Is one battery enough for 2 Engines?

ed_dash · 01 March 2011, 16:43

Hi,

I currently have 2 * 85amp batteries one for each engine, and the electronics run off one of the batteries. There is a slight drain from the electrics so im having to disconnect every time.

I'm thinking of moving one of the batteries (the older one) into the console to power the electrics and then wiring it to the other battery through an isolator. This will enable me to run the radio and sounder/GPS without worrying about being able to start one of the engines after and would act as a backup if the main one died.

Is 1 * 85amp battery man enough to run 2 * 60hp 2 strokes, they do both have emergency pull cords which i think i would be able to use if needed.

I'm trying to use things i have rather than buying a 3rd battery and trying to wire it up to the other 2.

I have thought about connecting the batteries together through an isolator switch but as the batteries are right by the transom i dont think a switch would last long.

Any thoughts?

Cheers

Channel Ribs · 01 March 2011, 16:53

One battery being charged by two engines is not a good idea, and being able to start each independently has to be a good thing?

Disconnecting everything, ie isolating, the batteries is a good idea when leaving the boat.

jyasaki · 01 March 2011, 16:57

Quote:

I currently have 2 * 85amp batteries one for each engine, and the electronics run off one of the batteries. There is a slight drain from the electrics so im having to disconnect every time.

You mean when storing the boat? Put the electronics power feeds on a switch and shut it off when not running them.

If you're talking about while you're using the boat, I would think a starting battery should run the electronics all day without draining it too much to start the motor.

jky

ed_dash · 01 March 2011, 16:57

hadnt thought about both engines charging the same batteries, cheers.

May look into a small battery for the electronics then.

ed_dash · 01 March 2011, 18:01

would a battery like this be fine for running the electronics off?

http://cgi.ebay.co.uk/LUCAS-BAIT-BOA...item25618b6976

I have a VHF, and a Garmin 188c combimed GPS & sounder. Id mostly be running with the GPS & VHF.

Cheers

Poly · 01 March 2011, 18:04

Ed,

Rather than add another battery why not fix the "problem"? If the drain is from the stuff in the console then just add a master switch / isolater in the console.

ed_dash · 01 March 2011, 18:22

I thought about the isolator switch and i plan on fitting one what ever i decide. That will solve the issue for when the boat is laid up.

Its more when im out with the electronics on and the engine not, im sure the battery will have loads of power to start the engine, just being paranoid.

Maybe i will need to dig out the manuals and check what current they will draw and i can at least be happy with knowing how many hours i should safely have.

walruz · 01 March 2011, 18:52

I think you might be being overly paranoid.

I have a 70 Ahr battery starting my 90 and running all electrics (Ok it's only 1 chartplotter).

If you have a lot of electrics why not spread them over both batteries or if you really feel vulnerable upgrade the 1 battery you pull the electrics off and as others say fit an isolator for other times.

Ian

Poly · 01 March 2011, 19:43

Or you could run Battery A and Battery B independent of each other. Run all electronics on battery A and then you should always be able to start engine B. With some short jump leads (if you don't want a switch in a vulnerable position) you can start engine A using batter B if necessary.

jwalker · 02 March 2011, 13:38

My thoughts exactly Mr P.

Searider · 09 March 2011, 23:28

Is one of your batteries actually going flat?

If so, it sounds like you have a problem that needs to be sorted out rather than a set up that needs changing.

Battery in poor condition?
Faulty equipment drawing large current?
Partial short circuit somewhere?

If your batteries aren't going flat then I wouldn't worry.

My current boat has two batteries - but only ever use one at a time for both starting and electronics. Always leave the plotter and sounder running if leaving the boat for a couple of hours and heve never had any problems.

Previous boat only had one battery and again no problems.

r mcdonald · 10 March 2011, 09:47

Have a look at this site on twin battery setups,it may be of some help.
http://continuouswave.com/whaler/ref...alBattery.html
regards
rpm

ed_dash · 10 March 2011, 10:53

Thanks for that, i think i will adopt the 3rd way, so the electronics can be run from either battery and then i also have the option to have the batteries in parallel if one gets low.

Ed

dougal_22 · 13 March 2011, 11:15

my advise would be use the key type isolator but only keep 2 keys avalible, put one key away, this means you CANNOT accidently have both engines running charging the same battery