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Small battery limited to 3 amp charge rate ?

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nuckolls.bob(at)cox.net
Guest

Posted: Sat Jan 05, 2008 12:40 pm Post subject: Small battery limited to 3 amp charge rate ?

At 02:15 PM 1/5/2008 -0600, you wrote:

 	  Quote: 	
		  Wondering how this works ?  Help appreciated!



I have a 7ah battery on a separate bus for EFIS(alternate power)  that is 

not directly connected to the main bus during starting or normal 

operations.   However, I do have a charging circuit off the main bus 

through a D25 diode which should put 14.4 - .6 or 13.8 volts to the small 

battery during normal operations to keep it charged.  It is a fused 

circuit and intended to be hot anytime the main bus is on.  That way the 

Aux Bat should be always charged, available to run the EFIS before and 

during starting with no draw on it, and not drain back if the main bus is 

off.   And no switching required during normal ops.



The Z35 Light Aux Bat 

figure 

<http://www.aeroelectric.com/PPS/DCPwr/Z35K_Light_Aux_Battery.pdf>http://www.aeroelectric.com/PPS/DCPwr/Z35K_Light_Aux_Battery.pdf 

is similar except that I think it is intended to be turned on after 

starting and not be available from before to after starting.



My question:  It was just pointed out to me that the 7ah battery has a 3 

amp charging limit (per B&C spec sheet) and I am wondering if there should 

be a resistor in this circuit to limit the charging current?  I see that 

the full size batteries do not have a charging limit.   Is there any 

danger if the smaller 7ah is fully discharged that it could draw enough 

charging current to damage it without a limiting resistor.



If it does require a resistor for the small battery, wouldn't the same 

thing apply to the Z35 figure since you could easily have a fully 

discharged aux bat, start the airplane, and then hit the switch putting 

full current to the fully discharged battery?


	


   The only time the recharge limit might be exceeded

   is if the battery is connected to and alternator-supported

   bus after being completely discharged. This should be a

   rare event and you should be aware of it before it happens.

   I.e., you were forced to use the aux battery sans alternator

   until the battery was at or nearly depleted.



   This scenario generates a maintenance event that includes

   repairing the failed alternator and might as well include

   putting a smart charger on the aux battery to GENTLY return

   it to it's 100% state of charge.



   On the rare occasion that you find it useful/necessary

   to recharge the aux battery using ship's alternator, then

   yes . . . the battery will see an out-of-spec recharge

   rate for a short period of time. But we wouldn't expect

   to see it happen often.



   If you use this battery in a repeated charge/discharge mode

   of operation . . . like to be the sole source of energy

   for running a radio in a sailplane, then it's prudent and

   even practical to acquire a recharging system that pampers

   the battery for the purpose of extending service life.



   However, in the case we're considering, the aux battery

   may be replaced in an few years never having been deeply

   discharged over the lifetime of its service. It's my

   considered judgement that adding the extra gee-whiz

   components for pampered recharge only adds to parts

   count and pilot/maintenance workload and would contribute

   no measurable increase in service life of the battery.

   Bob . . .

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Bill Schlatterer

Joined: 09 Jan 2006
Posts: 195

Posted: Sat Jan 05, 2008 3:02 pm Post subject: Small battery limited to 3 amp charge rate ?

Thanks Bob, with no chance of sparks and a rare shot at battery damage ($35)

it would seem the answer is to simplify as usual.



Thanks Bill S 



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bobf(at)feldtman.com
Guest

Posted: Sat Jan 05, 2008 3:03 pm Post subject: Small battery limited to 3 amp charge rate ?

I'm getting sorta tired of replacing my Concorde attery in the Glastar every 14 months or so cause they just won't hold a charge. I need something more reliable than that. -- I know I know - avoiding long times in between useage, cold weather, deep discharge (like starting) short flights - all that stuff. Without getting into too much of a commerical war - does folks have preferences for Concorde vs gill (now Teledyne Continental) etc? 

And yes I am using an off the shelf Auto zone recharger - maybe that is the problem although it has the setting for different types and automatic shutoff etc.

bobf

On 1/5/08,  Robert L. Nuckolls, III <nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)> wrote:[quote] --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)>

At 02:15 PM 1/5/2008 -0600, you wrote:

 	  Quote: 	
		  Wondering how this works ?  Help appreciated! 

I have a 7ah battery on a separate bus for EFIS(alternate power)  that is

not directly connected to the main bus during starting or normal

operations.   However, I do have a charging circuit off the main bus 

through a D25 diode which should put 14.4 - .6 or 13.8 volts to the small

battery during normal operations to keep it charged.  It is a fused

circuit and intended to be hot anytime the main bus is on.  That way the 

Aux Bat should be always charged, available to run the EFIS before and

during starting with no draw on it, and not drain back if the main bus is

off.   And no switching required during normal ops.

