# 12v batteries



## kernewek (Jan 31, 2006)

Iam in the market for new coach batteries for my Class C Motorhome and have found these locally
Any opinions as to whether 2 of these will do the job?
they are advertised as marine/trolling motor batteries

Deep Cycle batteries offer lasting power of up to 160 amps and 
endure repeated deep discharge from trolling motors and electronic equipment. 

Provides up to 750 mca and 205 minutes of reserve capacity 

Endures repeated deep discharge 

13.1 x 6.9 x 8.9" 

Amp Hour Capacity: 103


----------



## Krazeehorse (Jan 31, 2006)

12v batteries

Remember, the cheap ones usually claim the same or better numbers than the good ones.  Also, if I were you I would consider two large 6 volt batteries in series as opposed to the two 12V in parallel.  The 2 x 6 volt series configuration seems to have more reserve and stay up well when not in use (if they are good quality batteries).  But wait and see what some of the other guys have to say.  Krazee.


----------



## MOtech (Feb 1, 2006)

12v batteries

Yes 2 6vlt batteries are better, If they Fit. 2 6vlt batt. connected in parallel equal more amp hours 400 200 each if Im not mistaken. I would suggest 2 6vlt Trojan sealed batteries.


----------



## MOtech (Feb 1, 2006)

12v batteries

Yes 2 6vlt batteries are better, If they Fit. 2 6vlt batt. connected in parallel equal more amp hours 400 200 each if Im not mistaken. I would suggest 2 6vlt Trojan sealed batteries.


----------



## ARCHER (Feb 1, 2006)

12v batteries

Well, I have to ask.  I have two 12 volt aux batteries for my Class A.  They are sealed batteries and so far are standing up pretty good.  Isn't 24 volt (2 12s) better than 12 volt (2 6s) for a Class A?  They are used to run 12 volt stuff when not hooked up to shore power and then converter operates the 12 volt things like lights, fridge, water heater ignitor, heater ignitor, etc.  Just courious as when I do need to replace the two 12s, I guess I should perhaps consider the 6s???


----------



## hertig (Feb 1, 2006)

12v batteries

Archer, it is unlikely you have 24 volts.  What you probably have is the 2 12 v batteries in parallel, providing 12 volts, but double the capacity of 1 battery.  There is nothing wrong with this setup, however 2 6 v batteries in series gives you 12 volts also, but the 6 v batteries are more 'heavy duty' and there is alleged to be an electrical superiority of a series connection over a parallel connection which I don't quite grasp.  6 volt batteries are also almost always taller than the equivalent 12 volt batteries, so make sure you have plenty of room above your batteries before even considering converting.  You may also need new cables if the ones you have now are 'fitted' to the parallel setup.


----------



## hertig (Feb 1, 2006)

12v batteries

By the way, when you are looking for coach batteries, you want one which is rated in 'amp-hours', not 'cranking amps'.  Such batteries are 'dual purpose' batteries which are not as good at either purpose as a battery designed for that one purpose.


----------



## ARCHER (Feb 1, 2006)

12v batteries

John, thanks for the info.  My battery compartment is large enough to handle two of the taller 6 volt batteries.  Does anything need to be rewired for switching to 6 volt?  Not sure I understand the difference between paralle vs series hook-up.  Sorry just a little slow... :dead:   Do I need to do anything with the converter?  Will it charge the 6 volt batteries just like the 12s?  tks again..   :laugh:


----------



## Krazeehorse (Feb 1, 2006)

12v batteries

Your two 12V are connected parallel.  That is the both positive terminals are coupled and connected to the positive coach cable and likewise with the negatives.  If you use 6V you put them in series.  The ground cable from the coach goes to the negative terminal on battery A.  There is a small "jumper" cable that goes from the positive of battery A to the negative of battery B.  The positive of battery B is connected to the positive coach cable.  Just like batteries in a flashlight.


