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Dual Battery Question

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mike(at)vision499.com
Guest

Posted: Thu Jun 30, 2022 7:47 pm Post subject: Dual Battery Question

Hello 

 

If I connect a second battery via a ground battery socket to assist my onboard battery what criteria do the 2 batteries use to determine how to  split the load between themselves?

 

Thanks

 

Mike Pienaar

mike(at)vision499.com (ike(at)vision499.com)

Home: +1 250-999-8121

Mike cell: +1 250-885-0554

1-1100 Tulip Ave, Victoria, BC, V8Z 0A2

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jul 01, 2022 3:27 pm Post subject: Dual Battery Question

At 10:46 PM 6/30/2022, you wrote:



  	  Quote: 	
		  Hello 



  



 If I connect a second battery via a ground battery socket to assist my onboard battery what criteria do the 2 batteries use to determine how to  split the load between themselves?



  	


  There is no reason to strive for any form of

  'load sharing' . . . each battery will request/

  accept charge as if it's the only battery in the

  system. Similarly, each will supply energy based

  on condition of chemistry, physical size, state

  of charge and internal resistance totally independent

  of any other battery(ies) in the system.



 



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

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Voyager

Joined: 30 Jun 2020
Posts: 77

Posted: Fri Jul 01, 2022 5:48 pm Post subject: Dual Battery Question

Internal resistance.



Sent from my iPad



 	  Quote: 	
		  On Jul 1, 2022, at 1:42 AM, mike(at)vision499.com wrote:



ï»¿  <![endif]-->   <![endif]-->

Hello 

 

If I connect a second battery via a ground battery socket to assist my onboard battery what criteria do the 2 batteries use to determine how to  split the load between themselves?

 

Thanks

 

Mike Pienaar

mike(at)vision499.com (ike(at)vision499.com)

Home: +1 250-999-8121

Mike cell: +1 250-885-0554

1-1100 Tulip Ave, Victoria, BC, V8Z 0A2

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user9253

Joined: 28 Mar 2008
Posts: 1926
Location: Riley TWP Michigan

Posted: Sat Jul 02, 2022 4:57 am Post subject: Re: Dual Battery Question

Another way to look at it is that an electrical load will always draw current from the source with the highest voltage.

After the voltage on one battery drops to that of the other battery, then current will be drawn from both batteries.

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_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jul 04, 2022 7:37 am Post subject: Dual Battery Question

At 07:57 AM 7/2/2022, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>



 Another way to look at it is that an electrical load will always draw current from the source with the highest voltage.

 After the voltage on one battery drops to that of the other battery, then current will be drawn from both batteries. 	


   Let me hypothesize a particular condition.



   Two batteries of different size are connected

   in parallel. One cap-checked at 80%

   of as-new capacity. I.e. ready for retirement.

   The other is brand new.



   Okay, put them into any system that offers

   a constant voltage distribution bus set for

   say 14.2 Volts (the magic number for regulator

   set point for nearly 100 years). Assume independent

   battery ammeters are installed.



   Operate the system for time sufficient to

   fully charge both batteries (recharge current

   drops to an Amp or less). Now, shut off the

   alternator. Leave normal system operating loads

   on. Start your stopwatch. When voltage drops below

   11 Volts, hit the stopwatch.



   You will discover that battery only operations

   track closely with energy measured as (Battery A x 0.

   + (Battery B x 1.00) = total stored energy.



   The two batteries have no way to know that the

   other battery exists. Both will ACCEPT maximum

   energy as limited by condition of their chemistry.

   Both batteries will DELIVER the same energy

   that was confirmed by cap-check. Whether they

   'shared' the load in any pre-ordained way is

   immaterial. Each will function to limits

   defined by its current physical condition.

   Because they're connected in parallel, they

   will arrive at 11.0 volts at the same time.



   This is analogous to having an airplane with

   two fuel tanks of unequal size and a fuel

   selector valve having a BOTH option. The

   engine will run until all fuel is exhausted

   irrespective of where it came from. 



 

 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

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