propper use of dual batteries

jeffruby

jeffruby

New Member
Aug 6, 2010
58
new york
Boat Info
2007 sea ray sundeck 260
Engines
6.2liter merc b3
On my sundeck, have two batteries. There is a switch, off, 1, both, or 2.

Obviously when not using boat....put to off

When chilling on boat, listening to music, etc....do I want it always on 1, or alternate 1 and 2 each day of use?

When I'm starting engine and driving boat......on both? Or always on 1 or 2

Thanks. Been getting conflicting advise. I think batteries both charge while engine on.
 
Short answer is never on "both" unless in emergency starting situation. Is one battery a starting battery and one a deep cycle? They should both charge regardless of switch setting.
If both are same type battery, I would alternate from one outing to the next.......clear as mud?
 
It was my understanding to have the switch to Both while running and 1 or 2 while parked and off when not in use.




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Both batteries will charge when on shore power regardless of switch position.
The alternator only charges the battery selected. So if you are out all day, and you want to charge your party battery on the ride home, switch to both. NEVER switch past OFF when engine is running, you will ruin your alternator.
If they are both the same type batteries, party on one battery and switch to the other to start and run home. As previously stated, switch it up every now and then as to which you use.
If one is a deep cycle, use that as your party battery.
 
I also have a dual battery setup and my dealer said to always run on both to charge both on the way home. One question I do have is when looking in the engine compartment, which battery is number 1 and which is number 2?
 
on mine, when looking at them both, the closest one to the front is 1; closet to transom 2
 
Do you connect to shore power? If you have a onboard charger, why would you need to switch batteries daily? I guess it depends on if you have a starting battery and a 'house' or deep cycle battery.

I do not switch to off when not at the boat, but maybe I should.

jeffruby said:
On my sundeck, have two batteries. There is a switch, off, 1, both, or 2.

Obviously when not using boat....put to off

When chilling on boat, listening to music, etc....do I want it always on 1, or alternate 1 and 2 each day of use?

When I'm starting engine and driving boat......on both? Or always on 1 or 2

Thanks. Been getting conflicting advise. I think batteries both charge while engine on.
Click to expand...
 
Looking at the wiring diagram of the 280 (both single and dual) leads me to conclude there is no 'house' battery. The single engine with two batteries is wired with the batteries in parallel when on 'both' giving twice the amps for starting. Position 1 and 2 provide electricity to all circuits on the boat. Twin engine 280s do have an isolated port battery that only services the port engine, unless someone puts in an aftermarket crossover.

So assuming SR wired the single engine boats consistently, the following would be things to consider:

1. Both batteries should be the same type and condition - when being charged on the both setting batteries with different charging profiles may not properly charge,
2. When at anchor, use 1 or 2, not both, so one battery stays in reserve. However, you should not dedicate a battery for 'house' service as you will wear it out faster and change the charging profile (see Item 1). Charge to re-charge frequency is one of the things that kills batteries. Alternating the house use will keep them in similar condition. We use 1 on odd numbered days and 2 on even number ones.
3. Start and run with switch on both. This will give both batteries equal time on the alternator. Also if you have a high amp option like a windlass, or spotlight you will see better performance with the switch on both.


Henry
 
So, I am trying to sort out the battery situation on my 280DA as well, as I am considering replacing starboard battery #2 (which we use as house) with a pair of high-Ah 6-volts. I was told by the previous owner that all the batteries charge when the engines are running, regardless of the switch position (i.e. both starboard batteries charge when the starboard engine is running whether it is in the 1, 2, Both, or even Off position (you could start the starboard engine using the emergency crossover switch)). I was not convinced, so I e-mailed Sea Ray. Here is the response I got:

-----------------------
Brian, both Batteries will charge when both Engines are running no matter what setting you have the Battery Switch in.

Chris Lovell
Product Support
Sea Ray Headquarters
-----------------------

Still sceptical, I asked for a wiring diagram of the charging circuit (none of the available documents for the 280DA properly show this), but all that could be provided was the same one I already have. I have asked if there is anyone at Sea Ray with tribal knowledge of this boat that could answer the question definitively.

I know the batteries charge from the AC converter regardless of the switch positions, but I am still unsure about the situation when charging from the engines. One thing that raises doubt, is if all the batteries are charged all the time from the engines, how can you damage an alternator by changing the battery selector when the engines are running?

Also, without seeing the charging circuit, I am concerned starboard battery 1 and 2 are simply charging in parallel, which would not likely work well with mismatched battery types (right?).
 
Put a volt meter on each battery while switch is set to "both" and engine is running. If you get around 13.5-14V they are being charged.
 
That's my planned experiment for next weekend!
 
The Ac converter charges each battery via a direct wiring connection to the positive terminal post - that is why the battery switch position is irrelevant. That is is not the case with the alternator charging circuit - which is via the main positive battery cables. The switch must be in a position that closes the circuit to the battery(s) that one wishes to charge from the alternator.
 
