Help - Adding 3rd battery to 2022 25LSV

[JamieBest]

Started looking at adding a 3rd battery to my current factory setup but need some help with connections.
 

The battery closest to the observer seat has a large, possibly 1/0 gauge, negative cable that turns down and goes back to the nest of positive and negative cables under the observer seat. It also has a negative cable that ties to the battery closest to the bow. The positive cable that comes off this battery is the same large 1/0 and travels back towards the observer seat. 
 

The bow battery also has a large positive cable that turns down and runs back towards the observer seat, but also has two, maybe 12 gauge wires with what appear to be inline fuses coming off of it. The negative terminal of this battery has 3 cables coming off of it; one that ties the two batteries together, and 2 large cables also running back towards the observers seat. 
 

There is a Blue Seas automatic charging relay, part number 7620. I assume it has one positive cable from each battery attached to the two separate terminals (1 for house and 1 for starting). 
 

I also have a Blue Seas dual circuit plus battery switch part number 6011 with 2 battery terminals labeled 1 and 2. I assume 1 is for house and 1 is for starter. 
 

I’m thinking I will insert this battery between the current two (current batteries designated 1 and 3, 1 being closest to the observers seat and 3 being closest to the bow) disconnect the current negative cable tying the batteries together and run the negative cable between batteries 1 and 2 and add a second negative cable between batteries 2 and 3. Then run a second negative cable from battery 2 back to the observers seat nest (should I find and attach to a ground block for this cable?). I would then run a positive 1/0 cable back to the nest and connect it where?  To the same terminal at the ACR where battery 1 is connected?

 

thanks

Jamie

[Stevo]

Are your batteries led acid or AGM? 
 

You will be adding a 3rd battery in parallel with the other 2. See attached pic.

I have the same set up with 2 AGM batteries and have considered adding a 3rd, my plan to do so would be to purchase the 3rd battery and another +- cable 1/0 to match the attached diagram.

the smaller gage wires with in line fuses are most likely for Auxiliary electrical components 

[csleaver]

Why would you need a third battery?  Upgrade the two batteries in the boat and use an onboard charger.

[JamieBest]

5 hours ago, Stevo said:

Are your batteries led acid or AGM? 
 

You will be adding a 3rd battery in parallel with the other 2. See attached pic.

I have the same set up with 2 AGM batteries and have considered adding a 3rd, my plan to do so would be to purchase the 3rd battery and another +- cable 1/0 to match the attached diagram.

the smaller gage wires with in line fuses are most likely for Auxiliary electrical components 

Odyssey Extreme AGM 34’s

[JamieBest]

4 hours ago, csleaver said:

Why would you need a third battery?  Upgrade the two batteries in the boat and use an onboard charger.

Longer run times for the stereo while sitting with engine of. 

[Stevo]

6 hours ago, csleaver said:

Why would you need a third battery?  Upgrade the two batteries in the boat and use an onboard charger.

My reason would be to minimize the voltage drop from the stern turn. 
 

I didn’t have any electrical problems last year , but with how dependent the operating system is dependent on proper voltage I figured this would be cheap insurance. 
 

I believe there is a reason malibu bumped up the alternator for 2023 to 250amp from the 170amp  . A 3rd battery doesn’t compare to the additional 80amp replenishment, but I figured I’d start small.

 

[MLA]

4 hours ago, JamieBest said:

Longer run times for the stereo while sitting with engine of. 

All you need to do is connect the two house batteries in parallel, simple as that, as the original house battery is already part of the circuit. 

However, I would use your existing AGM G-34's for your parallel bank, and get put the new one in place as the new starting battery. Its not ideal to connect a new, unused battery to a used battery thats had some discharge/charge cycles. 

 

[JamieBest]

On 4/30/2023 at 6:17 AM, csleaver said:

Why would you need a third battery?  Upgrade the two batteries in the boat and use an onboard charger.

Longer run times for the stereo while sitting with engine of. 
 

@MLA how do I determine which current battery is house and which is start?  They both end up in the nest of wires under the observer’s seat.