boater56

New Member
May 28, 2020
5
Boat Info
2005 Searay 240 Sundeck 5.0 Merc Bravo
Engines
OW344212
We have a SeaRay 240 Sundeck and it has the ability to have 2 batteries and a battery switch. Its time to replace batteries again, and I am always curious if it is better to have 2 starter batteries or 1 starter and 1 deep cycle. Most of the time, the radio and bilge pump are the only electronics used during beaching or anchoring out, usually 3-6 hours at a time. It usually takes about 1 hour to get to our destination. What is recommended under these circumstances? Thank you ahead of time for any help.
 
Please explain your battery set up.

Do you have one battery switch selector A, B, A&B, Off?

If you do change out your batteries get both the same ..... you will be better off.

I would suggest to replace both with deep cycle AGM batteries.
 
If you're running the stereo for that length of time, use the DC battery. Use the DC when the engine is off. For "best practice", start the engine on the starting battery and then switch over the DC for your 1 hour return run. The starting battery will get charged back up fully on your next run out the spot.

The starting battery will last longer when used for starting only and the DC battery will last longer when NOT being used to start the engine.

Switching while the engine is running is only safe for the alternator assuming you have the original battery switch - or installed a similar one ("make before break").
 
If you're running the stereo for that length of time, use the DC battery. Use the DC when the engine is off. For "best practice", start the engine on the starting battery and then switch over the DC for your 1 hour return run. The starting battery will get charged back up fully on your next run out the spot.

The starting battery will last longer when used for starting only and the DC battery will last longer when NOT being used to start the engine.

Switching while the engine is running is only safe for the alternator assuming you have the original battery switch - or installed a similar one ("make before break").
This is what I do. It works well. But depending on how long I run after anchoring I may put the selector on "Both".
 
What size battery? I'm assuming Group 27? If not upgrade to Group 27 from your Group 24. I've been buying batteries for my boats for too many years but learned that it's one area where use and pricing are your decision makers. In the early days we had a starting battery and a house battery then switched to Deep cycle but they don't crank like a starting battery. These days as per my mechanic I buy Group 31 1000CA starting batteries and haven't looked back. My last boat I upgraded from Group 24 to Group 27 1000CA starting batteries and so far both boats with these starting batteries have never failed me.
You're a day boater like I am and with two fridges running plus everything else that is on I've never had a problem. When I get back to the dock I plug in and charge the batteries. The advantage is the wet cell batteries are cheap and I've been getting five years out of them.
 

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