discharge and charge limits?
both excellent questions
as we all know or should know a 225amp/hr battery can deliver perhaps a couple thousand amps for a short period, into a dead short, so that is the extreme and likely hard on the plates of a true deep cycle battery.
i have read that one can take for instance 225amps out of a 225amp/hr battery but not for an hour because the electrolyte will statify, but it is safe to do so without damage to the battery, so i would expect that is probably the maximum safe limit of discharge although probably still not what most would like to do.
so maybe one half that or maybe 100amps from a 225amp hour being likely a safe max discharge? that is probably as hard as would want to draw down a deep cycle and not with any regularity.
charging is another thing all together, when the battery is down to about 50% SOC
and below, it is able to take a rather large amount of amperage without issue.
certainly 25% of the amp/hr capacity and, (if monitored for temperature gain) up to 40% of amp/hr capacity is not unknown. i have even seen reference to even higher rates of charge.
all things change at or about 80-85% SOC where the gassing starts to occur or
if the battery temps exceed ~110F, in either case the charge rate will have to be reduced accordingly.
most folks will find that getting to 25% charge rate a problem, and still more will find it near impossible to attain 40% charge rate on all but the smallest of battery systems. not many folks can generate and deliver 250-400amps into a 1000amp/hr battery bank. but it is not only possible but desirable for larger battery banks for efficient charging using fuel powered gensets, where runtimes being reduced = reduced fuel consumption= less dollars spent= lower cost per kwatt/hr generated, converted and stored.
for such a simple and well understood product (flooded lead acid battery) it becomes a bit more complex when you factor in all the other variables that make up a complete system.
there ought to be an E=MC(2) equivalent equation 
but sadly in my opinion there is not a single equation but a whole black board full of them using dozens of variables some of which are not static numbers but are variables in their own right.
thank god a lead acid battery is fairly forgiving, if not for this attribute
system failure rates would be as high as picking "winning" weekly lottery tickets.
the window of success is fairly wide, the goal being not to either habitually undercharge or overcharge the battery, keep in around 75F, clean and watered.
not much different than how we want to be treated!, i think most of us would last longer with fewer issues if we are fed right, not underfed or overfed (charged), worked within our ratings (discharged maybe to 50% capacity and not till we are flat beat to death), kept at around 75F, given good clean water, our back scrubbed (terminals/connections/case cleaned), blood pressure/sugar levels checked (voltage and specific gravity).
seems reasonable to me
seems a bit analgus to an old trucker who after 40 years and over 2.8 million miles on 3 mack trucks had never lost a single clutch, transmission, engine or anyother major component when asked what his key to success was...
"i drive my truck the way i would want to be driven if i had 80,000 lbs on my back"
can't fault that!
bob g
