Using 3 Batteries

Hey everyone, looking for battery setups using a TOTAL of 3 batteries. I plan on having one battery dedicated for starting. The other two batteries for the stereo/house. Please chime in on configurations that work. I was thinking of getting away from my diode isolator which is only meant for a total of 2 batteries. Thanks

I kept my isolator and ran the house/stereo batteries in series 12 volt and it still charges all three, just like it had two, but I get way more stereo, ballast time, out of two house batteries. I think combining your aux batteries in series is your only option.

Once two batteries are wired together in parallel, they become one large battery. Your diode isolator wont know the difference. The diode's voltage drop will effect the recharging of a 2 battery house bank the same way it will effect the recharging if a single battery. I would move away from the diode for other reasons.

If you plan on heavily depleting the batteries, then relying on shore charging is a must. In that case, the small voltage drop across a diode Isolator should not be a factor. Unlike an ACR/VSR, the diode will not cycle open/closed, when 2 depleted batteries are introduced to the alternator after a day at the party cove. It this point, we reached the limits of the ACR and need to override ACR manually with the dual-battery switch in order to get some charge back into the house bank. A diode setup can be totally passive.

For a simple yet effective system, all that's needed is a traditional dual-battery switch. This allows the house loads (stereo) to pull off of witch ever battery bank you have the switch turned to. Totally manual, but works just fine.

Using an ACR/VSR with a dual battery switch is combo passive/manual setup. Both banks receive a charge while the engine is running, yet the main cranking is isolated from the house loads when the engine is off.

There is no one size fits all battery setups. each has their own pros and cons, so the total scope of the stereo system and how the system will be used all need to be taken into account.

Just to clarify, 12 volt batteries need to be wired in parallel so they remain at 12 volt, a pair of 6 volt golf cart batteries need to be wired in series in order to become one 12 volt battery, thus allowing them to be used in a 12 volt system like a boat or car. In parallel, the bank stays at the same voltage but the amp/hours are stacked. In series, the voltage is stacked. but the Ah's remain at the level of a single battery.

Thanks for your replies! If I keep my 90a diode isolator I can keep my starting battery group 24 flooded and then put two batteries in parallel on the other side of the same type and group? Is a perko switch recommended with use of an isolator too just incase the isolator fails? Both my batteries currently sit in the back of the boat on either side of the motor. I wanted to get some feedback on the various ways people did their configurations using three batteries and then decide which is the best for me! So I do appreciate feedback!! Cheers~

If there is room next to your current house battery for a 2nd battery, then it makes for a simple upgrade to wire the 2nd house battery to the existing. On the down side, if the house bank is on the opposite side of the boat from where the amps are going, then the amp cable length and size need to be considered.

The odds of a diode isolator failing is slim due to their simple design and operation. Adding a traditional dual-battery into the mix would allow for starting the engine off either bank.

The problem does exist with the batteries for the house on the starboard side and the amp location being in the port side locker up front. With that in mind I would imagine using a 1/0 gauge cable up to the distribution block would be okay!? I would guess 10 or 12 feet from bank to amps. I am surprised to hear that my diode isolator would work with what I am looking to do!! And as for adding a perko switch it sounds like that would give me the flexibility to start boat off bank incase starting battery failed!! Seems good! I only want to do this once so I want to make sure I can use my diode isolator and not be upgrading to vsr/acr and perko? Thanks for the info

House bank located aft/STBD and amps located port mid-chip, I think you're looking at 2x your 12ft estimate. On a 22ft boat with the batteries on the port side aft, it usually takes my 20-22 ft of cable to cleanly run the amp cabling from the batteries to the amp wall.

I dont want you to get ahead of yourself, Although I stated a diode isolator will work with 2 group-24's wired in parallel as a house bank, Im not necessarily saying it will be the best route for you to keep that diode. Still some unknowns here in this thread. Designing a system from the ground up, I would not do a diode Iso and dual battery switch, but instead do an ACR/dual-battery switch. But since you have a diode Iso already part of the factory wiring scheme, its worth investigating whether it will work or not. Knowing which battery is located on which side of the boat would play into my design. Reducing the amount of cable that needs to be run, especially the amp cable, is a plus. Also cutting down on the length cable running from the main cranking to the switch and from the closest house battery to the switch is important,

The option to keep all batteries in the back has come up, as well as bringing only the house/stereo bank up front under portside locker has been thought of as well. I am looking for LOTS of ideas. The fact that I have a diode isolator currently is what is really making me wonder if this is something I should keep, or ditch. The bottom line is finding out if it will work for what I am trying to do? I have not found that out yet? Its apparently a Noco brand isolator. There is a fair amount of cable to be run. Another option is having the stereo battery seperate from the alternator charging system. Say 2 parallel batteries totally seperate from the starting battery and house battery, and on a charger every night (OVERKILL) in my opinion. Did we touch on the batteries being all the same in terms of construction, group (size), brand? Will this matter? I would think that mixing AGM batteries for stereo bank with my current group 24 flooded would not be a good idea? I thought some group 27 or 31 flooded deep cycles would be good though! All of these questions being answered by anyone reading sure helps move me in the right direction. What works for 3 battery setups and how is it layed out^? Thanks

The XS Power XP series of batteries works great for what you are wanting to do. Check out the XP3000. It is a Group 31 and is one of the most powerful batteries you will find.

Originally Posted by mattxspower

The XS Power XP series of batteries works great for what you are wanting to do. Check out the XP3000. It is a Group 31 and is one of the most powerful batteries you will find.

Shameless plug almost 2 months late.