25 Bertram Backyard Refit. Do I want 3 batteries? Do I need Three?

[ttownthomas]

I'm doing a DIY Refit on a 1972 Bertram(Twin L6 Sterndrives, MC-1 Drives). My first order of business was to get the machinery in order which I'm working through. I have done some engine work and some fuel system work and I'm moving my way back and I'm onto the drives and steering. I decided to upgrade to hydraulic steering and newer style Alpha trim pumps but the pumps really don't fit in the motor well and I decided to move them to the floor in the battery area. So now I'm detouring to wiring.

The battery area is fore of the bilge but under the cockpit with hatch access. In order to fit the floor mounted pumps I only have room for 2 batteries in there.

The boat has 2 good starting batteries but one is wired as a house battery and they are wired together with Guest switches.

If I went to 3 batteries I would have to locate a new house battery someplace else, possibly in deck furniture that is yet to be built. But I could also just stay with 2.

Can I get some input on what is really needed?

I do plan to take the boat offshore eventually but it will mostly be used for coastal exploring and near shore fishing. I do not know how many electrical loads it will have but we all know these things tend to grow over time.

 

[eric102]

If you are planning anything high draw like a windlass, thruster, inverter or refrigeration a 3rd battery would be recommended. I can go several days on the hook without recharging my two group 27 AGM house batteries that run a small fridge, inverter, lights etc. The 3rd AGM battery is only for backup or the occasional engine start if the house batteries are getting low.

 

[Chris1956]

3 batteries is probably what you want. The house battery could be a deep-cycle type.

If it were me, I would wire the switches so I can start either engine with either starting battery. Switches are "make-before-break", right?

 

[dingbat]

I'm running a single outboard with a full component of navigation and fish finding electronics.

I started with a starting battery for the motor and a deep cycle for the house on a 1-2-both switch.

Really struggled with battery management issues. Constantly playing with the switch trying to keep power to the boat.

In the end I swapped out the starting battery for a deep cycle. Installed an ACR (on-off-both) for charging duties and moved primary navigation electronics (chart plotter, VHF) from the house over to the starting battery. Let backup chart plotter, back up VHF, depth finder and radar on house battery.

 

[Tassie 1]

30 ft flybridge cruiser ( not a bertie )
moored in salt water
twin 5.7 merc shaft drives,
fridge
tv
am/fm
3 auto bilge pumps 1 manual
two chartplotters, x2 vhf, assorted other " modern must haves" like phone/laptop chargers etc etc blah blah
deck/ bow lights

have 3 batteries, 2 start, 1 house,

l need another battery me thinks

 

[ttownthomas]

I have been looking at wiring diagrams for days. Seems like ACR's would allow me to locate the house battery away from the heavy gauge switches. Is that accurate?