Today's Message Index:
----------------------
1. 08:22 AM - DC clamp meter (blues750)
2. 06:12 PM - Re: Re: Z-12 Architecture, Back-Up Alternator Wiring (Robert L. Nuckolls, III)
3. 06:12 PM - Charging two EarthX batteries (Hariharan Gopalan)
4. 07:27 PM - Re: DC clamp meter (Robert L. Nuckolls, III)
5. 07:43 PM - Re: Charging two EarthX batteries (Robert L. Nuckolls, III)
Message 1
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Looking for recommendations on a suitable DC clamp meter to do capacity checks
on my EarthX batteries. Prices seem to be all over the place. Am curious what
kind others might be having good experience with. Thanks all!
Dave
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496171#496171
Message 2
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| Subject: | Re: Z-12 Architecture, Back-Up Alternator Wiring |
At 05:12 PM 5/1/2020, you wrote:
>
>So I took your advice and crafted a Z-12 version.
<SNIP>
>--------
>Michael Fleming
Michael,
Did about 200 miles of 'asphalt engineering'
yesterday on this thread. Picked up some parts
for a friend's welder/generator in Enid. His
Chute is electro-hydraulic and he had some
cattle to work today
I've incorporated some of your input along with
musings from the List and my own starry-eyed
stare down the highway.
https://tinyurl.com/y9n57vlw
This drawing needs some notes to explain
on some new ideas:
Z12 lite could be pretty simple. No optional
busses. Dual alternator dependability combined
with a dutifully maintained battery would
take you far and in confidence. This drawing
illustrates and preserves the aux alternator
installation as offered by B&C.
Depending on proposed accessories and operating
modes one might wish to add battery or
clearance delivery/endurance busses. Purely
optional . . . if you gotta use for one,
add it.
Question: your drawing shows a fused feeder off
the battery to the p-mag. What is the rational
for utilizing this source as opposed to simply
tying it to the main bus? What is the
current draw of this feature on the p-mag?
Bob . . .
Message 3
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| Subject: | Charging two EarthX batteries |
I have two earthX batteries and use an external port to connect an optimate
TM-291, 5 AMP charger to charge these two batteries. Current setup is to
manually connect / disconnect the cable from the port to either battery.
The only problem with this approach is that when one battery is charged, I
have to manually connect the second battery. Some kind of a voltage sensing
relay to switch out the first battery and and connect the charger output to
the second battery would be an ideal solution.
Wonder if anyone has any tips? I looked at some dual battery chargers, but
not sure how these would work with the optimate charger and earthX
batteries.
Thanks
Hari
Message 4
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| Subject: | Re: DC clamp meter |
At 10:20 AM 5/3/2020, you wrote:
>
>Looking for recommendations on a suitable DC clamp meter to do capacity
>checks on my EarthX batteries. Prices seem to be all over the place.
>Am curious what kind others might be having good experience with. Thanks all!
>
>Dave
Help us out with your mission. A 'capacity test' is
a measured depletion and recharge of a battery
to deduce its contained energy.
This could be accomplished at a prescribed discharge
rate commensurate with your anticipated 'endurance
loads' (useful capacity of a battery varies with
load).
In the attached chart you can see how a battery
rated at 18Ah under a 20Hr discharge rate
delivers only 12Ah if discharge over 1Hr rate.
2/3rds of its capacity is tossed off as internal
heating of the battery.
To accomplish a capacity test, you need a means
for establishing a constant current load at
some selected rate while recording the battery's
output voltage until it falls below some
artfully selected cut-off voltage.
Alternatively, consider a device like
this:
https://tinyurl.com/moaoaus
I have used these on numerous projects
over the years. I'm thinking of upgrading
my 20+ year old device. The newer ones
have some really nice software features.
I'm wondering if you're interested in the
battery's cranking (load bearing) characteristics.
This is a different test that quantifies the
battery's internal resistance -and- state of
the chemistry under heavy load.
