AGM battery test results and what should I do next?

[Naio]

I have 5 AGM batteries: 1 new for the chassis, and 5 used Fiamms for the house. All have their quirks. I want to report back on how I've tested them this week, and hear you folks' thoughts on what I should do next.

Chassis: I bought the newest I could get locally, 6 months old. Couldn't get it above 12.85 volts with the meanwell. I tried running it down to 12.00 and recharging.

This seemed to help -- it got up to 12.91 the first time I did it and 12.93 the second time. But after sitting for a week, with the negative post disconnected, it is back to its old 12.85v.

Should I exchange this battery? If so, any tips on choosing a better one for the next try? I can ask the shop if they can order me a fresher one...

House: These are 4 Fiamm telecom batteries I bought used a couple years ago, and have been sitting ever since with occasional top offs, due to health and life problems. I want to use them! I tested them using a 40 amp load (a space heater and MSW inverter).

Problem is, I didn't realize that the smart charger I was using to top them off was sometimes quitting early. (It's been a great charger for me for many years, but either it has developed a problem or it just doesn't get along with the Fiamms. It has a lifetime warranty, so I'm thinking I will call tech support when I get around to it.)

Anyway, the upshot is that when I started the test the batteries were not at their true full voltage :(.

Battery A:
12.67 starting voltage.
I tested this battery first, and the terminals got so warm it scared me off. After 4 minutes it was 108 degrees, and 12.06 volts, so I chickened out and switched off the load. Temp went up to 111 degrees. Voltage was 12.51 about a minute after shutting off the load and 12.54v 20 minutes later (77 degrees).

I put the meanwell on it at 14.55v to 2.8 amps. After charging, and resting for 2 hours it was at 13.10 volts, the next day 13.00, and the following day 12.96v.

What do you all think about the temperature under load for this battery?

Battery B:
12.54 starting voltage.
11.87 under load at 10 minutes, 108 degrees (at the end, but it stayed 95 to 98 through most of the test, so I didn't get scared). 30 seconds after removing load 12.39 volts, 12.49 after 20 minutes.

After the test, I kept messing with the meanwell trying to get this battery to charge to a higher voltage. The van is in storage and my access is limited, so I was doing it on a timer a few hours per day.

Yesterday it was at 12.74v, and when I put the meanwell back on it at 14.37v, it was taking about 1amp. I put the meanwell on the timer for a few hours, but the timer failed and the meanwell was on for about 22 hours. When I got it today, it was reading about 0.4 amps. I will see tomorrow what the voltage is. I hope I haven't hurt this battery.

Does its low voltage under load mean that it was not good to start with? Would it be a problem if paired with another battery?

Battery C:
12.75v start.
12.12v and 99 degrees under load. 30 seconds after taking load off, 12.55v, and 12.65 after 20 minutes.

Meanwell on overnight at 14.37. Still taking 2.83 amps in the morning, but I took the charger off. Subsequent days, resting voltage 13.23 and 13.14 so I think is full. A healthy battery?

Battery 😧
12.66 starting voltage.
After 10 minutes load, 101 degrees, 11.99v under load. After 30 seconds no load, 12.47 volts. I forgot to check the 20-minute voltage.

Meanwell at 14.37v to 0.4 amps, resting voltage now 12.94v.

---

So, what do you all think of the performance of these batteries? If they are all good, I will put them into banks of two. Suggestions welcome for which pairs will work best together.

Or, are there other tests that I ought to run, now that the batteries are fully charged? (I realize more data is always better, but please keep in mind that I will have very limited days to work on the van before snowbirding in it this fall, and a day that I spend on batteries is a day that I don't spend on something else.)

Speaking of, I do have more data. If you folks have questions, it's possibly might have answers. I took measurements about halfway through each test, and have notes on my charging, which took place over quite a few days in little increments.

--

Thank you all SO MUCH for reading this mega-post, and for any ideas you have. I feel pretty clueless compared to some of you.

[Naio]

2oldman wrote:

Naio wrote:
(PS Are you camping near Ely? Beautiful country!)

I am. It's gorgeous here, and much cooler than Pahrump! Gawd.. I can't take 100+ temps anymore and neither can my coach. Since being in that heat, my slider windows are all difficult to move.

Post a trip report! I am working at my S&B for the summer, and need my vicarious camping :B

[MEXICOWANDERER]

You might want to refresh the status of those AGM batteries. Start with a 14.7 volt recharge on those Lifelines. Means from a discharged state not from a 14.40 otherwise full charge. Surprise....(?)

