Everstart Maxx Marine 29dc Usable Ah Test

[Tunafish]

This is alittle test i did on the Everstart Maxx Marine 29dc batteries. I have searched but didnt see any detailed Ah test, so this is mine. I know its not to the standard 10.5v but i drained it what i believe is a safe voltage of 12v.

There are two batteries in parallel, both manufactured 6/23 according to the sticker. Both have been on a float since purchased a month ago. Combined voltage at start was 12.8v.

I put a load from a few light bulbs that equaled 225w (from a meter not the bulbs themselves) the inverter is 1500w continuous with a efficiency of 85%. By my calculation that is 21.5 amps. I went down to 12v in 6.5 hours... This was resting voltage not load voltage, load at end was 11.6v but went up to 12v after no load and hours time.. This gave me a about a 140 Ah capacity between the two or 70Ah for one.. Not bad...

 

[sunshine_eggo]

It's often hard to find C5, C10 or non-C20 ratings.

A 300W load will be about 25A. This allows you to test the reserve capacity (RC) rating, which is pretty common on most batteries. When you run a higher current, you are permitted a lower cut-off voltage, but if you cut discharge at 10.5V, you're not squeezing everything out of the battery and leaving several Ah in the tank while still testing close to the standard.

I use RC testing regularly to determine the effectiveness of equalization cycles on FLA batteries.

 

[Tunafish]

Oh one thing to note is thes was done at 66f degrees. 300w would be a little more than 28A with my efficiency. My inverter got alittle warm during the 6 hours but not to the point the fan kicked in.. Still energy loss...

 

[Vigo]

That's a circuitous path to a capacity 'result' but i take it for what it is.. an overall good sign, all things considered.

I have a pretty high opinion of walmart 29dc batteries, to be honest. I think they're basically the best value lead acid to play with that's not a true deep cycle design. You might be able to do better here or there on deals that lack repeatability, but as far as being able to in any major city drive 15 minutes and spend money and come back with hundred of lbs of batteries to play with, they're the best CONSISTENTLY REPEATABLE deal i know of.

 

[sunshine_eggo]

That's a circuitous path to a capacity 'result' but i take it for what it is.. an overall good sign, all things considered.

I have a pretty high opinion of walmart 29dc batteries, to be honest. I think they're basically the best value lead acid to play with that's not a true deep cycle design. You might be able to do better here or there on deals that lack repeatability, but as far as being able to in any major city drive 15 minutes and spend money and come back with hundred of lbs of batteries to play with, they're the best CONSISTENTLY REPEATABLE deal i know of.

Agreed. I had one that was both abused (currents and states of charge) and well maintained (SG regularly checked and equalized as needed) that lasted much longer than the price suggested...

 

[Tunafish]

Different charts that i have seen marks 12v at different depth of charge. I have seen 50 to 30%. Interestly if i assume 40% and a linear discharge i would be right at the advertised 114 Ah rating. This is assuming alot but still interesting. Also note that the 114 Ah is a 100 hour rating.

 

[sunshine_eggo]

Different charts that i have seen marks 12v at different depth of charge. I have seen 50 to 30%. Interestly if i assume 40% and a linear discharge i would be right at the advertised 114 Ah rating. This is assuming alot but still interesting. Also note that the 114 Ah is a 100 hour rating.

You have to find charts that correlate to a given C rate as most charts are for resting voltage only, and discharge is not linear.

The RC testing I mentioned yields results that are accurate without many assumptions.

When you fail to discharge to a low cutoff, you may be missing out on a single cell that has notably lower (10-20%) capacity than the other five. You won't be able to see the impact until you discharge to cut-off voltages.

If the approximation works for you, awesome.

 

[Sabre36]

here in the Northeast the 29DC is made by East Penn and they are really a G-31 with 105Ah (East Penn PN DC31DT) In many parts of the country the 29DC is a crap JCI battery That’s barely worth the scrap lead price. If it says made in Mexico you got the JCI battery. If you got the East Penn version they are not too bad But far from a deep cycle product. A a proper capacity test on the EP made battery is done at 77F @ 5.25A until 10.5V.

 

[Tunafish]

By no means do i think my test was a true Ah test because a true Ah test risk damaging the battery which i wasnt interesting in doing. But its information i was looking for and couldnt find when researching the batteries so it might be useful to someone else.

