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Battery discharge during normal cruise

 
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paul.zimmer00(at)gmail.co
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PostPosted: Tue Mar 03, 2020 8:05 pm    Post subject: Battery discharge during normal cruise Reply with quote

Sorry for the following cut and paste of a previous thread.  However after being unable to respond with my follow up post due some unspecified error on the matronics server, (which I thought was something I was doing wrong), I have still been unable to add my follow up to the thread.  Hopefully by sending a new email, my follow up will get through.
Paul said:
I use and monitor two Hall effect current sensors on my RV.  One measures the current flow on the "B" lead from the main alternator, and the other measures the current flow to/from the main battery.  
What doesn't make sense to me is there are periodic and frequent current flows to/from the battery (1 to 5 amps) during normal cruise operations, this during periods of static and relatively light load (12-15 amps) on the electrical system, much smaller than the capacity of the 60A Plane Power alternator.    I would expect all power to be supplied directly from the alternator as it is supplying the current at a higher voltage (~14.5v or so) than the battery.  These periods of flow to/from the battery are short in duration normally lasting only a few seconds.
Is this normal and to be expected, or does it suggest a problem with the internally regulated alternator, or perhaps with the current sensor itself?
Any insight explaining what I am seeing will be appreciated.
Thanks


Bob said:
<snip>

Quote:
These periods of flow to/from the battery are short
in duration normally lasting only a few seconds.

Is this normal and to be expected, or does it
suggest a problem with the internally regulated
alternator, or perhaps with the current sensor itself?

Any insight explaining what I am seeing will be appreciated.


  The battery's physics reacts to BUS VOLTAGE.
  Any period battery energy outflow MUST be
  paired with a drop in bus voltage to something
  below the battery's present open-circuit 
  voltage.

  The voltage doesn't have to drop to
  the battery's natural delivery
  level (~12.5 volts for SVLA) . . .
  a battery across an operating bus
  will support small outflow currents
  at voltages higher than 12.5.

  What is your normal bus voltage and do
  you notice any depression of voltage
  that corresponds to battery outflow
  events?

Paul said:

  Bob . . .
Quote:
I can’t say that I’ve noticed a bus voltage drop during these times of battery outflow, but before I say one way or the other, I’ll need to pay a little closer attention, and perhaps record the engine monitor parameters during a flight which would allow for an after the fact thorough analysis of what actually went on.  I’ll circle back at a later date.  Thanks
Paul said:
Follow up. I flew for about 30 minutes, during which I recorded the data collected and reported by my GRT EFIS.  The sampling rate is about once per second.  I converted the data to an EXCEL spreadsheet, and the following are the results.  
During normal cruise (following start and battery recharge after start), the bus voltage varied from ~13.7 to ~14.0V. The current flow to/from the battery varied both in and out up to a max of 9 amps out all the while battery voltage remains steady at ~13.9V. During these times of battery discharge, load was static (which is to say the load was not deliberately changed).  I have a spreadsheet with the data from this flight that was generated from the EFIS, which I don't think I'm able to attach to this Email.  
Thanks

Quote:




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PostPosted: Wed Mar 04, 2020 6:41 am    Post subject: Re: Battery discharge during normal cruise Reply with quote

It sounds like a bad connection in the alternator field circuit. Suggest that
you monitor the field voltage right at the alternator.


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PostPosted: Wed Mar 04, 2020 7:27 am    Post subject: Battery discharge during normal cruise Reply with quote

Quote:
What doesn't make sense to me is there are periodic and frequent current flows to/from the battery (1 to 5 amps) during normal cruise operations, this during periods of static and relatively light load (12-15 amps) on the electrical system, much smaller than the capacity of the 60A Plane Power alternator. I would expect all power to be supplied directly from the alternator as it is supplying the current at a higher voltage (~14.5v or so) than the battery. These periods of flow to/from the battery are short in duration normally lasting only a few seconds.

Is this normal and to be expected, or does it suggest a problem with the internally regulated alternator, or perhaps with the current sensor itself?

It's not 'normal' but it might not be
significant. Current flows into and out
of the battery are manifestations of
and exchange of energy into or out of
the battery.

The battery's physics tells us that significant
energy flows out of the battery at sustained
voltages well below the normal bus voltage . . .
some value below 13 volts.

Since you're not reporting a commensurate
drop in bus voltage associated with these transients,
I am inclined to consider an anomaly in the
data gathering/interpretation/display for
battery current.

Has this always existed with this configuration?
Given the absence of corroborating data I
think I'd just wait and see what happens. In
any case, I don't see a cause for concern.


Bob . . .


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ceengland7(at)gmail.com
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PostPosted: Wed Mar 04, 2020 8:40 am    Post subject: Battery discharge during normal cruise Reply with quote

On 3/4/2020 9:23 AM, Robert L. Nuckolls, III wrote:

Quote:
Quote:
What doesn't make sense to me is there are periodic and frequent current flows to/from the battery (1 to 5 amps) during normal cruise operations, this during periods of static and relatively light load (12-15 amps) on the electrical system, much smaller than the capacity of the 60A Plane Power alternator.   I would expect all power to be supplied directly from the alternator as it is supplying the current at a higher voltage (~14.5v or so) than the battery.  These periods of flow to/from the battery are short in duration normally lasting only a few seconds.

Is this normal and to be expected, or does it suggest a problem with the internally regulated alternator, or perhaps with the current sensor itself?

It's not 'normal' but it might not be
significant. Current flows into and out
of the battery are manifestations of
and exchange of energy into or out of
the battery.

