Adding a secondary battery.

[mgs917]

Can someone explain the process of adding a second battery for a stereo. I currently only have one battery, but I want to add a second battery for tower speakers and an upgraded stereo.

How do I connect the battery to the current battery?

How do I chose a second battery?

Does the second battery need a charger? How do I add this if it is needed?

Do I run anything else off the second battery? I am planning on adding two amps and placing these on the second battery.

Thanks for any and all help

[xrichard]

I'd put in a group 27, 29 or 31 lead acid battery depending on space. There are only a few manufacturers of flooded batteries in the US, so buy one with a good return policy such as at Costco. A deep cycle or "hybrid" deep/start (often labeled marine) is better than a starting battery. If you have enough room, two 6v golf cart batteries are the best IMHO. If all depends on your draw and how long you want it to play. There are some advantages to AGM but I don't think enough to justify the disadvantages.

You'll hook it up in parallel to your existing battery via a battery switch (e.g. a Perko 8501 or similar) or an ACR like a Blue Seas Add-A-Battery kit. The ACR is worth it.

The second battery does not need a separate charger in the boat...both batteries get charged from your alternator. If you use a switch, you'll need to make sure you switch is set so that both batteries get charged. If you have an ACR, it takes care of the switching for you.

At your house, you should charge each battery separately with the battery switch in the off position (there can be an issue with the ACR closing during charging...depends on how you've wired it). I have a two bank battery tender mounted on the ceiling above my boat. I put quick connects on the boat and charger leads....I just plug them in when I get home. FWIW, my starter batteries typically last 6-7 years doing this. My stereo batteries only a 3-4 years because I draw them down too far.

Personally, I run all loads except the starter off of the "house" or second battery. The downside there is that your house battery might get drawn down so far that your boat ECM will have trouble running. In that case, you can combine the batteries at the switch and be on your way. Or you can run the ECM and the starter off of one battery and all other loads off the house battery. I haven't wanted to run new wiring to the ECM, so I figure I'll just use the switch to get adequate current if the house battery gets low. It's happened to me once.

BTW, for your amps, I'd run a 1/0 cable from the battery to a location near the amps and then distribute power to the amps with a 4 gauge (or larger...depends on the amps) via a fused distribution block. You would also want to put in a battery switch on that run if you're not running it through the main Perko switch.

[distinguishedmotorsports]

group 27 is easy to fit under most of the seats and is the same as most of the factory batteries with the exception of a few.

you need to grab some battery lug cables from a place like interstate battery or online (amazon) red and black. you CAN use a perko battery switch (on/off) to regulate the extra battery. its not required but a good idea. if you are not switching the batteries they should be the same make, and model and specs so they don't discharge into each other.

unlike above, i would NOT recommend another battery switch to your amps. i would recommend a marine rated breaker with a capacity of at least what your amps will pull, but NOT to exceed the wires rating. 0 gauge OFC is typically 300 amps max. fuses are OK, except you need spares and 300 amp fuses are not cheap.


i would recommend doing a upgrade of the big three before adding an additional battery. "the big three" is upgrading the wire size on the three major electrical wire runs of the boat. took me about 45 minutes to do on my ZR6 motor. upgrade all the wire to 4gauge at a minimum, 2 or 0 gauge would be better. three runs are: alternator positive to battery positive (or battery switch), engine ground to chassis ground (subframe for motor) and battery ground to chassis ground. This will make sure you alternator is putting out all of its available capacity and all your grounds are not a problem.

adding a battery with out increasing the alternators capacity will have some diminishing returns somewhere north of 180 amps of draw. most stock Alternators on the fuel injected NA boats is 95 or 100 amps.

just my $0.02

[jslipher]

group 27 is easy to fit under most of the seats and is the same as most of the factory batteries with the exception of a few.

you need to grab some battery lug cables from a place like interstate battery or online (amazon) red and black. you CAN use a perko battery switch (on/off) to regulate the extra battery. its not required but a good idea. if you are not switching the batteries they should be the same make, and model and specs so they don't discharge into each other.

unlike above, i would NOT recommend another battery switch to your amps. i would recommend a marine rated breaker with a capacity of at least what your amps will pull, but NOT to exceed the wires rating. 0 gauge OFC is typically 300 amps max. fuses are OK, except you need spares and 300 amp fuses are not cheap.


i would recommend doing a upgrade of the big three before adding an additional battery. "the big three" is upgrading the wire size on the three major electrical wire runs of the boat. took me about 45 minutes to do on my ZR6 motor. upgrade all the wire to 4gauge at a minimum, 2 or 0 gauge would be better. three runs are: alternator positive to battery positive (or battery switch), engine ground to chassis ground (subframe for motor) and battery ground to chassis ground. This will make sure you alternator is putting out all of its available capacity and all your grounds are not a problem.

adding a battery with out increasing the alternators capacity will have some diminishing returns somewhere north of 180 amps of draw. most stock Alternators on the fuel injected NA boats is 95 or 100 amps.

just my $0.02

Where should you ground the 2nd battery to help reduce any engine noise in audio system? Should you ground the second battery in the same spot, or different so it doesn't pickup alternator whine?

[distinguishedmotorsports]

Where should you ground the 2nd battery to help reduce any engine noise in audio system? Should you ground the second battery in the same spot, or different so it doesn't pickup alternator whine?

sorry for the delay in response. the fewer the grounding points the better. but if you are grounding on the subframe/engine cradle it is essential the same ground through out.