Battery Configuration and Confusion

There are so many posts and articles on battery configurations that now I'm more confused than ever. I have a 2014 Sundancer 280 and am looking to this group for advice on battery configuration.

There are two batteries. I bought the boat recently and the current set up is a deep cycle on #2 one and a starting/cranking battery #1. The Sea Ray manual states to use the same batteries for both 1 and 2, starting battery with minimum of 800 CCA.

So what is the best configuration? Same battery for #1 and #2? Or deep cycle when "on the hook" and starting battery for starting???

If I have two starting batteries like the manual suggests, does that provide enough power when anchored "on the hook" for the day for minor electronics leaving enough power to start the boat? I like the thought of having a Deep Cycle and a Starting which is not recommended - but is the current configuration from a previous owner.

Another confusing part. The manual states to start and run the boat with the battery switch to "both" on the dial. On the boat, there is a sticker near the battery switch that says start and run on #1, and when the engine if off "on the hook" switch to #2. Sea Ray is saying two different things.

Also, when at the dock and hooked up to shore power, we always the turn the battery charger on. Do the smaller power needs like refrigerator, radio, TV still run on the 12V battery even when hooked up to shore power? So my assumption is that the 12V sources run off the battery, which is continuously being charged from the shore power - is that correct?

If that is the case, what should the battery switch be turned to? I read that when hooked up to shore power, the charger/converter charges both batteries no matter what the switch is turned to. Is that correct?

My assumption is to configure batteries according to the manual, but I'm not sure it makes the most sense. Please advice.

Wishing everyone a happy New Year.

Steve

Keep things simple: a start battery (#1) and a house battery or 2 in parallel (#2). You turn the switch to ALL when starting and running so the alternator charges both start and house batteries. Once on the hook and the engine is off turn your switch to #2 so you don't accidentally discharge your start battery.

You are better off with deep cycle batteries for the house because they tolerate a large discharge better. The start battery is designed for short bursts of high amperage output. Your two or three bank automatic charger should turn on when shore power is connected. It provides power to the 12 volt system through the house batteries. Your fridge will likely switch over to 120 volts on shore power. You can leave the battery switch at #2 when on shore power. Shut it OFF when you leave the boat. The charger should be wired so the batteries will still be maintained.

If you install an automatic charge control relay it simplifies the switching back and forth.

In the traditional "1/2/Both" switch scenario I believe you should be running the same batteries on both sides. It's similar to the banks of batteries on the larger boats. We're not supposed to run both starting and deep cycle within the same "bank", they need to be the same to charge and discharge properly.

Your setup is technically a single "bank". You just have the option to switch between one or both batteries on that bank.

I was going to recommend to you the same "dual purpose" batteries a lot of us use but your CCA requirement is quite high. You're in the "ultra starting battery" range with the Duracell's I've been using for a while.

I'd put two high quality starting batteries in your boat and trust the manual. It's the proper setup for your CCA requirement. Alternate between the batteries when starting and parking, charge both when running and enjoy that boat.

best option is to add a "house" battery bank and keep the motor batteries dedicated to only the motor

Take a look at the wiring diagram for your boat; I think you will find that both batteries are used for starting and for various other duties (house and other demands). Also, you will find that the battery charger (sometimes called a "converter") is common for both batteries. Consequently, both batteries should be the same type and if at all possible same age. Additionally, for these boats, batteries should be dual purpose like Group 27 or Group 31. If you should have like in your configuration a cranking battery and a deep cycle battery the charger will never be able to establish a full charge for either as the charge rates are different.

And, by the way, deep cycle batteries should only be used in a stand-alone configuration with a dedicated charging system. For our boats setting up for a dedicated house battery system is rather intrusive from a wiring perspective.

Let's start with some clarification. Your signature says you have a "450" engine with "drives" (plural). The assumption would be that you have a 350 engine with a SINGLE Bravo 3?

The sticker by your battery switch sounds like something a previous owner did.

"So my assumption is that the 12V sources run off the battery, which is continuously being charged from the shore power - is that correct?" This is correct, save for the fridge. The fridge will automatically default to AC power (as long as the AC breaker is on).

Battery switches... there are different schools of thought here. I prefer to start on one battery only - that way you know if one is going bad or not. This also allows you to have two separate types of batteries for different purposes. I also prefer to charge one battery at a time for better charging. If you have the original battery switch, you can switch from 1 to 2 to Both without causing any issues. This means you can have a starting battery and a large deep cycle. If you're away from the dock, and the DC battery is getting low... start the engine on the starting battery, then use the switch and move to the DC battery.

From my experience with the same setup/use, I used a Group 27 DC battery (as the "2nd" battery) with great results. If you can fit it, you could upgrade to a Group p29 or even a 31 for not much extra money, but noticeably increased reserve power.

To further the comments above, I was always told that switching batteries while the engine is running is a nono, as it can cause alternator and/or regulator damage from voltage spikes. Can anyone comment on that? I always thought it would be great after being on the hook all night to start on #1 the once running to switch to #2 to charge it once underway.

You are correct on the alt , disconnecting it will surge everything in the system. Generator could be disconnected but NEVER an alt . Same goes for removing a battery terminal in an auto when running. Alt goes wild up to 30 or 40 volts.
If your worried about switching ,start on "both"

Ted Russell said:

To further the comments above, I was always told that switching batteries while the engine is running is a nono, as it can cause alternator and/or regulator damage from voltage spikes. Can anyone comment on that? I always thought it would be great after being on the hook all night to start on #1 the once running to switch to #2 to charge it once underway.

Click to expand...

You can switch from 1 to ALL to 2 but never to OFF while the engine is running. You are correct: alternator damage can result.

Running the engine with the alternator disconnected from the battery will not destroy the alternator diodes. An alternator field connection with no voltage will not create a field and therefore no electricity if the engine is started with the batteries disconnected. In other words, an alternator will do nothing if you run it while it is disconnected from the battery. What will kill the alternator is any voltage spike caused by the alternators field collapsing when you either connect or disconnect the alternator while the engine is running. Disconnecting the alternator when the engine is running is a bad idea!

You can also damage an alternator by running it with the voltage sensor wire disconnected. The regulator will sense the voltage is too low and keep increasing the field voltage until the alternator diodes are destroyed.

"Assuming" the battery switch is the one that Sea Ray originally installed, it is a "make before break" switch. In this case, it IS ok to switch between 1-2-Both... just not off. If the switch is something different, then it is NOT ok to switch while the engine is running.

Lazy Daze said:

"Assuming" the battery switch is the one that Sea Ray originally installed, it is a "make before break" switch. In this case, it IS ok to switch between 1-2-Both... just not off. If the switch is something different, then it is NOT ok to switch while the engine is running.

Click to expand...

OK this is good to know. My preference after a night on #2 would be to start on #1 then once running, switch to #2 and charge that battery on its own, then switch to both.