Need More Battery power

If I get two 12 v batteries wired in parallel will I have more lasting power than two six volt batteries in series to produce 12 v? This is for my motorhome. I used the deep cycle battery from my tractor and it didn't seam to last very long, before it was low. My motorhome only has one battery now. I want to increase the lasting 12 v power. Thanks, Stan

two twelve volts should last longer,if they are equal batteries. but also remember youll have to charge them twice as long. dont use batteries of different sizes,one will drain down faster and pull the other down. i dont know what type of lights you have but the old ones would really pull a battery down fast.sometimes its cheaper to install new lights than buy batteries.my old motor home was a 73 model and with three batteries in it you would have to charge them daily. i traded it off and bought a small truck camper,and i think you could leave the led lights in it on all the time and it wouldnt drain one.one thing you may check,take a voltmeter and see if battery is actually charging when your rv is plugged in.I had that problem once also.

If two batteries are wired in Paralell:

a) Amps availability (like say CCA) IS
ADDITIVE
(i.e. if each had say 500 CCA you now
have 1000 CCA Capacity)

b) Energy Storage (Amp hrs) IS ADDITIVE
(i.e. if each battery were 125 Amp hrs
you now can store 250 Amp hrs of energy

c) Voltage obviously stays the same


HOWEVER if two are wired in series

Voltage is ADDITIVE but the amp capacity does not, i.e. if each had 500 CCA, two in series still only has 500 CCA. The sum of avaialble current isnt greater then the weakest battery can deliver.

Its BEST if the two are identical in size, brand, design, type and age etc. When two are together the weaker can detract/feed from/cannibalize from the stronger battery.

For house batteries in an RV its more ENERGY STORAGE CAPACITY that youre lookin to increase (to run fans n lights n vents n furnaces etc) so 12 volt batteries in paralell keep adding energy storage as batteries are added........

My current RV (house batteries) has three 12 volt, 125 amp hour, Group 31, RV/Marine (Quasi Deep Cycle) batteries in paralell for 375 Amp Hrs

My next RV will use four 6 volt deep cycle Golf Cart (like Trojans or other similar brands) in series paralell for 440 Amp Hrs Energy Storage and I will be using a Xantrex 3 stage smart charger instead of the cheapie RV Inverter for better battery life (more life cycles) hopefully

Its my opinion if there will be a lot of deep cycle draw down useage, i.e. many life cycles (typical for an RV when dry camping or running furnace all night) youre better off with true deep cycle golf cart type of batteries versus so called RV/Marine what Id consider quasi deep cycle batteries. You dont need short term high current draw capacity like for an engine starter motor,,,,,,You need longer term capacity lower current useage like when an RV runs lights n fans n furnaces THATS WHY I THINK A DEEP CYCLE GOLF CART TYPE OF BATTERY IS BEST IN THAT APPLICATION

Thats my story n Ima stickin to it

John T Long time RV owner who has done a bunch of long term dry camping

Guess it depends on the capacity of the batteries. In a 6 volt setup, wirted in series, the weakest (smallest) battery is the limiting factor. In a 12 v parallel setup, you should buy two batteries new, mate them for life. Otherwise, the weaker will draw down the stronger. Otherwise, you need to isolate them with an isolater, or a mechanical switch. (Which wouldn't be a bad idea, anyway.)

Like Jonn T sez....

(quoted from post at 15:46:52 09/26/12) If I get two 12 v batteries wired in parallel will I have more lasting power than two six volt batteries in series to produce 12 v? This is for my motorhome. I used the deep cycle battery from my tractor and it didn't seam to last very long, before it was low. My motorhome only has one battery now. I want to increase the lasting 12 v power. Thanks, Stan

Click to expand...

lasting power" in general means ampere-hours and that generally means physically larger battery. Two 6v, 80A-H batteries in series would give you a theoretical 12v at 10amps for 8 hours. In reality, the number of 'A-H' will be fewer at say a 20 amp drain than at 1 amp drain, i.e., all loads will not yield same A-h availability. A single 12v, 80A-H battery should give same performance. Two 12v, 40A-H batteries in parallel should also give same performance. Series or parallel always yield some compromise, since you won't have truly "matched" batteries. One will always go dead before the other. This can lead to applying a reverse voltage to one of the series batteries or one 12v in the parallel scheme discharging into the other. One BIG battery is the better technical option.