----------



## MOtech (Feb 2, 2006)

12v batteries

1-6vlt battery has 3 cells in it at 2vlts per plate = 6 vlts.
1-12vlt battery has 6 cells in it at 2vlts a plate = 12 volts
2 12vlt batteries connected in series =24vlts
2 6vlt batteries connected in series =12vlts


----------



## benwd (Feb 2, 2006)

12v batteries

kernewek--Get someone to help you put the batteries in and to hook them up. A mistake regarding the series parallel stuff could really mess up your rv.

Regardless of whether you choose 12v bats or 6v bats the volts to the rv will be 12v, and the rv won't know the difference.

12v bats don't generally come in deep cycle which doesn't give you as much life. 6v bats have to run at twice the current per bat under load and aren't quite as efficient because of it, however, you would never notice the difference.

12's, because they have to be connected in parallel, means that if one bat developes a shorted cell that the other 12v bat will be pulled down in short order trying to supply current to the reduced voltage bat. Very quickly all the charge is lost. Some have said,'I'll catch it before that happens' not a chance.

6's in series allows a shorted cell without pulling down the bats, the voltage just drops from 12 to 10. However, if not caught soon, the charger will boil out the bats fairly quickly as the charger thinks the bats are not charged because of the reduced voltage.

There are advantages and disadvantages to both setups. Most people prefer 6's because they will give longer life and are more rugged.


----------



## s.harrington (Feb 2, 2006)

12v batteries

L----(+   -)-----(+   -)-----G
How to hook up two six volt batteries

L=load
G=ground
(+   -)=battery


----------



## kernewek (Feb 3, 2006)

12v batteries

Thanks for all the input, guys, It seems to mee that 2 x 6v is the way to go if I can accommodate the extra size
On a related topic, while I was researching the whole battery thing, I
I read some suggestions to replace the converter with a 3-Stage battery charger, I am not interested in doing this, but was wondering how the 12v system works with this set-up when you are connected to shore power, does it just come off the batteries which are kept charged by the 3-Stage charger or is that too obvious


----------



## benwd (Feb 3, 2006)

12v batteries

You can leave the converter in place and add an inverter/charger [three stage] across the bats. And the more you read up on these the more interested you will become in doing it.


----------



## MOtech (Feb 3, 2006)

12v batteries

3 stage charging system =3 stages of charge modes.
most older paralex converters (put out as much voltage as they are receiving)this would aver charge batteries.
3 stage systems recognise the voltage at the batter and limit itwhen charging prventing the batteries from over charging.
Most of the 3 stage chargers also are an inverter allowing to run limited amout of 110Vlt/watts when running only on batteries.


----------



## ARCHER (Feb 3, 2006)

12v batteries

I thought a converter changed 110 volt to 12 volt to run things inside motorhome like fridge panel, 12 volt lights, waterheater ignitor, furnace ignitor, etc., WHILE your plugged into shorepower (and it also charges your coach batteries as needed).  The coach batteries are not actually being used while your on shore power, as I understand it.  One guy told me to disconnect the aux batteries while I was on shore power for the wintering months (like 4-5 months) and I would save a bundle on electric bill and also to RUN THE FRIDGE on LP would also drastically reduce the power usage.  Any comments??


----------



## MOtech (Feb 3, 2006)

12v batteries


The new 3 stage converter/inverters have 2 lines 1 feeding the 12vlt side and 1 feeding 1 or 2 110vlt outlets, }depends on the wattage}they can only feed so much wattage usage.

I dont think you would save any money discontecting your batteries, the converter puts out on in charge side the same amount if your batt. are hooked up or not. correct me if im wrong.


----------



## benwd (Feb 3, 2006)

12v batteries

archer----IMO you are right. However, disconnecting the batteries while on the converter for a long time keeps from boiling out the bats as most converters are a little high in voltage for long time charging.
I've read comparison posts of propane versus 110 on the fridge and it's about a wash cost wise. The fridge however, is better off on 110 because propane gives off water that rusts the stack.
A three stage charger will charge batteries probably 20 times faster than a converter. First stage is bulk current upwards to 100 amps, stage 2 is absorbtion holding the voltage contstant while the current drops off, stage three is float that holds a voltage. If you use a gen then the charge time is reduced to an hour or so depending on the setup.


