I have a 2003 Sundancer 300 with...

[MrB18]

I have a 2003 Sundancer 300 with no generator and 3 batteries and 2 refrigerators.  When we go to dine somewhere I would like to leave both on while we are docked with no power most times about 3 to 4 hours.  Does anyone have a good suggestion for a house battery size and type and do the starting batteries suffer without shore power in this situation.  Just for ref my 260 Sundancer had 2 batteries and withing 2 hours the single refrigerator would draw the battery down significantly. Thank You Allen

[Korkie]

The boat we had before we bought our 340 was a Maxum SCR 2700 / 2002. It had no generator, but did have a 2000 watt inverter for house 120AC. We added an additional set of batteries (one to each bank) so that we had 4 total. When we would go into restaurants / friends house / on the hook - etc, we would only leave one set on. The fridge (only 1) and the stereo would stay on constantly along with a small 120v cabin fan running off the inverter. I used Deep Cycle Interstate Marine Batteries bought from Auto Zone. The primary set would poop out after 2-3 seasons and I would move the other set over to primary and put a new set in as secondary. Also would keep gps on as it had a low voltage warning that would let me know the system voltage has fallen below 11.2 volts. Would simple start up motor and recharge for about 20 min or so. We spent a lot of time on the hook using this system and it never let us down.

[wingless]

The important step to implement is to have layers of redundancy. Ensure that there are multiple charged good battery banks with at least one being isolated from loads as a reserve.

Do some supply / load calculations for the issue. An example is: Battery w/ 100Ah capacity, 10A load active 50% of the time gives 20 hours of run time.

A battery is typically considered end-of-life when the measured capacity is less than 50% of the nameplate rating.

The boat operation should ensure that the starting point is that the batteries are fully charged, such as the boat being plugged-in to an appropriate charger while not at use.

An option is to properly add additional batteries to increase unplugged capacity. The modification must be fully compliant w/ ABYC for safety. This modification frequently requires also exchanging the existing on-board charger. Batteries should be the same date code, chemistry and capacity for proper charging / discharging.

[Steal_Away]

I had same exact boat, 2003 with no gen and 2 refrigerators. Dozens of times, I left boat for hours with both refrigerators on, and had zero issues. I recommend good batteries like Interstate 31P-MHD.

[TitanTn]

I have an older 300 Weekender - no generator. One battery should be isolated as a cranking battery only. Unless someone has changed something, it should have come that way from the factory. That leaves two more batteries. You can get high amp hour 12 volt batteries as suggested, or another option to consider is what I did. Replace one of those with a high amp hour 12 volt battery, and then replace the remaining battery with 2 - 6 volt batteries. Much easier to get in high amp hours - similar to golf cart batteries. Connect them together to create a 12 volt battery and I bet that would take care of your need by itself.

[BigBri]

I have a 2002 Sundancer 300 with a generator. We will go camping on the lake for two days and two nights without using the generator. We also have two fridges which are both on during that time. We changed out the two starter batteries for two deep cycle batteries, these are the two batteries that operate the two refrigerators. These two batteries also start the starboard 6.2 l engine. We have had no problem with that setup. Make sure you have good quality batteries of the right capacity. Our boat has four batteries, two starter (for the port engine) and the two deep cycle for the starboard engine and cabin accessories.