Boat U.S. - January 2009 - (Page 28) techconnection BY CHUCK HUSICK Listening To The Guys At The Yard had a DC Digital Voltmeter installed on my 28-foot Carver to monitor my 8D deep-cycle house battery. The guys at the boatyard said I shouldn’t let it get below 12.50 volts before recharging because it becomes discharged at 12.40 volts. Is this correct? I’ve read that there’s a grad- Q. I ual discharge that becomes steep and unrecoverable below about 11.90 volts. How should I interpret my voltmeter readings? R. Deutsch Seattle, WA A. The guys at the yard are incorrect about the relationship between battery voltage AskChuck@BoatUS.com Technical editor and whiz kid Chuck Husick — engineer, sailor, pilot, former president of Chris-Craft — welcomes your questions on diesel engines, new gear, and the latest technology. No worries, Chuck’s here: AskChuck@BoatUS.com. 40 BoatU.S. Magazine January 2009 and state of charge. A fully charged lead-acid battery will deliver an open-circuit voltage (no load applied) of 12.6 volts (or higher). The voltage will decrease by 0.2 volts for each 25% reduction in the amount of stored energy remaining in the battery; 12.4 v = 75%, 12.2 volts = 50%, 12.0 v = 25%, and 11.8V = 0% charge (for a deep-cycle battery). The battery will continue to deliver power even when the voltage decreases below 11.8 volts (even as low as 7 volts; however, continuing to draw power when the voltage is less than 11.8 volts can cause significant damage. All batteries will self-discharge over time; the rate at which this occurs depends of the type of battery (deep-cycle, starting, flooded cell, gel cell or AGM) and the temperature of the battery. Batteries that have been discharged below 11.8 volts can usually be recharged successfully provided the recharging is done promptly. Flooded cell batteries (the type with openable cell caps) left in a deeply discharged state for more than a few weeks may
Table of Contents Feed for the Digital Edition of Boat U.S. - January 2009 BoatU.S. - January 2009 Contents At The Helm Reader Forum BoatU.S. Reports Brokerage Boats Invasion Of The Access Snatchers Don’t Move A Mussel Tech Connection BoatsGearWheels A Defect And Its Aftermath Obama Onboard? Fast-Water Fly-Fishing How I Got That Shot A Loop Through The Heartland Why Boats Sink At The Dock Install Your Own Trim Tabs BoatU.S. Exchange At Your Service/Mbr. Benefits Boat U.S. - January 2009 Boat U.S. - January 2009 - (Page Intro) Boat U.S. - January 2009 - (Page Cover1) Boat U.S. - January 2009 - (Page Cover2) Boat U.S. - January 2009 - Contents (Page 1) Boat U.S. - January 2009 - At The Helm (Page 2) Boat U.S. - January 2009 - At The Helm (Page 3) Boat U.S. - January 2009 - Reader Forum (Page 4) Boat U.S. - January 2009 - Reader Forum (Page 5) Boat U.S. - January 2009 - BoatU.S. Reports (Page 6) Boat U.S. - January 2009 - BoatU.S. Reports (Page 7) Boat U.S. - January 2009 - BoatU.S. Reports (Page 8) Boat U.S. - January 2009 - BoatU.S. Reports (Page 9) Boat U.S. - January 2009 - BoatU.S. Reports (Page 10) Boat U.S. - January 2009 - BoatU.S. Reports (Page 11) Boat U.S. - January 2009 - BoatU.S. Reports (Page 12) Boat U.S. - January 2009 - BoatU.S. Reports (Page 13) Boat U.S. - January 2009 - BoatU.S. Reports (Page 14) Boat U.S. - January 2009 - BoatU.S. Reports (Page 15) Boat U.S. - January 2009 - BoatU.S. Reports (Page 16) Boat U.S. - January 2009 - BoatU.S. Reports (Page 17) Boat U.S. - January 2009 - BoatU.S. Reports (Page 18) Boat U.S. - January 2009 - BoatU.S. Reports (Page 19) Boat U.S. - January 2009 - Brokerage Boats (Page 20) Boat U.S. - January 2009 - Brokerage Boats (Page 21) Boat U.S. - January 2009 - Invasion Of The Access Snatchers (Page 22) Boat U.S. - January 2009 - Invasion Of The Access Snatchers (Page 23) Boat U.S. - January 2009 - Invasion Of The Access Snatchers (Page 24) Boat U.S. - January 2009 - Invasion Of The Access Snatchers (Page 25) Boat U.S. - January 2009 - Don’t Move A Mussel (Page 26) Boat U.S. - January 2009 - Don’t Move A Mussel (Page 27) Boat U.S. - January 2009 - Tech Connection (Page 28) Boat U.S. - January 2009 - Tech Connection (Page 29) Boat