Adding a 2nd Battery?

[plattpd60]

Would it be a problem if I connected a second battery to the current battery. My Class C had 2 Batteries, Class A only has 1.

[wolfe10]

Dennis,

If comparing the warranty on a battery installed when a vehicle is built vs aftermarket one, the answer is that the OEM gets a price break for specing a shorter warranty term. Same for shocks and other items.

[Executive45]

Why is it NEW car batteries only carry a TWO yr warranty but when you replace it with an IDENTICAL battery it carries a FIVE yr warranty??? Asking for a friend...:)....Dennis

[wa8yxm]

Alan_Hepburn wrote:
...and like any socialist society, all the individuals will eventually balance out to the lowest common denominator. In other words: weak batteries will prematurely weaken good batteries...

I have seen no evidence of this in 15 years of doing it. Now batteries have multiple failure modes. SHORTED. yes a SHORTED battery will "Suck down" the rest of the set.. Don't matter if it's a week old (Had it happen) or 5 years (Never had it happen).. But the most common failure is what I call high resistance or loss of capacity... And in those cases the battery simply disparages and causes no damage.. Replaced 2 of those last month. Out of 3 (the 3rd passed load test with flying colors)..

So not As I said it's not a people socialist, it's a PERFECT socialist arrangement. Something not possible with people.

I've been doing this for a long time..

I had one battery (Car starting) fail within a week of purchase. .The identical replacement lasted many years.. Which goes to show "identical" is not always identical.

I've never had a bad battery in a parallel arrangement take down the others.

[ScottG]

Yep, Unbelievable.

[2oldman]

Only took 2 pages for a post about parallel batteries to get political.

[Alan_Hepburn]

wa8yxm wrote:
The batteries form a perfect commune.. The ultimate Socialist society.. (Works for batteries. I won't comment about where it does not work) in that when charging each takes what it needs and when working gives what it can.. they all remain at precisely the same state of charge relative to each other (If one is at say 90%. then all are) at all times.

...and like any socialist society, all the individuals will eventually balance out to the lowest common denominator. In other words: weak batteries will prematurely weaken good batteries...

[Desert_Captain]

I have to ask the OP... What brand/model of Class A only comes with one house battery and so small that running the furnace sounds problematic? :h

[2oldman]

ScottG wrote:
get every last coulomb of juice out of a battery ..

Ooh.. don't see that word very often! good one

[ScottG]

We had a floor sweeper at work that had wildly mis-matched batterys in it and it did fine.
If you're trying to get every last coulomb of juice out of a battery system then all the matching and extreme gymnastics is helpful. Otherwise, it's no big deal.

[Matt_Colie]

Plattpd,

If you parallel two 12V jars that are less than identical, your result will be way less than the sum of the capacity. How much less? That depends on many things, too many to go into here.

As a short term fix, it might be good, but carry a new box of baking soda. You may need it. I have seen very few battery explosions that did not involve jars in parallel.

For reference, for a time our coach had a single 4D house jar. It could run the heat all night if I did not start it until we went to bed. We now have a pair of GC2 (actually T105s now) and that will run the heat evening into the next morning, but they are done.

Matt

[rgatijnet1]

It is impossible to find two batteries that are identical. Just make sure that when you add the second battery that it is hooked up to provide 6 volts and not 12 volts and not 24 volts if you are paring two 12 volt batteries. Also make sure that the polarity is correct so that you have pos to pos and neg to neg. Unless the existing battery is already bad, the two batteries will soon balance out.

[wa8yxm]

2oldman wrote:
2 batteries work better together if they're the same brand and age, but I've seen people hook just about anything together.

I keep hearing this... IF you put a pair of GC-2 (six volt) in series you get 12 volts at around 220 amp hours (Give or take a bit depending on specific battery) you can safely use HALF this power.... And yes they should be "Twins" (Same age, type, make, size, and so on)

With 12 volt's in parallel. Most are MARINE/deep cycle or MARINE/rv which means you can only use about 1/4 the capacity. but they need not be identical. There is an advantage (Slight) or disadvantage depending... But I run a mix. currently one each Group 27 29 and 31 with a pair of GC-2 all in parallel. they work it out.

Lots of "Oh this will happen" or "That will happen" It does not. The batteries form a perfect commune.. The ultimate Socialist society.. (Works for batteries. I won't comment about where it does not work) in that when charging each takes what it needs and when working gives what it can.. they all remain at precisely the same state of charge relative to each other (If one is at say 90%. then all are) at all times.

Less one fails.

[valhalla360]

PastorCharlie wrote:
A second battery is good and four batteries are a double plus. It is best if they all be the same and same age but if not they will still work but may not be as proficient.

The problem if the batteries are in different condition is one will tend to hold a higher voltage resulting in the 2nd constantly drawing juice...this will wear out the better battery...hence why you don't want to add a nice new battery to supplement and old worn out battery...your nice new battery will quickly achieve the same condition as the old worn out battery.

Also, make sure you can keep them close by and use good quality connections to avoid losses in the connections.

[Johno02]

My classA has three. One for the engine and chassis, two in parallel for the coach. Only problem is the cost, on our last trip, one of the coach batteries blew up, so I replaced both at the same time. Very high capacity deep discharge monsters. OUCH!!!