Bob — I would consider sizing the wiring aft from the forward batteries to allow at least 100 amps, with a maximum 10% voltage drop. This would require at least 4AWG cabling from under the v-berth to the electrical panel aft; better would be 2AWG, which would allow you to pull 30 amps with a 3% voltage drop. Don’t forget that you’ll need a battery switch located very close to the bank under the v-berth; and I would also put a 100-amp breaker (a 285-Series surface mount would do the trick: https://www.bluesea.com/products/7187/285-Series_Circuit_Breaker_-_Surface_Mount_100A) after the battery switch to protect the long wiring running aft.
The biggest issue with doing this is that trying to start your engine by switching over to the forward bank is most likely not going to work, as your starter wants more current than your wiring would be sized for. Trying to upsize the wiring to accommodate this would be VERY expensive, and not ideal in any case. If you move two batteries forward and keep two aft, basically splitting your house bank into two banks, you’d have a better chance using the aft bank as an emergency engine start source; but your wiring for charging and selection is going to be more complicated. Does this help at all, or just set you up for more questions? :^) — Fred Fred Street -- Minneapolis S/V Oceanis (1979 C&C Landfall 38) -- on the hard in Bayfield, WI :^( > On Nov 19, 2015, at 10:24 AM, Robert Boyer via CnC-List > <cnc-list@cnc-list.com> wrote: > > I am equipping my boat for 8 months per year of cruising in the Bahamas. I > have added a 19-gallon auxiliary diesel tank where my holding tank was > located (under the navigation seat) which adds weight aft. I currently have > 4 group 27 batteries which will be eventually upgraded to Group 31's--these > also are located aft. > > I have been considering moving 2 or 3 batteries from the aft cockpit locker > to some dead space under the v-berth. This would take some weight from the > aft and add it forward. (My boat currently sits about 2" high at the bow and > maybe 1 inch low at the stern with no one aboard but full fuel tanks.) > > I could configure the batteries such that the new forward bank could be the > house bank and the starting bank (which I could probably reduce to 1 or 2 > batteries) could remain aft. My problem is sizing the cables that would run > from the forward batteries to the aft controls. As I see it, these cables > would never carry more than 30 amps (maximum charging from my solar panels) > unless I needed them for starting (in the event of a dead starting battery). > > Does anyone have any comments or suggestions on this matter? > > Bob > > Bob Boyer > S/V Rainy Days / Annapolis MD > 1983 C&C Landfall 38 - Hull #230 > email: dainyr...@icloud.com <mailto:dainyr...@icloud.com> > blog: dainyrays.blogspot.com <http://dainyrays.blogspot.com/>
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