Charging AGM batteries
I have never owned an AGM battery, but the new trailer I am getting will have 2 of them. I replaced the converter/charger in my previous RV with a PD4655V, and am thinking of installing the same i...
Forum Discussion
AGMS used as engine starting batteries in general never get discharged much, and therefore do not require specific absorption voltages be met for hours.
Using my ammeter, well my AGM battery eventually gets to the point where it accepts 0.0x amps at any voltage when charged as charged as it can be.
If I start the engine at chrged as charged can be, when amps taper back to 0.0x amps at 14.7v, the battery again will be fully charged.
So how long does it take for amps to taper back to 0.0x at 14.7v after starting my 5.2 liter gas V8 engine? Under 45 seconds.
Manufacturer prescriptions/recommendations as to recharging are what they decided will yield the least amount of warranty returns. They will tweak them as needed to maximize their potential maximum profit. The CEO's mistress' jewelry collection depends on it.
Obsessing over precise charging voltages is not healthy, especially when one cannot control their vehicles voltage regulator anyway, or if their converter does not exactly meet the specs listed by the battery manufacturer. BEsides, without battery temperature compensation, which very few chargers have, well how many batteries are precisely at 77F every time they are charged?
An AGM that exceeds the absorption voltage limit at its given temperature is not an instantly dead AGM, and perhaps even cumulatively seeing a higher voltage, could last longer than an AGM chronically undercharged from too timid a absorption/max voltage.
While some le$$er AGMS say to limit charging amps to 30% of capacity, well, these are the higher resistance AGMS's. How hot will they get if that 30% is exceeded? How often can they exceed this before they vent the electrolyte? How many times can they do this before getting too dry?
I don't know. I have a Northstar AGM which regularly saw 14.9v and much warmer than 77F temps early in its life before I could control my alternator's target voltage. I have over 500 deep cycles on it now, and overnight voltage under load is still impressive and it is by far the most impressive lead acid battery i have owned.
I'd not stress exceeding ideal absorption voltage by a few tenths, unless perhaps ambients were 110F and I had 100 amps available of charging source into a well depleted 110f AGM.
I'd stress undercharging more, and in the case of my Northstar AGM-27 at 90AH capacity, I'd stress never being able to exceed a 30 amp charging rate as low and solar only recharges have performance( judged by voltage held under load, and morning voltage) begine to tank after 5 low and slow solar only recharges.
My battery seems to crave high amperage rechrging from its most depleted state every so often, and of course the true 100% recharged, determined when amps at 14.7v taper to 0.45 or less.
The time it takes amps to taper to 0.5% of capacity at 14.7v has increased a lot in the last 100 cyles.
Prematurly initiated float voltage equals premature battery death, in my opinion.
Use a hydrometer or ammeter with battery at absorption voltage to determine full. Far too many people believe that their charging source dropping to float voltage indicates full charge. Without verification this is extremely unwise, if one cares about achieving good to excellent battery longevity.
If one does not care, then why bother reading on an Rv tech forum in the first place?
Ammeters are now cheap. Seeing how many amps are flowing at that voltage is extremely enlightening during both charging and discharging.
Using my ammeter, well my AGM battery eventually gets to the point where it accepts 0.0x amps at any voltage when charged as charged as it can be.
If I start the engine at chrged as charged can be, when amps taper back to 0.0x amps at 14.7v, the battery again will be fully charged.
So how long does it take for amps to taper back to 0.0x at 14.7v after starting my 5.2 liter gas V8 engine? Under 45 seconds.
Manufacturer prescriptions/recommendations as to recharging are what they decided will yield the least amount of warranty returns. They will tweak them as needed to maximize their potential maximum profit. The CEO's mistress' jewelry collection depends on it.
Obsessing over precise charging voltages is not healthy, especially when one cannot control their vehicles voltage regulator anyway, or if their converter does not exactly meet the specs listed by the battery manufacturer. BEsides, without battery temperature compensation, which very few chargers have, well how many batteries are precisely at 77F every time they are charged?
An AGM that exceeds the absorption voltage limit at its given temperature is not an instantly dead AGM, and perhaps even cumulatively seeing a higher voltage, could last longer than an AGM chronically undercharged from too timid a absorption/max voltage.
While some le$$er AGMS say to limit charging amps to 30% of capacity, well, these are the higher resistance AGMS's. How hot will they get if that 30% is exceeded? How often can they exceed this before they vent the electrolyte? How many times can they do this before getting too dry?
I don't know. I have a Northstar AGM which regularly saw 14.9v and much warmer than 77F temps early in its life before I could control my alternator's target voltage. I have over 500 deep cycles on it now, and overnight voltage under load is still impressive and it is by far the most impressive lead acid battery i have owned.
I'd not stress exceeding ideal absorption voltage by a few tenths, unless perhaps ambients were 110F and I had 100 amps available of charging source into a well depleted 110f AGM.
I'd stress undercharging more, and in the case of my Northstar AGM-27 at 90AH capacity, I'd stress never being able to exceed a 30 amp charging rate as low and solar only recharges have performance( judged by voltage held under load, and morning voltage) begine to tank after 5 low and slow solar only recharges.
My battery seems to crave high amperage rechrging from its most depleted state every so often, and of course the true 100% recharged, determined when amps at 14.7v taper to 0.45 or less.
The time it takes amps to taper to 0.5% of capacity at 14.7v has increased a lot in the last 100 cyles.
Prematurly initiated float voltage equals premature battery death, in my opinion.
Use a hydrometer or ammeter with battery at absorption voltage to determine full. Far too many people believe that their charging source dropping to float voltage indicates full charge. Without verification this is extremely unwise, if one cares about achieving good to excellent battery longevity.
If one does not care, then why bother reading on an Rv tech forum in the first place?
Ammeters are now cheap. Seeing how many amps are flowing at that voltage is extremely enlightening during both charging and discharging.
