Today's Message Index:
----------------------
1. 06:11 AM - Diodes - Ground Pwr/Battery Master Contactors (Drummond Grinalds)
2. 06:24 AM - Re: Diodes - Ground Pwr/Battery Master Contactors (Robert L. Nuckolls, III)
3. 06:27 AM - Re: Diodes - Ground Pwr/Battery Master Contactors (Charlie England)
4. 06:42 AM - Re: Re: Measuring battery internal resistance (Robert L. Nuckolls, III)
5. 02:02 PM - Re: Re: Measuring battery internal resistance (skywagon185guy .)
6. 03:06 PM - Re: Re: Measuring battery internal resistance (Robert L. Nuckolls, III)
7. 05:19 PM - Re: Re: Measuring battery internal resistance (skywagon185guy .)
Message 1
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| Subject: | Diodes - Ground Pwr/Battery Master Contactors |
Hi - This is my first question for the forum.
I am building RV8 w single aft battery/ dual alternator. Ground power
contactor and battery master battery contactors are aft. Obtained both
contactors from B&C with 1N5400 diodes. Total of 3 diodes (2 on the
Ground Pwr Contactor and 1 on the Battery Master Contactor.)
Diagram from Aircraft Spruce with the Piper jacks written by AeroElectric
showed using 1N5402 diodes on the Ground Pwr contactor. Are there
compelling reasons to swap out my 1N5400 diodes with 1N5402 or other?
Thanks for reading and for responding.
Drum
Message 2
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| Subject: | Re: Diodes - Ground Pwr/Battery Master Contactors |
At 08:04 AM 6/28/2020, you wrote:
>Hi - =C2 This is my first question for the forum. =C2
>
>I am building RV8 w single aft battery/ dual
>alternator.=C2 Ground power contactor and battery
>master battery contactors are aft. =C2 Obtained
>both contactors from B&C with 1N5400
>diodes.=C2 Total of 3 diodes =C2 (2 =C2 on the Ground
>Pwr Contactor =C2 and =C2 1 on the Battery Master Contactor.)
>
>Diagram from Aircraft Spruce with the Piper
>jacks written by AeroElectric =C2 showed using
>1N5402 diodes on =C2 the =C2 Ground Pwr
>contactor.=C2 Are there compelling reasons =C2 to =C2
>swap out =C2 my 1N5400 diodes with 1N5402 or other?
>
>Thanks=C2 for reading and for responding.
The 1N54xx series devices are essentially
identical for our purposes. The XX denotes
reverse voltage rating that range from 50
to 1000 volts. See:
<https://www.vishay.com/docs/88516/1n5400.pdf>https://www.vishay.com/docs/88
516/1n5400.pdf
For our purposes, any of those devices
will be operated within limits on a
14v aircraft.
Bob . . .
Message 3
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| Subject: | Re: Diodes - Ground Pwr/Battery Master Contactors |
On Sun, Jun 28, 2020 at 8:15 AM Drummond Grinalds <dgrinalds@gmail.com>
wrote:
> Hi - This is my first question for the forum.
>
> I am building RV8 w single aft battery/ dual alternator. Ground power
> contactor and battery master battery contactors are aft. Obtained both
> contactors from B&C with 1N5400 diodes. Total of 3 diodes (2 on the
> Ground Pwr Contactor and 1 on the Battery Master Contactor.)
>
> Diagram from Aircraft Spruce with the Piper jacks written by AeroElectric
> showed using 1N5402 diodes on the Ground Pwr contactor. Are there
> compelling reasons to swap out my 1N5400 diodes with 1N5402 or other?
>
> Thanks for reading and for responding.
>
> Drum
>
> Same current rating. Voltage ratings of 50V vs 200V.
http://www.datasheetcatalog.com/info_redirect/datasheets/newjerseysemiconductor/1N5400-1N5408.pdf.shtml
When I buy diodes, I usually get higher voltage ratings because they
typically don't cost much (if any) more in small quantities than lower
voltage ratings. But if B&C shipped 50V rated diodes with their contactors,
I'd be confident that 50V is good enough. (Even 1A current rating would be
good enough for the shunt around the coil, but the 3A diodes are physically
more rugged.)
Charlie
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Message 4
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| Subject: | Re: Measuring battery internal resistance |
At 10:29 PM 6/27/2020, you wrote:
><dick@thetaskerfamily.com>
>
>Oops. For your example, the delta current is actually
>2.444-1.235=1.209A. So the R=0.015/1.209=12.4 milliohms.
>
>You forgot to subtract the first reading. Other than the simple
>math error (something I do all the time...) the rest of the
>explanation is spot on.
>
>Dick Tasker
>
Good catch! Thank you sir.
BTW . . . I've been playing with my
newly acquired CBA IV battery analyzer
from West Mountain Radio.
