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Baclup Battery monitor

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mgoodrich(at)tampabay.rr.
Guest

Posted: Fri Feb 24, 2006 7:50 am Post subject: Baclup Battery monitor

Hello All,



I am installing a backup battery for a dual EI installation.

I'm looking for a way to monitor w/warning, the voltage and

possibly load on it. Any ideas??



Mitchell Goodrich

VEZE 60P

Tampa,FL





--

frank.hinde(at)hp.com
Guest

Posted: Fri Feb 24, 2006 8:24 am Post subject: Baclup Battery monitor

Simplest way is to take a second battery and charge it through a diode

from the main bettery. That way if the main battry has a major short

somewhere it will not drag down the second batery with it.



The problem with diodes is they all have a forward volt drop, standard

diodes are about 1 volt drop. So if your system charges at say 14.2

volts, your second battery will only see 13.2V.



I believe the Shotkey (sp?) diode has a much lower drop...Althouigh I

don't know what it is.



My way round this issue on my current plane is to use a smaller battery

for the second ignition that requires a lower charging voltage.



So my first battery is a 18AH and my backup is a 3AH, and is used to run

one EI and a Facet fuel pump, nothing else.



No points of interconnect between the systems except for the diode.



Make sure the diode is sized to flow enough current to run your backup

EI and you can simply run your backup EI from the second battery all the

time, i.e no chageover contactors or other components that could fail.



If you do it this way there is really no need to montior the second

battery as you will be changing it every year or so anyway...I use a

simple digital voltmeter and check it before each flight.



All the best



Frank

Zenair zodiac 400 hours

RV7a...ALMOST finished.. 



--

BigD(at)DaveMorris.com
Guest

Posted: Fri Feb 24, 2006 8:46 am Post subject: Baclup Battery monitor

Facet pumps draw about 1.5A, don't they?  And your EI draws how much?  3AH 

seems awfully small to me.  I'm guessing the Duration vs Current curve for 

that battery gives you 3A for 30 minutes.  Is that enough?



Dave Morris

www.N75UP.com



At 10:22 AM 2/24/2006, you wrote:

 	  Quote: 	
		  So my first battery is a 18AH and my backup is a 3AH, and is used to run

one EI and a Facet fuel pump, nothing else.

nuckollsr(at)cox.net
Guest

Posted: Fri Feb 24, 2006 9:02 am Post subject: Baclup Battery monitor

At 08:22 AM 2/24/2006 -0800, you wrote:



 	  Quote: 	
		  

<frank.hinde(at)hp.com>



Simplest way is to take a second battery and charge it through a diode

from the main bettery. That way if the main battry has a major short

somewhere it will not drag down the second batery with it.



The problem with diodes is they all have a forward volt drop, standard

diodes are about 1 volt drop. So if your system charges at say 14.2

volts, your second battery will only see 13.2V.


	


    Which is a major issue for recharging the standby battery

    to 100% of capacity.

 	  Quote: 	
		  I believe the Shotkey (sp?) diode has a much lower drop...Althouigh I

don't know what it is.



My way round this issue on my current plane is to use a smaller battery

for the second ignition that requires a lower charging voltage.


	


    Battery size does not drive ideal charging voltage. We use the

    same Battery Tender products to maintain 1.5 a.h. batteries as

    for 50 a.h. batteries. Ideal voltage for charging is driven by

    chemistry first and temperature second.



    There's been some discussion about optimizing charging protocols

    based on flooded vs. gel vs. RG which have proven to be a third

    order concern. IF you use a battery as motive/standby power

    and IF it's regularly discharged to a fraction of capacity and

    immediately recharged then you MIGHT see some increase in service

    life with a pampering suggested by folks who program smart chargers.



    For all others where you crank first, stabilize alternators second

    and supply standby power perhaps once in a lifetime of the battery,

    the magic charging protocols yield no measurable return on investment.

 	  Quote: 	
		  So my first battery is a 18AH and my backup is a 3AH, and is used to run

one EI and a Facet fuel pump, nothing else.



No points of interconnect between the systems except for the diode.



Make sure the diode is sized to flow enough current to run your backup

EI and you can simply run your backup EI from the second battery all the

time, i.e no chageover contactors or other components that could fail.



If you do it this way there is really no need to montior the second

battery as you will be changing it every year or so anyway...I use a

simple digital voltmeter and check it before each flight.


	


    As described in other posts, an open circuit voltage check

    of a battery is a very gross examination of battery condition

    (at least it's not discharged) and yields no accurate data

    as to capacity. The yearly change-out is the practical hedge

    against the unknown.