 >

 	  Quote: 	
		  The Z35 Light Aux Bat

figure

<http://www.aeroelectric.com/PPS/DCPwr/Z35K_Light_Aux_Battery.pdf> http://www.aeroelectric.com/PPS/DCPwr/Z35K_Light_Aux_Battery.pdf

is similar except that I think it is intended to be turned on after

starting and not be available from before to after starting.

 >My question:  It was just pointed out to me that the 7ah battery has a 3

 	  Quote: 	
		  amp charging limit (per B&C spec sheet) and I am wondering if there should

be a resistor in this circuit to limit the charging current?  I see that 

the full size batteries do not have a charging limit.   Is there any

danger if the smaller 7ah is fully discharged that it could draw enough

charging current to damage it without a limiting resistor. 

If it does require a resistor for the small battery, wouldn't the same

thing apply to the Z35 figure since you could easily have a fully

discharged aux bat, start the airplane, and then hit the switch putting 

full current to the fully discharged battery?

   The only time the recharge limit might be exceeded

   is if the battery is connected to and alternator-supported

   bus after being completely discharged. This should be a 

   rare event and you should be aware of it before it happens.

   I.e., you were forced to use the aux battery sans alternator

   until the battery was at or nearly depleted.

   This scenario generates a maintenance event that includes 

   repairing the failed alternator and might as well include

   putting a smart charger on the aux battery to GENTLY return

   it to it's 100% state of charge.

   On the rare occasion that you find it useful/necessary 

   to recharge the aux battery using ship's alternator, then

   yes . . . the battery will see an out-of-spec recharge

   rate for a short period of time. But we wouldn't expect

   to see it happen often. 

   If you use this battery in a repeated charge/discharge mode

   of operation . . . like to be the sole source of energy

   for running a radio in a sailplane, then it's prudent and

   even practical to acquire a recharging system that pampers 

   the battery for the purpose of extending service life.

   However, in the case we're considering, the aux battery

   may be replaced in an few years never having been deeply

   discharged over the lifetime of its service. It's my 

   considered judgement that adding the extra gee-whiz

   components for pampered recharge only adds to parts

   count and pilot/maintenance workload and would contribute

   no measurable increase in service life of the battery.  [quote][b]

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cjensen(at)dts9000.com
Guest

Posted: Sat Jan 05, 2008 4:07 pm Post subject: Small battery limited to 3 amp charge rate ?

Bob,

  

 Get a  680 or 925 Odyssey and be done with your worries.  If its not a 6 cylinder,  then the 680 should be ample for your needs.  Highly and uniformly  recommended.

  

 Chuck Jensen  

 [quote]   --

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schaefer(at)rts-services.
Guest

Posted: Sat Jan 05, 2008 6:19 pm Post subject: Small battery limited to 3 amp charge rate ?

What Bob is also hinting at is that a "RESISTOR" current limiter does not

allow for proper care and feeding of a battery. The smart battery tenders

that allows proper recovery from a battery in any arbitrary discharge state

is fairly complex and is managed by very smart devices. (Current limited

profiles initially followed by low float current and constant voltage). 

If you never let the battery get significantly discharged you do not need to

worry about this complexity. If the fuse popped, check the condition of your

battery, and recover or replace it. 



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cjensen(at)dts9000.com
Guest

Posted: Sun Jan 06, 2008 6:12 am Post subject: Small battery limited to 3 amp charge rate ?

Bob  F.

  

 I  amend my earlier posting and concur with Bob N.(I'll bet he feels  relieved).  It looks like a system problem more than a battery  problem.  Nonetheless, the Odyssey is a heck'va  battery.

 

Chuck Jensen  

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bobf(at)feldtman.com
Guest

Posted: Sun Jan 06, 2008 8:40 am Post subject: Small battery limited to 3 amp charge rate ?

Appreciate the valuable information - indeed the Odyssey looks super! I do have a Fluke, which I trust - so will make the various measurements. Flad I asked the question so the entire list can learn about this ever so common problem with airplanes - battery problems! Main problem is I don't fly enough! 



bobf



On 1/6/08, Chuck Jensen <cjensen(at)dts9000.com (cjensen(at)dts9000.com)> wrote:[quote]        Bob  F.

  

 I  amend my earlier posting and concur with Bob N.(I'll bet he feels  relieved).  It looks like a system problem more than a battery  problem.  Nonetheless, the Odyssey is a heck'va  battery.

 

Chuck Jensen  

--

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