Adding a 3rd battery to existing batteries
 

I have a two battery set up right now, one starting and one deep cycle. Both are about a year old and in good condition. I want to add a second deep cycle but obviously don't want to buy two new deep cycle's if the one I already have is still good. I know the batteries should be bought at the same time and similar.

How bad is it really to add a battery that isn't the same age as the other one????

Not the end of the world, that's for sure. Especially with a 1 yr old deep. Link em up

bought my tige in july '12. used it the first season and didn't add the second deep cycle until January '13. no issues yet.
did make sure they were the same brand/rating tho.

Ideal? No. But neither is a single alternator output with two battery banks. 1 year old versus 3 or 4 seasons makes a difference. If the existing battery accepts a charge well and holds a charge well, I wouldn't hesitate.

Thanks

I'm in the process of replacing the alternator now. So I'm going to pick up another deep cycle to help not over work the alternator. I'm guessing this will help??


When I was testing to see why I was having voltage problem again. I unhook my pro marine charger and let the batteries sit for over 24 hours and then checked the voltage and for the next two days both showed 12.9 to 13.0 on the voltmeter.

So then I hooked my fakelake up and ran the boat in the driveway and no matter what RPMs the engine is the voltage wouldn't go over 12.1. Since this alternator is alittle over a year old I got a free one on the way.


Will having a bigger stereo battery bank help the alternator not work so hard????????????

it will keep large bass hits from depleting a single battery and then taxing the alternator as its trying to keep up with a stereo and a low battery, but will also require longer time to charge your battery bank. Lots of variables to consider and it all depends on how you use your boat and your system. I run 3 costco deep cycle batteries and a hard wired battery charger. I can go back to the houseboat and turn on the charger so theyre topped off and not rely on the alternator to keep them charged but more often than not i forget to do that. Im on my 3rd year with it and at this point i haven't had to mess with it at all. When i do i'll buy 3 more and keep the same setup as its worked for me. I have a 70a alternator that i put in 4 years ago prior to the batteries as it was shot when i got the boat. I'd do a 90 or 100a if i could do it again but i needed it that day and it was the only one in stock.

If because you have more battery capacity you have more A/H depletion at the same low voltage level you will work the alternator even harder. So make sure that you do not deplete the stereo battery bank below 12.0 volts when at rest. So with limiting the depletion, with a stereo battery bank consisting of no more than two reasonably sized batteries, your alternator should not have a problem.

Thanks David I need to add a digital read out that show that voltage of the batteries at rest. You have any suggestions.

Something like this:
http://store.earmarkcaraudio.com/Xca...cat=261&page=1
, fused, in a shaded and viewable location, with an easy to reach momentary switch.

Blair, check this out....

https://images-na.ssl-images-amazon....L._SL1200_.jpg

http://i824.photobucket.com/albums/z...pssyjlpthi.jpg

It's less than half the price of the stinger unit david linked, and it's to your house in two days if you have prime.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Is it super accurate? Meh, mine reads 1-2 tenths lower than my multimeter on the battery posts. But I've used the stinger one in a prior install and it has done the same. What it is good for is giving you an idea of what your resting voltage is, what the charging voltage of your alternator is, and how much you are running the battery down at rest.

I like that Shawn, I could add that to my glove box no problem.

Having 3 batteries will def tax your factory alternator and more then likely blow it if you run that voltage too low. I've blown a few trying lol. That stinger voltage gauge is nice though cause you can dial it in with like a fluke multimeter and its fairly accurate. Adding a newer battery wont harm your older battery bank as long as you've maintained your older bank properly. Maintained meaning not running voltage below 50 percent or 30percent depending on manufacture claims, leaving battery at low voltage for extended periods of time, or not using a battery tender while not in use .

Do you tie it into both stereo batteries?

Or if you have both batteries already hook up it reads both as just one battery?

Frankly, I would just purchase the meter from Odin at Earmark Marine. For a few dollars more you'll likely get a full page of instructions on issues that aren't even being considered here.

It's hooked to the stereo side of my blue sea add-a-battery. I only have one stereo battery, but if I had two stereo batteries they'd be wired in parallel as one big battery anyway.

So the voltmeter gives me the resting voltage of my stereo battery when the boat's not running, and when the boat is running it gives me an indication of whether the VSR has combined the batteries or not.

I'm not sure why anyone would need a full page of instructions to hook up a voltmeter (though if anyone can give the encyclopedic response, it'll be David).

Wired right, a single volt meter can show you the static and charging level of both banks.

sure. No reason you couldn't wire any old volt meter up to a dpdt switch. Amazon and Ebay are thick with pre-assembled kits for that purpose.

https://www.amazon.com/BANDC-Voltmet...tery+voltmeter

no reason you couldn't take that concept and wire up a dpdt switch to the voltmeter/usb charger linked earlier in the thread. I didn't see the utility in my case, because my house battery is already wired to the voltmeter in my factory dash gauges.