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.

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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.

[MEXICOWANDERER]

Rising amperage with rising battery heating is a problem with gelled electrolyte.

[Naio]

landyacht318 wrote:
12AWG is designed to carry 20 amps Ac or DC, depending on which ampacity chart you choose to believe..

600 watts at 120V is 5 amps
600 watts at 12v is 50 amps.

MEXICOWANDERER wrote:
It wasn't being used to connect inverter to batteries right? That would be equivalent to trying to tow your rig with a quarter inch rope.

Yes, this is what I did. I'm really not sure I should be trusted around batteries, ever.

BFL13 wrote:
"A second puzzle: When recharging with the meanwell at 14.37v, amps went down normally to about 1, and then started to go up. 2 hours past the 1 amp mark, it was at 1.75a. I was tired and hot and my timer is broken, so I shut down the meanwell and came in to ask you guys. Or I can just see how it is tomorrow."

Could be a problem or not--Mex or somebody who knows his AGMs will have to clarify.

I had something similar happen to my AGM, and Mex said that when the amps go back up it means you are past full and should reduce the voltage to Float. The rising amps after getting full is just going to heat. I had the IR gun on the batt and its temp was rising as the amps went back up. In my case it was all minor amounts, so no big deal.

Of course that goes against his other advice that you can safely leave the AGM at the absorption voltage long past the time the battery is full. So it should not heat up too much.

So it is possible your battery is getting hotter too soon after getting full. I can't say. It should get down to 0.5a per 100AH. So 1 amp would be for 200AH. Can't remember the size of Battery A.

So, IMO leave things be till you hear from Mex, or others here who know more about it.

Mex, whatcha think about this bit?

[MEXICOWANDERER]

What was coursing through the veins of the orange extension cord? Red human AC blood or martian DC green blood? Me no unnerstand why a special or modified extension cord entered the picture stage left. Can't a standard extension cord connect inverter to heater?

It wasn't being used to connect inverter to batteries right? That would be equivalent to trying to tow your rig with a quarter inch rope.

[landyacht318]

12AWG is designed to carry 20 amps Ac or DC, depending on which ampacity charge you choose to believe..

You asked it to pass 50. How long before its insulation released its magic smoke?

Shore power is 120 volts more or less, inverter is likely less than 12/

volts times amps = watts.

600 watts at 120V is 5 amps
600 watts at 12v is 50 amps.

Amps increasing to maintain the same voltage, Mex told me on the screwy31(flooded marine battery) thread that this was the beginning of thermal runaway.

I've never noticed amps increasing on my Northstar AGM when held at Vabs well past the 'full' threshold. They've always decreased or just levelled off. I guess it is possible the times I expected to see 0.1 amp, and instead saw 0.2a, it had hit bottom and started climbing again and I simply did not observe the ammeter when it went lower as I was likely asleep.

[BFL13]

"A second puzzle: When recharging with the meanwell at 14.37v, amps went down normally to about 1, and then started to go up. 2 hours past the 1 amp mark, it was at 1.75a. I was tired and hot and my timer is broken, so I shut down the meanwell and came in to ask you guys. Or I can just see how it is tomorrow."

Could be a problem or not--Mex or somebody who knows his AGMs will have to clarify.

I had something similar happen to my AGM, and Mex said that when the amps go back up it means you are past full and should reduce the voltage to Float. The rising amps after getting full is just going to heat. I had the IR gun on the batt and its temp was rising as the amps went back up. In my case it was all minor amounts, so no big deal.

Of course that goes against his other advice that you can safely leave the AGM at the absorption voltage long past the time the battery is full. So it should not heat up too much.

So it is possible your battery is getting hotter too soon after getting full. I can't say. It should get down to 0.5a per 100AH. So 1 amp would be for 200AH. Can't remember the size of Battery A.

So, IMO leave things be till you hear from Mex, or others here who know more about it.

[Naio]

Update:

I tried to retest battery A with the 40amp load again, but things went south again. I think it's me, though, not the battery.

In order to decrease variables, I didn't use my funky old battery cables. Instead, I stripped the ends of a 12" piece of extension cord and used that.

I watch the temperature of the battery terminals like a hawk, and they were fine. Started at 77°, maxed out at 82°.

But, 5 minutes into the test, the extension cord housing at the inverter and started to smoke. I shut everything down of course, and then checked the temperature of the cord. 117° then, that was maybe 15 seconds after I shut stuff down. I'm guessing it was more like 130-140° when running.

Why did this happen? I was running a space heater on low, I think it is 600 watts, through an inverter. I run that heater on high, 1500 watts, with the same kind of extension cord and shore power, no problem. I realize the inverter increases the draw, but not that much, right? Was it the shortness of the cord? I know a long cord is more resistance, but I suppose it is also more heat dissipation?

