It's true: 11.7V pretty much means that the battery is at 25% state of charge. It's a good place to stay above: "Occasional dips into [this range] are not harmful, but continual discharges to those levels will shorten battery life considerably." ["State of Charge," http://www.windsun.com/Batteries/Battery_FAQ.htm#Battery%20Voltages] 10.5V at 77 degrees F is considered fully-discharged. Determining a battery's state of charge by reading its voltage is not real accurate; measuring each cell's specific gravity with a hygrometer is the most accurate method, but it's messier business than I care to deal with inside our Westy. Given the inaccuracy of the voltage method, maybe 11.7 volts as a trigger point ain't bad. But one wonders how accurate that cut-off gizmo's voltage measurement circuit is. It comes down to how deeply you are willing to discharge the battery. I try to keep our house battery at no less than 80% state of charge (per the XBM battery monitor, no less than 12.4V on the volt-o-meter). -- Mike "Rocket J Squirrel" Elliott 71 Type 2: the Wonderbus 84 Westfalia: Mellow Yellow ("The Electrical Banana") 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano KG6RCR
TC typed: >> Yes, but it cuts out at 11.7 volts.... too high to be of any use for RV's. >> David (dsl82westy) > please explain I thought that was about when a 12v battery has 25% charge > left > 12.8-13.2v is ~ full charge, & fully discharged is about 11v > so 11.7v is really low discharge pt even on deep cycle batteries if you want > optimal life of the battery > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > ~~~~~ >>> Would this sort of low voltage cut-off gizmo do the trick ?? >>> >>> Tom >>> >> http://canadiantire.ca/browse/product_detail.jsp?PRODUCT%3C%3Eprd_id=845524 > 443294641&FOLDER%3C%3Efolder_id=1408474396672454&bmUID=1182208017428 > |
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