Adding 3rd battery

JoeStang

So after doing some research it seems like to add a 2nd house battery all I have to do is wire the new battery in parallel to the existing house battery, and I dont need to change my switch at all. It will treat both batteries as basically one large capacity battery. Is that correct?

Also, should I get a 2 bank or 3 bank charger for them? Since they are wired in parallel should I let the charger bring them up to 100% together, or have a 3 bank and charge them independently.

Cableguy Greg

You can connect them in parallel to make the house one large battery. If you get a charger, get a 2 bank charger since that is all that you will have.

My 280EC has a starting battery and 2 deep cycle batteries, which are wired in parallel. I have a 2 bank charger and all works well that way.

reneechris14

Yes one deep battery. So you still only have 2 batteries your charger will do. Like cableguy said. Good idea if you going to run the amp on anchor.

Willhound

Just be sure to add the same type and series of battery. Battery condition is also important. When wired parallel the system is only as good as the least effective battery. 

Dream_Inn

Also, have the incoming ground go to one battery, and incoming positive go to other. @MichaelT made a diagram a while back.

JoeStang

I'm going to buy all new batteries this year, so they'll be all the same condition. I'm going with the group 31 Duracell from Sams club. 

https://m.samsclub.com/ip/duracell-marine-battery-group-size-29hm/prod3590216

Cableguy Greg

They are nice batterys made by EastPenn (Deka). I had two of the AGM's that I thought were going bad, but found out that the wires on the battery breakers weren't tight causing the batteries to not charge. That was an expensive mistake. Lesson learned...

J3ff

JoeStang said:

I'm going to buy all new batteries this year, so they'll be all the same condition. I'm going with the group 31 Duracell from Sams club. 

https://m.samsclub.com/ip/duracell-marine-battery-group-size-29hm/prod3590216

I always get the cheap ones from home depot, replace every 3 years or so.. usually they are about 98 bucks in the store, not sure why it's a little higher, either way these have NEVER let me down, just as I suspect your g31duracells will not either!

https://www.homedepot.com/p/Nautilus-31-Deep-Cycle-Marine-Battery-31MDC/205309650

J3ff

This was before cleaning up down there.. but after grabbing two new house batteries.. 

JoeStang

So when adding the charger, I assume it doesn't matter which house battery I physically mount the charger to? Since it's in essence one large battery, it just charges them equally until they reach peak voltage. Is that right?

zaverin1

No you will need separate leads 

JoeStang

So why wouldnt I get a 3 bank charger then?

J3ff

you could go that way, or give me 50% of this price + half of whatever it costs to ship... https://www.amazon.com/gp/product/B003JSJS5I/ref=oh_aui_search_detailpage?ie=UTF8&psc=1 Bought this one and never used it... it comes with a REGULAR plug, not the boat kind, which may or may not be what you're looking for.

A three bank would probably charge faster, but in the end it doesn't seem to matter much going with 2 vs 3 when you have 2 of them in a parallel configuration. Now that I typed that out, maybe it's bad to have 3 charging when 2 of them are hooked together, not sure! 

Dream_Inn

JoeStang said:

So when adding the charger, I assume it doesn't matter which house battery I physically mount the charger to? Since it's in essence one large battery, it just charges them equally until they reach peak voltage. Is that right?

Joe, you are correct.  It will charge it as one large battery, and hence take longer.  You cannot charge them individually when they are connected in parallel.

JoeStang

Dream_Inn said:

JoeStang said:

So when adding the charger, I assume it doesn't matter which house battery I physically mount the charger to? Since it's in essence one large battery, it just charges them equally until they reach peak voltage. Is that right?

Joe, you are correct.  It will charge it as one large battery, and hence take longer.  You cannot charge them individually when they are connected in parallel.

Thanks for clarifying!

J3ff said:

you could go that way, or give me 50% of this price + half of whatever it costs to ship... https://www.amazon.com/gp/product/B003JSJS5I/ref=oh_aui_search_detailpage?ie=UTF8&psc=1 Bought this one and never used it... it comes with a REGULAR plug, not the boat kind, which may or may not be what you're looking for.

A three bank would probably charge faster, but in the end it doesn't seem to matter much going with 2 vs 3 when you have 2 of them in a parallel configuration. Now that I typed that out, maybe it's bad to have 3 charging when 2 of them are hooked together, not sure! 

