Battery duration

[Ela1948]

Would like some thoughts on what should be a normal battery life expectations. I have a bank of almost 3 years old US batteries. I'm not a full timer. We use the rig approximately 4 months a year. Most of that is dry camping. When not in use, shore power is constant. This past year was the first time that I needed to add appreciable water to the batteries during routine maintenance. Daily draw down is perhaps 70%. Any thoughts on expected longevity??

[jcoyle]

A couple things we would need to know first. What type of batteries? What discharge rates? Even the temperatures the batteries are used in could make a difference. I would say though that if you were draining them to 70% discharge and they are regular deep cycles then you have probably done well to get 3 years. Many of the deep cycles are not recommended to be discharged past 50%.

[Seann45]

As batteries age they use more water. Did you make sure to use distilled water when refilling them? Anything else will shorten the life of the battery. I get 7+ years from my batteries but never take them below 50% (12.0 volts). As you can see from my stats below I boondock over 200 days a year.

[Ela1948]

I gave some distorted info. The batteries are normally drawn down to the 70% range remaining in the batteries. They are true deep cycle 12 volt batteries. Not marine deep cycle batteries. I always use distilled water for battery refill. I was just trying to get a handle on expected battery life from some that have been there before. Thank you for you input!!

[Mustang65]

Clarification... You indicate that you have 70% of battery power remaining so if that is true, then you have a DOD of 30%.... correct?

Do you equalize your batteries at least a couple times a year?

Don

My Registry

RVing with SOLAR

[Ela1948]

That is correct! As far as the equalization, I have attempted that on 4 different occasions since the batteries were new. I think that I have finally found a workable blue print that makes sense. I have hooked separate battery chargers up to the two separate banks of batteries. Which put a charge of 15.4 volts on the batteries for 1.5 hours. That info. came from US battery. Your thoughts, Mustang??

[Mustang65]

Originally Posted by Ela1948

I think that I have finally found a workable blue print that makes sense. I have hooked separate battery chargers up to the two separate banks of batteries. Which put a charge of 15.4 volts on the batteries for 1.5 hours. That info. came from US battery. Your thoughts, Mustang??

That is exactly what the Morningstar MPPT SOLAR charge controller puts out and is usually about 1.5 hours, battery temperature permitting. I manually start the Equalization about 2 or 3x a year. Recommended to start Equalization when batteries are fully charged. I will share a study done by an independent testing firm for USBattery comparing their batteries to another major brand. I have not researched this finding.

When I purchased the Trojan T145 batteries, I wanted the USBattery equivalent battery. I was leaving in 3 days and the dealer was unable to get the model/Ah I wanted in that time frame, so I went with Trojan which they had in stock.

DON

My Registry

RVing with SOLAR

[Ela1948]

Interesting!!
Do you agree with Seann45? Is 7+ years a reasonable expectation??

[Mustang65]

Originally Posted by Ela1948

Interesting!!
Do you agree with Seann45? Is 7+ years a reasonable expectation??

WOW, that is tough question to answer. Sooooo many variables.

I guess I need to ask the important question.... What you expect those batteries to produce in 7+ years? More so, what will you be able to survive with?

Let's say you use 120Ah, 12DC batteries and let's use a 10% reduction in Ah each year. This will give you about 60Ah (each battery) after 7 years. Each year your 30% DOD will need to increase to keep up with the same load and time needed, due to age. You will notice each year that your dry-camping will discharge your batteries sooner and sooner, but they will still be charging, holding a charge and voltage will look great, just that they get discharged earlier and earlier in your outings.

EXAMPLE: SOLAR charges my batteries everyday by 2PM, but I notice that in the mornings there are more amps going into the batteries now, then compared to when they were new 5+ years ago. Usage is the same. I notice that the battery voltage is lower in the mornings now, compared to when they were new by .2VDC.

Batteries are like humans, we both age and the wear and tear of everyday life takes its toll on our systems. Like humans, no two batteries will be the same. We can go through life being a vegetarian, watching everything we eat, take vitamins, exercise daily and still get terminated before the average age for our gender or before the person that never ate a healthy thing in their life.

If you go by cycle life of your batteries (30%), you should easily get 2000 cycles out of them. Since you do not put any stress on them for 2/3 of a year, your 2000 cycles should bring you to 7+ years, Seann managed 7+ years and he used his batteries 2/3 of the year.

As in humans, your batteries only need one bad day and those numbers can be trashed.

My thoughts are if you continue your maintenance, and they don't have a bad day, you should easily make it... but the output will be as mentioned above. Can you live with those numbers? That will determine the useful life of your batteries.

Oh, battery temperature also plays an important part in a batteries life.

Hope this helped

Don

My Registry

RVing with SOLAR

[Ela1948]

I understand exactly what you are saying. If I can live with a little less battery as time passes, I can get longevity, barring a premature battery failure. I understand that not all batteries will give identical life, even under the same conditions. Thank you for your time and thoughts!!