I would avoid 6 Volt batteries when possible because I don't think they build them near as good as some of the 12 volt options you can get.
Except maybe an optima ? but then they are really expensive.
Most 6 V always had short life and most of them wanted to seep acid from the caps.

I sure AGREE with you for auto type of batteries, but if were talkin true deep cycle quality golf cart batteries (like he would want for an RV), then a 6 volt can be pretty darn good quality AND YES EXPENSIVE GRRRRRRRRRRR LOL

John T

Add a wind generator to the RV, so when driving they charge the batteries.

Many batteries are marketed as "deep cycle" and are not. If you want storage batteries for an RV - to run all the stuff inside and NOT for engine cranking - a couple of Trojan or Deka 6 volt flooded lead-acid batteries (FLA) will outlast any conventional automotive type 12 volt battery or a Walmart 12 volt marketed as "deep cycle."

By the way - I've got two RVs. Both are on their 8th year with a pair of Deka GC-2s. That's pretty good. Trojan T-105s and Deka-East Penn GC-2 are pretty much the same in power and longevity. Nice thing about the Dekas though is you can buy through NAPS and therefore no shipping charges.

I bought my Deka's 8 years ago for $45 each. Now they are $150 each.

One thing I forgot to mention. True deep cycle batteries will not charge properly off the alternator in your motorhome. It's okay to let it charge them on trips. But when at home and in storage - you should have a battery maintainer on them made for deep cycle batteries. They require a higher charging voltage than standard cranking batteries.

A good old-fashioned flooded lead acid "scrubber" or "golf cart" 6 volt battey will greatly outlast and outwork a conventional 12 volt starting battery and any Optima AGM. When you figure dollar per power you get over the life of the battery - the Trojans and Deka 6 volt deep-cycle batteries are still by far - the best buy.

I don't have an RV and am unaware of the peak loads. If you wire batteries in series, the internal resistance of each battery adds together to give you 2x the resistance in series with your load which inhibits current flow......current flow when accompanied by the available voltage drop means WATTS....work....which is why you have them in the first place and it is totally lost in heat in the batteries (conservation of energy).

However, if you hook them up in parallel, all other things excepted, when you need some amps, the resistance of each battery, whatever it is, more or less than 6v, don't know and don't care, but these resistances are now in parallel and the equivalent resistance to current flow is halved, not doubled so rather than puking your available wattage on internal resistance of the batteries, you have 1/4 the series resistance power loss allowing more wattage to send to your load......load being whatever it is that you have the batteries to operate.

I had this JD 4230D Cab that had a 6 volt on each side of the cab, wired in series, and grounded on the opposite side of the tractor from the starter. I ripped all that crap out and put in 2ea 31 series 12v batteries wired in parallel with 2/0 cables. On the battery adjacent to the starter I hooked the + on a 2' cable to the solenoid and the - on a 1' cable to the starter mounting bolt making all connections nice and shiny and tight.

The resultant starting torque was so extreme that I blew out 2 tires on the rt side of the tractor HA!.......naw not really, but it solved my cold starting requirement to have a starting aid.

My 2c,
Mark

i agree with if your building up a battery bank type deal the real batteries built for this usage is the best option. but your going to be looking at some real money these days also. Another thing to watch is the weight factor,your talking about a lot of weight so plan accordingly. its also very helpful to know the actual charging rate of your inverter or alternator also. sometimes you have to charge far longer than you would think to bring batteries back to full charge. especialy on the older inverters that put out only a few amps. a rule of thumb is to put in what you take out. if your drawing say 10 amps for four hours,and your charging at 5 amps you would want to recharge for eight hours basically. thats not a real number of course but it works most of the time to keep batteries up. I think a lot of times folks just dont realize they need to recharge as long to keep bateries at peak charge. a solar maintainer can be a real help.

Small portable gas generators are under $100.oo and run so quiet, you won't even know it is running..
I would go that route..

NAPA price went down recently which is kind of surprising. The Deka equivalent to the Trojan T-105 is the Deka GC-2 and NAPA # 8143. $130 which isn't bad in today's world.

The Deka GC-2s in my cabin just turned 9 years old which tells me they're every bit as good as the Trojans.

Joking or serious?

Joke directed to John T, he previously made a comment about wind generators. You were moose hunting.