Which setting do i need to charge both batteries

[Max123]

I was under the impression that you should never change positions on the switch when motor is running?

Edit: I googled it and saying I can switch between batteries but not to the off position when motor is running

A dual battery/combine switch is going to rotate between batteries as 1 > combine > 2 > off. To switch between batteries you should always rotate through 'combined' - never through 'off' when the engine is running.

The switches use what is called 'make before break' connections. The switch never disconnects until after the new connection is made.

As a side note, I agree about weight issue. Take a close look at what you are running and what you need. Lots of us don't need a house battery, and a house battery is not necessarily the best backup starting battery. When I bought my boat it came with x2 lead-acid group 27 batteries - these were both deep cycle batteries that had just enough output to act as starting batteries as well. I have minimal accessories, and really just needed a rock solid starting battery plus some sort of emergency backup. I switched to a single high output Group 24 AGM - which is a way better starting battery, and then I bought a battery booster pack. Net result was a better starting system, tons of capacity for my needs, an independent backup, and I lost 50-60 pounds from the back of the boat.

I hugely recommend the booster pack - it will start virtually anything from stone dead. Likewise, I've never needed it for myself, but I've used it quite a few times for other people who showed up at the ramp with dead batteries. Nothing worse than messing around with jumper cables on the water in an aluminum boat...

 

[sly_karma]

A dual battery/combine switch is going to rotate between batteries as 1 > combine > 2 > off. To switch between batteries you should always rotate through 'combined' - never through 'off' when the engine is running.

The switches use what is called 'make before break' connections. The switch never disconnects until after the new connection is made.

As a side note, I agree about weight issue. Take a close look at what you are running and what you need. Lots of us don't need a house battery, and a house battery is not necessarily the best backup starting battery. When I bought my boat it came with x2 lead-acid group 27 batteries - these were both deep cycle batteries that had just enough output to act as starting batteries as well. I have minimal accessories, and really just needed a rock solid starting battery plus some sort of emergency backup. I switched to a high output Group 24 AGM - which is a way better starting battery, and then I bought a battery booster pack. Net result was a better starting system, tons of capacity for my needs, an independent backup, and I lost 50-60 pounds from the back of the boat.

I hugely recommend the booster pack - it will start virtually anything from stone dead. Likewise, I've never needed it for myself, but I've used it quite a few times for other people who showed up at the ramp with dead batteries. Nothing worse than messing around with jumper cables on the water in an aluminum boat...

+1 for the lithium booster pack. I keep a Noco GB70 in my truck, and bring it with me on the boat as a justin. Have successfully boosted a couple of V8 trucks in cold winter conditions with it. Can Tire puts them on sale a couple times a year, well worth the money.

 

[brutus]

I also have the gb70 for backup

 

[ClintR]

Plus 2 on the booster pack. Essential equipment if you ask me.

 

[Eden Island]

On the rare occasions I've mistakenly depleted both batteries to the point the main engine won't start, my first line of defence is to try starting the kicker. On the 2 occasions that's failed in 23 years, I manually start the 9.9 and have a coffee until the batteries are charged enough to start the main motor. I am, however, considering a larger capacity house battery for those days where I'm storm-bound overnight and half the next day.