Boat batteries

[wallsendpaul]

Hello, I have a question regarding the possibility of running 2 outboards on one battery. Is there enough power in the battery to charge and start the engines off the one battery or does each engine require a seperate battery. Both engines also have manual start.

Thanks in advance.

[mickthefish]

do you have other electrics to run off battery? ff ,gps ,vhf etc..
1 battery for 2 engines and standard electrics ?
i would have 2 batteries with an isolation switch.

[wallsendpaul]

Thanks for the reply.

No electronics, just the engines. Are 2 batteries still required in this case?

[mickthefish]

i couldnt give a definitive answer to that mate ,
you could try and run with 1 battery risk free if you can start manually and see how it goes.

[Charlton]

I only had one engine on my boat, but always had two batteries, one as a spare via an isolation switch, batteries can go dead for many reasons, confucious say "two batteries one engine better than two engines one battery"

[davem2005]

Hi paul.
There is no reason at all why you should not run both engines from one battery. But for obvious reasons two would be better and wire them in parralel through a isolator switch which are available at chandlers. I assume you have two seperate ignition switches as the only problem could be overloading the battery lead by starting both at once.

A better and easier option is to wire them so that one battery does the starting and the other will always automatically charge when the engines are running but never takes any part in starting the boat unless needed.The reason for this is if you use an isolator you can flatten the main battery and switch over to your spare to find its flat due to not being used.

Dont go to a caravan shop/chandlers and buy an auxiliary charging relay go to a car shop and get a 30 amp relay for car spotlights they are exactly the same thing and one costs a tenner less than the other. This would give you a charged starting battery and a fully charged spare in emergencies. On boats with vhf and fishfinders this is the one that powers the electronics when the ignition is off . The relay prevents the onboard electronics from discharging the main starting battery so you never need to worry that your fish finder will leave you with a flat starting battery. Real peace of mind for small boat owners.

For a step by step walkthrough on how to wire it up google "second battery instalation on 4x4's" there are loads of forums covering it. If you need more info pm me and I will try to help. You can not beat the confidence that no matter how long you sit on a mark with your electronics on you will always have the power left to start your engine(s) and get home.

Cheers
Dave

[wallsendpaul]

Thanks very much for all of your help and information, all taken on board.