Mixing deep cycle and starting battery

[edshoc0]

I've read a few posts regarding dual-batteries, but let me throw out my situation.

2004 Bayliner 185BR, 4.3 Merc

I just bought the boat and the previous owner had a marine starting battery (connected) and a deep cycle battery (not connected) in the boat.

I'd love to utilize an extra battery so I don't get stranded with a dead battery.

Generally, the stereo and iPod are the only drain on the battery. I don't use a trolling motor or anything like that. In my old boat, we never killed a battery, but we have much longer day trips planned with the new boat (fireworks shows, etc.).

Should I bother installing a switch of any sort? Or should I just carry a set of jumper cables so if we kill the starting battery we can use the deep cycle as a jump?

Thanks in advance.

 

[BeaufortTJustice]

Re: Mixing deep cycle and starting battery

I suppose you could go the jumper cable route, but I would much prefer the convenience of a switch with both batteries wired in. I'd much rather simply flip a switch to start the boat. Less potential for Murphy to mess with you that way...IMHO.

A Perko or Guest switch can be had for les than $40 and wire will run you another $20 (depending on length). The switches can be found right here on iboats.

BTW, welcome to iboats!

 

[Mark_VTfisherman]

Re: Mixing deep cycle and starting battery

I'd probably just carry a few wrenches

 

[Triton II]

Re: Mixing deep cycle and starting battery

Depends on how much you want to spend. The cheapest solution is mentioned by Mark_VT above, the Rolls Royce solution is to use a voltage control relay such as this:

http://www.bainbridgetechnologies.c...d=460&option=com_virtuemart&Itemid=48&lang=en

The relay will automatically allow you to mix the batteries, simply wire them in so the accessories are wired to the deep cycle battery and the motor is wired to the start battery. The relay controls when each battery is charged with the start battery taking priority until charged, then the relay switches the motor's charging system to the deep cycle.

If you "take wrenches" then you'll also have a back up in case your start battery spits the dummy.

 

[Silvertip]

Re: Mixing deep cycle and starting battery

In your application the voltage sensing relay is not an option as it does not allow starting the engine from the second battery. It is merely an isolation and charging device. Jumper cables is a viable solution but it does not allow the engine to keep the deep cycle charged. The most versatile and inexpensive solution is the battery switch. Charge 1, charge 2, charge both, run on 1, run on 2, run on both, or kill everything in the off position. There are a couple types of switches and since you have an I/O you should have one with the "field disconnect option".

 

[Fl_Richard]

Re: Mixing deep cycle and starting battery

Kill everything in the off position.... That's too true. If your engines running and the switch is moved to off you may quickly kill your charging circuit on the engine. Dont do it!

The 4.3 may not die as quickly as an outboard but it's never good to ever run the engine with the batteries off.

 

[Triton II]

Re: Mixing deep cycle and starting battery

In your application the voltage sensing relay is not an option as it does not allow starting the engine from the second battery. It is merely an isolation and charging device. Jumper cables is a viable solution but it does not allow the engine to keep the deep cycle charged. The most versatile and inexpensive solution is the battery switch. Charge 1, charge 2, charge both, run on 1, run on 2, run on both, or kill everything in the off position. There are a couple types of switches and since you have an I/O you should have one with the "field disconnect option".

Hi Silvertip, that's why I stated "take wrenches" in my post. The nice thing about the relay system is that you can't forget to charge one of the two batteries, as you know, the electrickery does it for you and gives priority to the starting battery. Merry Christmas guys, we're just getting into cooking the bird here and afterwards we're going out on the bay (it's 80 degrees F here).

 

[Silvertip]

Re: Mixing deep cycle and starting battery

Switches are like seatbelts. Once you get used to using them, it gets about as automatic as it can get. And yes -- don't turn the switch off with the engine running. What's complicated about starting on BAT 1, switch to BOTH, run to wherever you are going. If it's a spot to fish or just chill and listen to tunes, you switch to BAT 2 (the deep cycle). When ready to go start on BAT 1, switch to BOTH and away you go. When done, stop engine(s) and switch to OFF.

 

[Fl_Richard]

Re: Mixing deep cycle and starting battery

Switches are definately better than spinning wrenches on a heaving boat.