My aging Northstar group 27

[Sternwake]

No 'problems' here, just some observations of its declining performance, hoping for some discussion by those with experience.

It is now nearly 38 months old, has at least 450 deep cycles, with probably 50 to 60 of those well below 50%, 320 or so in the 50% range, and the rest around the 70 to 75% range. Several thousand engine starts too, many of those when depleted in that 50% range. Still cranks the engine with gusto even cool and depleted.

I Have 200 watts of solar, 40 amp adjustable voltage power supply I sometimes parallel with a Schumacher for 65 total amps, and manually controllable alternator voltage regulator and a '120' amp alternator, thickly wired.

When New It was able to suck up 106 alternator amps and not instantly hit absorption voltage. A few months ago it was still able to accept 65 amps for at least 20 minutes before climbing to absorption voltage
Now it quickly climbs to near absorption voltage when well depleted, with around 50 amps.

What I find strange is that overnight loads, the voltage held for AH removed under X amount of load, is almost the same as it was when new.

I can pull 45 AH from this 90AH battery in ~6 hours at an average 8.0 amps, remove all but ~0.4 amps of load, and voltage quickly rebounds up above 12.2v, even in cooler overnight temperatures with the battery in the mid 50's(f).

If I was not able to instantly achieve absorption voltage with high amperage, and judged performance by voltage held under my normal overnight loads to ~50% DOD, I would think the battery was still performing 'like new'.

Other things I notice about the aging process, is that it takes much longer for amps to taper to 0.5% of capacity at absorption voltage. Also, when newer, I would reduce it to float voltage and hold it for 12+ more hours it would eventually accept somewhere under 0.05 amps, and If I goosed voltage back upto 14.7v, amps would again taper to somewhere under 0.05a quickly.

Now, this never seems to taper less than 0.2 amps no matter how long I leave it at absorption or float voltage when plugged into the grid. This 0.2 amp thing is a very new observation, it did not occur 3 weeks ago, it still would taper to somewhere under 0.05a at float or absorption voltage, eventually.

I wonder if Odyssey's 'reconditioning' procedure would be effective in returning my former observations of when the battery was younger, or if it would simply be abusive and hasten its delcine.

http://www.odysseybattery.com/docume..._Procedure.pdf

I can also perform Lifeline's 'conditioning' procedure of 15.5v for 8 hours after a normal 'full' charge.

I just wonder if it is worth trying or if these performance declines I have noticed are simply expected.

The battery has 'been ridden hard', but has rarely ever been 'put away wet'. I was hoping for at least 800 deep cycles, but with the extended times in absorption required for amps to taper to 0.5% of capacity, I think it will start being put away damp and thus decline more rapidly from here.

Anybody else notice these same declining attributes in their TPPL or other AGM batteries?

I've been extremely impressed with this battery so far, but wonder if I just hit one of the 'knees'

[john61ct]

I don't have the experience to advise on the tech issues, but philosophically I'd say consider your investment fully amortized, any lifetime from here on out is a free ride thanks to your carefull stewardship!

[Paul L]

Have you tried to get an equalization recipe from Northstar? I had a Northstar battery that failed. The distributor tried multiple equalizations on request by Northstar. It didn't help.

[Sternwake]

I once E-mailed Northstar with a technical question as to initial amperage requirements/recommendations, and got no response, and have not tried again.

While impressed with the battery performance, their documentation and customer service, at least regargin respondng to emails, has left me wanting.

Mainesail Indicated that 14.7 v absorption, over Northstar's 14.46v at 77f would help stave off sulfation in PSOC duty. I have in general been following Odyssey's recommendations as to Vabs(14.7v) and initial currents (40%) when depleted.
I have also not really gone more than 5 to 7 cycles without a full recharge. Perhaps once I went as many as 12 deep cycles in PSOC duty, and then absorption took so long for amps to taper to 0.4, I made it a point not to allow that again.

The two batteries make some many of the same claims, that Odyssey's more indepth literature makes adopting their recommendations easier to swallow.
One thing which gives me pause is Odyssey full charge resting voltage is claimed to be lower than Northstar's. Perhaps lower Specific gravity electrolyte??

My Northstar would maintain 13.06v for at least 3 weeks resting when it was newer. Now it never rests, so I do not know how true that resting full charged voltage claim is anymore.

I wonder how similar the two brands are. Lifeline does not advertise thin plates proudly like NS and ODY, so Perhaps the 15.5v for 8 hours would not be a wise recommendation for an attempt at restoring lost performance.

Odyssey's drain it to 10V under a significant load then recharge at 40% or higher until amps taper to near zero, lather rinse repeat, regimen would seem to be more along the lines of Northstar, butI wonder if this woud simply be abusive to a battery that is starting to show some signs of wanting mercy, not more abuse.

[Maine Sail]

Honestly at 450 cycles you are doing far better than 99.5% of the marine battery users out there. Consider that quite exemplary performance in the real world. The lab data these companies suggest is just that "lab data" and no matter how hard you try you'll never duplicate that performance in the real world before hitting 80% of as new Ah capacity. Both Northstar and Odyssey are excellent quality AGM batteries and both fended off sulfation better than even Lifeline did, in the PSOC testing, even after the Lifeline was equalized.

What you are seeing are the effects of sulfation and permanent capacity loss... Once that sulfate has hardened (like dried dead skin) there is no turning it back to active material (live skin) no matter how much hand cream you apply.. All an EQ or reforming process can do now is re-convert the sulfate that may still be quasi hard and perhaps drop some of the "dead skin" from the surface of the plates. In my experience a 1-3% increase in capacity is about all that can generally be expected from an EQ or reforming process unless caught very early on, which is extremely hard to do..

