Regarding high charging rates affecting the lifespan of an AGM battery i.e. low charging rates degrading lifespan...
A dozen like batteries would have to be put under test. Fifty % DOD. Three to be recharged at full charge acceptance at 14.4, three at 50% charge acceptance potential three at 30% charge acceptance potential and the last three at 10 amperes (for a 100-a/h battery.
At end of lifespan test, if a definite correlation can be shown as a descending cycle life with regards to charge potential utilized, then and only then would it be likely that high potential charging affects battery lifespan. One or two examples of "My batteries have last X years with X charging potential", does not cut it. There are too many mitigating factors.DOD, time spent in various degrees of discharge, et al.
Top notch companies with similarly top gifted design engineers are the only valid source of information about their product. Concorde says without stuttering, that low charging potential will adversely affect their product. Concorde merely manufactures a carefully crafted product. Their close tolerance plate to mat clearances affords lower impedance. But that in itself cannot possibly alter chemistry and physics. So Concorde does not manufacture a Magic Mountain product. If the tendency is valid with a Concorde battery then it is every bit as valid with an AGM Full River, Trojan, or Hung Chow, special.
China is weird. If top notch engineers and supervisory personnel control the manufacturing process, a good product is assured. When Honda, or Sony, or Meanwell have the reins at a factory, it is going to produce good quality material for the market. It's the Kung Fu Butterfly, independents that cheat and slop together goods then ship them out without testing. Korean overlords are hated. They are the strictest, meanest, and most disbelieving of the foreigners used to maintain quality control. The Americans use Koreans, so do the Japanese. (info provided by Lin Xao Peng).
You may remember a post I made about Lin announcing to me the introduction of quality AGM batteries. I was wondering about that. Senor Pianotuna suggested that Rolls is using Chinese AGM batteries. Interesting. But Lin emphasizes that LITHIUM is the big enchilada. More than a thousand Chinese manufacturers are betting the shirt off their back that Lithium is the battery of the future. I can offer this - lithium is a whole new ball game engineering and quality-control wise and this golden ring is a long, long, reach from the Chinese merry-go-round. Because China is coal rich, and petroleum poor, the Central Committee decided to prioritize electric motor vehicles. Heads will roll, blood will flow, but China will beg, borrow and steal the technology to get the job done.
If I had to guess, I would say 2018 is the year China comes online with large bank lithium alternative energy blocks. The blocks will contain monitoring and energy management instruments and control. 50,000 ton shiploads of lithium rich ore are sailing from Australia every day. This is amazing to "watch".
The market is -not- the USA. It is the Indian sub continent, Africa, South and Central America. China is bound and determined to electrify the earth with affordable solar panels and batteries so light a cargo truck can haul five times the amp hour capacity max load limit, thousands of miles from a port. The Chinese may not be top innovators but they are smart - crafty is the word. Lin told me, the government wants to relocate coal burning gigawatt grade generating plants a thousand miles away from cities and transmit ultra high capacity kw via million(s) volt DC power lines. Cars and huge trucks will be electric as will the trains. Cargo containers for everything. Mind boggling.