AGM battery

[wirejock]

My other post was deleted. My fault. Non RV related.
Anyway, the question is still on my mind.
What do the voltage readings on an AGM battery mean?
Or
What voltage is good, bad, etc?
Perfect?
Too High? If there is such a thing.
Too low? Below what voltage is toast?
Should it be checked before jump starting or charging? What voltage before and after?
Mine is new but I'm interested.

 

[Ralph Inkster]

Guide I follow (right or wrong?)
between 14-2 to 13.3 - just off charge or after engine run charge - GOOD
standing 12.5 or higher - GOOD
standing 12 or lower - no go, re-charge & test, if settles back to under 12.5 - toast

 

[gasman]

What do the voltage readings on an AGM battery mean?

What voltage is good, bad.... 12.8 is full charge= good. 12.5 = charge it.

Too High? If there is such a thing.... Anything over 14.2
Too low? Below what voltage is toast?... see note below
Should it be checked before jump starting or charging? What voltage before and after?.... Before... anything below 12.5. After will be 12.8+ after 30 minutes off of charger.


note... What is too low?.... I left the master on and drained my PC680 down to nothing. I connected a 500ma converter (simple 120v ac to 12v dc converter) or... https://www.harborfreight.com/12v-automatic-battery-maintainer-59000.html and let it charge slowly to 12.2 volts. Then I connected my regular charger that I use https://www.schumacherelectric.com/...lly-automatic-battery-charger-and-maintainer/ purchased at Wal-Mart, and let it top off to 12.8v resting.

I used that battery for the next 4 years and finally changed it out to a new PC680. I placed that old 680 in my riding mower.... it has been there for the past 5 years. I place the charger on it every 6 months.

If my plane doesn't fly for more than a month, I charge to 12.8v before flight. I never leave a charger/maintainer on the battery between flights.

 

[lr172]

In a flooded lead acid battery, 12.8 standing is considered a 100% SOC. IIRC, for an AGM it is 13.0. Remember that you must wait several hours after charging to get the standing voltage. It holds .2-.3 volts for a while after being charged or floated.

 

[wirejock]

What do the voltage readings on an AGM battery mean?

<snip>

note... What is too low?.... I left the master on and drained my PC680 down to nothing. I connected a 500ma converter (simple 120v ac to 12v dc converter) or... https://www.harborfreight.com/12v-automatic-battery-maintainer-59000.html and let it charge slowly to 12.2 volts. Then I connected my regular charger that I use https://www.schumacherelectric.com/...lly-automatic-battery-charger-and-maintainer/ purchased at Wal-Mart, and let it top off to 12.8v resting.

<snip>

Am I reading correctly. Zero volts? Is that possible?

 

[gasman]

Am I reading correctly. Zero volts? Is that possible?

It has been many years. I don't remember the reading, but it sat for days with a small load and was considered dead.

My point was, slow discharge to dead battery responds best to a small (500ma) charge over several days may (it did for me) bring the battery back.

My flying during that time were between airports (both considered home base) that if the battery failed on me, it would be no big deal.

It has made a great battery for my riding mower. And will spend the rest of it's life there.

 

[lr172]

Am I reading correctly. Zero volts? Is that possible?

Yes. If you have a very light drain for a long time, the battery will drop to a volt or less and this usually trashes the battery or takes a lot of life out of it. With a higher load, the device stops draining juice at a higher voltage and creates less damage. Chip based devices tend to stop draining at a higher voltage. It is the resistive loads, like the contactor that will drain really low and cause the most damage.