Adding an additional battery.......

[pachanga27]

I have a 1989 Sea Ray Pachanga 27 with twin 5.7 Mag Mercruisers ? each motor having its own battery.
I have two extra known good marine batteries that I would like to ?add? to the current two batteries- as in add a battery to each motor so that each motor has two batteries. The current batteries have their own ?on-off? switch.
The engine compartment has lots of room and physically adding the batteries would not be a problem ? using new additional battery holders.
One question that pops up - the alternators - can they handly the extra load?
Is there a way ?in a safe manner ? to add the extra batteries to the system? As to the why I want to do it ? redundancy and never having to tell my wife the batteries are dead and I can?t crank the motors are my reasons. She does not handle being stranded on the lake very well.

 

[Silvertip]

Re: Adding an additional battery.......

Simple, inexpensive, and versatile are "Dual Battery Switches" (one for each engine. Dual battery switches are discussed to death in this forum but in a nutshell, they are replace your ON/OFF battery swtich. They have OFF, BAT 1, BAT 2 and BOTH settings. OFF is obviously off for both batteries. BAT 1 allows you to start the engine, run accessories, and charge battery #1, Set the switch to BAT #2 and you start the engine, charge battery 2 and run accessories from battery #2. Set the switch to BOTH and both batteries are on-line to start the engine, run accessories and both are charged. As I said - simple, versatile and inexpensive.

 

[glenn property of pam]

Re: Adding an additional battery.......

"One question that pops up - the alternators - can they handly the extra load?" alternator only puts out a certain amount of ampage so it doesnt care how many batteries

 

[pachanga27]

Re: Adding an additional battery.......

Thanks - I did find that Perko (from the iboats.com parts page) sells a switch just as you described. I plan to install these switches to do exactly as you said.

 

[pachanga27]

Re: Adding an additional battery.......

"One question that pops up - the alternators - can they handly the extra load?" alternator only puts out a certain amount of ampage so it doesnt care how many batteries

Ok. thanks - that answers that concern. Appreciate the info.

 

[Silvertip]

Re: Adding an additional battery.......

When you do install them, the COM terminal on the switch is where the loads are connected. Loads are all the things that require power. The only thing that gets wired directly to a battery are bilge pumps with float switches. Those should be connected to the auxiliary battery. As for the alternator issue -- when BAT 1 is selected ONLY BAT 1 is being charged. When BAT 2 is selected ONLY BAT 2 is being charged. When BOTH are selected BOTH are being charged. So use a little thought when operating the switches. Set them to the battery that needs the most charge. Leaving the switches set to BOTH when you are anchored for hours at a time will ensure that you kill both of them so you are still without the ability to start the engine. Set the switches to BAT 2 when anchored for long periods or to OFF when at the dock. When you leave the anchorage, leave the switch on BAT 2 so the full alternator output can go that battery. Once you figure out how this works you do not need to continually fiddle with the switch. A typical scenario goes like this.

1) At the dock switches would have been OFF to prevent any current draw.
2) Switch to BOTH, start engines and make the outbound trip.
4) If you will not anchor but are simply making a round trip with one or two brief stops, leave the switches on BOTH.
5) Back at the dock STOP engines THEN switch to OFF.
6) If you anchor for a an extended period and run a stereo & other accessories, switch to BAT 2.
7) When you leave anchorage leave the switch on BAT 2 for the return trip.
8) Back at the dock, STOP engines and switch to OFF.
9) When you leave on the next trip again switch to BOTH and start engines and go boating. Both batteries will again be on-line and since BAT 2 (the most used on the last trip) was charged at least partially on the last return trip this outbound trip will top off both of them if the trip is of any distance at all.

The switches are traffic cops for the charging system. Be a smart traffic cop.