Also i am not saying anything about the quality of said battery because first they are new so i cant give any info on the life span and second these wont have a ruff life. They will only be used for the few times a year we have power outages to power the TV and maybe a fan. So definitely not a battery i would of choosen if i was relying on it or cycling it often.

 

[Vigo]

Well, don't take our feedback as trying to downplay your test or your battery choice so heavily. You did something that was good enough for your purposes in both respects. I think based on what you said your expectations will actually be exceeded by these, as long as your charging strategy maintains them properly.

 

[sunshine_eggo]

By no means do i think my test was a true Ah test because a true Ah test risk damaging the battery which i wasnt interesting in doing.

This is a common misconception.

Pretty much all non-starter batteries are good for 250+ cycles to empty. The chances of a single full depth discharge test on a brand new fully charged battery isn't non-zero, but it's right next to zero.

 

[Tunafish]

I have a sc1282 charger hooked up.. It keeps the voltage at 12.8v on float. Seems low but i think and i havent seen it in action yet that it only charges when needed. I have seen range between 12.8 to 13.0v on float. I asked the company about why it floated so low and they said that was in specs. They describe the charger as "set-it-and-forget-it battery charger—simply hook it up and it will charge and maintain without further action." So we will see.

 

[sunshine_eggo]

13.2 (FLA) -13.8 (AGM) are typical float voltages when specific levels aren't mentioned. I typically go for 13.5 if I don't have a spec. 13.5V also works GREAT for LFP.

 

[Vigo]

So in my time researching this stuff over the past year and a half or so, ive realized that car batteries are a unique context. There’s really not THAT much difference between car batteries that are expected to last 3-5 yrs on average, and the large stationary deep cycle lead acid batteries which can occasionally last 20yrs. The main difference is the fastidiousness with which they are managed during their lifetime.

Car batteries get treated ‘good enough’ and achieve a ‘good enough’ lifespan because 3-5 years matches the expectations. But, car batteries almost never get truly optimal treatment (basically impossible in a car) and if they did, they may last well in excess of a decade.

Basically, 12.8v float may fall under some ideas of ‘good enough’ in the context of car batteries, but considering all its really competing with is to a DEAD battery that was stored long term with no maintenance charging, thats not a very high bar. If you want to maximize your battery life it pays to be picky.

If you want to be in full control you can do something i have done various times, get a cheap adjustable dc power supply, set it to a slightly higher voltage than what you’ll actually use, and then feed it through a cheap PWM solar charge controller which has adjustable setpoints for absorption and float voltages, as well as giving you an adjustable load port you can use to add some kind of alarm or failsafe feature to the system if you chose to.

 

[Substrate]

Oh yeah, the Everstart - always reminds me of the classic youtube vid from years back when the guy from Compass Marine was showing people how nasty an unregulated solar panel can be on them when used as a maintainer when *already* in a fully charged condition:

 

[CV6]

I have a sc1282 charger hooked up.. It keeps the voltage at 12.8v on float. Seems low but i think and i havent seen it in action yet that it only charges when needed. I have seen range between 12.8 to 13.0v on float. I asked the company about why it floated so low and they said that was in specs. They describe the charger as "set-it-and-forget-it battery charger—simply hook it up and it will charge and maintain without further action." So we will see.

Mr. Fish,

My knowledge base is from the World War II era but then the physics of lead acid battery electrical action does not change over time. I keep my standby inverter system's 29 DCs and 31s (FLAs) at 13.4 volts. I use an 800 milliamp Moto Power brand type battery tender for all four batteries in parallel. About every minute or so, there will be a brief power pulse to the batteries to keep them at this voltage. About once a year, I isolate the batteries and individually pull them down with 125 amp resistive load automotive battery charger two times for ten seconds each (with tester cooldown period in between). I then parallel them up, charge them with a smart 20 amp charger, which I then take off and hook up the 800 milliamp maintenance unit. So far, the voltage under load has been consistent. Years and years of experience would lead to my guess the batteries will be useful for 6-8 years. Should I have a prolonged standby period of use, where the battery voltage would be pulled down for an extended time, I could expect to use 10% of the battery life per occurrance that would occur after the batteries were three years old.

At one time, I was a jobber for US Battery Manufacturing out of San Diego, CA. I had a lot of experience with the inevitable battery failure for lead acid, starting, deep cycle, and forklift batteries. The most destructive process was to leave a fully discharged to near-fully discharged battery without recharge for an extended period of time. On the other hand, batteries under three years old were amazingly forgiving if they were recharged promptly.

Information is free and worth every penny.

A.T. Burke