A second puzzle: When recharging with the meanwell at 14.37v, amps went down normally to about 1, and then started to go up. 2 hours past the 1 amp mark, it was at 1.75a. I was tired and hot and my timer is broken, so I shut down the meanwell and came in to ask you guys. Or I can just see how it is tomorrow.

PS: Standard orange outdoor extension cord. I think those are 12ga?

[Naio]

See next page for update.

[MEXICOWANDERER]

The last trip to California I was asked by an old customer in San Diego to take a look at a full pallet (48 units) of group 65 Delco AGM batteries. This is what I discovered...

Made in China

5+ lbs each lighter than an Odyssey or Lifeline battery

Build date was 15-16 months before I examined them

Testing them was difficult as I had little except a DMM with me. Most batteries checked in the low 12.60 high 12.50 volt range. They definitely resisted charging with an Associated wheeled 60/80 amp 12/24 volt charger. I was not impressed when a 5-7 amp charge rate created 16 volts of potential.

The batteries were offered at a price of ninety dollars each. Considerably less than other AGM group 65 batteries.

I do not know the outcome but I suspect it was that the purchase was not completed.

Advice?

Beware gift horse prices. An equine smile might reveal wooden dentures.

[landyacht318]

Johnson controls acquisition of Optima AGM batteries had them go from many reports of ' gee i can't beleve this thing is still going', to many reports of 'it died in two years or less.'

Their rectangular AGM's.... who knows? You are my Guinea pig regarding them, unless my neighbors click 'place order'

If corrosion had formed on your ring terminals, it could easily have wicked up the stranding, imparting resistance between crimp and the copper stranding. I've seen one such wire, polished to perfection by a proud owner who declared it could not possibly be the problem, refuse to carry any current until I resquished the the barrell with a pair of channellocks, then it worked, but got really hot passing less than 20 amps.

It seems the Fiamms are viable. The JC AGMs resting full charge
voltage might be normal for that battery.

Separate them and check their resting voltages when fully charged or at same level of depletion occassionally, keep records you'll be able to see which of them has more capacity left with more observations and any which should be culled from the herd before they infect the others.

If anybody buys battery cables from the Autoparts stores, most of these use Stamped steel ring terminals. Steel tubing stamped over the copper stranding then a hole punched through both. These are horrible wire/cable terminations which WILL become highly resistive and heat up, and then become more so, and corrode faster.... The only question is how soon.

SAE wire gauge is aso 6 to 12% thinner than AWG wire with corresponding voltage drop, and autoparts stores packaged cables are SAE gauge.

Wirebrushing corroded terminals from green an white corrosion means the corossion has already wicked inside these stamped steel ring terminals. Cut the SOBs off and crimp on some real lugs.

Take a magnet to all conductor terminals. Those 'copper clamps' might attract a magnet.

Beware of marketers and their intentions, as they are not honest, only greedy.

[time2roll]

Considering they are all used I would strap them all together in a bundle and use the asterisks out of them. Keep them charged 100% whenever possible charging at max voltage down to a couple amps. Use them up and save some money for a good replacement set when needed in a couple years. Due to the varied resting voltages I would separate them if stored without a float charge.

[BFL13]

Naio wrote:
The way this forum substitutes asterisks for certain words always makes my language look much worse than it really is :B

No worries. We know you always say, "Tarnation!" instead.

[Naio]

The way this forum substitutes asterisks for certain words always makes my language look much worse than it really is :B

[Naio]

Thanks Landy!

> It might also want 50% discharge cycle and 25+ amps applied until 14.4v is reached, then held until amps taper to 0.5% of capacity, before it will hold any higher resting voltage.

I did this, with the chassis battery, twice. On your recommendation! I didn't measure the voltage while charging, but I set the meanwell at 14.55v when disconnected from the battery, and charged until the battery was below 0.5 amps.

The chassis batt IS a Johnson Control. I bought it for reasons other than magic, as mentioned in the previous page :-).

As for the connections between the house batteries and the load, I used the same thing for all of them: bolted-on battery cables. The same cables for all. But the cables are old, and have some corrosion. My meanwell clips onto the bolts with (real) copper jumper cable clamps.

> If one is going to perform tests for comparision, one needs to eliminate as many variables as possible, and have the same starting and end points. No, this is not always possible or worth the effort. Tests without accounting for the variables in comparison, would merely point out a used battery not worthy of employing, if excessive resistance at the battery terminal itself from a crappy electrical connection, is not the reason for the perceived poor performance.

Yes. Given my limited time and access to the van, I was mainly just testing the house batteries to find out if any of them were ****. In setting up my electric, I want to know how many batteries I have.

I realize this is not very scientific. But I have a lot of limitations on my time and energy.

