the number for the boost pump number is a bit low. The
automotive injection pumps typically used in a/c boost pumps typically
draw a *minimum* of around 4.5A; most will draw closer to 6A. That draw
doesn't really change with engine power, since they pump the same
quantity of fuel at the same pressure, regardless of flow to the engine
(excess is bypassed back to the inlet). The Walbro pumps (not the one
used by AFP) recommend a 20A circuit protection, due to startup surge
current.

I didn't do a line-by-line analysis, so you can probably find more power
savings.

Charlie
[/quote]

thank you, Charlie. will try!
...without experience in Experimental Aviation field, especially systems design, this task seems to be unrealistic. i can't aloow myself to rely just on my assumptions. thinking how to figure out...


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PostPosted: Wed Aug 19, 2020 5:39 am    Post subject: RV10 primary elec sys wiring Reply with quote

Quote:

I didn't do a line-by-line analysis, so you can probably find more power
savings.

Charlie


thank you, Charlie. will try!
..without experience in Experimental Aviation field, especially systems design, this task seems to be unrealistic. i can't aloow myself to rely just on my assumptions. thinking how to figure out...
[/quote]
Value to be secured in conducting detailed
load analysis is 2-fold.

(1) legacy design goals for TC aircraft dictate
that under worst case running loads, the ship's
alternator is loaded to only 75 or 80% of nameplate
rating.

This design point makes sure that there is
ample headroom in available energy not just
to run the ship's electro-whizzies . . . but
with energy left over to RECHARGE the battery
within a reasonable interval after takeoff.

This goal correctly assumes that the battery
will be capable of supporting design goals
for battery only endurance within some
acceptable time after takeoff. Of course, this
dovetails with another design goal that
calculates/demonstrates battery only endurance
with a battery that is nearing end-of-life
at 80% of new capacity.

The second goal for doing a load analysis
is to establish loads for the various phases
of flight to be compared with a hopefully
KNOWN battery condition. This exercise is
analogous to KNOWING how much fuel is aboard
to reduce the risk of mission failure for
having exceeded what should have been
easily predictable limits.

Your customer has stacked a lot of hardware
on the project . . . big engine, fat alternator,
big battery, backup battery and perhaps
things like heated pitot tubes. Assuming
all things are working as installed, this
project has energy to burn.

But some of this stuff is for backup . . .
to save the day in the 'event
of failure'. But all the backup in the
world may be of poor or no value if it
is not SIZED AND MAINTAINED to step up
to certain calculated/demonstrated
tasks.

This is good practice for any aircraft . . .
TC or OBAM.

Given the cited selection of hardware
for this project, I'm exceedingly
disappointed that a second engine
driven power source was not included
even if it's just a 4-pound, SD-8
spline driven alternator.

I'd trade a dozen stand-by batteries
for a single second-source of engine
driven power. Batteries are like house
plants . . . they demand consistent
attention. Alternators are more like
hammers . . . they'll be there when you
need them.

But of course, all this is academic
and un-quantified until the homework
is done.

"Knowing is not understanding . . . you
can KNOW a great deal and still UNDERSTAND
nothing." --C.F. Kettering--

"Until you have measured something and can
talk about it in numbers, your understanding
has barely scratched the surface of science."
--Lord Kelvin--





Bob . . .


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airknot



Joined: 12 Aug 2020
Posts: 11
Location: Europe

PostPosted: Wed Aug 19, 2020 5:50 am    Post subject: Re: RV10 primary elec sys wiring Reply with quote

(1) legacy design goals for TC aircraft dictate
that under worst case running loads, the ship's
alternator is loaded to only 75 or 80% of nameplate
rating.

This design point makes sure that there is
ample headroom in available energy not just
to run the ship's electro-whizzies . . . but
with energy left over to RECHARGE the battery
within a reasonable interval after takeoff.

