Best way to use dual battery switch?

[Rclement6]

I just bought a 2005 sea ray 220 select bowrider. I had my local shop install a 2nd battery and the dual battery switch. The switch has a off, all, battery 1, battery 2 position. I'm wondering how to make the most of the batteries without having a battery run out. Should I use battery 1 for starting the engine and running all day and then switch to battery 2 in party cove to play music? Is there a situation where I would want to set the switch to ALL? I just want to make sure I never run a battery dead listening to music?
Thanks, Ryan

 

[MolsonCanadian]

Re: Best way to use dual battery switch?

When I had the same setup I'd run one battery one weekend, then run the other the next. Just keep alternating batteries. You can run on "both" to let the alt charge them while getting to your destination, but remember to switch back to 1 or 2.

 

[tpenfield]

Re: Best way to use dual battery switch?

The benefit of the dual battery setup is that you can run on just one battery when you are anchors and blasting the music, etc, while saving the other battery in case you run the other one down too low to start the engine.

It is best to run in the 'All' position for some time during each use of the boat (while underway) so that you keep both batteries charged.

Each person has their own preferred way of managing the 2 batteries.

I usually start the engines on 'both', run on 'both', and then switch to one of them when anchored and using power, etc.

 

[agallant80]

Re: Best way to use dual battery switch?

It depends. There are some 12v things that are hard wired in the battery1 on my boat no matter where the switch is turned. (bilge pump c0 detector). I use battery 2 most of the time, switch it to all when running. Some times I will run off of 1 for a bit to cycle it but most of the time I use 2 because it is going to be pulling power any ways.

 

[ImRich]

Re: Best way to use dual battery switch?

Other ideas are here so I won't add to them. But I will add that you should be very careful not to switch to the 'off' position while your engine is running.

The safest thing is to only switch the position when the engnie is off, then you won't have to worry about an issue.

 

[PatrickBoyle]

Re: Best way to use dual battery switch?

This is the best way. Connects the two batteries and charges both from the engine's alternator when running, isolates your "accessories" battery when you're blasting tunes, keeping your start battery ready for duty. Small price to pay for not having to worry what position your switch is in.

 

[Home Cookin']

Re: Best way to use dual battery switch?

I heard an explanation why you should not charge two batteries simultaneously, if they are not charged (or discharged) equally. I don't remember the reasoning--something about not pouring over when one is full--but it made sense at the time and I stuck with it.

I try to alternate, if I can remember--one way is to use one going out and one coming home. I don't anchor and use the battery for long stretches (although I drift with a VHF and GPS/fish finder on, but not more than 45 minutes at a time). But if I did, I think I'd dedicate one for starting and one for accessories (aka "house").

Some people buy two different types of batteries, one is better for starting and the other kind better for house.

I also find that my GPS's annoyingly over sensitive to "low battery" and although it goes off often, have never had even the least hesitation with starting when it does that.

and always carry jumper cables

 

[The Famous Grouse]

Re: Best way to use dual battery switch?

When I had the same setup I'd run one battery one weekend, then run the other the next. Just keep alternating batteries. You can run on "both" to let the alt charge them while getting to your destination, but remember to switch back to 1 or 2.

The benefit of the dual battery setup is that you can run on just one battery when you are anchors and blasting the music, etc, while saving the other battery in case you run the other one down too low to start the engine.

It is best to run in the 'All' position for some time during each use of the boat (while underway) so that you keep both batteries charged.

Each person has their own preferred way of managing the 2 batteries.

I usually start the engines on 'both', run on 'both', and then switch to one of them when anchored and using power, etc.

I would agree with both of these, but I would be very careful using the "both" setting unless it is necessary to either charge both batteries OR to draw on both batteries in the event both were low.

The key with the 1/2/Both switch is to isolate one battery from the other so that in the case of one battery being discharged, the other battery is available. If you regularly run on the "both" setting, you are risking the exact situation that having 2 batteries and a selector switch is designed to avoid.

Personally, I follow Molson's recommendation. I run on A one week and B the next, so I'm working the batteries equally and each one is getting charged on a regular basis.

There ARE special exceptions depending on how your boat is set up. Some boats have the automatic bilge, bilge alarm, and other safety features wired so that the A/B/Both switch does NOT cut off power to these accessories. In the case of an automatic bilge, I believe the recommendation is to wire these pumps to both batteries to maximize the amount of run time for the pump. The idea being that if the boat is taking on water, you want the alarm and the bilge pump working as long as possible to give help a chance to arrive and save the boat or at least get it supported to prevent it from sinking.


In the case of an automatic bilge, if the pump tends to run after a heavy rain, you want to be sure you're recharging whatever battery(or batteries) drive the pump.

Grouse

 

[emilsr]

Re: Best way to use dual battery switch?

I just bought a 2005 sea ray 220 select bowrider. I had my local shop install a 2nd battery and the dual battery switch. The switch has a off, all, battery 1, battery 2 position. I'm wondering how to make the most of the batteries without having a battery run out. Should I use battery 1 for starting the engine and running all day and then switch to battery 2 in party cove to play music? Is there a situation where I would want to set the switch to ALL? I just want to make sure I never run a battery dead listening to music?
Thanks, Ryan

Funny you should mention that scenario; I did exactly that last spring with the switch on both. Learned my lesson at the end of a tow rope.

Keep one battery "in reserve"; doesn't really matter much which one.

Get a good battery charger, and use it. A 65 amp alternator will not fully charge more than 1 battery....barely will charge 1 with all the modern electronics that are on modern engines (and using valuable juice).

 

[doyall]

Re: Best way to use dual battery switch?

... Get a good battery charger, and use it. A 65 amp alternator will not fully charge more than 1 battery....barely will charge 1 with all the modern electronics that are on modern engines (and using valuable juice).

Agree. Stock alternators are intended to keep a battery charged while supplying juice for normal operating functions, not recharge it after it runs down. Had a buddy tell me yesterday he burned out several alternators trying to continually recharge multiple batteries. If you are going to do it, better invest in a high-output unit.

 

[airshot]

Re: Best way to use dual battery switch?

Have to agree with "doyall" on this one, you will wear out your alternator quickly. On my boat this is how I do it....one battery operates the starter and main engine and that is all. The second battery is a 105 amp deep cycle and all accessories are connected to that, radio,gps,depth finder etc. I have two bilge pumps, one connected to each battery. The main engine charges the starting battery on a regular basis, I can charge the deep cycle off the alternator but prefer to use a seperate deep cycle charger at home. In the last two seasons I have only had to charge the deep cycle battery once during the year. I wait until it reaches a 50% discharge before recharging.
I have sat all day on the boat with radios, depth finders, gps and lights going with very little discharge to the DC battery.

Airshot

 

[tpenfield]

Re: Best way to use dual battery switch?

There ARE special exceptions depending on how your boat is set up. Some boats have the automatic bilge, bilge alarm, and other safety features wired so that the A/B/Both switch does NOT cut off power to these accessories. In the case of an automatic bilge, I believe the recommendation is to wire these pumps to both batteries to maximize the amount of run time for the pump. The idea being that if the boat is taking on water, you want the alarm and the bilge pump working as long as possible to give help a chance to arrive and save the boat or at least get it supported to prevent it from sinking.


Grouse

Keep in mind that if you wire a bilge pump to both batteries, then they are connected together, which is the same as having the battery switch set to "both" permanently. I know that in my boat, the bilge pump is connected to one battery and the bilge alarm and radio memory is connected to the other battery.

 

[crabby captain john]

Re: Best way to use dual battery switch?

For decades on many boats -- I run battery A one trip and battery B the next time out. Works for me..