Thanks for all the replies, here's an update.
I repeated the test on the 1st charger and it tripped into float early just like the 2nd one... this was a real bummer because I thought just one charger was the problem. It seamed unlikely two chargers would have identical faults so we had to once again consider that the fault could lie elsewhere. Anyway after another marine
electrician had us beef up the wiring
from chargers to batteries with no improvement we took it upon ourselves to buy (but kept the receipt should it not help) a new Xantrex 40A charger from Budget Marine
in St Martin
. The idea was if it works, brilliant we know the chargers were at fault, if it didn't help we could eliminate the chargers as a problem. Well... it worked, so we bought a second 40A Xantrex and their remote
control/display panel that allows parallel installation
(actually very nice to have the remote
display to see what's going on). Now our charging is text book perfect!!! We see 80Amps going in during the bulk phase and it doesn't dwindle at all until the absorption stage begins. The Xantrex chargers also have an Equalization
mode that runs for 1hr and we ran it 6 times and our hydrometer went from a best reading of 1.20 to 1.24 (still not perfect but a fair improvement, we'll do it again shortly). Our daily genset runtime has dropped from round 4hrs to less than 2!!!
With the help of the last technician after replacing the chargers we analyzed why the alternator
was giving us a low output. This had been a big riddle for us because if the alternator was also having trouble charging the batteries how could we say the fault was with the chargers as they're on totally different circuit. This too pointed to the fault being with the batteries or in the wiring somewhere. Well the answer was we were reading the output on our Xantrex Link Pro which is only connected to the service
bank, we weren't seeing the charge going into our start or bow thruster batteries. As these were also not fully charged because of the charger faults they were taking a big share of the alternator output, leaving us a low reading into the service
I can't tell you all how much of a relief it is to have this solved
, now we can get on with the job of worrying about far less important things