----------



## MOtech (Feb 3, 2006)

12v batteries

Yes your fridge running on 110vlt, requires 10.5 volts to run the heating element, thats a good draw on batteries.6amps
If your fridge has electronic display/controlls on top then it requires 12vlts for running the upper board on lp or 110.
If it has manual controlls it dont require 12vlts then it wont draw on your battery running on LP.


----------



## team3360 (Feb 3, 2006)

12v batteries

as far as developing a short in a 6v-12v system either system can be wired to isolate each battery to keep a bad one from pulling the other batteries down. its been a long time since I rewired completely but it can be done   team3360


----------



## benwd (Feb 3, 2006)

12v batteries

MOtech--edit your post---every 2 way and 3 way fridge uses a 110 volt ac heating element.


----------



## benwd (Feb 3, 2006)

12v batteries

team3360----How?


----------



## team3360 (Feb 3, 2006)

12v batteries

HEY BENWD    YOU HAVE TO USE A BATTERY ISOLATOR .ALL DUAL BATTERY SETUPS SHOULD HAVE THAT, MY TRUCK IS FACTORY INSTALLED .  ISOLATORS ARE AVAILABLE AT AUTO PARTS STORES , SOME RV SUPPLY STORES .  YOU RUN YOUR CABLES INTO THE ISOLATOR  AND OUT TO THE BATTERIES . THE ISOLATOR SEPARATES THE TWO BATTERIES ,ALLOWS CHARGING,AND USE OF EACH BATTERY BUT NOT DRAWS FROM BATTERY TO BATTERY.  AS I SAID EARLIER ITS BEEN AWHILE SINCE I DID A DUAL SETUP, THAT WOULD HAVE BEEN FOR THE LOCAL FIRE DEPT, WITH THOSE WE USED A BATTERY CUT OFF SWITCH ALONG WITH THE ISOLATORS  .    TEAM3360


----------



## benwd (Feb 3, 2006)

12v batteries

Are you talking about a diode isolator?


----------



## team3360 (Feb 4, 2006)

12v batteries

CHECK OUT THE WEB PAGE (http://www.campingworld.com/browse/products/index.cfm?prodID=1869&src=SRQB    CAMPING WORLD  TEAM3360


----------



## benwd (Feb 4, 2006)

12v batteries

That looks like it would work out.


----------



## Kirk (Feb 4, 2006)

12v batteries

team3360

I don't see anything on the CW link that says who made it or the exact specs but it would seem to be a diode isloator. While they do work very well, they do have the draw-back of a .7V drop across them. Probably not a serious problem unless you are a hard-core dry camper. In that case it could be somewhat of an issue. Most avid solar users prefer to go with the relay type of isolator to avoid that extra load. Not being much of a dry camper, it wouldn't bother me.

  quote:You can leave the converter in place and add an inverter/charger [three stage] across the bats. And the more you read up on these the more interested you will become in doing it.
     benwd

I don't have, or plan to install an inverter, but I do have a question for those who have one. I thought that most factory installed inverters were a direct replacement for the converter and served not only as a source of 120V-ac when on the batteries, but that they also replace the converter to supply the 12V-dc to the lights and other such items in the RV as well as serving as a multi-stage charger for the coach batteries?  Are you saying that you need both?


----------



## hertig (Feb 6, 2006)

12v batteries

No, a converter will provide 12v and so will an inverter with charger.  The inverter will often provide a better charger (3 stage as mentioned) and 120 vAC as well, so is to be preferred where practical.  The only time you would need both is if the inverter did NOT have a charger built in.  This would be the case on some of the smaller inverters.  Generally when you get up to 2KW inverters and above, most have chargers built in.

I think you'll find that the batteries are part of the 12v circuity.  They are across the output of whatever is providing the 12v, and not only provide storage, but filtering of the power.


----------

