Thx all  - very helpful. I had a battery issue on the 1st. This thread is 
timely. 
R
Tom 
Therapy 
C&C 29 MkII
Solomons, MD

Sent from my iPhone

> On Jul 5, 2019, at 7:26 PM, Josh Muckley via CnC-List <cnc-list@cnc-list.com> 
> wrote:
> 
> I know Gary!  You only had to read it!  Imagine my difficulty, I had to write 
> it!
> 
> Josh
> 
>> On Fri, Jul 5, 2019, 7:23 PM Gary Russell via CnC-List 
>> <cnc-list@cnc-list.com> wrote:
>> 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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