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Battery Charger as Ground Power

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ChangDriver

Joined: 15 Sep 2007
Posts: 266

Posted: Mon May 11, 2009 10:11 am Post subject: Battery Charger as Ground Power

Bob:



I've been reading some posts on ground power and noted that some people are using a battery charger as a ground power unit.  From what I remember about the output voltage of almost all battery chargers, there is a significant potential to overvoltage the aircraft isn't there?  The voltage from most chargers is not filtered and is not as clean as you'd want for powering avionics, etc.



Am I right,



Craig

woxofswa

Joined: 12 Aug 2008
Posts: 349
Location: AZ

Posted: Mon May 11, 2009 10:22 am Post subject: Re: Battery Charger as Ground Power

I'm no expert, but I think you are right.



I think a  12.5 volt "maintainer" would make much more sense.  They can be had at Harbor Freight for $5



For ground tests and assembly, I plan on using a cheapo lawn tractor battery with a maintainer hooked up to it.  The battery would then serve as a sink if there is a problem with the maintainer.

_________________
Myron Nelson
Mesa, AZ
Flew May 10 2014

nuckolls.bob(at)aeroelect
Guest

Posted: Mon May 11, 2009 1:00 pm Post subject: Battery Charger as Ground Power

At 01:11 PM 5/11/2009, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Craig Winkelmann" <capav8r(at)gmail.com>



 Bob:



 I've been reading some posts on ground power and noted that some people are using a battery charger as a ground power unit.  From what I remember about the output voltage of almost all battery chargers, there is a significant potential to overvoltage the aircraft isn't there?  The voltage from most chargers is not filtered and is not as clean as you'd want for powering avionics, etc. 	


    "Battery Charger" is non-qualified. Technically, any

    source of energy that is capable of reversing current

    flow into a battery is a 'charger'.



    The quality of output power from chargers can be all

    over the map.  The very first charger I owned was a

    6v Tungar rectifier electro-whizzy. 



 [img]cid:.0[/img]



    The output quality of this thing would have been

    REALLY noisy, ZERO voltage regulation, hideously

    inefficient, but entirely suited to keeping my '41

    Pontiac straight-6 ready to start on a cold morning.



    By the way, anyone interested in exploring/reliving

    some of the history of lead-acid battery technology,

    feel free to download this item. (Caution 9+ MB)



  http://tinyurl.com/owad89 



    45 years later and at the other end of the spectrum,

    we can purchase light, relatively inexpensive, high

    quality switch-mode power supplies that will serve as

    both ground power supplies for system operations but

    battery chargers as well.



    Unfortunately, devices tailored to serve as "smart"

    chargers (quick recharge, indefinite storage) probably

    don't make good ground power supplies because their

    internal battery-pampering software gets confused when

    the "battery" being maintained keeps changing terminal

    voltage and load.



    A few years ago, we made a great buy on a quantity

    of Samlex 1223 power supplies. 



  http://www.universal-radio.com/catalog/hamps/2423.html



    We offered these as "alternator simulators" with the

    suggestion that they could be used to make the ship's

    systems believe that a 23A alternator was running.

    This would allow the ship's battery to be charged

    and ship's systems of up to 20A draw (about anything

    but pitot heat) to be tested in the shop.



    The short answer is that not all battery chargers

    are suited for use as ground power supplies perhaps

    due to their particular noise/voltage-regulation

    characteristics. However, you can hook any charger

    across a battery and give it a try. Make sure you

    know how it behaves in the long term (watch bus

    voltage) and know it's specific limits. With

    a modicum of due-diligence, the experiment offers

    minimal risk to system components.



 

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

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Matt Dralle
Site Admin

Joined: 08 Nov 2005
Posts: 26321
Location: Livermore CA USA

Posted: Mon May 11, 2009 2:33 pm Post subject: Battery Charger as Ground Power

At 01:58 PM 5/11/2009  Monday, you wrote:

 	  Quote: 	
		  At 01:11 PM 5/11/2009, you wrote:

>

>

>Bob:

>

>I've been reading some posts on ground power and noted that some people are using a battery charger as a ground power unit.  From what I remember about the output voltage of almost all battery chargers, there is a significant potential to overvoltage the aircraft isn't there?  The voltage from most chargers is not filtered and is not as clean as you'd want for powering avionics, etc.