[BFL13]

Yes, different brands of AGMs have different voltages per SOC. Mine (12v) are 13.0 full and 12.4 half full, but Trojan AGM T-105s (6v) are lower than that. Lifelines also have a lower charging voltage spec--14.4, while mine are in the high 14s.

I got confused by the statement that while being charged the voltage would not go above 13.

[2oldman]

Naio wrote:
(PS Are you camping near Ely? Beautiful country!)

I am. It's gorgeous here, and much cooler than Pahrump! Gawd.. I can't take 100+ temps anymore and neither can my coach. Since being in that heat, my slider windows are all difficult to move.

[Naio]

2oldman wrote:

Naio wrote:
An AGM should be above 13 when fully charged..

Not my Lifelines. I have 8 of them and not one has ever held that kind of charge. 12.7 is more like it.

Oh, that is interesting! I didn't realize different kinds were different. The ones I have had have all been around 13.04-13.10. (PS Are you camping near Ely? Beautiful country!)

[2oldman]

Naio wrote:
An AGM should be above 13 when fully charged..

Not my Lifelines. I have 8 of them and not one has ever held that kind of charge. 12.7 is more like it.

[Naio]

Thank you all, so much!

Mex: Yes, I spent $200 on that chassis battery. At that price, I expect perfection! (I would have bought cheaper, but my memory problems + the fact that I am used to AGM caused me to kill several cheap wet batteries. I can't keep track of the differences.)

Is your first post ("Discharge reluctant battery to 12.2 volts") referring to the house battery that overheated? You said that was a fail, but then you go on with instructions for discharging and recharging. So I'm not sure if you're talking about the same battery there, or if you are talking about the chassis. Clarification, please?

BFL13: The chassis voltage readings are at rest. Not sure of your question, but no, it wasn't ever above 13 after resting from the charging. That was with a meanwell at 14.55v.

And no, I didn't do the 40 amp load test on the chassis battery. The first time, I started the engine four times, and then hooked up 12 amps (two incandescent lights). The second time, I used the lights for the whole thing. That was before I busted my space heaters out of storage for test loads 🙂

Good point about loose terminals being a possible reason for the heat on battery A. The terminals were tight, but I forgot to mention that the cable ends were a bit corroded. I sandpapered them, but maybe not enough. And maybe the fact that it was the first battery I used them on is significant. I could retry.

Sadly, I did not think to check the temperature of battery B when it was being excessively charged. I can't really tell you if it got hot. I'm kicking myself now, that I didn't do that.

2oldman: An AGM should be above 13 when fully charged, and should hold its charge for months when not connected to anything. I was maaaaybe gonna settle for the 12.93, but not if it can't hold steady at that voltage.

[MEXICOWANDERER]

Keep in mind these batteries are warrantied. I don't know of any AGM that after being properly charged can been seen drooping into the 1.280's after a few days.

Given a full life cycle that battery is going to fail quicker than those units that maintained a tenth or two higher resting voltage.

When I went through pallets of Golf car T-105's I culled those 6.35 volts. They were same day products picked up direct in Santa Fe Springs. The culls went to single unit off-the-street T-105 purchasers. The rest were golf course cherry-picks. All of my Lifelines arrived showing voltage at the 13.00 mark. All the winners and all the losers get a top charge. Jeez I got better things to do then suffer premature battery problems.

Even that snotrag Gohner calcium/calcium flooded battery in the toad passed the 13.00 test and whadd'ya know here it is at the 5-year point. But it is under storm trooper supervision never to see the slightest cycling.

[2oldman]

Naio wrote:
it got up to 12.91 the first time I did it and 12.93 the second time. But after sitting for a week, with the negative post disconnected, it is back to its old 12.85v. .

What's wrong with 12.85?

[BFL13]

Naio wrote:
I have 5 AGM batteries: 1 new for the chassis, and 5 used Fiamms for the house. All have their quirks. I want to report back on how I've tested them this week, and hear you folks' thoughts on what I should do next.

Chassis: I bought the newest I could get locally, 6 months old. Couldn't get it above 12.85 volts with the meanwell. I tried running it down to 12.00 and recharging.

This seemed to help -- it got up to 12.91 the first time I did it and 12.93 the second time. But after sitting for a week, with the negative post disconnected, it is back to its old 12.85v.

Should I exchange this battery? If so, any tips on choosing a better one for the next try? I can ask the shop if they can order me a fresher one...

House: These are 4 Fiamm telecom batteries I bought used a couple years ago, and have been sitting ever since with occasional top offs, due to health and life problems. I want to use them! I tested them using a 40 amp load (a space heater and MSW inverter).

