AGM Battery Charging THE PRIME DIRECTIVE

[MEXICOWANDERER]

I have gotten several communications about AGM battery maintenance. Using solar voltaic charging.

The big error I read is that the subject of total and complete recharging is not mentioned. And that is the # 1 most important mandatory requirement in AGM management.

If panels cannot do it and your electricity charger cannot do it you are condemning the battery.

The battery must be subjected to enough power to allow resistance to rise so that applying 14.4 volts across the battery...

One group 24 battery allows .4 AMP or less into the battery

Group 27 or 31 .5 amp

GC220 1.1 amp

Multiple batteries? Add each additional battery. Four golf car batteries -- 480 amp hour total = 2.2 amps maximum at 14.4 volts

Forget amo hour counting, slide rules or hocus pocus -- one half amp per hundred ampere hours at 14.4 volts. That's the battery's law not mine.

And this is a CHEMICAL matter, so time spent discharge is critical. Cycled to 50% every day is not as significant as cycling to 50% and then allowing the battery to remain at 50% level for days on end.

The CLOSER you can recover to that 1/2% flow of amperage the longer you can go without actually reaching the half percent at 14.4.

The deeper the discharge the more critical it becomes

It's exactly like radiation dosage. Accumulation is far more important than intensity or time. Only in this case it is depth of discharge and time spent at depth. A battery that is discharged to only 70% total capacity and then spending many weeks at that level is affected every bit as much as a battery that is discharged to 40% state of charge for 10 days.

But no matter what getting the battery at 14.4 volts and one half of one percent amp hour capacity amperage flow is key.

A measly 400 watt megawatt power supply can take over when your converter falls flat on it's face delivering less than 35 amps and the megawatt which is set a 14.4 volts will finish the job.

[Smitty77]

pianotuna wrote:
Ty Mex.

Mine get to those numbers on the Magnum inverter charger. The solar does a lot of the "heavy lifting". I do use load support even if I'm running 50 amp shore power.

I just completed a 900 kilometer trip and did not blow any shore power breakers. It made my life so much nicer.

Curious which Magnum you have that will show you the AH's going into the battery?

MS2812, at least as far as the Magnum Tech explained to me, does not give you the 'Charging Amps' going into the battery. It is the combination of AH's being consumed, and AH's going into the battery bank, that is displayed. (If your Shunt is seeing say 10 Amps of draw from the bank, and the Magnum Inverter/Charging is putting out 6 AMPS, the Magnum Remote display would reflect 16 Amps. It might also display on Line One of the display, that the battery is Absorb mode, where as the Line 2 should display the Voltage (Say 14.4V for this example.) that the Absorb is programmed to. Along with also on the Line 2, the Amps of '16A'.

I must have asked at least three different ways, was their anywhere with the ARC-50 Remote Display and the BMK-Meter option that I could see the actual Charge Amps, as in Taper Down to Amps, specially going into the Batter Bank. The end result was always, nope!!!

Hard to reach the appropriate fully charged Tapered Down Amp, when you have not display of this value:)!

(MidNite Classic 150 with WhzBngJr module allows what they call 'Ending Amps' setting to determine when to move from Absorb to Float. (4 Amps for my battery bank.) I have this set, and am in the process of still reviewing all of the Classic 150's other settings. And again trying to get the Software updated to the latest release. Then will start looking at their download logs to see what is what... I never have mastered this process, and admit I did not pursue it too carefully - as I had always felt the MS2812 with SOC finishing the Absorb bath 100% level - had the bank covered. (You, MW, and many other helped me thru the learning process as I found out this was not the case:)!). So with this replacement bank of Batteries I have, I really want to fully explore and understand the tools available via the Classic 150.

Now, if you have found away with the Magnum tools to tell when I've reached the Tapered Down to Amp value - that would be info I'd really like to know how to do myself:)!

Best to you, and to all,
Smitty

[MEXICOWANDERER]

"That otter be enough"

Has killed tens of millions of batteries. Whether it's running the generator or simply "plugger in and walk away".

Jesus and I discussed this attitude a week or so ago.

I told him the no-effort lifestyle had to reach all the way to the galley where push-a-button-and-and-wait-for-the-ding meals must predominate. A salad had the rank right up there in the most labor intensive list of meal preparation, right up there with how to handle a squirt gun for putting out flaming hamburgers on the gas grille. A vacation included leaving the 23-year old unemployed son, home, in his basement bedroom trying to hack his way past the National Security Agency firewall.

(On a beach way down in Mexico - I am parked way down past the end of a line of maybe 20 rigs)

"Whatcha doin?"

Building a fire

"Must be a hunnert degrees out here"

Yeah

"Whatza pot for?"

Beans

"A clay pot?"

