Today's Message Index:
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1. 08:04 AM - Re: RV10 Single Batt + Dual Alternator (bobmeyers)
2. 03:42 PM - Re: RV10 Single Batt + Dual Alternator (supik)
3. 06:53 PM - Re: Measuring battery internal resistance (Robert L. Nuckolls, III)
4. 08:37 PM - Re: Re: Measuring battery internal resistance (Dick Tasker)
Message 1
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| Subject: | Re: RV10 Single Batt + Dual Alternator |
I would rethink what you are trying to accomplish.
With all the monkey motion going on, it would seem you would be better served
going with a Z-14 rather than a gummed up Z-101.
Why an avionic bus at all let alone two? I would kill them both and their relays.
A utility bus seems way over the top. If you wish to control a utility device just
have a power switch for that device co-located with it. I would kill the utility
bus
If the motivation for the avionics buses is to avoid brown out of all the avionic
devices not on the GAD 27, a Z-14 system will solve that for you. Most of the
Garmin devices have a second power input you can connect to a second bus. You
can use a bridge rectifier to enable dual power feeds to any device that only
has one power input.
When I wired my RV14 I first drew up something similar to the ideas behind Z-101.
If the current Z-101 had been around I may have been more confident in using
that kind of layout. I went with a Z-14 layout instead.
When I get in my plane, I turn on batt 2 and all the avionics come up and stay
up. I turn on batt 1 as part of my startup checklist and during engine start,
no brown outs to the avionics occur.
This is the only reason I didn't go with my sorta Z-101 back then. I can think
of no other reason to choose between a straight Z-101 or a Z-14.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=497058#497058
Message 2
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| Subject: | Re: RV10 Single Batt + Dual Alternator |
Version 35
-UTIL BUS eliminated / rebranded to MAIN BUS fuse block (non essential stuff)
-AutoPilot head unit + servos moved to ESS BUS
https://i.ibb.co/VwNhKK5/Diagram-OM-ELA-Igor-v-035.jpg
--------
Igor
RV10 in progress
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=497060#497060
Attachments:
http://forums.matronics.com//files/diagram_om_ela_igor_v035_322.jpg
Message 3
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| Subject: | Re: Measuring battery internal resistance |
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.=C2 And there is a strong need to keep
>track of their condition and it seems like
>tracking IR could be the 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_BTJr+C
CCY_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 4
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| Subject: | Re: Measuring battery internal resistance |
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
Robert L. Nuckolls, III 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. And there is a strong need to keep
track of their condition and it seems like tracking IR could be the 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_BTJr+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 . . .
>
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