[/quote]

Bob, thank you

I have read about this and hence affraid we should replace 60 Amps alternator with at least 70 Amps, or I understand this incorrectly?
but anyway such huge load is strange.

regaring secondary alternator - perheps we will do an upgrade later, as I am 100% feel the same as you

Alex


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PostPosted: Wed Aug 19, 2020 5:57 am    Post subject: RV10 primary elec sys wiring Reply with quote

On Wed, Aug 19, 2020 at 2:11 AM airknot <airkbp(at)gmail.com (airkbp(at)gmail.com)> wrote:

Quote:
--> AeroElectric-List message posted by: "airknot" <airkbp(at)gmail.com (airkbp(at)gmail.com)>

OK, got it. 1st thing I noticed is that you didn't totalize current for

the various phases of flight. Even without looking there, your 'typical'
consumption for everything is only 36 A. I'd look at cruise, with pitot
heat and boost pump included for worst case numbers. Re-examine what
you've included for each phase of flight. ex: Looks like you show 1 A
for the flap motor, for all phases of flight. Also, look carefully at
recommended circuit protection values for each device. ex: Even though
the flap motor may only consume 5 A, IIRC, the docs for it recommend
closer to 15 A for circuit protection due to startup surge.

I suspect that the number for the boost pump number is a bit low. The
automotive injection pumps typically used in a/c boost pumps typically
draw a *minimum* of around 4.5A; most will draw closer to 6A. That draw
doesn't really change with engine power, since they pump the same
quantity of fuel at the same pressure, regardless of flow to the engine
(excess is bypassed back to the inlet). The Walbro pumps (not the one
used by AFP) recommend a 20A circuit protection, due to startup surge
current.

I didn't do a line-by-line analysis, so you can probably find more power
savings.

Charlie
[/quote]

thank you, Charlie. will try! 
..without experience in Experimental Aviation field, especially systems design, this task seems to be unrealistic. i can't aloow myself to rely just on my assumptions. thinking how to figure out...

[/quote]Naa... you can do it; you're just learning how right now. You've started with the right techniques, and you're smart enough to ask if there's stuff that you don't know that you don't know. 
You have the basic analysis tool already, with the loads spreadsheet. Just tweak it a line at a time. 'Fly' each component line, from startup to shutdown, and update the spreadsheet to reflect that. Ex: Flaps would (possibly) get activated for a few seconds prior to takeoff, and again for a few seconds after liftoff. Negligible load on the alternator for those actions, and then zero load until in the pattern for landing. And in most light planes, not a requirement for landing, if conservation of electrical energy was critical for other stuff, like landing lights at night. Plug that into that line of the spreadsheet. Then move to the next line and go through the same process. Slightly different for something like a Comm radio; it will have very low but continuous energy demand, except when transmitting. But transmit demand is 'reasonable' (unquantified, I know), and will be in very short, infrequent 'blips'. So while you can't ignore the demand when sizing circuit protection/wire size, you might be able to ignore the peak transmission demand when looking at alternator capacity. Those intermittent loads rarely all hit at the same time, so the alternator would rarely (if ever) be tasked with supporting max consumption of every device at the same time.
As I think I mentioned earlier, many mfgrs don't bother to give you accurate current consumption numbers for their products in an 'idle' state since they're focused on having you size circuits for worst case consumption. I think you can already see that your 60A alternator has plenty of capacity for your loads. If you're set on using a backup battery for an 'E' bus, you could wait until you have all the hardware on hand to measure each component's real world consumption, and size the battery to handle total real world loads for your desired duration. (If you need help with how to do that, just ask.)  
But I must say that if I were planning on an IFR platform that's totally dependent on electrons to keep the panel lit, I'd give serious thought to Bob's recommendation of adding a 2nd alternator rather than a 2nd battery. That 2nd battery is like a very heavy, very small tank of aux fuel, that will have a relatively small capacity, and due to the aging process, a shrinking capacity. An aux alternator, on the other hand, will cost a bit more up front but will be lighter, and will supply energy until available fuel is exhausted or the prop stops turning. If that happens, you're going to be on the ground in less time than any decent primary battery will last, anyway. With a primary alternator failure, it could be the difference between knowing you have to be on the ground in 45 minutes (with everything under you below minimums), to paying a bit more attention to bus voltage while you continue your original flight plan to your destination.
Having fun yet?
Charlie


