The Boating Forum - Run twin engine on one battery?

Hello!

I do have two batteries on my boat, one start battery and one house battery, if I connect one battery to each engine i will have to choose which one of the batteries to connect my house cables to, and that means that i will have no other choise than only run the same engine while at trolling speed to be able to charge my house battery.

Could I connect both engines to my perko switch and then by using the perko switch chose battery one, two or both?

Or will i damage my alternators by having two engines charging the same battery?

My future plan (next winter) is to install BEP twin engine three battery cluster and add one more starting battery, but due to my financial situation i have to let this wait for a while.

Any other suggestions on how to do this?

I always run only one engine while fishing at max 3 knots, i would like to be able to choose which engine to run without leaving my house battery uncharged.

Engines, 2008 Suzuki DF140.

Let me know what you think.

Thanks in advance.

Kjellzen

There is no problem doing it that way, but you will only be charging the battery that is on. Also, when starting the boat, 1 engine at a time so you don't overload the battery or cables.

I do have two batteries on my boat, one start battery and one house battery, if I connect one battery to each engine i will have to choose which one of the batteries to connect my house cables to, and that means that i will have no other choise than only run the same engine while at trolling speed to be able to charge my house battery.

Engine #1 alternator charges start battery. Start battery connected to both engine's starters.
Engine #2 alternator charges house battery. House battery connected to house loads only.

At idle or trolling speeds, the alternator is not doing any charging of the batteries, so your concerns in that regard are moot.

Could I connect both engines to my perko switch and then by using the perko switch chose battery one, two or both?

Best to delete the 1,2,BOTH,OFF switch. Use the BEP VSR setup to manage charging duties automatically.

My future plan (next winter) is to install BEP twin engine three battery cluster and add one more starting battery, but due to my financial situation i have to let this wait for a while.

Excellent idea. You'll never be sorry that you have lots of battery. Consider upping your house battery bank too. This adds a wider safety margin as you can use the house bank as emergency start batteries. Always put your alternator output into the house bank and use a VSR to bleed off voltage to the start bank.

I always run only one engine while fishing at max 3 knots, i would like to be able to choose which engine to run without leaving my house battery uncharged.

Again, at that speed no charging happening.

Kjellzen - 8/4/2008 3:32 AM


Could I connect both engines to my perko switch and then by using the perko switch chose battery one, two or both?

Or will i damage my alternators by having two engines charging the same battery?

any other suggestions on how to do this?

Kjellzen

The setup you describe is fine, with some considerations. how far away is your switch? make sure your cables are large anought for the length of the run.

You wont damage the alternators with this setup.

On my boats (both twin O/Bs) I have the engines directly connected to the batteries. then I have a 1,2,B switch that supplies power to the panel. Each engine has its own start battery that way, and I can combine both batteries using the switch. this is a simple install that doesn't take up alot of roon on the batt switch.

mm yes i understand that, but when selecting the "both" position on my perko then i should charge both batteries no matter which engine is running?

From the switch to my engines i have approximately 4-5´.

What i was thinking was that, instead of connecting any of the engines directly to a battery(other than the negative - cable) i could connect red cables from both engines to the "out" position on the perko.
In that way i will be able to select"both" position if i need some extra cranking amp.
and i will also charge both batteries with only one of the engines running.

Like I said earlier, my plan is to install two engines three battery cluster, but i will have to wait and wants to use my boat in the meantime..

/Kjellzen

You've got it right, connect both engine's pos. line to the output from the battery switch, and you'll be fine. If you want to charge the house battery, you can select "both". Be careful not to switch from 1 position to another while your outboards are running, though. You could kill your alternators.

Kjellzen - 8/4/2008 8:38 AM


i could connect red cables from both engines to the "out" position on the perko.
In that way i will be able to select"both" position if i need some extra cranking amp.
and i will also charge both batteries with only one of the engines running.

/Kjellzen

Yes that will work fine, but the same can be accomplished in my setup. each engine has its own battery, but both batteries can be combined into one by turning the switch to BOTH, this would allow extra cranking power and charge both batteries from one engine. One upside to my design is that even if you accidentally turn the batt switch to off with the engines running, the engines will not be affected.
The one drawdack in my system is this example:
your starboard battery is bad for whatever reason. there is no way to isolate it from the starboard engine. but with twins, you could start the port engine with the port battery, then switch to both and start the starboard.