Batteries wired in parallel or switch?

[Ozz13]

I was wondering whether I should wire 2 batteries in parallel or get a switch. Switches are pricey but definitely preserves one battery after you drain the other on the sandbar playing the stereo all day. It's a Johnson 90 HP that will be charging the 2 batteries.

[GXPWeasel]

I currently have 2 of the biggest Marine Maxx (starting and Tolling ) batteries I could find, wired in parallel. Most on here will probably say I should have a switch, but a switch for me, is one more thing to worry about un-wiring and re-wiring every time I use the boat. I unhook both batteries after each use, and move them so they aren't in the public eye ( We store our boat in a fenced in storage area). I have never had a problem with the batteries going dead, and incase, I have a jump starter pack with me at all times anyways. I just start the boat every hour or two to ensure all is good.

[slingshot]

For me, I like to do a lot of overnighting (not a real word) on the boat and might run onboard lights and accessories to include the anchor light. I have two switched batteries and I'll use only one for the night leaving the other as a backup in case I drain it. Can't really pull start my 115 and it gives me peace of mind. As I cruise around I always make sure I have both batteries on line.

[LTB Racing]

but a switch for me, is one more thing to worry about un-wiring and re-wiring every time I use the boat.

???Just curious but.. Why? There wont be any more wires at the battery with a switch. Switches are very nice on the pontoon....I run off of one battery all day and save a good batt for start up and the end of the day.

[jafo9]

the biggest disadvantage to keeping them wired in parallel is that if one goes bad, it can literally suck the life out of the good one. then you are really stuck. just a simple 4 way switch would add alot of security and if you really wanted to run them both all the time you could. i'm also not sure about asking your motor to charge 2 batteries at the same time all the time. perhaps someone smarter than me can address that issue.

[Aint Skeered]

this is a good topic. I am doing the switch on mine with 2 batteries , what does a mercury out board alternator put out for amperage?

I am going to put a deep cycle trolling motor battery to run off of and if it leaves me stranded ill switch to my starting battery

[WaltF]

Just throwing out a warning again...

DO NOT switch between batteries with the MOTOR RUNNING!

Even a split second of time where the alternator has no battery hooked to it as you flip the switch, is enough time to FRY it..

[jafo9]

aren't most of the switches the "make before break" type. if so, you can rotate in either direction ("a"-"b"-"a+b"), just (as you pointed out) don't go to the "off" setting with the motor running. on my "add a battery" switch, i can go back and forth between the "on" and "combine" settings which the motor is running.

[jafo9]

what does a mercury out board alternator put out for amperage?

i was able to find the rating for mine in the "seloc manual" i bought. it will depend on the year and size of the motor. as best as i can tell, there is no standard. obviously a 40hp will likely put out fewer amps than a 300hp. IIRC, mine was around 80amps.

[Heatman]

Here's a picture of mine with the Perco switch. Pretty easy to do and fairly cheap.

[WaltF]

I hear what youre saying jafo9, and youre right. If it was a 'make it before break it' then youd be ok flipping...
but if not...