On Mon, Aug 01, 2011 at 02:15:29AM +0000, Capt. Mike wrote:
>
> I went with separate 12 volt house and 48 volt propulsion bank. I personally
> did not want all the eggs in one basket.
I wasn't thinking about it quite like that when I decided to go this
way, but - yeah, looking at it from that perspective, that was a pretty
major decision factor in my own thought process. Although Eric's
approach, which involves a "buffer" battery - that's a good bit of
thinking, there! - sounds pretty good, a pair of AGM 4Ds beats a box of
electronics in the reliability department any day. :)
Incidentally, does anyone know where I can buy 4D AGMs in the NYC area?
Universal Power UB-4Ds tend to run ~$310 each, which is fine, but the
shipping charges are pure murder. I'd like to find them locally, if I
can, so I can pick them up (at 130 lbs apiece, they're still manageable.)
> I will use the 48 volt bank to power
> some 12 volt items like my laptop but, find the sevcon converter gets rather
> warm with extended use and is only about 85% efficient. Not a problem if you
> are at a dock with AC available but, out at anchor it can eat a lot of amps if
> you are feeding the 12 house wiring with it for an extend stay away from the
> dock. Something you might want to consider.
Well, the upside - of course - is that I'd be saving weight if I went
with a converter. On the other hand - ooh, just had an idea. Whenever I
do get around to the full conversion, have a rotary relay that feeds a
small buffer battery, /a la/ Eric, from each 12V set/battery in the
drive bank, and trips (i.e., switches to the next set/battery in the
chain) at regular intervals (say, once an hour.) Seems like it should be
100% efficient - no conversion losses - and there wouldn't be much of a
switching load, since the buffer battery would handle that end. I've
seen relays like that in military equipment; should be easy enough to
find them in surplus stores.
Can anybody see a problem with that?
--
Ben Okopnik
-=-=-=-=-=-
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