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Charging Batteries

Bruce the Postie

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I have Duals with an Isolator switch as well.

If you are talking using a battery charger, In most cases batteries need to be dissconnected before charging. There are charges available where dissconnetion is not needed. Refer instructions.

What I do as each time I go out i isolate the battery I used last, leaving the battery that i used last time as backup. This way I am starting the boat at the ramp with the flattest battery.

The first time it gives be trouble I may charge it but if its too old or gives trouble a second time, its gone.

Good batteries give less problems


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What I do is disconnect the battery I am charging , no danger of damaging the rectifier / charging cct on the engine.

First start of the day , I use both batteries . Use battery one on the trip out , battery two for the return trip. That way I have 2 charged batteries.


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Both batteries should charge when the switch is in the dual position?

I crank on both batteries and leave it there when traveling so both can get charged. I only ever switch over to one at times of high current draw, fishing at night ect..


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G'day all,

I have dual batteries in my boat connected to an isolater switch and i have allways disconnected them before charging, is this really nesessary or can i leave them connected and just alternately charge them.


Bruce :beersmile:

Do you mean when your boat is on the trailer, or in the water.

Are they sealed batteries, lead acid or lead jelly.

How many amps is the battery charger.

Are they in a battery box or open units.

When underway at sea, the small amount of toxic fumes generated whilst charging, is generally dispersed safely into the air. It is a different story though, if on the trailer in a confined space (garage), there is more danger of ignition and or inhilation of the toxic fumes.

Food for thought.

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Hi Bruce, it is best to disconnect the positive leads when charging, as Ross said no chance of doing damage.

Robbie, the both position should only be used when one battery is not enought to start the outboard. Best to alternate between batteries, because as you are running the outboard it will not be charging both batteries equally and the weaker battery drains the stronger battery. Benefit on a dual battery system is exactly that, you have two batteries that are isolated and only when needed will they be connected via the 4 positon isolation switch.



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