For this you need a critter like this
https://tinyurl.com/yag4529y
I have a couple of these HF testers . . .
got a $high$ AutoMeter tester too but
the el-cheeso works just fine for our
purposes.
You hook this to your battery under test.
Just before you crank up the load such that
battery voltage falls to 9V, push the 15
second timer button. Adjust load
during the 15 second interval
to maintain 9V reading. Take note of
the CURRENT delivered by the battery
at the end of 15 seconds.
Acquire this benchmark value for a new
battery. Note the value with a sharpie
on the battery case along with date.
At any later time, should the battery
perform to less than 80% (*) of new,
consider replacing the battery. Same
thing goes with capacity checks 80%
is the 'retirement' value for
batteries in TC, flight-for-hire aircraft.
(*) Of course, you CAN establish your own
benchmarks if some other numbers make
more sense for how you operate your airplane.
But pick other numbers based on understanding,
not because your trying to squeeze more
service out of the battery.
EARTHX batteries (and all other LIFePO4
batteries) are special cases. Your load
test value will probably be more than
9V . . . internal resistance of these
batteries is very low and you probably
can't load it down to 9v without
tripping internal current limits.
If you want to capcheck your EARTHX,
fire up your airplane's anticipated
endurance mode accessories and measure
the time before auto-disconnect. Make
note of that time for the new battery.
Think about replacing the battery when
those minutes fall by 25% or so.
As for DC clamp-on ammeters, they've
been around for some time. I have
a Fluke meter I bought about 20 years
ago . . . hall-effect device . . . works
mostly okay for large measurements
(10+ amps) but flakiness typical of
contemporary technology at low current
levels.
I have one like this
https://tinyurl.com/y9gb4cgs
. . . but haven't had much occasion to
exercise it's capability. It has a
ZERO read function on DC amps that
wipes out most of the variability
in the hall-sensor at low current
readings. Seems to work well. Will follow
up when I've learned more . . . but
the price/performance numbers are
certainly attractive.
Bob . . .
Message 5
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| Subject: | Re: Charging two EarthX batteries |
At 08:09 PM 5/3/2020, you wrote:
>I have two earthX batteries and use an external
>port to connect an optimate TM-291, 5 AMP
>charger to charge these two batteries. Current
>setup is to manually connect / disconnect the
>cable from the port to either battery.=C2 The
>only problem with this approach is that when one
>battery is charged, I have to manually connect
>the second battery. Some kind of a voltage
>sensing relay to switch out the first battery
>and and connect the charger output=C2 to the
>second battery would be an ideal solution.
>
>Wonder if anyone has any tips? I looked at some
>dual battery chargers, but not sure how these
>would work with the optimate charger and earthX batteries.
>
>Thanks
>Hari
Why do you need to 'charge' these batteries?
How often do you fly. How long is your
longest storage interval?
There is 'tribal knowledge' that suggests
a benefit for hooking 'shore power'
to the battery(ies) in a parked airplane. But unlike
the flooded battery in your grandpa's '54, 6v Pontiac,
modern SVLA and LiFePo batteries have very low self-discharge
rates.
Unless you're storing the airplane for a long
period of time, shore power connection
isn't really useful . . . and if the charger
is poorly designed for such service . . . it
may be detrimental to the service life of the
battery.
What does EarthX recommend for battery maintenance
during various intervals of inactivity?
Here's a data-dump on the topic of self-discharge
in batteries . . . along with a wealth of other
battery info.
https://tinyurl.com/yczco6vp
If you're going to store for a long time and especially
if ambient temps are high, consider removing the battery(ies)
for storage under your bed . . . or some other environmentally
friendly space.
Otherwise, your batteries should live and perform
well with no external attention. You do need a charger
in case of inadvertent depletion of the battery(ies) . . .
in which case, I would charge them independently
before flight.
Bob . . .
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