lead acid charge current

[philwzen]

ok , this is probably a stupid question but i cant decide if what im seeing is correct.
I have four 12 v 200ah lead acids in pararalell for an 800AH total. now weird thing is they Never take more than 8amps charging, even when i know they are pretty dead. Solar (3kw at 36v of panels with 100amps of mppt) will only put in about 7  amps. Also charging via a 2.4KW 240V ac generator and a 20amp rated dumb charger only shows 5 to 6 amps on the chargers ampmeter. Recently constructed a DC charger from a large alternator and redundant engine, alternator is rated 90amp and 24v, It also has a 12V output as its 'y' wound. The 12V out reads 14.4 V fine i thought, but when connecting to batteries it still only draws max 8amps measured with inline meter!. I was hoping to use the alternator as a bulk charger, put the 24V into my mppt controllers and let them work it out potential for 180amp at 12v there. The question im asking is why do i only see max 8amps? even if the batteries are low, id expect them to suck as much charge as possible, maybe my understanding is wrong. 

[DamonHD]

Hi,

Are the batteries old/sulphated?

Rgds

Damon

[philwzen]

not impossible they seem to come up to voltage but dont have a great capacity. they are various ages. ideally would replace the lot but cash is a problem. I just tried charging only one with the 24v from the alternator into a 50amp mppt and it miraculously gave 36+ amps going into the battery.
 ill do the same for each of the four give it about a day on that and see what they sit at. im suspecting the whole bunch are junk but  i may be lucky, also thinking about flattening them complety then reverse charge individually. battery shed is 40 yards from house so any bang would be contained.  Just intersting how the mppt will put in 30 odd amps yet a direct connection only about 5.