accurate Amp Hours

Have an aging AGM and it is no longer what it once was. I am bumping up against my aspergers (subset of autism) in trying to get some handle on what remains. I am mind blind to math and similar kinds of organizational things.
I would think that a device could be cobbled together that would get an accurate Amp Hour reading. Current thinking, I am looking at some of 150 W dischargers along with a digital voltage cutoff and a digital timer. All of the items seem precise and doing a short term test, a fraction of the 50% discharge would/should be representative?
I would think that a device could be cobbled together that would get an accurate Amp Hour reading. Current thinking, I am looking at some of 150 W dischargers along with a digital voltage cutoff and a digital timer. All of the items seem precise and doing a short term test, a fraction of the 50% discharge would/should be representative?
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Since a quicker discharge effectively reduces the size of the battery bank it's hard to apply a load and test.
In addition, the process is electro chemical, so there are losses in heal at high charge/discharge rates.
All this makes for a non linear profile.
Here's some info that might help;
https://en.wikipedia.org/wiki/Peukert's_law
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
Under a heavy load, the battery voltage can sag and give a misleading result unless left to recover to "true" voltage.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
http://www.rc-electronics-usa.com/
The real question is does the system meet your needs? Say you want two days of storage with your loads (loads, radio, cell phone charging)--Running the two day test and Estragon says, measure the resting voltage of the battery to estimate how much stored energy it has left.
When the battery no longer supports your needs, then it is time to replace it.
Also, AGM batteries tend to fail by not recharging correctly... Basically, there is a small catalyst pellet in each cell that converts the Hydrogen+Oxygen gases (from charging) back into water. Over time, the catalysts "wear out". When this happens, the gases are not recombined and instead, the cells "over pressure" and vent gases (and a bit of electrolyte) and the battery eventually "dries out". And needs replacing (sealed battery, cannot replace water).
Note that failing AGM (and any lead acid battery) need to be replaced. It is possible for them to explode/catch fire if failing batteries are still being recharged. Does not happen often, but you do not want to risk the danger.
-Bill