Do I really need a battery swicth?

Hey guys,

Just bought a new to me boat, a 1997. Noticed that there is no battery switch on it, so I was gonna throw one in, but it occured to me that since this boat only has one battery, and I'm not planning on putting a second one in, do I really need to have a battery switch?

Do they provide any function other than switching between two batteries for charging/starting purposes? Do they provide any protection for anything?

I had a guy tell me that they are good in case the boat starts to go under at all, because if it's switched to OFF then you won't short any of your electronics, but it just seemed to me that it wouldn't matter, because once the switch went under, the saltwater would just short the switch and everything else, and just blow your fuses....not to mention that if my boat goes under, my battery switch and electronics will be the last of my worries.

Just thinking that if it's been OK for 10 years, why change it?

It's also got a biulge pump set up that I would need to swicth around in order to have constant power to the bulge pump float switch, which now runs up and is connected under the dash somehow.

So leaving it the way it is, is obviously easier, just wanted to see if it was not the right way.

Thanks.

Re: Do I really need a battery swicth?

While it may not be necessary to have the switch, I can think of several advantages to having one.
While the boat is in storage off season the switch can be turned off disconnecting it from all loads. A battery charger or maintainer can then be placed on the battery to keep your battery fresh while it is stored. This eliminates the possibility of even then smallest drain from the electrical system without the need to disconnect cables. (make sure the battery can vent as well)
A switch also adds safety. In the event of a major electrical short the battery can be switched off disconnecting the loads. This can save the battery as well as shutting down the short. Remember a short means heat, in some cases major heat and fire. Being able to shut it down quickly can make the difference between having some damage to repair or swimming home!
For whatever reason the boat manufacturer, (or the previous owner), felt that a battery switch was not necessary. My old boat didn't have one either. But I added one anyway. Its really up to you, but there are advantages to having a battery switch.

Re: Do I really need a battery swicth?

I agree that you want one. I always disconnect the battery when I work on the engine or wiring. A battery switch makes it all that easier.

Re: Do I really need a battery swicth?

Yeah it looks like the boat came from the builder without a switch, the wiring is bundled up like it would be from a builder, and there are no holes anywhere, so it looks like it's never had a switch.

I feel better having one, so I think I'll put one in, but I just wanted to see if there was any real reason other than for hwne you have 2 batteries.

The biggest problem in putting one in, is going to be the bilge pump float switch. Right now it runs up to a 3 way switch on the dash....Manual -Off - Auto. The switch has constant power to it directly from the battery, so that whe you switch it to Auto, you send power to the float switch and that will control the bilge pump when needed. Actually the whole dash has constant power to it, which I don't like.

Not 100% sure how I would go about wiring that in if I put a battery switch in, because obviously I'd take the constant power off of the battery and hook those wires into the switch also, so I could shut the whole dash down with the switch.

Re: Do I really need a battery swicth?

There are a couple things you could do.

1) Run a seperate fused wire from the battery to your dash switch.
2) Run a seperate fused wire to the float switch from the battery so it was always in auto mode but you could still turn it on manually from the front switch.

Re: Do I really need a battery swicth?

Bruce, I actually thought of that right after I posted.

I think I will take the wire off the Auto side of the dash switch, and just run a constant power wire to the float switch, then I should just be able to splice the output wire form the float switch into the same wire that comes down from the Manual side of the dash switch, that way I will have both still, but the float will always be on Auto, correct??

I was also thinking about getting a new bilge pump with a float switch in it already, they come with 3 wires, one for the dash switch, one for direct power off the battery and a ground, but that is more expensive than just using what I have already.

Re: Do I really need a battery swicth?

Cricket Too said:

way I will have both still, but the float will always be on Auto, correct??

Click to expand...

That is correct.

I prefer the pumps with the seperate float switch.

Re: Do I really need a battery swicth?

Thanks Bruce. So just splicing the power output side of the float switch into the power coming from the dash switch will be ok then?

Re: Do I really need a battery swicth?

I have never installed a switch on My 1980 boat and I do have two batteries. Installed and used correctly they have some advantages but I belive they have blow up more alternators than any other device.
If you put one in make sure it is a "make before break" and if your alternator has an external regulator get a switch with a field disconnect. The field disconnect protects the alternator if someone turns the switch with the motor running.

Re: Do I really need a battery swicth?

Boatlist....Yeah this switch is a make before break switch, so I will be safe if I ever do install a second battery.

How exactly do you run two batteries without a switch? I'm assuming this is on one engine. How do you can youy keep one for starting and one for house without a switch, or how do they get charged correctly?

Re: Do I really need a battery swicth?

Alternator output goes to a battery isolator form there it charges both batteries. Works very well and have never had a battery that did not last at leas 6 years. Alternator same one that came on the boat in 1980.

Even with the make before break switch still must not turn thru the off position with the motor running or you will need a new alternator or at least diode block.