   Unfortunately, devices tailored to serve as "smart"

   chargers (quick recharge, indefinite storage) probably

   don't make good ground power supplies because their

   internal battery-pampering software gets confused when

   the "battery" being maintained keeps changing terminal

   voltage and load.

   A few years ago, we made a great buy on a quantity

   of Samlex 1223 power supplies. 

       Bob . . .

I've got one of these Black and Decker BC40EB units that has adjustable charge output limits in addition to a 110amp starter booster.  I'm plugging it into my GPU plug and use it to run the avionics, charge the battery, and I'm hoping eventually to jump start the engine when the battery is on the low side.  The only downside seems to be that the unit has to see 4-5volts on the "battery" before it will turn on its output.  This means that it won't flip the GPU relay and you have to have an external switch to do that.

Bob, does this seem like a good charger/GPU product for aircraft systems?

        http://www.blackanddecker.com/ProductGuide/Product-Details.aspx?ProductID=17925

Matt Dralle

RV-8 #82880 N998RV

Carpet CAD Drawings...

(1200+ Hours Build Time...)

_________________
Matt Dralle
Matronics Email List Administrator

skywagon

Joined: 11 Feb 2006
Posts: 184

Posted: Mon May 11, 2009 5:43 pm Post subject: Battery Charger as Ground Power

The little, cheap Harbor Freight "maintainers" work quite well.  I have used several.  One key point however,  ...many of them come set a tad too high in their fixed "float" voltage, to my thinking.  I have seen them as high as 13.9 v. 



The good news, is they can be adjusted to the float voltage that you want.  The little controller box should have a back lid that is lightly glued in place.  Carefully work a very narrow blade screw driver or other tough, but thin device into the glued seam and work it until the back pops off.  Inside is a small circuit board and potentiometer.  It may have a spot of RTV on it. Work this loose.  Turning the pot CW lowers to float voltage.  I like about 13.2 v.  Others may want a slightly different setting.  I usually locate where the pot slotted screw adjust hole is located next to the little case and drill a 3/16 hole.  That way, it can be adjusted from the outside.  The little unit is quite stable after you get the setting where you want it. David

---- woxofswa <woxof(at)aol.com> wrote: 



=============




I'm no expert, but I think you are right.



I think a  12.5 volt "maintainer" would make much more sense.  They can be had at Harbor Freight for $5



For ground tests and assembly, I plan on using a cheapo lawn tractor battery with a maintainer hooked up to it.  The battery would then serve as a sink if there is a problem with the maintainer.



--------

Myron Nelson

Mesa, AZ

Emp completed, legacy build fuse in progress





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p 43569#243569

ChangDriver

Joined: 15 Sep 2007
Posts: 266

Posted: Mon May 11, 2009 6:13 pm Post subject: Re: Battery Charger as Ground Power

Bob:



Thanks, BUT some GPUs bypass the battery because they are not meant to be a port for charging the battery.  In these cases, whatever comes out of the charger goes on the main bus.  I suspect the right thing is to see how conditioned and stable the output voltage is prior to plugging the unit into a plane full of expensive avionics.



Craig

nuckolls.bob(at)aeroelect
Guest

Posted: Mon May 11, 2009 7:42 pm Post subject: Battery Charger as Ground Power

 	  Quote: 	
		  I think a  12.5 volt "maintainer" would make much more sense.  They 

can be had at Harbor Freight for $5



For ground tests and assembly, I plan on using a cheapo lawn tractor 

battery with a maintainer hooked up to it.  The battery would then 

serve as a sink if there is a problem with the maintainer.


	


  Actually, the ideal maintainer voltage is just

  above 100-200 millivolts the battery's open circuit

  voltage 24 hours or so after taking it off the charger.

