Arrgh!  My brain hurts.  šŸ˜
Gary
~~~~~~~_/)~~~~~~


On Fri, Jul 5, 2019 at 6:54 PM Josh Muckley via CnC-List <
cnc-list@cnc-list.com> wrote:

> Edd,
>
> As I recall you are still on a mooring right?  You're using the motor and
> solar to keep the batteries "charged"?  If so then it is unlikely that you
> are ever really getting all the way 100% charged.
>
> As others have mentioned the only good way to use voltage as a measure of
> the state of charge is by reading the NO LOAD (and No CHARGE) voltage.
> Seems simple enough.... But it's not.  There is also a  effect known as
> surface charge.  This is the residual voltage that is greater than 12.7v
> read after applying a charge.  Immediately after charge you'll see 14.7v
> and slowly dropping over 24 hours until it stabilizes at 12.7v.  The
> surface charge can  represent ~1% of battery capacity.  To remove the
> surface charge you need to apply a relatively small load.  In your case
> 4.5A-hrs....so 4.5 amps for 1 hour...or just let the battery sit
> disconnected for ~24 hours.  With the surface charge removed the volts
> should read 12.7v and every 0.1v below 12.7v is roughly equal to 10%
> capacity.
>
> So during charge there are 3 different stages of charge (bulk, acceptance,
> float).  You'll see volts climb steadily through the first stage finally
> stopping at ~14.7v.  At the end of the first stage a lay person might
> casually look at the battery voltage, see 14.7v, and think that the battery
> is fully charged.  The reality is that it is only about 80% charged.  Most
> battery monitors like your blue sea are kinda dumb.  At best they measure
> A-Hr in VS A-Hr out.  Some reset to 100% charged when 14.7v is reached.
> Some keep accumulating A-Hrs from a pseudo-float while actually still in
> the acceptance (2nd stage).  Some can be reset to 100% manually.  Some need
> to be reset.  I say pseudo-float since charge sources like solar can be
> sized insufficiently to actually change the chemical state of charge to get
> the batteries out of the 2nd stage and sometimes not even out of the 1st
> stage.  So while a charge current IS being applied (and
> measured/accumulated by the battery monitor) the state of ACTUAL state of
> charge is not actually changing.  I believe this is probably what is
> happening in your case.
>
> Summary of stages of charge:
> 1st = BULK = constant current and charger max current with steadily
> climbing voltage up to ~14.7v
> 2nd = ACCEPTANCE = constant voltage at ~14.7v with current steadily
> lowering from max to ~2 amps.
> 3rd = voltage maintained at ~13.6v.  If the current required to maintain
> 13.6v goes above ~2amps then the charger will switch back to stage 2 mode a
> d you'll see volts jump up to ~14.7.
>
> I know you asked for simple... Sorry.
>
> Josh Muckley
> S/V Sea Hawk
> 1989 C&C 37+
> Solomons, MD
>
> On Fri, Jul 5, 2019, 12:23 PM Edd Schillay via CnC-List <
> cnc-list@cnc-list.com> wrote:
>
>> Listers,
>>
>> Last year, I installed a Blue Sea battery monitor and Iā€™m a little
>> perplexed about the readings I am seeing.
>>
>> Last night, before an amazing fireworks display at Hempstead Harbor
>> (thanks to fellow Lister Neal Gallagher for the guest mooring), I looked at
>> the display. Out of the 450 amp hours in the House bank, we had used around
>> 6 amps between using the electric head, cell phone charging, etc. for
>> several hours ā€” with the display showing 99% capacity.  But the voltage was
>> showing 12.38, which I understand to mean closer to 75%.
>>
>> Someone on a YouTube video said that the Voltage reading is not really
>> the one to go by, as the voltage will increase when you start switching
>> things off.
>>
>> Is that all true? Is what Iā€™m seeing normal? Can one of you Amperage Aces
>> or Voltage Vixens explain this to me? (Please keep it simple - way too much
>> Romulan Ale and Klingon Blood Wine flowing last night.)
>>
>> - Confused on City Island
>>
>> All the best,
>>
>> Edd
>>
>> -------------------------------ā€”-
>> Edd M. Schillay
>> Captain of the ā€œStarship Enterpriseā€
>> C&C 37+ | Sail No: NCC-1701-B
>> Venice Yacht Club | Venice, FL
>> www.StarshipSailing.com
>> -----------------------------------
>> 914.774.9767   | Mobile
>> -----------------------------------
>>
>>
>> Sent via iPhone X
>> iPhone. iTypos. iApologize
>>
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