Date: Sun, 23 Sep 2012 12:42:18 -0400
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: Alternator continuous-duty rating?
In-Reply-To: <505F1524.1070802@flatsurface.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed
At 09:56 AM 9/23/2012, Mike S wrote:
>"Electrical output must provide adequate current for all normal
>continuous loads. Twenty-five percent of intermittent loads such as
>brake lights, turn signals and radio transmitters should be added to
>continuous load; 50% for school buses, twenty percent...for battery
>charging...Generator output should be 50% more than vehicle load
>requirement."
Mike, that's great, thanks a lot.
Jack's looking at continuous output in terms of the alternator
running flat out for several hours at a time, charging deep-cycle
batteries. That's the (an) intended usage of those "light-duty" six-
and seven- series Balmars. He doesn't need the explosion-proofing
(they call it ignition-protection nowadays, clearer but boring), but
it's more an industrial than automotive application as such.
The history has gotten hazy in my mind, but I rather think that
Balmar (founded 1982) alternator production arose in response to
demonstrated failure of automotive alternators adapted for marine
service (recreational/cruising vessels) to survive deep-cycle battery
charging regimes, once properly designed multi-stage regulators were available.
The multistage regulator I got for Scamp ?15? years ago (Ample Power
Next Step, first series - cost $400 then; the second series is now
under $300 with more capability, and I think the ones from Balmar now
operate as well and have similar prices) came with explicit warnings
that a standard alternator might not survive its attentions. I
continued to use the Motorola 35-amp alternator that came with the
engine in '63, and with our operating regime (cruising in Maine,
engine box temps below 120F, duty cycle ~eight hours flat out every
4-5 days for ~three weeks a year) it held up fine.
Some multi-stage regulators have provision to throttle the alternator
output, but Jack's looking to stuff charge as fast as he can during
limited driving time between campsites where he'll operate dry for
days at a time. On Scamp we traveled with no engine for days at a
time and then charged for roughly eight hours. A bigger alternator
would have been nice. My laptop was the biggest overall drain (radar
being next, followed by cabin lighting, Loran plotter, running lights
in that order). We used ice for refrigeration. For Jack the fridge
is the big item I imagine. He's looking for longer time between
charges with less battery capacity than we had (200 AH, cycled to 80%
discharge for lower weight and initial cost), but he's supplementing
with solar.
Interesting document here:
http://www.prestolite.com/literature/alts/PACU_097.pdf . Great
reading when you can get past the fancy brochures to the people who
have to actually make it work.
Yours,
David
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