Dual battery setup questions - pairing 24 batt with a 27 batt

[jvigier]

95 FW with VP 5.8 fi

Currently powered by an ac-delco 24 group battery.

Inherited a 27 group battery (advance auto brand) from my neighbor who just sold the boat he was going to put it in.

Battery is brand new.

I have a multi battery selector that was in my old boat.

Should I be concerned about hooking up a multi battery setup with a 24 in parallel with a 27?

 

[RushFan]

Re: Dual battery setup questions - pairing 24 batt with a 27 batt

If you have a multi-battery selector switch with battery 1 and battery 2, you can hook each battery up independently. The batteries have the same voltage and the alternator will handle charging them too.
The 24 series will have a lower cranking amperage than the 27 series, but if you put the battery selector switch on "all" or "both" there shouldn't be any problems. Be sure to hook the positive wire from each battery to either #1 and #2 on the back of the selector switch and the Common will go to the starter or solenoid on the engine.
You can run seperate ground (negative) wires to the engine block or put a wire from each battery ground and then one wire to the block. I prefer independent ground wires myself.

Oh, and make sure you use the proper battery tray or box to secure the batteries. You don't want them bouncing around in the bilge.

Hope this helped

 

[jvigier]

Re: Dual battery setup questions - pairing 24 batt with a 27 batt

Thanks Rush, much appreciated

 

[veritas honus]

Re: Dual battery setup questions - pairing 24 batt with a 27 batt

The main reason for a dual battery switch is to separate your usage to avoid draining both batteries and leaving yourself stranded. If you have a starting battery and a deep cycle battery, use the deep cycle battery for your accessories while the motor is off. If you just keep the switch on both, you're kinda defeating the "safeguarding" purpose of a dual battery switch.

Rushfan has told you the proper way to wire the switch. I recently installed mine. I got 2ga battery cable from Advance Auto for only 1.88 per foot.

 

[jhebert]

Re: Dual battery setup questions - pairing 24 batt with a 27 batt

The identifier of a battery's Group size only refers to the physical dimensions of the case and perhaps the terminal arrangement. It does describe the electrical capacity. One could never assess the suitability for connecting batteries in parallel based only on their Group size number.

Batteries that are to be connected in parallel should be as electrically identical to one another as possible, that is, they should be the same brand, the same model, the same age, and the same condition. If batteries of different brand, model, age, and condition are connected in parallel, they may not operate properly, and, more often than not, the weaker or less capable of the two batteries will tend to pull current from the stronger and more capable of the two.

There is seldom any situation in a small boat where it is necessary to operate with two batteries in parallel as a normal configuration, and you should have proper concern for trying to connect in parallel two batteries of different brands, different models, different ages, and different condition.

 

[pootnic]

Re: Dual battery setup questions - pairing 24 batt with a 27 batt

The identifier of a battery's Group size only refers to the physical dimensions of the case and perhaps the terminal arrangement. It does describe the electrical capacity. One could never assess the suitability for connecting batteries in parallel based only on their Group size number.

Batteries that are to be connected in parallel should be as electrically identical to one another as possible, that is, they should be the same brand, the same model, the same age, and the same condition. If batteries of different brand, model, age, and condition are connected in parallel, they may not operate properly, and, more often than not, the weaker or less capable of the two batteries will tend to pull current from the stronger and more capable of the two.

There is seldom any situation in a small boat where it is necessary to operate with two batteries in parallel as a normal configuration, and you should have proper concern for trying to connect in parallel two batteries of different brands, different models, different ages, and different condition.

Just a question,always kinda bugged me.
Isn't 12 volts...12volts?
I can see if 1 battery(12v) is almost dead,then hooking it up parallel to a new 1 battery(12v),could/would be bad but then thats not really 12volts,if 1 battery is almost dead.
A devise using 12 volts in parallel,reads it as 12volts,not 2 batteries making 12 volts.
I'm trying to figure out what would happen,if someone used a group 24 and a group 31,together in parallel.
Say both batteries are new,what would happen as they discharge?
I can't see nothing really bad happening,other then the 24,maybe lasting abit longer then it should and the 31,needing a charge alittle sooner.
I do agree with you that it would be best if you could get the same batteries but just wondering about other situations.
I could be way off the mark,maybe I should have started another post.