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Adding a 4th battery

Old 10-04-2011, 10:46 PM
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Default Adding a 4th battery

I currently have 3 batteries port-starboard- house, they are connected to a 3 bank charger. To add another house battery can i just connect the 2 positive(new house batt with existing) and 2 negatives (in parallel)? How would this affect my electronics? And will 1 bank from the charger charge both batteries?
Thanks for your help in advance
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Old 10-05-2011, 04:57 AM
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Originally Posted by mandyp View Post
I currently have 3 batteries port-starboard- house, they are connected to a 3 bank charger. To add another house battery can i just connect the 2 positive(new house batt with existing) and 2 negatives (in parallel)? How would this affect my electronics? And will 1 bank from the charger charge both batteries?
Thanks for your help in advance
Yes, but I would suggest buying and studying a book on boat wiring so you'll understand what you're doing and know how to do correctly it.

This will be fine for your electronics and the charger will charge both batteries just fine.

Make sure the battery you add is the same chemistry and capacity (and obviously, voltage) as the other house battery. Ideally, you would purchase them as a pair, but if the original is a year or so old and hasn't been abused, you can just add a new one.
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Old 10-05-2011, 06:55 AM
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thanks for your response, I'm pretty mechanically inclined and I've done some research, I just want to double check with others that have done the same. My boat does not have a perco switch, it has independent BEP switches for port-starboard-house-emergency parallel(p & s). A couple of marine electricians have come to give me quotes. And they both wanted to sell me on rewiring everything, one wanted $1000 plus the battery and new switches and the other wanted $800 and they each had a different way they wAnted to wire. My boats wiring is perfect all I want is an extra battery so that I can run my stereo longer and not have to worry about it.
I am planning on using the same size and brand as my current batteries, they are only 6 to 8 months old.
Any input or suggestion is greatly appreciated,
Thanks again
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Old 10-05-2011, 07:07 AM
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If your stereo is connected to your house battery and you aren't using other loads like a refrigerator, lights, etc., you should be able to run the stereo for a very long time without adding a battery.

I can't see your boat from here so I don't know why a marine electrician would recommend $800 or $1000 worth of work to your boat. There could be something that needs addressing that is not apparent from your post. Perhaps your existing wiring is not factory, but a DIY job by a previous owner that wasn't done correctly or with marine materials.
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Old 10-05-2011, 07:25 AM
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Ron, I have a couple of big amps driving my stereo system and it will bring down the house battery in just a couple of hours. If its just a little head unit then I think its a different story.
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Old 10-05-2011, 08:54 AM
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My boat is a 2002 intrepid and it has factory wiring, the electricians reason for changing the wiring was the BEP switches, they wanted to use perko switches. The wiring on my boat was all done by intrepid and has worked correctly since new. I'm going to replace my amp And speakers and I just wanted to be conservative and add a battery.
It just feels like nobody likes the smaller jobs down here. One of the guys even told me to replace my CCharger(that was factory installed and works properly) to a brand new charger, just because.
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Old 10-05-2011, 09:09 AM
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Originally Posted by TripleCrownNC View Post
Ron, I have a couple of big amps driving my stereo system and it will bring down the house battery in just a couple of hours..
I'm glad we're not boat neighbors!
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Old 10-05-2011, 11:36 AM
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Originally Posted by rwidman View Post
I'm glad we're not boat neighbors!
C'mon, I know there is a time and a place
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Old 10-05-2011, 11:42 AM
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wire the house batteries in parallel. Just use size 4 cable to do it. Replace original battery with a pair of new ones if house is more than 3 years old. Otherwise they won't charge to the same voltage.
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Old 10-06-2011, 01:16 PM
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I placed an 8D battery for my house battery. No more worries and it will take about the same space as 2 other batteries. Less wires, cleaner install, a real joy.
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Old 10-06-2011, 07:01 PM
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Originally Posted by deltarome View Post
wire the house batteries in parallel. Just use size 4 cable to do it. .
Or use the same size cable as the rest of the battery cables.
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Old 10-06-2011, 07:03 PM
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Originally Posted by superknt View Post
I placed an 8D battery for my house battery. No more worries and it will take about the same space as 2 other batteries. Less wires, cleaner install, a real joy.
A lot of us will have a difficult time hoisting that 8D battery into the space we have. They are pretty heavy unless you have a straight vertical shot and some help or a hoist.
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Old 10-06-2011, 11:21 PM
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Originally Posted by mandyp View Post
I currently have 3 batteries port-starboard- house, they are connected to a 3 bank charger. To add another house battery can i just connect the 2 positive(new house batt with existing) and 2 negatives (in parallel)? How would this affect my electronics? And will 1 bank from the charger charge both batteries?
Thanks for your help in advance
Yes this is fine. As long as you hook them in parallel as you said you are just increasing the capacity and not the voltage. Both batteries with get charged
and you will be able blast that stereo for hours now
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Old 10-07-2011, 09:03 AM
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Originally Posted by deltarome View Post
wire the house batteries in parallel. Just use size 4 cable to do it. Replace original battery with a pair of new ones if house is more than 3 years old. Otherwise they won't charge to the same voltage.
Althoght it is quoted frequently in bulletin boards, there is no need to match batteries when putting them in PARALLEL. How can they NOT charge to the same voltage if they are connected TOGETHER. It doesn't matter which battery you measrure they HAVE to be at the same voltage.

Matching battery size, chemistry and age is ony a problem when connecting batteries in SERIES.
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Old 10-07-2011, 09:36 AM
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Originally Posted by yandina View Post
Althoght it is quoted frequently in bulletin boards, there is no need to match batteries when putting them in PARALLEL. How can they NOT charge to the same voltage if they are connected TOGETHER. It doesn't matter which battery you measrure they HAVE to be at the same voltage.

Matching battery size, chemistry and age is ony a problem when connecting batteries in SERIES.
Yes they will charge to the same voltage, but if one has significantly less capacity than the other or if one is sulphated or otherwise not in "new" condition, once the charge current is removed and a load placed on the group, the newer or larger battery will attempt to keep the older or weaker batteries charged.
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