Attaching a new battery to the existing two on board for inverter-gctid819014

[dockofthebay]

Hey every one, I do not have alternating current on my Wellcraft Antigua. I do have a 2000 watt inverter that I got for just that purpose so I don't need a reeeeaaaaally long extension cord to the marina. I also have a new side and top post marine battery that I want to use specifically for the inverter. What would be the proper way to connect it to another battery on the boat and then to the inverter? I'd like the alternator to charge it as well. Both batteries operate all powered aspects of the boat. It does not appear to be one battery for cabin/accessories and one for motor. Can any one offer suggestions?

[SKUA_28_Contessa]

Sounds like you're going 12 volt battery. I would suggest ditching 2 of the 12's and getting a pair of 6V GC batteries wired in series. You will have more amp capacity,and true deep cycle ability. Then use the 1 12V for the engine starting battery.

[dockofthebay]

Hey Bounty, so is there a more appropriate way to set it up so that the alternator charges that extra battery?

[dockofthebay]

That makes more sense to run 12 volts in parallel. Same voltage but double that amp hour capacity, correct?

[2850Bounty]

"dockofthebay" post=819055 wrote:
Hey Bounty, so is there a more appropriate way to set it up so that the alternator charges that extra battery?

I would think of this as though there is no "extra" battery.

Your boat will be set up with two totally separate battery banks.

#1 bank will be your starting battery bank.

#2 bank will be your HLBB ( House load battery bank ).

The engine alternator will charge which ever bank is being selected at the time, and during engine operation.

.

[2850Bounty]

"dockofthebay" post=819057 wrote:
That makes more sense to run 12 volts in parallel. Same voltage but double that amp hour capacity, correct?

At first glance, it sounds as though it would be correct! However, when comparing batteries of the same approximate size, a 6 volt GC battery will offer more amp hours than two 12 V batteries will.

Plus...... the 6 volt GC battery is a true Deep Cycle battery.

.

[dockofthebay]

Gentleman I have so much to learn. Thank you. I am back to the drawing board then. No rush. Right now the AC current works fine in a marina ac outlet. The biggest concern was running the air conditioning in the boat while we were out on the lake for the family. In the mean time I just got done spending 2 hours running wires to figure out why my horn wont work.

[boatworkfl]

I just switched from 2 banks of 27 series lead acid batteries to 2 banks of 31 series AGM, also 1 spare 31 series AGM under the master bed in the bow as an emergency spare, I will add 1 more AGM next year fwd on my 3870, helps keep the bow down, I have gas engines, also an inverter I rarely use. Sams has the 31 series AGM batteries for $180.00

[Guest]

There is absolutely no way an invertor and battery will run an a/c unit out on the water! Depending on the size of the A/C unit it will take about 30 amps to start (instant kick) then about 10 amps to run. A 15 amp shore power circuit can take the start kick. A 2000watt invertor..I'm not so sure. 10amps X 120 volts is 1200 watts. Running on 12v that is 100 amps if the system were 100% efficient (which it is not). With a 200 A/H battery you may get one hour or so running of the A/C. Remember that 200 AH rating is at 20 amps. At 100 amps it's just a guess but if you discharge the batteries fully the life will be very limited! In my opinion to run A/C while on the water you need a generator.

[dockofthebay]

Thank you for the input. I wasn't 100% sure on how all of that worked anyway.