Is a Johnson AGM starting battery fully charged at 12.68v???

[Naio]

Buying a new chassis battery, it took me forever to find somebody who actually had an AGM one in stock, as opposed to just claiming they did.

Got it yesterday. Johnson Control,
sold under the Duralast platinum label from AutoZone. Dated August of last year.

Not topped off when I got it. I idled the van for a while yesterday, ran out of time. Battery ended at 12.76 but I assumed that that was just because I didn't charge it long enough.

Today, hooked up a smart charger, and it reads as fully charged, although voltmeter said 12.68 before plugging in charger.

Not much luck finding specs online for this particular battery, and guys at AutoZone didn't even know what AGM was, so I can't ask them.

Is it possible that it really is fully charged at 12.68, or have I got a dud battery? It did start the van, although weather is warm.

Don't know what I would do without you guys.

[NinerBikes]

Never had a problem with my surplus AGM DEKA 150Ah + Telcom battery... 12.88 to 12.90V depending on the temps in the garage where it's stored. 10 months from date of manufacture. As stated by Landyacht, cycle it, stir the chemistry up with a good 50 to 70% SOC discharge, and then top it up at 14.4V until it holds a low current that no longer is decreasing. This battery might not power a big inverter, but for my 21 ft travel trailer, it's the Energizer Bunny. Just keeps on going, and going, and going. I don't draw a lot of amps off of it, but I am sure I could run 2 days, probably 3 between a generator recharge at 2 hours, and 150w solar panel on a sunny day for the rest of the 3rd day to top it off, fully. It stores well, doesn't lose voltage very fast or discharge very fast at all in storage, when fully disconnected.

[MEXICOWANDERER]

Fifty bucks for a 500 amp carbon pile load tester from the Frightening Harbor store is a bargain. When you believe your car battery is charged, connect it. leave engine running. Load battery to 12.7

Allow around 12 amps for fuel pump and 10 more for fan if running. Homer Simpson alternator check. It's better meaning more accurate if you use an inductive DC current meter on the alternator output cable.

It's absolute fact unscrupulous vendors buy rolls and rolls of adhesive disc alphanumerical date code and update them. That's why OEM uses BRANDING IRONS and melt the code in the edge of the lid of the jar. Shows day and shift of assembly. Filling and greening are deduced from there.

[landyacht318]

The same outfit that delivered me the Lifeline GPL-31XT directly from the West Covina factory/warehouse, also delivered me a Crown1 Group31 AGM that was ~2 months old. It was reading 13.02v and its amps tapered as expected, and quickly, when I hooked it to 14.4v, so I assume it was put on a charger before delivery. I did a few initial tests with this battery( which had NO CCA rating) and found its voltage held under a 435 watt load was not impressive, but that could be a good thing, in terms of the number of deep cycles achieveable.

When I bought the Northstar in a distributor some 30 minute drive inland, I brought my voltmeter and chose the one off the shelf with highest voltage. At that same time I was returning a relabelled crown group31 marine battery that performed horribly voltage wise when depleted 50% of its rated Ah capacity the night before. I brought a bathroom scale when weighing the USbatteryG 31, and this screwy31 did weigh nearly 10Lbs more than the Crown Marine battery.

The salesmen thought I was just another customer, and when I returned with fire in my eyes he hid in the back and sent out the manager. The manager was compliant with my wishes and did not just repeat that 'A marine battery is a deep cycle battery' over and over.

But the outfit which delivers fresh batteries to my address for exellent prices, will likely get all my future business as long as he can get the battery I want.

And If My Northstar AGM failed today, I would buy another one, but it will not fail today, and voltage held under load is still impressive, but the almost scary quick cranking amp gusto is nowhere near what it was, when it was newer.

Not having a carbon pile tester, and not trusting any distributor's machinery, I think if i were really wanting to irritate the salesmen and/or manager I would bring my 800 watt inverter with short fat alligator clips, and an 800 watt resistance heater or similar, and a scale, and a multiple decimal point voltmeter, and stopwatch.

[MEXICOWANDERER]

Won't let you check voltage?

"You want the car? You want it or not. Tough. You can't see it before you buy."

Get the idea?

"Big Louie" salesmanship -- he showing a 46 teeth smile clenching a foot long cigar...

[Naio]

I did that when I bought my used telecoms. Feel kind of dumb but I didn't think about it when buying new.

