Mex's 20% AGM Rule Sucks.
Mex says deep cycle AGMs need to be recharged at a 20% of Bank AH rate even if they are not Lifelines (which do specify that). My AGMs are not that brand, and no mention is made of a minimum charg...
Forum Discussion
Be careful jumpstarting that underhood AGM engine battery, the alternator will be able to triple that maximum 'recommended' charge rate and it will blow up!!!!!
Because we read this in the news every day.
The Deka intimidator AGM is the most relabelled and likely widespread AGM in the US, and it too lists a 30% max recharge rate, and even with a g31 battery, the weakest alternator in any modern vehicle is going to be able to exceed that 30% rate just after startup when the VR is still asking for mid to high 14's, if the battery were accidentally discharged to the point it can accept high amperage.
I see manufacturer recommenedations as second guessing the intentions of the end user and trying to limit warranty returns. Max profit wins again. A few tenths of a volt or % points on amperage rates is not going to instantly destroy a battery or degrade it noticably.
It will affect the time it takes to fully charge, which is not an issue if one is plugging in to do the job.
Lifeline says if you cannot meet the 20% minimum in deep cyclic applications then finish the charge with a 2% constant current for 2 hours, or something along those lines. Not sure what voltage the battery would rise to with 2% constant current after the regular absorption stage has completed, but likely well over 15.3v.
Swing the amp hammer, monitor battery temperature, disregard recommendations designed to pad manufacturer's bottom line.
That said I want a battery whose spec/user manual sheet does not say anything about limiting charge amperage, so that leaves Lifeline, Northstar and Odyssey which are at the opposite end of the AGM spectrum from Chinese UPG's
If All I had to recharge was low and slow solar, then I would not choose these batteries.
Because we read this in the news every day.
The Deka intimidator AGM is the most relabelled and likely widespread AGM in the US, and it too lists a 30% max recharge rate, and even with a g31 battery, the weakest alternator in any modern vehicle is going to be able to exceed that 30% rate just after startup when the VR is still asking for mid to high 14's, if the battery were accidentally discharged to the point it can accept high amperage.
I see manufacturer recommenedations as second guessing the intentions of the end user and trying to limit warranty returns. Max profit wins again. A few tenths of a volt or % points on amperage rates is not going to instantly destroy a battery or degrade it noticably.
It will affect the time it takes to fully charge, which is not an issue if one is plugging in to do the job.
Lifeline says if you cannot meet the 20% minimum in deep cyclic applications then finish the charge with a 2% constant current for 2 hours, or something along those lines. Not sure what voltage the battery would rise to with 2% constant current after the regular absorption stage has completed, but likely well over 15.3v.
Swing the amp hammer, monitor battery temperature, disregard recommendations designed to pad manufacturer's bottom line.
That said I want a battery whose spec/user manual sheet does not say anything about limiting charge amperage, so that leaves Lifeline, Northstar and Odyssey which are at the opposite end of the AGM spectrum from Chinese UPG's
If All I had to recharge was low and slow solar, then I would not choose these batteries.
