On Tue, 26 Oct 2010 17:12:01 -0400, "Flying Pig"
wrote:

So...

Checked the connections to the starter and block. Took them off, burnished
them, the posts/bolts/washers, greased them up and put them back.

Metered all the connections at posts, not lugs (if it ain't at the lug, it's
not necessarily getting where you want it). No resistance; conclusion being
the connections are good. That's at the battery(ies - start and house), the
1-2-all switch, negative and positive busses, and anyplace else there was a
red or black wire which could feed the starter.

Batteries floated for a while, left to rest for an hour (loads still
connected). 6.47 or 6.48 on all 4 6V, 12.8 on the start. Turned over
starter for voltage drop test, attachment points engine ground and starter
positive lug. 4V drop! Following the voltage drop tests, it wouldn't start
immediately; I quit after 5 seconds or so of cranking, cuz my experience is
that it will go in 1 or 2, tops.


According to Trojan 6.37/12.73 is the fully charged Open Circuit
voltage.

Operating the starter causes system voltage to drop by 4 volts, i.e.,
from 12.73 to 8.73 (I assume during the cranking period) and after
this test the engine wouldn't start (again I assume because of low
cranking speed, not fuel starvation).

You do not state how much battery capacity is connected to the starter
but if you were connecting to the house battery bank and this voltage
drop occurred then your house batteries are knackered.

If you have a single battery connected to the starting circuit then I
would have to ask "WHY?". The proper set-up is with a switch allowing
the starter to be connected to either the house or starting batteries.
The house batteries are used normally but if they fail then you can
switch to your fully charged starting batteries to start the engine
(and hopefully charge your house batteries).

Hydrometer test showed all cells within .010, only one .005 up from the
norm, and only a couple .005 down. Adjustments for temp made; showed lower
(adjusted) specific gravity than would be full charge (right on the edge,
but should have been higher), yet apparent voltage was appropriate for full
charge, I'll get another tester and repeat.

Load tested all batteries, passed with flying colors, and no voltage drop to
speak of (less than 0.1) after the test, which was more like a full minute
than the recommended 15 seconds. Meter never moved during the entire test,
once energized Had to be careful about how I handled the tester, it got so
hot.

So, that's where we are right now. When the batteries are floated off, she
starts right up. Yet, with 880AH main, and a 15M-O deep cycle start
battery, seems it also ought to go right away at, say, 80% charge...

More as I know more.

L8R

Skip
Cheers,

Bruce
(bruceinbangkokatgmaildotcom)