The battery's physics tells us that significant
energy flows out of the battery at sustained
voltages well below the normal bus voltage . . .
some value below 13 volts.

Since you're not reporting a commensurate
drop in bus voltage associated with these transients,
I am inclined to consider an anomaly in the
data gathering/interpretation/display for
battery current.

Has this always existed with this configuration?
Given the absence of corroborating data I
think I'd just wait and see what happens. In
any case, I don't see a cause for concern.


Bob . . .
Bolded segment above reminded me of this:

My Dynon EMS D10 frequently and randomly shows a variable, up to 9A, discharge (negative current) with stable voltage. I discovered that the current shunt has a couple of inline fuse holders for glass fuses, and wiggling the fuse holders will make the negative readings go away. Obvious takeaway is that excess resistance in the sense lines confuses the current measurement, quite badly.

Charlie

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paul.zimmer00(at)gmail.co
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PostPosted: Thu Mar 05, 2020 7:21 am    Post subject: Battery discharge during normal cruise Reply with quote

Charlie, I too am beginning to suspect the sensor wiring is the likely source of the reported current flow.  While my sensors do not employ inline fuses,  I chose to use a molex connector forward of the firewall for a number of engine parameter data leads that feed the EIS, including my two current sensors.  A less than optimal mating of the pins at this connector could introduce a resistance variation error you describe.  Additionally, there is another point in the data line circuit where excitation voltage required by the sensor is introduced, which could also be suspect.  I will pursue investigation of both, and update the thread with my findings.

Thanks 
Paul

On Wed, Mar 4, 2020 at 11:46 AM Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:

Quote:

On 3/4/2020 9:23 AM, Robert L. Nuckolls, III wrote:

Quote:
Quote:
What doesn't make sense to me is there are periodic and frequent current flows to/from the battery (1 to 5 amps) during normal cruise operations, this during periods of static and relatively light load (12-15 amps) on the electrical system, much smaller than the capacity of the 60A Plane Power alternator.    I would expect all power to be supplied directly from the alternator as it is supplying the current at a higher voltage (~14.5v or so) than the battery.  These periods of flow to/from the battery are short in duration normally lasting only a few seconds.

Is this normal and to be expected, or does it suggest a problem with the internally regulated alternator, or perhaps with the current sensor itself?

  It's not 'normal' but it might not be
  significant.  Current flows into and out
  of the battery are manifestations of
  and exchange of energy into or out of
  the battery.
 
  The battery's physics tells us that significant
  energy flows out of the battery at sustained
  voltages well below the normal bus voltage . . .
  some value below 13 volts.

  Since you're not reporting a commensurate
  drop in bus voltage associated with these transients,
  I am inclined to consider an anomaly in the
  data gathering/interpretation/display for
  battery current.

  Has this always existed with this configuration?
  Given the absence of corroborating data I
  think I'd just wait and see what happens. In
  any case, I don't see a cause for concern.


  Bob . . .

Bolded segment above reminded me of this:

My Dynon EMS D10 frequently and randomly shows a variable, up to 9A, discharge (negative current) with stable voltage. I discovered that the current shunt has a couple of inline fuse holders for glass fuses, and wiggling the fuse holders will make the negative readings go away. Obvious takeaway is that excess resistance in the sense lines confuses the current measurement, quite badly.

Charlie



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PostPosted: Thu Mar 05, 2020 9:38 am    Post subject: Battery discharge during normal cruise Reply with quote

Charlie re DYNONInteresting.   My dynon skyview will run up to 60a before i get the red x over the read out.  It will then return and stabilize to 7-10a  depending on the load - the normal.     60a from a rotax alternator is a little optimistic so I was not too worried in flight.  I installed an separate hall effect sensor and round gauge on the fat wire to the battery and this shows no relation to the Dynon read out.  My conclusion is that this is something to with the Dynon shunt and system. I have hunted for the fault without success.
Will

William Daniell
+1 786 878 0246


On Wed, Mar 4, 2020, 11:46 Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:

Quote:
On 3/4/2020 9:23 AM, Robert L. Nuckolls, III wrote:

Quote:
Quote:
What doesn't make sense to me is there are periodic and frequent current flows to/from the battery (1 to 5 amps) during normal cruise operations, this during periods of static and relatively light load (12-15 amps) on the electrical system, much smaller than the capacity of the 60A Plane Power alternator.    I would expect all power to be supplied directly from the alternator as it is supplying the current at a higher voltage (~14.5v or so) than the battery.  These periods of flow to/from the battery are short in duration normally lasting only a few seconds.

Is this normal and to be expected, or does it suggest a problem with the internally regulated alternator, or perhaps with the current sensor itself?

  It's not 'normal' but it might not be
  significant.  Current flows into and out
  of the battery are manifestations of
  and exchange of energy into or out of
  the battery.
 
  The battery's physics tells us that significant
  energy flows out of the battery at sustained
  voltages well below the normal bus voltage . . .
  some value below 13 volts.

  Since you're not reporting a commensurate
  drop in bus voltage associated with these transients,
  I am inclined to consider an anomaly in the
  data gathering/interpretation/display for
  battery current.

  Has this always existed with this configuration?
  Given the absence of corroborating data I
  think I'd just wait and see what happens. In
  any case, I don't see a cause for concern.


  Bob . . .
Bolded segment above reminded me of this:

My Dynon EMS D10 frequently and randomly shows a variable, up to 9A, discharge (negative current) with stable voltage. I discovered that the current shunt has a couple of inline fuse holders for glass fuses, and wiggling the fuse holders will make the negative readings go away. Obvious takeaway is that excess resistance in the sense lines confuses the current measurement, quite badly.

Charlie



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