Battery recommendations for 1500W inverter

Specifications need to be READ people.

VOLTAGE
TIME

Affects ampere hours based percentage of discharge

Discharge a battery to 50% capacity using Two 2 Two 2 hours permitted discharge time

IS CALLED THE TWO HOUR RATE

HELLO PEUKERT

Compare this rate to the 2 hour rate, and it's like bragging "I own a car that tops out at 700 miles per six hours. Wuuuweee! 700 miles!

Compare that scale to a Concorde battery. This is good practice for people who wish to immerse themselves in numbers. Similar to an absurd advertisement 3,000 cranking amps at 60c with 1.350 acid.

Study the numbers, then run them through the Peukert machine.

Cycle Lifespan ratings have absolutely ZERO to do with ampere hour ratings at 20 hours. Remember the Battery Council International is owned managed and financed 100% by battery manufacturers.

Like the American Petroleum Institute.

Advertised cycle life graphs apply to telecom like conditions and not to long term discharges. ROUGHLY speaking the cycle life chart at 50% discharge would equal 37% discharged at the 20 hour rate.

Custom Tailored Batteries For My Lifespan Requirement

Zinc Carbon

(sigh)

theoldwizard1 wrote:

time2roll wrote:
My 4x GC2 from Costco have done just fine driving the microwave.

There is your answer.

I don't know man. A lot of benefits to AGM. Even Lithium if you plan to live 10 years.

theoldwizard1 wrote:
A couple of graphs from the Fullriver Battery web site. These were from their page on their Group 31 AGM battery, but the graphs are pretty close for ANY lead acid battery.

Discharging to less than 20% depth-of-discharge cuts the number of charge/discharge cycle by about 50%



This chart surprised me ! 80% state-of-charge is about 12.5V !

well, 75% DOD still gives over 500 cycles. way more than most any RV user will encounter before the batteries die from other causes.

BTW the cycle life is pretty close to what Trojan shows for t125 GC-2.

theoldwizard1 wrote:
This chart surprised me ! 80% state-of-charge is about 12.5V !

Why?

Your answer may be related to an observation of mine:

My twin Group 31 Fullriver AGM RV batteries DO NOT show fully charged at-rest terminal voltages in the low 13.XX's range - like my Group 31 Yellow Top AGM Optima battery does. When fully charged, my Fullriver batteries always read only around ~12.8 volts after their post-recharge surface charge has dissipated.

At first I was concerned about this, but I finally accepted that probably not all AGM batteries have the same electro-chemical characteristics.

As I've mentioned many times, I went with Fullriver AGM batteries because of their advertised float voltage range being an exact match to my RV's stock Parallax converter's output voltage range. At the time, the closest Lifeline equivalent batteries had a required float voltage range around 13.2 volts and the Lifeline rep stated that long exposure to stock converter output voltages would over time degrade Lifeline AGM batteries.

As I mentioned earlier, the Fullriver batteries were priced only slightly less than the Lifeline batteries, so I figured that anything manufactured in China but priced only a little less than the best that were manufactured in America ... must be pretty good. Subsequent research and experience has so far confirmed that about Fullriver AGM batteries.

A couple of graphs from the Fullriver Battery web site. These were from their page on their Group 31 AGM battery, but the graphs are pretty close for ANY lead acid battery.

Discharging to less than 20% depth-of-discharge cuts the number of charge/discharge cycle by about 50%



This chart surprised me ! 80% state-of-charge is about 12.5V !

pianotuna wrote:
The alternative is to have them in a heated space--but that means they would get to nearly -40 where I live. I'm certain that is not recommended.

Surely you don't mean your heated space is -40!

syperk wrote:
Thanks again for all the details - lots of good stuff here. I did indeed install the GC-2's after reading that they were "best" for off the grid camping (we pretty much never stay at places with electrical hookups), but the relatively high internal resistance is an unexpected problem.

Hunting through the archives I did actually find a post from full_mosey saying that they successfully ran a 1000W inverter off a single 12V AGM battery so it seems like a pair of those should do the trick (confirmed by som eother posts above). It's a bit of a pricey upgrade for the ability to reheat my coffee in the microwave (or run my Nespresso machine once a day), but having sealed batteries would also be nice. We'll see!

And I know that a generator would solve all my issues, but I'm a bit philosophically opposed to getting one - that's why I have the solar panels on the roof!

Part of going AGM is to have an ammeter so you can tell when they are fully recharged. I use my Trimetric. AGMology is a whole other topic, but you have to follow their procedures. It is not like Flooded batts and an hydrometer.

MEXICOWANDERER wrote:
.105" thick plates just beats the snot out of .060" plate for overall life. So does the ultrapremium grade of separator and especially envelope sealing that Concorde brags about. 50 amps draw per battery is no way connected to cold cranking performance. If the price per battery is within 50 dollars my vote goes solidly with the Lifeline.

Well ... maybe not too much snot:

1. Who/what has "only" .060" thick plates?

2. And who besides myself and my Fullrivers need advertised 13.5 to 13.8 volt float voltages in an expensive AGM because they think their 10 YO Parallax fixed voltage converter meets battery float requirements perfectly month after month?

Just for drill, a pair of 800 cca AGM batteries would allow you to use your microwave every day to heat coffee and still allow reasonable hotel draw (no heater blower!) for several days autonomously.

Jeez I wasn't aware that the cost of Full River was anywhere near the Concorde Lifeline. So I have to retract my earlier recommendation of selecting Chinese Full River brand.

.105" thick plates just beats the snot out of .060" plate for overall life. So does the ultrapremium grade of separator and especially envelope sealing that Concorde brags about. 50 amps draw per battery is no way connected to cold cranking performance. If the price per battery is within 50 dollars my vote goes solidly with the Lifeline.

REMEMBER Peukert is not linear! When a calculated draw is only 10% of CCA, judging the suitability of a battery by sheer CCA is being ignorant (politely stated).

If there is substantial money savings involved then I would tend to favor the lower cost battery, but in a heads-up comparison something about choosing a Chinese battery grates on me. Like selecting a 2-row core radiator over a thicker 4 row core and saving $20.00