Using dual batteries

[whichway]

Hi

I have dual batteries with an switch that allows, both, one or the other or no batteries to be connected.

When I am using the boat, what position should I have the switch in.

If I set it with both batteries connected, then if one is no good I won't know.

If I only have one connected, then the other one won't charge.

What do you do

Whichway.

[Feral]

Re: Using dual batteries

What are the batteries? are they the same size / type?
Generally the idea is to keep your starter battery isolated from all the ancillaries you might run. So while pulled up and using juice, you should be connected to your spare battery. For starting you should be connected to the main battery, if you have a reasonable charging circuit, you might set it to both whilst motor is running.

[Fatenhappy]

Re: Using dual batteries

Gooday whichway ....

When I asked a marine elecy, he told me to leave one or other of the two batteries isolated from the other at all times when at rest.

Start on one then switch to the other. It doesn't matter which of the batteries you start on. The rationale behind this is that if you have both selected and if there is a fault you could drain both batteries if set otherwise leaving you stranded.

The batteries will both/all charge in any case provided they have been wired in properly in the first place.

Same old mates explanation of the "both" setting was to use that only in an emergency when you are finding you can't deliver enough grunt from either battery to start.

Cheers
Greg

[Spaniard_King]

Re: Using dual batteries

Whichway,

I use this routine.

Leave ramp, start and travel to destination on first battery.

On arrival at fishing destination, imediately change over to second battery and remain on this battery for rest of fishing trip.

Stay on second battery untill your next trip performing the same routing but changing batteries back to the original once traveled to fishing spot.

This ensures you have charged up the first battery so after you change to the second you then know you can always go back to the first battery which should be good as you started and charged this on the way out.

does that make sense???

[Grand_Marlin]

Re: Using dual batteries

I do the same as Garry.

In times gone by, I used to run on "Both" and I never had any problems.

There was a thread on here a long time ago that discussed all the pros and cons of where to run the switch.
This thread changed my mind on using "both", as if you have a crook battery (even a new battery can fail) then you are in trouble.

Really, the battery switch should read 1, 2, Emergency Parallel instead of 1, 2, Both.

Also, remember to NEVER turn the switch through the "OFF" position when the motor is running, as it can damage the rectifier?? in the charging circuit.

Cheers

Pete

[finga]

Re: Using dual batteries

yes, never change the switch whilst the motor is going.

[Brumby]

Re: Using dual batteries

As one or two others have said, depends on what batteries you are running. I have a conventional marine battery (1) for starting and a deep cycle battery (2) as a house battery to power the fridge, lights, radio etc when the motor isn't running. I managed to cook the first deep cycle, not realising that it wasn't a conventional battery by starting then running on that alone - sparky explained to me that the deep cycles don't like the heavy current draw from starting and they REALLY don't like being charged fast.

Since then I start on 1 or both, but never 2, generally run on both and switch to 2 as soon as I anchor. Never switch when running is good general advice, but most better battery switches are "make before break" and it's ok to switch between 1,2 and both especially at idle. DON'T switch off though. You can check by running the accessories (engine off) and slowly switching between 1, 2 and both to see whether the accessories shut down in the in between position.

[dnej]

Re: Using dual batteries

finga,
It is OK to change the switch,while the motor is going,but you must go through both,then onto the alternative.As Pete says,never turn the switch to off position.

Hey Pete,get my message?
Garry is spot on.Also if you run on two,one can drain the other,if you have a fault,
Regards David

[finga]

Re: Using dual batteries

finga,
It is OK to change the switch,while the motor is going,but you must go through both,then onto the alternative.As Pete says,never turn the switch to off position.

Hey Pete,get my message?
Garry is spot on.Also if you run on two,one can drain the other,if you have a fault,
Regards David

Yes that's definitely true David.
I have seen just two nasty switches on other boats I've worked on that opened contacts whilst switching.
I'll admit they looked like cheap crap but from then I made a habit of not switching while the motors on just to be on the safe side.

[Grand_Marlin]

Re: Using dual batteries

G'day Dave,

Sorry Mate, no message received

Cheers

Pete

[whichway]

Re: Using dual batteries

Thanks

From now on, run on one, then switch to the other.

Whichway

[dnej]

Re: Using dual batteries

finga,
Gees,that would tear the fork out of your nightie.
David

[Cheech]

Re: Using dual batteries

Same with me. I start on 2, then run on one out and the other in.

A couple of years ago I ran on both out, and had one faulty battery that drained the other and was stranded. We managed to pull start the 100hp motor I had at the time. Ever tried to pull start a motor that size. Not fun.

[dnej]

Re: Using dual batteries

Cheech,
to get the best use,from your batteries,you should use only one battery,the high crank amp one ,for the start,and run out on the same battery.

Then switch to the house battery,when you get there.
Regards David

[Cheech]

Re: Using dual batteries

Cheech,
to get the best use,from your batteries,you should use only one battery,the high crank amp one ,for the start,and run out on the same battery.

Then switch to the house battery,when you get there.
Regards David

David, both batteries are the same and high crank, so makes no difference in my case which one I use for the out or the in. I start at the ramp on duel because when cold the extra ooph gets it started a lot easier. I am only on duel for the startup. Does this make a difference to your suggestion?