Quickly rising to absorption voltage during bulk and never seeing tail current drop down to previous levels are good indicators that the battery is in a declined or seriously declining state.

Years ago Sandia National Labs did a study on hybrid PV installations with deep cycle flooded batteries. They discovered that higher voltages, upwards of 15.3V, resulted in less sulfation. They also learned that the absorption times we are used to seeing, in off-grid type applications, are far too short even at 15.3V. This is the data that drove Trojan and others to move from 14.4V to 14.8V...

"Results show that the L-1 6 battery can quickly lose as much as 48% of its initial available capacity if the regulation voltage is too low, the time at regulation is too short, and the time between the finish-charges is too long."

Obviously you can't really go to 15.3V with VRLA batteries so your 14.7V is right on target for TPPL AGM's, for your application. That data also suggested that an absolute maximum duration between "finish charging" (100% SOC) should be no more than a week with 3-5 days max as much more preferable.

You're doing the right things and your battery performance is excellent because if it. Expecting lab like cycling results in the real world is the only fault I can see.....

[Sternwake]

Thanks Mainesail.

Looks like I need to come to terms with a battery mid life crisis.

One thing that triggered it is I recently had a chance to plug in for 10 days and floated the battery at 13.7 to 13.9ish due to cool battery temperature, and when cycling began after this is when I noticed the tail current not dropping off to near zero when i would plug back in, as I was used to seeing.

This Also Coincided with a drop in the current required to achieve absorption voltage with a depleted battery. A month earlier it was still taking ~65 amps for at least 20 minutes before climbing to 14.7v, after the 10 day float this was down by nearly 1/3 and 40 amps would have it right near 14.5v very quickly, to my disappointment, but this has gone back upwards to the low to mid 50's since regular deep cycling began again

The 10 days of floating 'seems' to have pissed off the battery.

The extended absorption times now required will have the battery degrading faster too as I simply cannot get there early enough and hold them long enough, but the longer days should help.

What I do find surprising is that if I were to judge battery performance only by voltage held under my regular overnight loads, as long is it is not 5+ cycles of PSOC, I could not tell the battery is aging. Even in colder temperatures I light up my monitor see the Ah removed, the load, and the voltage is 0.1v higher than I would expect to see, and 0.2v or more than my previous flooded battery ( that had 40more ah capacity) would have been.

It is only the tail current and the lesser amperages required to reach Vabs that indicate the battery is aging. My voltmeter during engine cranking has yet to indicate a drop below 10.6v, even when depleted 55 of the 90AH and a 55f degree battery.

[Maine Sail]

The only true way to know where you stand is a controlled 20 hour capacity test done at 75-80F using Ah capacity divided by 20 as the fixed load...

90Ah / 20 = 4.5A

Take the battery from full to 10.5V at 4.5A and time how long it took to get there. If it ran for 10 hours at 4.5A then the battery is at 50% of as new rated capacity.. Once you hit 10.5V recharge the battery to 100%..

[Sternwake]

I can't really perform an accurate 20 hour test, as I can't maintain a steady 4.5 amps load for the entire time, and contolling battery temperature is also not something I can easily achieve without a lot of effort no doubt better spent elsewhere.

Also, the battery is still in use so I would need/prefer to swap in another battery which is not a pleasant task.

I know the 50% discharge voltage is not accurate as to health/ capacity.

This is my first AGM, but I am loving its abilities so far.

Thinking ahead to its replacement makes me want to make it last until more data comes in on the Firefly, and part of me wants to set up a Lifepo4 bank to learn them.

Also The lifeline gpl-31XT or perhaps even the gpl-30HT are on my radar. Lose some CCA with them compared to the Northstar, but not sure that really matters in my usage.

When new the Northstar's ability to crank my starter motor violently fast was certainly a bit mind blowing, but the novelty faded, at least until I was 65Ah from full and could barely detect any slower cranking from it.

Thanks for chiming in MS, and all your online contributions, they really helped me learn, and certainly are partly responsible for the good to excellent life I am now getting from my lead acid batteries

[Paul L]

Originally Posted by Maine Sail

Honestly at 450 cycles you are doing far better than 99.5% of the marine battery users out there...

So are you saying that a bank in typical full-time cruising boat should only last a year and half?? Doesn't make sense. Or are you saying just the beginning of the degradation begins then?

[john61ct]

I believe the formal specs define end of life to be when AH capacity is reduced to 80% of their rating.

That's why you can get telecom banks very cheap that actually have lots of real-life left in them.

But not for most boating purposes, as their accelerated decline down to actual death could begin anytime. . .

[john61ct]

Originally Posted by Maine Sail

The only true way to know where you stand is a controlled 20 hour capacity test

Doesn't SmartGauge come pretty close accuracy for SoH, at least in the early stages of decline?

[smac999]

Soc has nothing to do with capacity. You can still have a fully charged battery that has lost half its Capicity

[smac999]

Why are you draining a single group 27 to 50% and under. Just think if you had boughten 2 of them, kept them at 75% (same daily usage). They'd probably last 3 times longer....

[smac999]

Originally Posted by Paul L

So are you saying that a bank in typical full-time cruising boat should only last a year and half?? Doesn't make sense. Or are you saying just the beginning of the degradation begins then?

I doubt you are cycling from 100 to 50 to 100 daily. Maybe weekly. Then you'd have many years to hit 400 cycles

If you are your bank is too small

[Paul L]

Originally Posted by smac999

I doubt you are cycling from 100 to 50 to 100 daily. Maybe weekly. Then you'd have many years to hit 400 cycles

If you are your bank is too small

So what's your definition of a cycle? 100 to 50 is one cycle. Does that mean 100 to 75 is half a cycle?