Arrgh! My brain hurts. š 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 Iām 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 Iām 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 āStarship 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 >> >> _______________________________________________ >> >> Thanks everyone for supporting this list with your contributions. Each >> and every one is greatly appreciated. If you want to support the list - >> use PayPal to send contribution -- https://www.paypal.me/stumurray >> >> _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > >
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