Yep

"You gonna waste that wood to cook beans? If it wuz me I'd save it for a nice campfire at night"

The wood is mesquite, no good for illumination.

"Beans, huh? Over a campfire in a clay pot on a hot day"

They need to cook about two to three hours

He gave me glances as he backed away. No way on earth for him, the DW would throw together a Groton's fish stick dinner and prepare coleslaw. Now that's living life easy...

[Almot]

BFL13 wrote:
Recharging AGMs once you get home is so easy !!!

Just set the adjustable voltage charger to 14.8 (if that is the "cycle use" spec) and make sure the charger is current- limited to no more than the spec for the battery (27 amps per 100 for my 27 format 100AH ones- so I use a 55 amp charger set to 14.8 on the pair)

Wait till amps fall to under an amp (needs an ammeter--I use the Trimetric) for under 0.5 each and then declare victory.

Pretty much same as on solar.

Controller brings it to 14.6 (as per specs), +/- whatever temp comp says, keeps it there until current drops to 1.5A per 300AH bank, which normally happens when fridge stops cycling (otherwise it's 2.3A), and goes to Float as programmed. No Trimetric is necessary.

Solar should be "big enough", meaning - oversized for your needs. I've been telling people this all the time, but everybody insists on learning through mistakes - tiny portable solar, then 200W on the roof, then finally something adequate 🙂

Declare victory? I wish. My AGM have developed a defect through either my mishandling (long storage prior to use), or as a congenital disease, being Chinese UPG. Low current now doesn't mean anything, big solar is the only thing that keeps system afloat.

[landyacht318]

If it is left at 14.4v for long enough, amps will taper to under 0.05 amps, when the 100AH agm battery is still healthy.

When mine was newer I could cran it upto 15v from that 14.7v and 0.05 amps, and amps would again quickly taper to 0.05 amps or less. 15.5v, same thing, it wont accept any more. Done.

Now well past the 650 deep cycle mark, amps will taper to 0.2 and kind of stop there.

Until I do the 50% or deeper discharge and the high amp recharge, then it will now taper to the 0.1 amp range.

I do not fear the occassional overnight plug in at 14.7 volts.

[BFL13]

pianotuna wrote:
BFL13,

I thought it was 75 amps max for the new battery? i.e. 0.3 c? 250 x 0.3 = 75?

Or should you use the 237 amp-hours for capacity?

The ESG link (My battery says ESG on it) says "under 100 amps" for a cycle use recharge at 14.1 to 14.4 volts. See that link in the OP of my thread) The similar(same?) battery with the other brand name says 0.3CA. later in another link. Whatever! 🙂

I am not too clear on the "overcharge" requirements though. It has various names.

After a few incomplete cycles with a Wet batt, you can't just charge it to zip amps and go to Float. The SG will not be up where it belongs.

So what about an AGM same situation? You can't check the SG. Do you just give it an overcharge anyway? How long? ( that one link says 14.8 for four hours) but that is not much of a higher voltage from 14.4 like 15.5 or somesuch as for a Lifeline "recondition". If you leave it at 14.4 extra time, past when amps get down to 0.5/100AH does that count as an "overcharge"?

[pianotuna]

BFL13,

I thought it was 75 amps max for the new battery? i.e. 0.3 c? 250 x 0.3 = 75?

Or should you use the 237 amp-hours for capacity?

[BFL13]

Recharging AGMs once you get home is so easy !!!

Just set the adjustable voltage charger to 14.8 (if that is the "cycle use" spec) and make sure the charger is current- limited to no more than the spec for the battery (27 amps per 100 for my 27 format 100AH ones- so I use a 55 amp charger set to 14.8 on the pair)

Wait till amps fall to under an amp (needs an ammeter--I use the Trimetric) for under 0.5 each and then declare victory. Crank the charger down to 13.8 Floating spec and leave it all till next camping trip.

Now I have another AGM (250AH) but it says to use 14.4 instead of 14.8. Whatever, same deal, only now I am allowed 100 amps for the 250 at 14.4. OK so drag out my PowerMax 100 amp adjustable voltage and set 14.4 and let her rip. Once amps get below 1.25, I can go to Float on that. Too easy!

Compared with Wet batt drill using hydrometer and the Trimetric and holes in your clothes, this is a picnic! 🙂

[MEXICOWANDERER]

I get frustrated seeing early AGM failures. Absolutely needless. About 80% are loss of capacity. Infanticide.

[pianotuna]

Ty Mex.

Mine get to those numbers on the Magnum inverter charger. The solar does a lot of the "heavy lifting". I do use load support even if I'm running 50 amp shore power.

I just completed a 900 kilometer trip and did not blow any shore power breakers. It made my life so much nicer.