I did call around and find the newest by date AGM in town.

Other times when I have bought new batteries, shops always top charged them before bringing them out. This one I had someone else pick up for me, so I don't know if that was done.

But it seems like it might be difficult to get someone to let me put a voltmeter on before they top charge it. Plus, how would I know?

[MEXICOWANDERER]

Excellent information sir!

If I may add something.

When purchasing an AGM, take a voltage reading. If the battery does not have in excess of 12.85 volts, reject it unless you intend to fuss with it at home. I used to call "aged" shelf batteries "Rip Van Winkles". Stands true for flooded batteries but at different volts point.

How important is this? A thoroughly aged RVW can deliver 90% of its amp hour rating and deliver 80% of max lifespan. Unless "conditioned" (see the Lifeline user manual) these batteries are sold "crippled" then go downhill from there.

OEM warrants new batteries to the distributor for one year. After the twelfth month the distributor EATS whatever warranty he had added onto the battery. Yes this includes Interstate, Wal-Mart, Costco and Sams Club.

When I ran the numbers for one vendor (distributor) he saw the light. I made a twenty battery charging station for him and guess what (?) his warranties during a one year period - zero - 2 years - zero - three+ years under 1%.

"If you bought your battery here, don't let it just sit! Bring it here and we'll recharge it FREE!" Saved the vendor a lot of money.

This is where I perfected the TOP CHARGING regimen using his power and his labor. Top charge and rotate stock were key words. Mark Daughtery, at RAMCAR used to roll his eyes when I purchased batteries for my own use. Armed with a Freas hydrometer and carbon pile load tester I would cherry pick the best of the best.

A pocket size digital multimeter is cheap. AGM's under 12.85 volts and flooded batteries showing under 12.6 volts should be rejected outright. If the vendor gets testy, this is a perfect BS Test. He will treat you like that if you show up with a warranty claim. Use your noodle... don't let the door hit you in the ***

[Naio]

That's very interesting, landy.

[landyacht318]

Naio, In june 2015, for a project for a friend, i had a Lifeline GPL-31XT delivered to me fresh from the factory in West Covina. It read 12.99v, and I hooked it upto the meanwell at 14.4v, and many hours later Amps seemed to stop tapering at 0.9a or something( working from memory here). The point is the amps stopped tapering before the requisite 0.625 amps was attained.

I gave up trying to get amps to taper to 0.625( 125Ah capacity battery)

I then was using it, and removed some 35Ah from it, then recharged it on the meanwell set to 14.4v, and this time the amps did taper to 0.625, and kept tapering.

After this initial shallow cycle and recharge, the surface charge refused to dissipate staying at 13.23v for a few days I wound up removing about 5AH and the voltage rebounded upto 13.16v and stayed there for days.

This was my second observation of an AGM behaving subpar until it got a discharge then recharged, being quickly brough to absorption voltage with 40 amps available.

Both AGM batteries that i had observed since new, seemed to require the initial discharge cycle before they started performing well.

We often hear how deep cycle batteries do not deliver their rated capacity until they deliver a 20 to 50 cycles.

Perhaps with AGMS they require a single deep cycle promptly followed by a higher amperage recharge to full before they too cooperate to expectations.

Anyway I will be doing this to any AGM battery, but especially one which is supposed to be an engine starter only. I am going to cycle it deep, and promptly high amp recharge it.

It would likely be 'just fine' without it, but I like to have a good known starting point for later comparison, and they seem lazy off of the factory floor, and need a smack across their bottom, IMO.

[MEXICOWANDERER]

Telecom battery operation assumes a lot of givens

• It is properly sized for the array
• Specific chargers are designated for specific amp hour banks -- a strict protocol
• When power is restored that bank will be approved to have a specific sized charger and since length of recharging time is a given
• Why deviate? It's all done by the book
• What's an RV?

Like for scrubber batteries and chargers: One or 2 1275's. Each has it's recommended charger size. When scrubbing is finished the batteries get plugged into a specific scrubber charger for 18 hours. What could be simpler?

[NinerBikes]

Naio wrote:
Thanks, Mex and Landy, for your posts earlier today, which I am just now reading.

The behavior of this battery is strange to me. It draws low amperages from the meanwell for hour after hour after hour.

