Dual batteries

I would like to use an extra b

I would like to use an extra battery for my depth finder and radio and cigarette lighter.Is it possible to hook it up with the existing battery so it can be charged from the engine? If so what do I need?

I never tried a second battery

I never tried a second battery in parallel on my outboard. I'm sure there is a off/swap/both switch available out there. Surely someone has done this with an outboard.
I just use a second battery for the all the "other" stuff on mine. I just charge the battery before going out. Lasts all day long and most of the next.
A depth finder and radio should not be a huge draw on a good second battery unless your running a power amp for the radio. A cigarette lighter I guess depends on how much use it gets.

"Gary, I've got two batter

"Gary, I've got two batteries in my Trophy, There's a switch (big round switch)for #1 #2 and All, I keep it on ALL, all the time, until I'm stopped and fishing or diving, Then switch to #1. That way #2 is not drained at all and can start the boat if #1 goes dead. and by keeping it on "ALL", both batteries are being charged all the time I running. Dennis"

"The switch can be found at mo

"The switch can be found at most boat stores ie. West Marine, Etc. maybe even on Ebay. It's about 5" round, Red & White. and you'll need some more battery cables."

"Gary, you can run it with a s

"Gary, you can run it with a switch as suggested above or simply run two batteries in parallel.

So simplist - run in parallel - connect two batteries (positive to positive and negative to negative)

Upside - cheapest set-up, only the cost of additional battery - both batteries charge off the alternator/stator

Downside - if you draw too much juice while the motor isn't running and drain both batteries (since the work basically as one) you better hope you have a paddle or can pull start your motor.

Better option - install a 4 positon battery selector switch - allows you to select battery 1, 2, both or off. Can get a decent switch for less than 50 bucks.

In theory when you first get in the boat you select both - start the motor using both batteries and run that way - both batteries get charged. When you shut off the engine you switch to battery 2 and run all your toys off of that - saving battery 1 for starting.

Upside - allows you to save a battery for starting

Downside - if you forget to change the switch could end up with 2 dead batteries - or if you move the switch with the motor running you can cause all kinds of electrical problems including a toasted ignition system on your motor.

Third choice - combination switch and isolator (what I run currently - Blue Sea "add-a-battery" system).

Upside - set it and forget it system - turn it on when you get on-board. With the motor running it charges both batteries

- when you hit the ignition it isolates the second battery from the power spike to save your electronics

- you have the option of manually switching to both batteries if your main starting battery ever fails you - the rest of the time it keeps the two battery banks totally separate except to charge them

- also if I stick a charger on the auxilary battery, it will also feed it back through the circuits to charge the starting battery, so regardless of the charging source (engine or charger) both batteries get juice.

Downside: runs about 150 bucks for the system, plus the cost of the battery - but that's cheaper than a tow back to shore when you drain your juice "