    A series of articles have been crafted dealing with second battery

    management techniques:



http://aeroelectric.com/articles/lvwarn/LVWarn-ABMM.html



http://aeroelectric.com/articles/lvwarn/9021-620.pdf



http://aeroelectric.com/Catalog/AEC/9005/9005.html



http://aeroelectric.com/Catalog/AEC/9005/9005-701B.pdf



    These are illustrated in appendix Z, most notably

    Figure Z-30 of:



http://aeroelectric.com/Catalog/AEC/9005/9005-701B.pdf



    where the aux battery switching device can be any

    size of switch or contactor suited to the task and the

    battery can also be selected for capacity suited to

    the task.



    Key considerations are: (1) connect the standby battery

    to the main system via lowest practical resistance i.e.

    toggle switch or relay. (2) Have active notification of

    low voltage that prompts you to open the switch or automatically

    opens a relay or contactor . . . it doesn't matter.

    You have PLENTY of time to react and there's little

    advantage in making this function automatic. The hard

    connection through a switch or relay insures that your

    standby battery gets the same benefits of recharge as

    your main battery.



    Bob . . .

frank.hinde(at)hp.com
Guest

Posted: Fri Feb 24, 2006 9:03 am Post subject: Baclup Battery monitor

I measured the Facet and it was less than an amp...Can't remember what

the EI draws but I did measure it at the time.

The Zodiac is strictly a VFR airplane and most failure modes would leave

some juice left in the main battery.



So I think I assumed about 20 minutes of flight on Batt #2.



If I were re-doing it today I think the more modern diode (with lower

volt drop) would mean I could use a bigger battery.



Frank 



--

rv8ch

Joined: 10 Jan 2006
Posts: 250
Location: Switzerland

Posted: Fri Feb 24, 2006 9:04 am Post subject: Baclup Battery monitor

 	  Quote: 	
		   The problem with diodes is they all have a forward volt drop, standard

 diodes are about 1 volt drop. So if your system charges at say 14.2

 volts, your second battery will only see 13.2V.

 

 I believe the Shotkey (sp?) diode has a much lower drop...Althouigh I

 don't know what it is.


	


Use one of Eric's Power Schotty diodes - they don't have much

voltage drop at all.



  http://www.periheliondesign.com/powerschottkydiodes.htm



-- 

Mickey Coggins

http://www.rv8.ch/

#82007 finishing

_________________
Mickey Coggins
http://www.rv8.ch/

frank.hinde(at)hp.com
Guest

Posted: Fri Feb 24, 2006 9:27 am Post subject: Baclup Battery monitor

Interesting,



The battery manufacturer actually dictated the charging voltage as being

lower for the smaller battery. Both are SLA's. 



The other piece I missed about my battery maintenance is that they are

connected to a smart charger when left in the hangar, so at least I have

a good charge when I start out. 



Based on the above would you recommend raising the charging voltage by

using a lower loss diode?...I could change for a switch but that gives

me something else I have to remember.

Cheers



Frank



--

mprather(at)spro.net
Guest

Posted: Fri Feb 24, 2006 1:03 pm Post subject: Baclup Battery monitor

Is the Facet pump used continuously?  Or only for takeoff, landing, or in

the event of a main (engine driven) pump failure?  If only intermittent

duty, leave it out of the backup battery power budget.  The chances of an

alternator failure, and an engine driven pump failure on the same flight

are exceedingly low...

Matt-



[quote] 

 (Corvallis)" <frank.hinde(at)hp.com>



 I measured the Facet and it was less than an amp...Can't remember what

 the EI draws but I did measure it at the time.

 The Zodiac is strictly a VFR airplane and most failure modes would leave

 some juice left in the main battery.



 So I think I assumed about 20 minutes of flight on Batt #2.



 If I were re-doing it today I think the more modern diode (with lower

 volt drop) would mean I could use a bigger battery.



 Frank



 --

frank.hinde(at)hp.com
Guest

Posted: Fri Feb 24, 2006 2:00 pm Post subject: Baclup Battery monitor

I have two electric pumps One in each wing root. No mechanical fuel

pump.



The FI RV is being set up the same way.



To switch tanks I simply switch pumps. 



--

mprather(at)spro.net
Guest

Posted: Sat Feb 25, 2006 4:15 pm Post subject: Baclup Battery monitor

Oh right..  I think I forgot that from the initial discussion.  Thanks..

Matt-



Hinde, Frank George (Corvallis) wrote:



[quote]



I have two electric pumps One in each wing root. No mechanical fuel

pump.



The FI RV is being set up the same way.



To switch tanks I simply switch pumps. 



--

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