Hi, all -
I recently installed a pair of brand-new 4D Deka AGMs aboard, and
they're behaving in a puzzling way. Perhaps I'm judging from the wrong
perspective - I've been shipmates with FLAs for the last 19 years or so,
and am used to their quirks - so I'm hoping someone can give me a clue.
First, my configuration: I've got a 105A alternator with a built-in
regulator (yeah, it's on the list of projects - thinking about an
external Balmar regulator) and a MeanWell 1kW battery charger (just
found out that it comes configured for FLAs, and changing it to AGMs
requires sending it back to the factory...)
Next, here's where I get really confused: when I charge the batteries,
via either method, I see the system voltage come up quite quickly -
i.e., if they're at 12.0V, then about an hour after firing up the
engine, I see 14.4V (measured at the panel, the batteries, and the
alternator; no significant loss in the wiring.) Then, when I turn the
engine off, the system voltage drops to 12.6V within a minute or so.
Here's what's confusing and frustrating, to me:
1) It's a 400AH battery bank. How the heck is 1-1.5 hours of charging -
which starts at ~90A, quickly tapers to ~60A, and then slowly drops to
~5A at the end, for an average of maybe 30-40A - bringing it up to
14.4V?
2) Unsurprisingly, the discharge curve reflects exactly that amount of
charge. A day of running my laptop + external monitor, lights, pumps,
etc. drains it back down to 12.0V. At ~5-6A average load, those numbers
make sense... but a 400AH bank, with, say, 200AH usable capacity, should
be giving me about 3.5X that charge/discharge capacity.
3) What I'm used to, with FLAs, is that the voltage comes up relatively
slowly - they warm up, then accept a reasonably high current for a good
while, and then taper off - and their resting voltage at full charge (as
indicated by the charge voltage reaching 14.4V) is right at 12.8V.
12.6V, which is what I'm seeing these days, indicates an incomplete
charge to me. I'd happily push the charging voltage to 14.6V if I could
- that's the limit stated on the batteries themselves - but I currently
have no way to do so unless I start tearing the alternator apart.
So... is there something else I need to do? Would regulating the
alternator differently and swapping out the MeanWell charger for
something AGM-specific result in something more reasonable? Or do I
have, despite their being brand-new, a bad pair of batteries? A load
test shows them to be OK, so I'm currently stuck for ideas.
--
Ben Okopnik
-=-=-=-=-=-
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