What is the AGM Wall?

I consider a regular full charge to be when amps taper to 0.5% of capacity at Vabs, which is 0.45 amps on my 90Ah rated battery


Since I have to lower voltage manually, well I have left it overnight at 14.7v, more than once, unintentionally.

When the battery was new, eventually at 14.7v, the amps would taper to somewhere less than 0.05.

NOw at 800 Deep cycles and approaching 5 years of age, if I forget and leave it overnight at 14.7v, amps will taper to 0.2ish
When I do a bunch of PSOC cycling and the battery is showing lesser voltages during the same AH removed I might see amps toggling between 0.4 and 0.3, I'll let it go a while longer, seeing if I can get 0.2.

When I return 10 to 15 minutes later, if the amps are 0.4 I quit Vabs, if it is solid 0.3 I will see if it toggles between 0.3 and 0.2. in another 15 to 20 minutes.

If it stops tapering or if amps start rising I quit Vabs.

Right now I consider 0.2a to be my Northstar AGM's wall. This is a TPPL AGM, thin plate pure lead, Like Odyssey AGM.

I have no Idea what your UPG AGM batteries wall will be or whether you should be seeking to find it with that brand.

If I want to hit the wall but it stops tapering at 0.3, and I have been doing lots of low and slow solar recharges to full, or perhaps not to full(0.45a), or obviouslyt no where near full, then I will intentionally drain well below 50% and hammer it with no less than 40 amps but hopefully 65.

When I hammer it with high amps from well belwo 50%, it then takes less time for amps to taper to 0.45, compared to if I had done a ~35 amp recharge from say 60% state of charge.

My battery will gain significant temperature with 65 amps into a 90AH battery.

I adjust voltage downward manually accordingly.
High amp recharges on this battery usually lower the amperage wall if I choose to see if i can hit it, or if I forget and leave it up high overnight.

Some might say I am overcharging. I do not do this every time, no more than 2x a month and not recently as it has been a warm summer.

If you choose to hold Vabs to see just how low the amps can taper to, it is another data point to compare to a later data point, but you want to know if it is still tapering and stop Vabs when it starts rising, preferably before. I've rarely seen amps begin rising and only within the last say 60 deep cycles when I've tried to see if the wall is still 0.2 and hopefully less.

I'd be happier if my Wall were back in the 0.05amp or less range, It is now somewhere between 0.2a and 0.3a, and 'full' is 0.45a.

Your battery will be different.

Good info LY, although it still appears you and Mex are using "wall" in different ways. I am not clear whether that means you are talking about two different things.

So the "good" 100 that sat overnight at 13.6 was jacked back to 14.8 and amps jumped to 3.5ish and then tapered down nicely to 0.1 amps. So I decided there is nothing wrong there, disconnected that one and connected the suspect 100 that got warm which was sitting this morning disconnected at 13.16 (full)

Converter set at 14.8 and amps were 4.x and tapering, going down evenly to 1.1 amps and stalled there--been there for an hour. Battery temperature has not gone up at all.

Not sure what to do now to figure out what if anything is the matter with this 100. It got warm after I tried to find the wall when after sitting at 14.8 and bottoming out for amps, I jacked up the voltage to 15.4. So like Groucho M, said, when playing a doctor, "Does it hurt when you do 'that'?" "Then don't do that!"

As it looks now, the 250AH 8D bottoms out around 0.7a or less, the good 100 at 0.1, and the second 100 at 1.1, but it does not heat up sitting there at 14.8 taking that 1.1.

If you were working with topnotch AGMs my eyelids would not be heavy.

Now that you have fixed reference points (you should do voltage / percentage references...

If they start losing those characteristics way down the road, you will know for sure. Something tells me your battery of interest entered your domain at a lower voltage.

Fixing basic references (not nearly as all consuming as what you did) makes future exams a snap. The first thing I did with my Lifelines was to measure voltage as arrived. Both were above 13.00 volts.

Hitchem to the yoke and makem pull the plow BFL!

That's what they're supposed to do for a living.

Just checked and amps now 1.0 instead of 1.1, but temp has sneaked up from 23C to 26C in the last hour or so. I will leave things going and check again later.

I don't have any idea what is normal for temperatures in this situation, except to note the other battery stays cool doing the same thing.

EDIT: more time and amps now 0.9 while temp still 26C. I will now put everything back together and pretend none of this ever happened. :)

Time spent better than watching reruns of Hee Haw

I'm not seeing any difference in mex's wall and mine.

Eventually the AGM's tapering amps at Vabs are going to stop tapering.

How and where the amps stop tapering are data points to collect for later comparison.

Perhaps your weird 27 was presulfated before purchase. The UPG AGMS have to come from China, and they do not have great self discharge figures, and I highly doubt that retailers are making sure their yet to be sold batteries are regularly recharged.

I also doubt that batteries are leaving the factory fully charged as that takes time and electricity and both eat into max profit, and that is all that is cared about in this day and age.

Your lazy G27 might benefit from a deep cycle and exceeding that maximum 27 amp recommendation.

Or it might not.

http://www.odysseybattery.com/documents/ODYSSEY_Battery_Reconditioning_Charge_Procedure.pdf

Odyssey are TPPL AGMs. Thickplate Lifeline AGM has a different procedure.

I've gone nowhere near the Odyssey procedure of draining to 10V under relatively high load on my Northstar, but the lower I drain it and the higher the amperage I can feed it till full, the better it performs thereafter.

Hitting it with 40 amps from 80% state of charge does not improve its performance as the amps start tapering within a minute.

"We don't need no dark sarcasm's"