  Lead-Acid batteries, this is 13.1 to 13.2 volts.



  The idea is that you want to hold the battery at or

  just above it's own chemistry voltage . . . thus

  any and all tendencies to self-discharge are supported

  by the external energy source. I.e. self-discharge

  currents do not tax the chemistry. See:



http://www.aeroelectric.com/Pictures/Curves/Battery_Tender_Recharge.pdf



http://www.aeroelectric.com/Pictures/Curves/Ideal_Recharge_Protocol.jpg



        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

nuckolls.bob(at)aeroelect
Guest

Posted: Mon May 11, 2009 7:44 pm Post subject: Battery Charger as Ground Power

At 09:13 PM 5/11/2009, you wrote:

 	  Quote: 	
		  

<capav8r(at)gmail.com>



Bob:



Thanks, BUT some GPUs bypass the battery because they are not meant 

to be a port for charging the battery.  In these cases, whatever 

comes out of the charger goes on the main bus.  I suspect the right 

thing is to see how conditioned and stable the output voltage is 

prior to plugging the unit into a plane full of expensive avionics.


	


   It's the system integrator's task to decide whether

   or not the battery is on line during ground power

   connection. I've heard the stories for both cases

   for BIG airplanes with BIG batteries and BIG ground

   power carts.



   For our purposes and considering relative sizes

   of our hardware, it's best to have a battery on

   line during ground power ops . . . especially

   if the power quality of the power source has not

   been fully qualified to the task.

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

icubob(at)gmail.com
Guest

Posted: Tue May 12, 2009 3:11 am Post subject: Battery Charger as Ground Power

i have 6 or 8 of these little chargers on all my toys. i have noticed on some some that the voltage was too low. i tried once to adjust the voltage but couldn't get anything to turn.i guess i will go back and try again to adjust the voltage on a couple that are too low. on the one that was too high i soldered a diode in line and dropped the voltage.

         bob noffs



On Mon, May 11, 2009 at 8:31 PM, David L. <skywagon(at)charter.net (skywagon(at)charter.net)> wrote:

[quote] --> AeroElectric-List message posted by: "David L." <skywagon(at)charter.net (skywagon(at)charter.net)>

 

 The little, cheap Harbor Freight "maintainers" work quite well.  I have used several.  One key point however,  ...many of them come set a tad too high in their fixed "float" voltage, to my thinking.  I have seen them as high as 13.9 v.

  

 The good news, is they can be adjusted to the float voltage that you want.  The little controller box should have a back lid that is lightly glued in place.  Carefully work a very narrow blade screw driver or other tough, but thin device into the glued seam and work it until the back pops off.  Inside is a small circuit board and potentiometer.  It may have a spot of RTV on it. Work this loose.  Turning the pot CW lowers to float voltage.  I like about 13.2 v.  Others may want a slightly different setting.  I usually locate where the pot slotted screw adjust hole is located next to the little case and drill a 3/16 hole.  That way, it can be adjusted from the outside.  The little unit is quite stable after you get the setting where you want it. David

  

 

 ---- woxofswa <woxof(at)aol.com (woxof(at)aol.com)> wrote:

 

 =============

 --> AeroElectric-List message posted by: "woxofswa" <woxof(at)aol.com (woxof(at)aol.com)>

 

 I'm no expert, but I think you are right.

 

 I think a  12.5 volt "maintainer" would make much more sense.  They can be had at Harbor Freight for $5

 

 For ground tests and assembly, I plan on using a cheapo lawn tractor battery with a maintainer hooked up to it.  The battery would then serve as a sink if there is a problem with the maintainer.