U.S. - January 2009 - Tech Connection (Page 30) Boat U.S. - January 2009 - Tech Connection (Page 31) Boat U.S. - January 2009 - Tech Connection (Page 32) Boat U.S. - January 2009 - Tech Connection (Page 33) Boat U.S. - January 2009 - BoatsGearWheels (Page 34) Boat U.S. - January 2009 - BoatsGearWheels (Page 35) Boat U.S. - January 2009 - BoatsGearWheels (Page 36) Boat U.S. - January 2009 - BoatsGearWheels (Page 37) Boat U.S. - January 2009 - BoatsGearWheels (Page 38) Boat U.S. - January 2009 - BoatsGearWheels (Page 39) Boat U.S. - January 2009 - BoatsGearWheels (Page 40) Boat U.S. - January 2009 - BoatsGearWheels (Page 41) Boat U.S. - January 2009 - BoatsGearWheels (Page 42) Boat U.S. - January 2009 - BoatsGearWheels (Page 43) Boat U.S. - January 2009 - A Defect And Its Aftermath (Page 44) Boat U.S. - January 2009 - A Defect And Its Aftermath (Page 45) Boat U.S. - January 2009 - A Defect And Its Aftermath (Page 46) Boat U.S. - January 2009 - A Defect And Its Aftermath (Page 47) Boat U.S. - January 2009 - A Defect And Its Aftermath (Page 48) Boat U.S. - January 2009 - A Defect And Its Aftermath (Page 49) Boat U.S. - January 2009 - Obama Onboard? (Page 50) Boat U.S. - January 2009 - Obama Onboard? (Page 51) Boat U.S. - January 2009 - Obama Onboard? (Page 52) Boat U.S. - January 2009 - Obama Onboard? (Page 53) Boat U.S. - January 2009 - Obama Onboard? (Page 54) Boat U.S. - January 2009 - Obama Onboard? (Page 55) Boat U.S. - January 2009 - Fast-Water Fly-Fishing (Page 56) Boat U.S. - January 2009 - Fast-Water Fly-Fishing (Page 57) Boat U.S. - January 2009 - Fast-Water Fly-Fishing (Page 58) Boat U.S. - January 2009 - Fast-Water Fly-Fishing (Page 59) Boat U.S. - January 2009 - Fast-Water Fly-Fishing (Page 60) Boat U.S. - January 2009 - Fast-Water Fly-Fishing (Page 61) Boat U.S. - January 2009 - How I Got That Shot (Page 62) Boat U.S. - January 2009 - How I Got That Shot (Page 63) Boat U.S. - January 2009 - How I Got That Shot (Page 64) Boat U.S. - January 2009 - How I Got That Shot (Page 65) Boat U.S. - January 2009 - A Loop Through The Heartland (Page 66) Boat U.S. - January 2009 - A Loop Through The Heartland (Page 67) Boat U.S. - January 2009 - A Loop Through The Heartland (Page 68) Boat U.S. - January 2009 - A Loop Through The Heartland (Page 69) Boat U.S. - January 2009 - A Loop Through The Heartland (Page 70) Boat U.S. - January 2009 - A Loop Through The Heartland (Page 71) Boat U.S. - January 2009 - Why Boats Sink At The Dock (Page 72) Boat U.S. - January 2009 - Why Boats Sink At The Dock (Page 73) Boat U.S. - January 2009 - Why Boats Sink At The Dock (Page 74) Boat U.S. - January 2009 - Why Boats Sink At The Dock (Page 75) Boat U.S. - January 2009 - Why Boats Sink At The Dock (Page 76) Boat U.S. - January 2009 - Why Boats Sink At The Dock (Page 77) Boat U.S. - January 2009 - Why Boats Sink At The Dock (Page 78) Boat U.S. - January 2009 - Why Boats Sink At The Dock (Page 79) Boat U.S. - January 2009 - Install Your Own Trim Tabs (Page 80) Boat U.S. - January 2009 - Install Your Own Trim Tabs (Page 81) Boat U.S. - January 2009 - Install Your Own Trim Tabs (Page 82) Boat U.S. - January 2009 - Install Your Own Trim Tabs (Page 83) Boat U.S. - January 2009 - Install Your Own Trim Tabs (Page 84) Boat U.S. - January 2009 - Install Your Own Trim Tabs (Page 85) Boat U.S. - January 2009 - BoatU.S. Exchange (Page 86) Boat U.S. - January 2009 - BoatU.S. Exchange (Page 87) Boat U.S. - January 2009 - BoatU.S. Exchange (Page 88) Boat U.S. - January 2009 - BoatU.S. Exchange (Page 89) Boat U.S. - January 2009 - BoatU.S. Exchange (Page 90) Boat U.S. - January 2009 - BoatU.S. Exchange (Page 91) Boat U.S. - January 2009 - BoatU.S. Exchange (Page 92) Boat U.S. - January 2009 - BoatU.S. Exchange (Page 93) Boat U.S. - January 2009 - At Your Service/Mbr. Benefits (Page 94) Boat U.S. - January 2009 - At Your Service/Mbr. Benefits (Page 95) Boat U.S. - January 2009 - At Your Service/Mbr. Benefits (Page 96) Boat U.S. - January 2009 - At Your Service/Mbr. Benefits (Page Cover3) Boat U.S. - January 2009 - At Your Service/Mbr. Benefits (Page Cover4)
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