I very well may take you up on this, and thats a very good offer. I already have the Noco plug for the boat, so this would work perfect. My only hesitation is that the ProSport 20 from ProMariner can send 100% of the amperage to one battery, if needed. So instead of 10/10 locked like the Noco, it decides which battery needs the amperage more. It is more expensive tho, the best price I've found is $130 shipped.

frenchship

Those batteries should be wires like below

Michael T

Yes! Exactly!

zaverin1

That’s not how his house batteries will be wired lol

Michael T

That is exactly how to wire two or three 12V house batteries - if you want to get maximum performance from them - in fact dramatically increased performance. A few years ago East Penn Deka presented workshops to technicians who had been miss-wiring batteries for years.

zaverin1

Ok,
i am not a rocket scientist but graduated from Lawrence tech.
you need a smart charger that is connected to house battery 1 and 2. It needs to see and maintain individual batteries. This way it maintains the cells properly. If you have one single bank charger going to two batteries it sees false readings and results.

Michael T

I guess the easiest way to explain it is if there are two or more batteries wired as indicated, the charger sees the bank as a single battery. As well, the bank discharges as a single battery greatly enhancing its endurance as opposed to one battery drawing down then trying to scavenge power from the next etc. etc.etc. I believe Intellipower (chargerrs) also had a great article on their site showing how to properly wire two or more house batteries along with charging and draw down voltages and amperages all across the charge/discharge spectrum. The tech who wired the set of AGMs in my 2013 EC 310 disputed this - so the area rep for EastPennDeka swung by the marina to show him the proper method (see @frenchship's diagram). In fact, the power available from three properly wired batteries exceeds considerably the individual capacities merely multiplied by three. I won't say the difference is geometric as compared to arithmetic but darn near. Anyone interested can see a pretty extensive discussion about this from a few years back - maybe even with links on the forum.

zaverin1

We can skin things many different ways 
issue is logical and mechanical approach.
why do we buy or why do they make 1-2-3-4 bank chargers?
to maintain each individual battery.
i can take a single bank charger and wire it to 3 batteries? How well would that work?
how many volts and Amps does it take to charge one battery?
if you wire inline you also double the load!
sorry I create logic control for most complex automotive lines and know little more compared to a reg joe

trip_n

i stayed @ a holiday inn last night

Willhound

The diagram as shown by @Michael T is exactly how a parallel battery bank should be connected. The issue of a 2 or 3 bank charger is another matter entirely. Yes, the newer computer controlled chargers with 3 sets of leads can be beneficial in that each battery benefits from its' own charge pattern as controlled by the charger. My two house batteries are wired parallel as per the diagram but my 3 bank Pro Mariner charger has one set of leads to each battery. I don't pretend to know how it works, but apparently the charger senses they are in parallel, but for charging treats them individually.
Now, if I only had a 2 bank charger and didn't have the bucks to upgrade to a 3 bank, the charger could still easily do a decent job charging all three batteries, just without the added benefit of the smart charger program.
Bottom line, if you can afford it, and are starting new, yes a 3 bank charger is the way to go, and hooked to the 3 best batteries you can afford, and keep the cables to the proper gauge and connections clean and tight and you're golden.

212rowboat

What zaverin is saying is correct IF youre using different batteries capacity and discharge on the same bank.  I think that is the disconnect here.  You CAN do it as described by MT with different size and discharge batteries, but you'll junk thkse batteries quickly.  IF theyre the same battery, and they should be, MT has provided the correct diagram. 

A person would be foolish or expecting a different outcome if they charged on the same bank two different sized batteries, unless they interjected an isolator between them. That defeats the purpose.   

zaverin1

Agreed 

zaverin1

I guess I don’t really know your set up Joe when It comes to how many batteries you currently have if you have a battery switch on it battery class and so on
All those details would make a big difference on how you wire and what kind of charger  you install

zaverin1

 Just look at it this way if I had three batteries same group size and one bank charger can you technically charge those batteries with one bank charger answer is yes it become a very weak trickle charger issue is you would never be able to maintain all three batteries an individual cells within the batteries with one bank charger  so that’s why we buy three individual banks and they maintain the cells within the batteries sorry for the run-on I’m using Siri laughing out loud 

212rowboat

you'd be able to maintain them just fine... it will just take longer.  the charger will push the same amperage at the same voltage no matter how many batteries are on it.  

zaverin1

Take longer and cause damage to the cells

Handymans342

Just got 2 Duracell 31s at Sams for 182 with tax