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PostPosted: Wed Aug 19, 2020 6:17 am    Post subject: RV10 primary elec sys wiring Reply with quote

On Wed, Aug 19, 2020 at 8:58 AM airknot <airkbp(at)gmail.com (airkbp(at)gmail.com)> wrote:

Quote:
--> AeroElectric-List message posted by: "airknot" <airkbp(at)gmail.com (airkbp(at)gmail.com)>

(1) legacy design goals for TC aircraft dictate
    that under worst case running loads, the ship's
    alternator is loaded to only 75 or 80% of nameplate
    rating.

    This design point makes sure that there is
    ample headroom in available energy not just
    to run the ship's electro-whizzies . . . but
    with energy left over to RECHARGE the battery
    within a reasonable interval after takeoff.

 


Bob, thank you

I have read about this and hence affraid we should replace 60 Amps alternator with at least 70 Amps, or I understand this incorrectly?
but anyway such huge load is strange.

regaring secondary alternator - perheps we will do an upgrade later, as I am 100% feel the same as you

Alex
[/quote]Bob,
Should that 'worst case running loads' thing be a bit more... nuanced (for lack of a more precise term), especially for new arrivals who are just beginning to understand electrical loads? The current situation is a great example. The literal worst case has flaps, landing lights, comm transmitter(s), etc etc all running at the same time, and continuously. This is obviously not going to happen. Hence the need for some..nuance... in defining 'worst case'.
Or am I totally wrong?
Thanks,
Charlie 


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user9253



Joined: 28 Mar 2008
Posts: 1907
Location: Riley TWP Michigan

PostPosted: Wed Aug 19, 2020 9:12 am    Post subject: Re: RV10 primary elec sys wiring Reply with quote

A 60 amp alternator will be more than enough for your plane unless you can
show that more is actually needed. One item needs to be removed from your
list: the alternator field current. A rating of 60 amps means that the alternator
will put out at least 60 amps in addition to the field current. In other words,
the alternator will put out 64 amps. The rating of an alternator is a nominal
value that depends on cooling and RPM. If kept cool and turned fast enough,
an alternator will put out much more than its nominal rating.
I would be surprised if your RV-10 electrical system will draw more 30 amps continuously.
Like Charlie suggested, measure the actual current. That can be done without
starting the engine by powering the system with a battery or power supply.


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PostPosted: Wed Aug 19, 2020 6:54 pm    Post subject: RV10 primary elec sys wiring Reply with quote

Quote:


Bob, thank you

I have read about this and hence affraid we should replace 60 Amps alternator with at least 70 Amps, or I understand this incorrectly?
but anyway such huge load is strange.

regaring secondary alternator - perheps we will do an upgrade later, as I am 100% feel the same as you

Like others on the List, I am skeptical of your
load figures. 60A is generally more than adequate
for a single engine airplane unless you have electric
cabin heater, heated seats, etc.

In all candor sir, we should beg your forgiveness for
loading such a task in the midst of pressing
demands from your 'clients'.

The 100% best way to get load values is go MEASURE
them. Easily done as you start lighting up the panel
with shore-power support. In fact, I just this minute
ordered another power supply like this

https://tinyurl.com/y42yceb4

0-16v, 0-10A, accurate digital displays. EXCEEDINGLY
handy for precision recharging of lithium cells in
a constant voltage, constant current mode. Would
be similarly handy for surveying your project's
accessory loads. Just pull the breaker/fuse for
an appliance. Apply 14.2 Volts to its feeder.
READ the running load from the face of the power supply.

I doubt you'll have many devices, if any, that
draw more than 10A each.

The critical feature of this exercise right
now is to segregate various loads into their
respective flight functions. There are few
airplanes that are operated with everything
up and running at the same time. Do not include
transient loads like landing lights and transmitter
current draws. You're attempting deduce the
ENERGY budget for various phases of flight.