I've confirmed suspicions that not
all 18650 cells are what they're 'marked
up' to be.
A few utility cells in the stable
are marked with truing amazing
capacity values like 3800 and 9000 mAh!
While doing cap checks on the cells I'm
noticing some common traits in LiFePO4
cells that contribute to and article/white
paper on system integration of lithium
onto our airplanes.
I do have a couple of cells by Panasonic
that were advertised as 2900 mAh devices.
They are proving to perform as advertised.
Just for grins, I conducted a quick
delta-I resistance check on one of the
cells last night. Snapshot attached.
The CBA IV software has a 'dynamic'
current mode that allows you to change the
load current while the test is running.
Pretty cool . . .
I've got brand new Aerovoltz and Hawker
batteries ordered on which I'll conduct
and record a library of performance curves
for comparison in the white paper.
Bob . . .
Message 5
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| Subject: | Re: Measuring battery internal resistance |
Thanks Bob and Dick for the details of measuring IR....
I will pursue a simple test setup....
Dave
On Sat, Jun 27, 2020 at 6:50 PM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 07:27 PM 6/26/2020, you wrote:
>
> Hi Bob,
> Thanks for the plot information...Maintainers and their profiles.
> Your details brought up a question.
> Would you have a suggestion for a simple setup for measuring internal
> cell/battery resistance, IR, of lithium based cells.
> Modelers use a lot of Lipo based batteries.=C3=82 And there is a strong
need
> to keep track of their condition and it seems like tracking IR could be t
he
> best option. A practical way to run the tests is sorely needed.
> Your suggestions are always appreciated.
>
>
> Hmmmm . . . internal resistance can be
> measured 'instantly' as opposed to doing
> a total-discharge cap-check. The results
> of a 'severe load' test considers
> a combination of chemical potential
> (capacity) -AND- internal resistance
> (ohmic losses). An internal resistance
> test can be conducted at lower energy
> levels than the load-test. Of course,
> all three tests require some instrumentation
> and process.
>
> The hammer-n-tongs way to measure cell
> impedance is to load with some handy value
> resistor, measure the voltage then increase
> the load by say, double or tripling it
> and read the voltage again.
>
> Example: Suppose your battery under test
> puts out 12.35 volts with a 10 ohm load.
> Your base current is 12.35/10 = 1.235 amps
>
> Temporarily add a second load resistor . . .
> any practical value, let's say another
> 10 ohms. Let's assume the new reading is
> 12.220 volts. Okay, total R across the
> battery is now 5 ohms. 12.22/5 = 2.444
> amps.
>
> So, for a delta current of 2.444A
> we read a delta-volts of 0.015V
>
> .015/2.444 = 6 milliohms
>
> One could craft a test box containing
> the necessary resistors, push-button
> and meter connections to simplify the
> setup but you'd still have to get out
> the calculator and do the math.
>
> I designed a direct reading battery
> resistance meter about 20 years ago.
> It featured a constant current load
> system that was switched with a
> multi-vibrator at about 10 cycles
> per second.
>
> It toggled between 1 and 11 amps.
> A pk-to-pk reading voltmeter would show
> the ripple voltage created at the battery
> terminals as the electronic load oscillated
> between the two current values.
>
> Internal resistance was nearly direct
> reading where 10 mv pk-pk equated to
> 1 milliohm of resistance. I've probably
> got those drawings around here somewhere.
>
> In my recent studies of on the garden
> tractor battery . . .
>
>
> http://www.aeroelectric.com/Pictures/Battery_Tender_Jr_Performance/03_BTJ
r+CCCY_Energy.jpg
>
> I was able to command the CBA IV battery
> analyzer to deviate between two accurately
> known load values while accurately reporting
> the battery voltage. That delta-E/Delta-A
> deduced a rather high internal resistance of
> about 60 milliohms.
>
> So there's three ways to go about it ranging
> from the hammer-n-tongs to poke-n-read.
>
>
> Bob . . .
>
Message 6
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| Subject: | Re: Measuring battery internal resistance |
At 03:58 PM 6/28/2020, you wrote:
>Thanks Bob and Dick for the details of measuring IR....
>I will pursue a simple test setup....
>Dave
What are the highest and lowest voltage battery
packs you want to test?
Bob . . .
Message 7
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| Subject: | Re: Measuring battery internal resistance |
Bob,
Majority are 3 to 6 cell packs.
The highest would be a 6 cell pack. Thus, 6 x 4.2 or about 25 vdc.
The lowest would be a 3 cell pack. About 12.5 vdc.
Dave
On Sun, Jun 28, 2020 at 3:11 PM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 03:58 PM 6/28/2020, you wrote:
>
> Thanks Bob and Dick for the details of measuring IR....
> I will pursue a simple test setup....
> Dave
>
>
> What are the highest and lowest voltage battery
> packs you want to test?
>
>
> Bob . . .
>
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