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
BFL13 wrote:
PT, what is a "regular" AGM anyway? Why does Mex insist on the 20% minimum recharge when the battery specs say nothing about that--not being Lifelines?)
It wouldn't matter if all AGMs were identical. Marketing and the lawyers will find some mumble speak to differentiate their product. Read their specs and manuals with some level of skepticism :)
I have had 2 135AH UPS type AGM over 3 years now. The only specs I got were charge - 14.4-15V and Float 13.5V, max charge of 50A. They are in constant cycle use by running two 12V compressor fridges. The AGMs are charged daily by a 15A Morningstar solar controller(CC). I have set the CC to reach the 0.5% Amps ABS at 14.4V +/-TempComp daily; somewhat like with Lifelines.
I record a log, with a Raspberry Pi computer, at 1 minute intervals. I have over a year of logged data. I use this log to watch the daily Abs Amps.
If the battery volts trend down, the CC extends the Abs time to catch up the next day. This is process repeated daily to the point of cancelling Float to have Abs all day. If I know bad weather is approaching, I will use the 50A of the inverter/charger to catch up quickly. This is a 25% charge rate.
Each of the three years I have run a capacity test to demonstrate that the AGMs can continue to do what I want. I am very confident that the AGMs don't spend more that a day under 80% SOC.
The AGMs are likely 8+ years old based on the claim by the vendor that they were around 5yo in 2015 when I bought them.
HTH;
John