Tell me if I'm wrong, but the consensus seems to be that I should retest battery A, the one that got hot, and that the other three are good enough?

[landyacht318]

The chassis AGM, is it not an ACdelco AGM?

These have been coming up on Amazon searches in most car jar group sizes, with free shipping and a good price, for an AGM, and people see the AGM and seem to think it is then a super magical, physics defying battery, and the extra price over a flooded jar then confirms it in their minds.

2 of my neighbors are asking me about these AGMs, and I say i'll let them know what I think of this brand if they get them, but if they are Johnson Controls made, I would no bother with one over a flooded starting battery, as all of them seem to believe leaving the doors open overnight with dome light on is of no consequence as the alternator instantly and magically recharges it to full in that mile drive to the store and back, and it is 'still going strong' despite falling to 8.1 volts when turning their starter motors at 70F ambient.

The CCA's of these budget friendly AGM are hardly if any any better than their lighterweight flooded counterparts. The main benefit would seem to be lack of, or reduced terminal corrosion, if the owner installer actually cleans off the existing post clamps before installing them on their new 'super AGM' battery which is somehow perceived to be magically immune to abuse because of those 3 letters and the extra price paid.


Battery Marketers are well aware of this cash cow. I wonder how many corners can be cut on manufacturing of an AGM. I'd expect them cut diagonally, on batteries marketed towards starter battery duty and sold with free shipping.

When I saw the heat report on that first battery I thought about the connections, and any corrosion cleaned of with sandpaper still screams resistance, heating and invalid test results regarding the heating, and the voltage held during load.

Regarding resting voltage, One needs a basis for comparison. All these Fiamm's seem to get charged for different amounts of time and various degrees of 92+ %, rendering the full charge resting voltage meaningless, as they are not fully charged, except for the one that was held overnight at 14.4v.

And 14.4v overnight once is not going to heat it or damage it. My AGM has been held at 14.4 to 14.7 12 hours after the amp threshhold indicating full charge, has been breached dozens of times. Amps just keep tapering and my battery termperature is barely elevated at all. When newer, amps would taper to 0.0x amps at 14.7v given enough time, the X as my ammeter's cannot accurately measure hundredths of an amp less than 5. Now at ~800 deep cycles and many years of use this tapering stops in the 0.1 to 0.2 and perhaps 0.3 range, but a significant depletion event followed promptly by 65 amps applied until 14.7v, then holding it for extended periods will have it taper to 0.1 again and performance seemingly restored.


The 12+ hours of 14.4v likely will have that specific battery outperform the other batteries if all the variables are removed from the testing from battery to battery.

As for 12.85v on that ACdelco AGM, that could be perfectly normal for that specific starting battery.

It might also want 50% discharge cycle and 25+ amps applied until 14.4v is reached, then held until amps taper to 0.5% of capacity, before it will hold any higher resting voltage. My Northstar AGM refused to hold above 12.9v no matter how long I top charged it when new.

It took one deep cycle and 25+ amps recharge rate before it would hold its 13.06v resting voltage. It also cranked the engine noticeably faster after that first deep cycle and high amp recharge, and it still does this today 4.5 years later. Low and slow recharges after deep or semi deep cycles, piss it off and performance declines with each one, but a 50% depletion with 40+ amps until that ampthreshold is reached has it happy and holding impressive voltages under load thereafter for several cycles.

So I would not consider what you did as a valid test, I would see it as collecting some data for future comparison with a large number of asterix's next to those results.

HOld each battery at absorption voltage until they decline to a certain level, then let them rest for the same period of time, idealy at the same temperatures for no load voltage testing, and then perform your load test, and whatever method you are using to hook load to battery needs to have minimal resistance and be the same for each battery.

Alligator clamps with corroded clamps with corrosion 'sandpapered off' cannot and will not yield a good electrical connection. They will not even yield a comparable connection from battery to battery, rendering results invalid.

Alligator clamps are designed to dig into the soft lead(PB) of the terminals and the post clamps of batteries. If they are not digging into them, there is Very little surface area contact between the two.

AND most alligator clamps are just steel. Hardly a great conductor to begin with.

If one is going to perform tests for comparision, one needs to eliminate as many variables as possible, and have the same starting and end points. No, this is not always possible or worth the effort. Tests without accounting for the variables in comparison, would merely point out a used battery not worthy of employing, if excessive resistance at the battery terminal itself from a crappy electrical connection, is not the reason for the perceived poor performance.

So I'd gt a new way to connect load to battery, and fully charge each battery until the amp threhold is reached for the resting voltage a day later, and then load test it with those good electrical connections.

Results of those tests I would put some weight into, but testng batteries not known to be fully charged, and with variable quality of electrical connection, is not worth the effort of testing, in my opinion.