 

 --------

 Myron Nelson

 Mesa, AZ

 Emp completed, legacy build fuse in progress

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=243569#243569

 

 

 

 

 

 

 

 

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 -List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

 ="_blank">http://www.matronics.com/contribution

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 [b]

nuckolls.bob(at)aeroelect
Guest

Posted: Wed May 13, 2009 6:16 am Post subject: Battery Charger as Ground Power

At 06:08 AM 5/12/2009, you wrote:

  	  Quote: 	
		  i have 6 or 8 of these little chargers on all my toys. i have noticed on some some that the voltage was too low. i tried once to adjust the voltage but couldn't get anything to turn.i guess i will go back and try again to adjust the voltage on a couple that are too low. on the one that was too high i soldered a diode in line and dropped the voltage.

         bob noffs



 On Mon, May 11, 2009 at 8:31 PM, David L. <skywagon(at)charter.net (skywagon(at)charter.net)> wrote:

   --> AeroElectric-List message posted by: "David L." <skywagon(at)charter.net (skywagon(at)charter.net)>

 

  The little, cheap Harbor Freight "maintainers" work quite well.  I have used several.  One key point however,  ..many of them come set a tad too high in their fixed "float" voltage, to my thinking.  I have seen them as high as 13.9 v.



  The good news, is they can be adjusted to the float voltage that you want.  The little controller box should have a back lid that is lightly glued in place.  Carefully work a very narrow blade screw driver or other tough, but thin device into the glued seam and work it until the back pops off.  Inside is a small circuit board and potentiometer.  It may have a spot of RTV on it. Work this loose.  Turning the pot CW lowers to float voltage.  I like about 13.2 v.  Others may want a slightly different setting.  I usually locate where the pot slotted screw adjust hole is located next to the little case and drill a 3/16 hole.  That way, it can be adjusted from the outside.  The little unit is quite stable after you get the setting where you want it. David 	
 

   David's suggestions are worthy of consideration but

   he doesn't mention specific model numbers from

   H.F. I've tested several battery charger products

   from H.F. and found some that were not suited to our tasks.

   

   What we're looking for are devices that first

   "top off" a battery and then "drop to maintenance".

   This kind of behavior is illustrated in . . .



  http://www.aeroelectric.com/Pictures/Curves/schumacher_3.jpg



   This curve is from the Schumacher 1562 series chargers available

   from WalMart for about $20. There are dozens of other

   products that produce similar charge/maintenance profiles.

   This one  . . . 



  http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=42292 



   . . . does not.



   I found a pot inside to adjust the output voltage . . .

   but only ONE pot. It's a device suitable for maintaining

   an already charged battery (adjust it for 13.1 volts) but

   will not charge a battery.



   Based on its description and price, this device



  http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=99857 



   shows more promise. Haven't had time to go get one and

   check it out but in the mean time, the Schumacher

   1562 is a sure bet



  http://aeroelectric.com/Pictures/Battery_Chargers/Schumacher_Chargers/1562.jpg 



 

   Bob . . .    [quote][b]

tonybabb(at)alejandra.net
Guest

Posted: Fri May 15, 2009 1:16 pm Post subject: Battery Charger as Ground Power

Hi  Bob,

  

 Perhaps you could help me understand what the words  were that you saw in the advert that made you think HF item number 99857  might do the job (I understand you'd want to test it to confirm) versus very  similar words in the ad for HF item number 42292 that you said definitely won't  do the job. Both say they "maintain a full charge  without over charging". 

  

 Below  is the description for 99857 from the HF web site

  

 [*]Three-stage fully automatic charging protects and prolongs battery life  [*]Auto on/off trickle charging stage keeps 12 volt batteries fully charged  without overcharging  [*]Equipped with overload protection, short circuit protection, and reverse  polarity protection for added safety  [*]Also great for maintaining batteries while in storage  [*]Has LED charge indicators  [*]Includes a bracket for permanent mounting   

 and  here's the description for 42292 from the HF web site

    Use on 12 volt batteries while in storage or during cold weather    
Floating circuit maintains a full charge without overcharging    
Automatic safety shutoff  Is  there any way the electron challenged such as myself could tell or do we just  have to buy and test - or follow your recommendations. Am I being naive in  believing manufacturers claims? 

  

 Thanks  for this and all your other explanations.

  

 Tony  Babb

 [quote]   

   --

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