Surprisingly enough, engine starters, flap
motors and transmitters are all but insignificant
in this study. ENERGY is measured in watt-seconds,
etc. A starter demands lots of WATTS but for
only a few seconds and then only once per flight
cycle. A suite of legacy incandescent navigation
lights (3 bulbs at 2A each) takes 3 x 2 x 14 x
10800 about 900,000 watt-seconds over the course
of a 3-hour night flight! Nav lights used to
be the most energy hungry system on most light
aircraft. You DID NOT include nav lights in
your battery-only endurance calculations.

That's what all those columns are for in the
load analysis . . . we can be 99% confident that your 60A
machine will be plenty.


Bob . . .


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airknot



Joined: 12 Aug 2020
Posts: 11
Location: Europe

PostPosted: Fri Aug 21, 2020 9:22 pm    Post subject: Re: RV10 primary elec sys wiring Reply with quote

thank you, Gentlemen, for all your advises!
working on ELA...

Alex


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airknot



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PostPosted: Thu Aug 27, 2020 12:41 am    Post subject: Re: RV10 primary elec sys wiring Reply with quote

Dear Gents,

Revised my ELA calculations with assumtions:
-Comm system is working continiously during flight
-To start and taxi phases power consumtion for backupbatteries charging (G5, 2 -Skyview dispalys and IBBS backup battery) was added
-Pitot heating works during takeoff, approach and landing phases(icing conditions)
-fuel pump works during start, taxi, t/o, landing

please, critic me )

https://tinyurl.com/y6q2jrma

p.s. feel myself extremely self-doubt...

to check all real-life consumptions I must build primary elec system on airplane. and hookup all the devices. or i am not right (


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PostPosted: Thu Aug 27, 2020 6:03 am    Post subject: RV10 primary elec sys wiring Reply with quote

On Thu, Aug 27, 2020 at 3:47 AM airknot <airkbp(at)gmail.com (airkbp(at)gmail.com)> wrote:

Quote:
--> AeroElectric-List message posted by: "airknot" <airkbp(at)gmail.com (airkbp(at)gmail.com)>

Dear Gents,

Revised my ELA calculations with assumtions:
-Comm system is working continiously during flight
-To start and taxi phases power consumtion for backupbatteries charging (G5, 2 -Skyview dispalys and IBBS backup battery) was added
-Pitot heating works during takeoff, approach and landing phases(icing conditions)
-fuel pump works during start, taxi, t/o, landing

please, critic me )

https://tinyurl.com/y6q2jrma

p.s. feel myself extremely self-doubt...

to check all real-life consumptions I must build primary elec system on airplane. and hookup all the devices. or i am not right (

You're doing fine; it takes multiple iterations to debug a design.
Go through it line by line, and play 'what if' for every situation you can think of, related to that device, that leaves you able to make choices. If night flight, lights on continuously. If mech fuel pump failure, boost pump on continuously.  Etc etc.
Go through again, line by line, asking how/when the device uses power, and whether it's significant. The big deal is total energy (power * time-active). Stuff that is almost never active can be ignored as part of your continuous load. Ex: trim, flaps, comm's transmit current draw (which is several times higher than 'idle' current), etc etc. Bob mentioned 'watt-seconds' earlier. If you have only one alternator, then after it fails (assume that it will), then the battery(s) has some number of watt-seconds of energy available in its 'tank'. An example battery might have 12V * 18AH = 260 watt-hours, * 60 minutes = 12960 watt-seconds. (Please check the math...) If, for example, the trim is activated for 2 seconds, it uses  0.15A * 12V =  1.8 watts, * 2 seconds = 3.6 watt-seconds of energy while trimming. You probably couldn't use more than 100 watt-seconds from the battery for trimming, on the entire flight. Point is, it's such a tiny percentage that it can be ignored, unless you have dozens of those tiny items which could become significant if all operated, and all operated continuously.
Examples of things that could be tweaked in the spreadsheet (not a line-by-line analysis):
The comm can be listed at its lowest current. It only consumes the max while transmitting, which is a tiny fraction of total time.
If you're going to fly IFR, the pitot heat should be listed as continuous, because you may be in a marginal icing situation where you can't turn it off. (That's what the 'worst case' thing means.)

