I wish to tie 2 12 volt deep cycle (matched & new) batteries in parallel resulting in constant voltage but doubling the amps. The boat is a 1980 H25 (this will be my 3rd season with this boat) and I doubt the wiring has been upgraded in its life. My question - will applying this amp increase through the old wiring just fry it. Seems to do fine with a single battery. Will be running depth sounder, gps, sound, vhf, cabin lights occasionally, running and anchorage lights and an occasional outboard start. Know nothing about electricity - maybe one of those battery switches should be installed. Thanks Dennis
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Capacity not Current Draw
Dennis, My understanding of what you're doing will increase your amp-hour capacity but will not in itself increase the amps flowing through your electrical system. In other words, it will take longer to deplete your batteies, but there won't be any higher amperage flowing through your wires unless you add appliances with a greater current draw. Make sure you wire your batteries together with postive to positive connections and negative to negative. If you do it the other way you will double the voltage with no increase in amp hours and then you will fry your electrical system. Nigel Calder's Boatowner's Mechanical and Electrical Systems book, available in the chandlery on this site makes a good reference on this type of issue. Hope this helps. Gary Wyngarden S/V Wanderlust H37.5
Dennis, My understanding of what you're doing will increase your amp-hour capacity but will not in itself increase the amps flowing through your electrical system. In other words, it will take longer to deplete your batteies, but there won't be any higher amperage flowing through your wires unless you add appliances with a greater current draw. Make sure you wire your batteries together with postive to positive connections and negative to negative. If you do it the other way you will double the voltage with no increase in amp hours and then you will fry your electrical system. Nigel Calder's Boatowner's Mechanical and Electrical Systems book, available in the chandlery on this site makes a good reference on this type of issue. Hope this helps. Gary Wyngarden S/V Wanderlust H37.5
Paralleling Batteries
Dennis, Look into installing a 'battery combiner' between the two batteries. They are available thru the usual boat stores. This will prevent a stronger battery from discharging into a weaker battery in the future.. If there is ANY voltage difference between the two, the one with the higher voltage will force a circulating current thru the batteries to discharge the higher one until it is the same as the lower voltage one. Dick Carey S/V Puffin 1990 H-33.5
Dennis, Look into installing a 'battery combiner' between the two batteries. They are available thru the usual boat stores. This will prevent a stronger battery from discharging into a weaker battery in the future.. If there is ANY voltage difference between the two, the one with the higher voltage will force a circulating current thru the batteries to discharge the higher one until it is the same as the lower voltage one. Dick Carey S/V Puffin 1990 H-33.5
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