Battery No 1 is usually wired as "house battery".

By that I mean - this is where your MerCathode and your Bilge Pump is connected to directly. So they are being used non-stop. (so to speak)

So if you have two batteries - switch them around every quarter.

To test leave boat in water - before you leave- check voltage on both. When you return after a few days - one battery will be lower than the other - that is where MerCathode and Bilge Pump is connected.

If you trailer - I do not know how much will get drained from MerCathode when there is 0 current flow. But drain will be a lot smaller if boat is on a trailer.
 
When I had my 240DA I used the following approach:

1. When plugged in to shore power or right before starting the engines the switch goes to BOTH.
2. When anchored out, I made an easy decision to always use #1. This way I would keep #2 always fully charged.

If I see that the voltage drops (after a day and an overnight) on #1, I turn the switch to BOTH and start the engine to charge the #1 (actually both since I turned the switch on both). However, I think that very rarely I had to do it as the battery usually holds fine for 1.5 days.

I liked this method as I always could count on #2 giving me all the juice I need to fire up the engine.
 
I tested my 2009 SeaRay Select yesterday. Battery 2 on mine is house battery :)

and charging follows battery setting. So set to battery 2 - only charges battery 2. Set to all - all batteries charge - set to 1 - battery 1 charges.

I have ordered two "battery/DC loggers" - a little battery driven unit that can measure at custom intervals - and you can plug straight into the computer via USB for analysis. They are about $70,- on eBay (Lascar EL-USB 3 - http://www.lascarelectronics.com/temperaturedatalogger.php?datalogger=153)

They can record about 32000 "data points" - so if I do 5 minute intervals - that is about 110 days of logging before log is full. (or about a year at 15 min)

That should give a good indication on how well the batteries are doing - and when it is time to replace them.

Dependent on my trials - i'll install a solar charger and "PowerFilm" Velcro attached 14watt panel. I have sun about 8-12 hours pr day 350 days a year - so I hope that will be enough to keep my MerCathode with sufficient power.
 
kaz911 said:
I tested my 2009 SeaRay Select yesterday. Battery 2 on mine is house battery :)

and charging follows battery setting. So set to battery 2 - only charges battery 2. Set to all - all batteries charge - set to 1 - battery 1 charges. ......
Click to expand...

That makes it very simple. Keep the selector on BOTH anytime you're plugged in or the engine is running. When on the hook with the engine off switch to #2 (your house battery). This will leave #1 reserved fully charged for engine start. I don't know why you'd need anything else.
 
Here is the latest from Sea Ray. As someone else mentioned, all the batteries charge from the AC converter regardless of the switch position (I will confirm this on the weekend if someone else doesn't first). When the engines are running, as confirmed by kaz, the batteries will charge per the switch setting. I will check this on my 280DA this weekend to confirm if it is the same (again, unless someone beats me to it!).

One more thing, it is ok to switch from 1 to Both to 2 (or vice versa) while the engine is running, just don't go past or to "Off". This is because the switch connects the next contact before disconnecting the previous one as the dial is turned.
 
Keep the selector on BOTH anytime you're plugged in or the engine is running. When on the hook with the engine off switch to #2 (your house battery). This will leave #1 reserved fully charged for engine start. I don't know why you'd need anything else.

That's what I do!....Mike.
 
There is a lot of conflicting info here. Let me add to it. (single engine 2 batteries off/1/2/both Perko switch)

1. At the dock plug your boat in and set the battery switch to OFF when you leave the boat.
The on-board charger will charge both batteries and the bilge pump will work if wired properly. (easy to check pour water into the bilge until the pump kicks on if it kicks on your good if you sink your not)
2. Start your motor with the switch on 1 or 2...not both.
Each day you alternate between 1 and 2,(it's like rotating your tires) do not use both unless it's a dire emergency and that's the only way the motor will start.
3. Do not switch between 1 & 2 while the motor is running
Most new switches will allow you to do this because it switches to the next setting before disconnects the previous. However if this safeguard fails you will take out your alternator. Why take that chance?
4. When you are not plugged in and using electrical devices don't use both batteries.
When your out anchored for the day and using electricity use the 1 or 2 setting not both. Save one battery for strictly starting your motor and the other for powering your goodies.

This is what I believe to be true regarding this mysterious switch responsible opposing viewpoints welcomed.
 
Last edited:
One note: My 1987 21' Monaco with the 260 Mercruiser had the trim wired to Battery #1 only. So if I tried to only use Battery #2 - I had no trim (and who knows what else - I never checked). Battery #1 ran all accessories. So I would use Battery #2 while on the hook listening to music etc and Battery #1 (or sometimes Both) to start and run the engine.

-Steve
 
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