You could probably zero out the trim current. Like the radio, it's only operating a tiny fraction of the time, and shouldn't draw any current at all while not operating.

Ask the mfgr about the oil cooler servo; like the trim servos, it shouldn't draw any current unless operating.

Boost pump should be shown as continuous. 'Worst case' of mechanical fuel pump failure during cruise would require running boost until landing.

Having fun yet?
Charlie


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PostPosted: Thu Aug 27, 2020 8:21 am    Post subject: RV10 primary elec sys wiring Reply with quote

Very nice tutorial.
If the boost pump is normally off in cruise I'd also ignore that load
for an alternator failed scenario, same as for landing lights.
Ken

On 27/08/2020 9:58 AM, Charlie England wrote:
Quote:


On Thu, Aug 27, 2020 at 3:47 AM airknot <airkbp(at)gmail.com
<mailto:airkbp(at)gmail.com>> wrote:


<airkbp(at)gmail.com <mailto:airkbp(at)gmail.com>>

Dear Gents,

Revised my ELA calculations with assumtions:
-Comm system is working continiously during flight
-To start and taxi phases power consumtion for backupbatteries
charging (G5, 2 -Skyview dispalys and IBBS backup battery) was added
-Pitot heating works during takeoff, approach and landing
phases(icing conditions)
-fuel pump works during start, taxi, t/o, landing

please, critic me )

https://tinyurl.com/y6q2jrma

p.s. feel myself extremely self-doubt...

to check all real-life consumptions I must build primary elec
system on airplane. and hookup all the devices. or i am not right (

You're doing fine; it takes multiple iterations to debug a design.

Go through it line by line, and play 'what if' for every situation you
can think of, related to that device, that leaves you able to make
choices. If night flight, lights on continuously. If mech fuel pump
failure, boost pump on continuously.  Etc etc.
Go through again, line by line, asking how/when the device uses power,
and whether it's significant. The big deal is total energy (power *
time-active). Stuff that is almost never active can be ignored as part
of your continuous load. Ex: trim, flaps, comm's transmit current draw
(which is several times higher than 'idle' current), etc etc. Bob
mentioned 'watt-seconds' earlier. If you have only one alternator,
then after it fails (assume that it will), then the battery(s) has
some number of watt-seconds of energy available in its 'tank'. An
example battery might have 12V * 18AH = 260 watt-hours, * 60 minutes =
12960 watt-seconds. (Please check the math...) If, for example, the
trim is activated for 2 seconds, it uses  0.15A * 12V =  1.8 watts, *
2 seconds = 3.6 watt-seconds of energy while trimming. You probably
couldn't use more than 100 watt-seconds from the battery for trimming,
on the entire flight. Point is, it's such a tiny percentage that it
can be ignored, unless you have dozens of those tiny items which could
become significant if all operated, and all operated continuously.

Examples of things that could be tweaked in the spreadsheet (not a
line-by-line analysis):

The comm can be listed at its lowest current. It only consumes the max
while transmitting, which is a tiny fraction of total time.
If you're going to fly IFR, the pitot heat should be listed as
continuous, because you may be in a marginal icing situation where you
can't turn it off. (That's what the 'worst case' thing means.)
You could probably zero out the trim current. Like the radio, it's
only operating a tiny fraction of the time, and shouldn't draw any
current at all while not operating.
Ask the mfgr about the oil cooler servo; like the trim servos, it
shouldn't draw any current unless operating.
Boost pump should be shown as continuous. 'Worst case' of mechanical
fuel pump failure during cruise would require running boost until landing.
Having fun yet?