Problem is, I didn't realize that the smart charger I was using to top them off was sometimes quitting early. (It's been a great charger for me for many years, but either it has developed a problem or it just doesn't get along with the Fiamms. It has a lifetime warranty, so I'm thinking I will call tech support when I get around to it.)

Anyway, the upshot is that when I started the test the batteries were not at their true full voltage :(.

Battery A:
12.67 starting voltage.
I tested this battery first, and the terminals got so warm it scared me off. After 4 minutes it was 108 degrees, and 12.06 volts, so I chickened out and switched off the load. Temp went up to 111 degrees. Voltage was 12.51 about a minute after shutting off the load and 12.54v 20 minutes later (77 degrees).

I put the meanwell on it at 14.55v to 2.8 amps. After charging, and resting for 2 hours it was at 13.10 volts, the next day 13.00, and the following day 12.96v.

What do you all think about the temperature under load for this battery?

Battery B:
12.54 starting voltage.
11.87 under load at 10 minutes, 108 degrees (at the end, but it stayed 95 to 98 through most of the test, so I didn't get scared). 30 seconds after removing load 12.39 volts, 12.49 after 20 minutes.

After the test, I kept messing with the meanwell trying to get this battery to charge to a higher voltage. The van is in storage and my access is limited, so I was doing it on a timer a few hours per day.

Yesterday it was at 12.74v, and when I put the meanwell back on it at 14.37v, it was taking about 1amp. I put the meanwell on the timer for a few hours, but the timer failed and the meanwell was on for about 22 hours. When I got it today, it was reading about 0.4 amps. I will see tomorrow what the voltage is. I hope I haven't hurt this battery.

Does its low voltage under load mean that it was not good to start with? Would it be a problem if paired with another battery?

Battery C:
12.75v start.
12.12v and 99 degrees under load. 30 seconds after taking load off, 12.55v, and 12.65 after 20 minutes.

Meanwell on overnight at 14.37. Still taking 2.83 amps in the morning, but I took the charger off. Subsequent days, resting voltage 13.23 and 13.14 so I think is full. A healthy battery?

Battery 😧
12.66 starting voltage.
After 10 minutes load, 101 degrees, 11.99v under load. After 30 seconds no load, 12.47 volts. I forgot to check the 20-minute voltage.

Meanwell at 14.37v to 0.4 amps, resting voltage now 12.94v.

---

So, what do you all think of the performance of these batteries? If they are all good, I will put them into banks of two. Suggestions welcome for which pairs will work best together.

Or, are there other tests that I ought to run, now that the batteries are fully charged? (I realize more data is always better, but please keep in mind that I will have very limited days to work on the van before snowbirding in it this fall, and a day that I spend on batteries is a day that I don't spend on something else.)

Speaking of, I do have more data. If you folks have questions, it's possibly might have answers. I took measurements about halfway through each test, and have notes on my charging, which took place over quite a few days in little increments.

--

Thank you all SO MUCH for reading this mega-post, and for any ideas you have. I feel pretty clueless compared to some of you.

Chassis battery voltage did not rise above 13 when on a charger at 14.4? How long was it on that charger? Something strange there. Also no load test mentioned for that one. The shop should do a load test and exchange if required.

Battery A terminals hot could be just a loose connection--needs another try to confirm it's not that.

Battery B did ok - voltage drop 0.67v and bounced back. Staying at 14.4 for extra time shouldn't matter since it did not over-heat. 0.4 shows it got to full. The time at 14.4 might have been just what it needed!

Battery C did ok- voltage drop 0.63v and bounced back.

Battery D did ok-voltage drop 0.67 and bounced back

IMO B,C, and D could be put in service and should get better after a while when they can be fully recharged after each cycle. A needs that second test for getting too hot or not.

You didn't need to get them to true full to do that load test, so results are valid IMO. (In service, you would run the microwave or whatever on them when they are part full.)

[MEXICOWANDERER]

Battery that overheats during a suitable load test protocol -FAIL

Discharge reluctant battery to 12.2 volts measured after 24 hours discharged

Charge battery to 14.40 volts and when charging amperage drops to one half of one percent sustained as calculated against amp hour capacity (example 130 amp hour battery .5% = point six five amperes at 14.40 volts)

Would not be unusual residual voltage to remain in the low thirteens for 24 hours or longer. Dropping to the very high twelves.

I would not like to see voltage drop to less than say 12.85 volts over a period of a month's time when temps are 72F or more.