So You Own An AGM Battery...

[MEXICOWANDERER]

AGM batteries can sulfate just like any other lead acid battery. Other than by Ouija Board how would YOU determine if a battery has become sulfated and how severe is the sulfation, and if desulfation (equalization) has been done properly.

I'll make this real interesting. Let's take a bank of eight AGM batteries and attempt to sort things out.

This is not a campground test BTW. An at-home test with time and resources at your disposal. How would you handle it?

I'm going to stay out of this and see the answers until and if I am asked to participate...

[MEXICOWANDERER]

westend wrote:
I'd have to break down the 8 battery bank into a more usable configuration. In fact, if pulling them all to do at home, each would be treated individually.
Since we can't measure with a hydrometer, measuring volts and current would be our tool.
Most AGM mfg's have a equalization or capacity recovery voltage listed for this purpose. I know mine is 15v. I would first charge the battery as usual and have an observable baseline voltage at full charge. I would discharge the battery with a purely resistive load like a heater, dummy load, or light. I would observe the time it took to reach a low voltage setpoint, that might be 12.0v. I would then charge the battery as per usual until full and then charge using the capacity recovery voltage. The battery would be drawn down again, to the low voltage setpoint and time observed. If the equalization/capacity recovery was successful it should take longer to reach that setpoint.

A SOLID "A"

Passing grade, Mex? I'm sure there is a better way but that's what I come up with.

[TechWriter]

MNtundraRet wrote:
You have to remember that That most people could "care less" until Murphy's Law happens. Then they come :h and ask for help. :B

Mmmmm . . . exaggerate your importance much?

MNtundraRet wrote:

Besides most of us are camping now. A technical question like this works best in the early spring when most of us have "cabin fever" and are waiting for Winter to end. 😉

This part is right.

[MNtundraRet]

Hi Mex:

You have to remember that That most people could "care less" until Murphy's Law happens. Then they come :h and ask for help. :B

Besides most of us are camping now. A technical question like this works best in the early spring when most of us have "cabin fever" and are waiting for Winter to end. 😉

Mark B.

[Tom_M1]

MEXICOWANDERER wrote:
AGM batteries can sulfate just like any other lead acid battery. Other than by Ouija Board how would YOU determine if a battery has become sulfated and how severe is the sulfation, and if desulfation (equalization) has been done properly.

Desulfation and equalization are two different processes. You equalize wet cell batteries to distribute the acid equally within a cell. You can not equalize an AGM or gel battery. Here's an excerpt from a Deka battery document:

Acid stratification can occur in conventional wet cells. During charge, acid is released at the plate surfaces. During discharge, acid is consumed at the plate surfaces. Since the concentration is not uniform, diffusion (spontaneous mixing by random molecular motions) begins. If this mixing occurred rapidly, stratification would not occur, but it is relatively slow, allowing lighter parts of electrolyte to “float” toward the surface and heavier parts to “sink” toward the bottom.

The top portion of the plates do not perform as well in contact with lower concentration electrolyte. The bottom portion of the plates do not perform as well with the higher concentration, and will corrode prematurely. High voltage “equalization” charging is sometimes used in wet batteries to make gas bubbles that re-mix the electrolyte.

Because the immobilized gel will not “float” or “sink” within itself when a non-uniform concentration exists, it cannot stratify. Therefore, no high-voltage equalizing charge is necessary. Simply recharge at the standard 13.8 to 14.1 voltage setting. This means longer life and consistent performance in stationary and standby applications.

Electrolyte in an AGM battery is strongly held by the capillary forces between the glass mat fibers, but not completely immobilized. Stratification is possible in extremely tall cells, but cannot occur in batteries of the size covered in this document.

[tplife]

Walmart sells load testers for around $40. They work on lead-acid, AGM, or gel batteries...

[westend]

I'd have to break down the 8 battery bank into a more usable configuration. In fact, if pulling them all to do at home, each would be treated individually.
Since we can't measure with a hydrometer, measuring volts and current would be our tool.
Most AGM mfg's have a equalization or capacity recovery voltage listed for this purpose. I know mine is 15v. I would first charge the battery as usual and have an observable baseline voltage at full charge. I would discharge the battery with a purely resistive load like a heater, dummy load, or light. I would observe the time it took to reach a low voltage setpoint, that might be 12.0v. I would then charge the battery as per usual until full and then charge using the capacity recovery voltage. The battery would be drawn down again, to the low voltage setpoint and time observed. If the equalization/capacity recovery was successful it should take longer to reach that setpoint.

Passing grade, Mex? I'm sure there is a better way but that's what I come up with.

[Son_of_Norway]

The theory would be over my head but I would look at increasing internal resistance as determined by a bench-test. Ideally you would keep track of each battery over time, but you could also use a new battery as a baseline.

Miles

[mena661]

These responses are why I kept it short MEX.

[TechWriter]

MEXICOWANDERER wrote:
If I could "care less" about something I ignore it. Threads, conversations, remarks, and opinions. This isn't about the subject matter merely the stated level of disinterest in the subject.

Well that's you, isn't it?

[MEXICOWANDERER]

If I could "care less" about something I ignore it. Threads, conversations, remarks, and opinions. This isn't about the subject matter merely the stated level of disinterest in the subject.

[mockturtle]

TechWriter wrote:

RJsfishin wrote:
I couldn't care less.

Ditto.

Double ditto.

[full_mosey]

I have two AGM/solar systems.

I recently starting watching morning volts by looking for a declining Voltage daily trend. If the 12V fridges are running, I note the overnight low Volts as well(a feature of the Turnigy meter).

I also MAY note if the transition from ABS to float is later each day. I don't sit around staring at the controllers!

This method works because I rely on solar for Absorb and float. With solar, the batteries get no charging overnight. Therefore, there are no surface charges to foul up Volt readings.

When morning Volts are low, out comes the genny to power 120V chargers to bulk up the batteries. These batteries were not always treated this well.

In short, a glance at a meter tells me if I need to deploy the genny. It takes longer to explain.

I will know to replace the batteries, due to low capacity, when the genny run does not result in a higher low Voltage the following morning.

I have dry-camped as many as 31 consecutive days before and plan 42 days in Quartzite in Jan-Feb next year with these batteries. The batteries will be 4 and 5 years old at the beginning of the trip.

Am I doing it wrong?

HTH;
John

[TechWriter]

RJsfishin wrote:
I couldn't care less.

Ditto.

[RJsfishin]

I couldn't care less.I've run AGMs hard for 15 yrs, and the first set lasted 8 years, and it never ever seen equalization or anything but 14,6 charging then float at 13,2. I couldn't ask for any more, That doesn't mean they are worth the horrific price they carry. That being said, I also run 6v LAs on a PD 9155 w/ equalize etc etc, and they lasted 9 yrs when I sold it. Anything after 8 yrs, I couldn't care less.

[WoodGlue]

If one or both of my AGM batteries fail within the first 4 years, I get 100% replacement/refund. After 4 years, it's prorated.

That's my contribution!

WoodGlue