Charlie


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user9253



Joined: 28 Mar 2008
Posts: 1907
Location: Riley TWP Michigan

PostPosted: Thu Aug 27, 2020 9:41 am    Post subject: Re: RV10 primary elec sys wiring Reply with quote

The battery contactor only draws 0.75 amps. See https://www.gigavac.com/sites/default/files/GX11B-GX12B-GX21B-Temp-Considerations.pdf
The USB sockets will not draw any current unless something is plugged in.
Even then, the 12 volt current draw will be less than half of the 5 volt current (assuming switching power supply)
The clock only uses 0.1 amp. See https://iflyei.com/wp-content/uploads/SC-5-OI.pdf
The com radio only uses 0.6 amps unless the transmit button is continuously held in.
The TCW - SERVO VALVE will not run continuously. Do not count its current.


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PostPosted: Thu Aug 27, 2020 10:17 am    Post subject: RV10 primary elec sys wiring Reply with quote

On 8/17/2020 9:41 PM, Robert L. Nuckolls, III wrote:

Quote:

  With that engine, why are you including a backup
  battery?  A 8-10A standby alternator on a vacuum
  pump pad offers UNLIMITED endurance with about
  a 4 pound penalty. I go out of my way to avoid
  adding batteries to a design over and above
  those normally expected to start engines and
  back up the primary alternator.

  Do you not PLAN to conduct periodic airworthiness
  checks on the main battery?


  Bob . . .

OP - I too have an RV10 with  the 2 mag engine and a 3 display GRT panel.  I'll just add a couple of observations  based on 9+ years and 1200+ hours of IFR intensive operation.
Bobs point above is dead on target for RV10 folks in particular - I have a 40 amp main alt and a 20amp alt on the vacuum pad (B&C externally controlled).  That 2nd amp removes the main failure point that threatens to actually shorten a flight and force a alternative landing. I had a number of backup batteries connected to various avionic components but found that it was a challenge maintaining them to the proper standard for true reliance in case of failure.  They've all come out and I simply focus on my main battery.  2 Alternators and 1 battery is a real sweet spot.
But that's not what i have.  I installed a Z-14 -2 alts, 2  batts, 2 buses, also known by Bob as 'everything and the kitchen sink' electrical system.  It's overkill by many measures but I love it.  However I'd recommend that the 'Z' with 2 alts and 1 battery is the optimal config from a price-performance perspective.  And like Bob said, get rid of those other backup batteries.
It is commonly said that:
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Another point is to protect equipment during engine start
Absolutely NO equipment needs to be protected during engine start. There is no such thing as voltage spikes during starting. That is an old wive's tale. Are you going to believe rumors based on 1950's technology or Bob N. who has written the book on aircraft electrical systems?
True enuff I suppose but my panel did suffer from low voltage sagging during some starts (cold wx combined with panel running before start with a less than fresh battery and no extra avionics switches to manage total power reqmts). It now simply reboots the displays if the voltage is too low but earlier it was possible to corrupt the software if the load was abnormally interrupted. A SW bug for sure but it happened.

Those displays, which come on with my master switch, are amp hogs. So I added a now discontinued product from TCW - IPS (intelligent power stabilizer) which has kept me from losing my displays for 5 years now. A well managed, big battery combined with modern avionics should avoid this issue entirely.

So I'd suggest adding a small alternator on the vacuum pad, eliminating the extra batteries and not worrying about the 60 amp alternator's ability to handle anything you throw at it. It still has a battery behind it - the most reliable component in the system. The Z designs are really well crafted and don't require modification to use them successfully.

BTW, the Odyssey AGM batteries are really easy to manage and maintain with a volt meter. Read the owners manual and follow it to the letter: 1) make sure your charging system is set to run between 14.1 and 14.7 volts 2) Use a proper charger if and when needed, 3) Keep it fully charged when inactive, 4) if 24hours after charging, the voltage is less than 12.5 volts (75% capacity), replace it. You might do that at 12.6 volts.

Bill "not reading the owners manual cost me 3 or 4 batteries before I became fully literate" Watson
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