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FYI: New kid in battery charger/maintainers

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nuckolls.bob(at)aeroelect
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Posted: Thu Aug 17, 2023 7:35 pm Post subject: FYI: New kid in battery charger/maintainers

At 07:26 PM 8/17/2023, you wrote:

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



 I purchased a similar one of those chargers.

 Pros:

 Charges quickly, up to 8 amps._

 Cons:

 The wires are too short, only a couple of feet long.

 The wires are stiff, might be stranded but not very many strands.

 When clamping onto a battery, a spark jumps.  That tells me that the charger 

 is drawing power from the battery before the AC cord is plugged in. 	


    Did you measure-to-confirm? Might just be a

    capacitor across the output of what must

    be a switch-mode power supply. I'll check

    the one that's still here in the morning.



  	  Quote: 	
		  An internal fan runs while charging. 	


     Yeah, that's a 100+ watt power supply

     in that little package. Simple convection

     venting would be inadequate. Adding a

     thermostat to shut it off except when

     needed would add to complexity.



  	  Quote: 	
		  I would not trust leaving the charger connected overnight. 	


    I've conducted numerous charge cycles with

    these on a constellation of batteries. They

    have behaved as expected. They are advertised

    as 'maintainers' which tells us they're intended

    for long term service powered up.



 

   Bob . . .



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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Aug 23, 2023 7:54 am Post subject: FYI: New kid in battery charger/maintainers

At 01:00 PM 8/21/2023, you wrote:

  	  Quote: 	
		  Joe's charger comment is very correct about the potential discharge problem.



 This is true also of the small maintainers like the Battery Tender.

 They don't appear to have a blocking diode to prevent battery discharge.

 If your wall power fails, due to a GFI failure, power line failure,etc., the chargers will slowly discharge the battery,

 This can be really bad on some batteries. If discharged totally they may not be recovered or have severelyÂ limited capacity when charged. 	


   Just for grins, I just checked on a test Battery Tender

   test cycle that just finished topping off a Genesis AGM.



   I put an ammeter in series with the BT battery leads

   and measured approximately 20 mA (charging) with the

   BT still powered up and battery voltage at the 'maintenance'

   level of 13.2 volts.  With the BT unplugged, current

   drain was approx 200 uA.



   Circuitry within the BT must have some sense of

   battery voltage but the electronics to sample that

   value need not draw a lot of current.  For this particular

   variant on the Battery Tender Jr, that sampling current

   is very small. Further, other electronics involved in

   normal operation appears to 'disconnect' from the

   target battery should the mains power be interrupted.



   I'll check other battery maintenance examples as things

   progress . . . but I'm thinking it's pretty easy to

   avoid power-down discharge of the target battery. I suspect

   we'll find similar conditions with other products.



 

   Bob . . .



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    < show me where I'm wrong.      > 

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    of the-best-we-know-how-to-do based

    on physics and good practice.

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Aug 23, 2023 12:15 pm Post subject: FYI: New kid in battery charger/maintainers

At 01:52 PM 8/23/2023, you wrote:

  	  Quote: 	
		  Bob,

 Thanks for doing the discharge measurements.

 I have lost some deep cycle RV batteries due to the GFI popping for some unknownÂ reasons.

 It's usually the case where they have been put away for long periods of time, maybe over winter, and not being around to occasionallyÂ check for power. If I can't check on their condition routinelyÂ I will not plug the BT's in a GFI controlled circuit.

 Using a non GFI controlled line, even if the power goes off and later is restored power is established back to the maintainer. 	


   Hmmm . . . if these batteries were at 100% when

   the power went off, it should have taken considerable

   time for them to self-discharge to levels of self

   destruction. Flooded lead acid batteries have

   self discharge rates on the order of 1%/month

   for new; 3% for one nearing end of life (temperature

   dependent also).



   Was there any chance these batteries were

   burdened with a parasitic load while on

   storage?



   In any case, arranging for a self-recovering

   maintenance charger seems a well reasoned

   decision!



 

   Bob . . .



                    //// 

                   (o o) 

    ===========o00o=(_)=o00o========= 

    < Go ahead, make my day . . .   > 

    < show me where I'm wrong.      > 

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

  

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    of the-best-we-know-how-to-do based

    on physics and good practice.

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