Starting yesterday at 12.76v, it took 2 amps with the meanwell set at 14.7. After 4 hours it was down to 1 amp, and I had to go home and make dinner. Getting back to it this afternoon, it started out at 12.87v, again happily drawing 2 amps. After about 3 hours, it was down to about 1.3 amps, and I left again to make dinner.

Why does it want this low amperage for such a long period of time?

(On the slim chance that it's relevant: I do have 3 dashboard solar panels connected to this AGM, although I'm not really sure they are doing anything and have not checked them for continuity lately. Two of them at least used to work. I'll try to remember to check them tomorrow, but it's a busy week.)

I haven't felt comfortable leaving the meanwell hooked up overnight on a timer, at the place I have the van stored. But I'm moving the van tomorrow, and then I could do that.

The voltage does drift upward at the battery terminals while charging. So far it seems to take 2-3 hours to go up .1 volt. If I'm going to set the timer and go home and go to bed, how many hours should I set it for?

Disconnect the battery from any of the car + and - terminals, then plug in the meanwell, then recharge at 14.4V until you see 0.4 amps. It will probably take 3 hours, maybe 4.... You have phantom current draw from the van at all time when it is connected up to the battery. Alarms systems, memory for Electronic Control Module, all kinds of little bits drawing current out of the battery as it sits with the motor not running. When you disconnect the - terminal, all those suckers quit giving you false readings on current drawn while recharging the AGM.

I do the same thing for my big 158 AH surplus Telecom AGM battery... 14.4V setting when I get it home, and current it will take is down to .70 to .80 amp usually in 2 to 3 hours, sometimes 4. You can't and won't hurt the battery leaving it on the MeanWell at 14.4V overnight, the battery will be fine at that voltage setting.

I strongly recommend, as stated before, a good chemistry mix up by discharging the battery to around 50% State of Charge. Then put the Meanwell on it and let it take it's time bringing it up to 14.4V and 0.4 amps. That's a good "stirring" of the acid inside the battery and the plates. It should then take a very good "top charge" all the way up, once you do that.

[Naio]

Thanks, Mex and Landy, for your posts earlier today, which I am just now reading.

The behavior of this battery is strange to me. It draws low amperages from the meanwell for hour after hour after hour.

Starting yesterday at 12.76v, it took 2 amps with the meanwell set at 14.7. After 4 hours it was down to 1 amp, and I had to go home and make dinner. Getting back to it this afternoon, it started out at 12.87v, again happily drawing 2 amps. After about 3 hours, it was down to about 1.3 amps, and I left again to make dinner.

Why does it want this low amperage for such a long period of time?

(On the slim chance that it's relevant: I do have 3 dashboard solar panels connected to this AGM, although I'm not really sure they are doing anything and have not checked them for continuity lately. Two of them at least used to work. I'll try to remember to check them tomorrow, but it's a busy week.)

I haven't felt comfortable leaving the meanwell hooked up overnight on a timer, at the place I have the van stored. But I'm moving the van tomorrow, and then I could do that.

The voltage does drift upward at the battery terminals while charging. So far it seems to take 2-3 hours to go up .1 volt. If I'm going to set the timer and go home and go to bed, how many hours should I set it for?

[BFL13]

MrWizard wrote:
could be that 20% is the minimum rate for almost any agm chemistry ?

That's what I am asking about. If so, there is nothing at all about it in my brand of AGM charging specs. ISTR it is part of some other brand's specs(forget which one--we had some threads on this a while back) and wondering if Mex has got that on his brain as though for all AGMs or not.

It matters to me because recharging at home on a long extension cord, I cannot use a high amp charger or it blows a breaker in the house. I can use a lower amp charger that does the proper charging voltage, but that is less than the 20% for amps. Since that all happens at home, I don't care that it takes longer to reach Full with the lower amps.

It can also matter if on solar, which is by nature low and slow but you can get the right voltages.

[MrWizard]

could be that 20% is the minimum rate for almost any agm chemistry ?

[BFL13]

Mex, my AGM specs say nothing about a minimum charge rate, although I gather some AGM specs have that.

You have mentioned the 20% minimum before as though all AGMs have that requirement.

Mine have a max charging rate spec of about 30%. Some AGMs have no maximum like that and say you can use a very high rate. (Might be the same ones that have the minimum rate?)

So what's the story on all that? Thanks.