Date: Thu, 30 Sep 2004 13:49:19 -0400
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: Monitoring aux battery charging?
In-Reply-To: <415C2CC8.8090304@colorado.edu>
Content-Type: text/plain; charset="us-ascii"; format=flowed
At 11:56 9/30/2004, Richard A Jones wrote:
>>But sitting there at camp hearing the engine run, it's not clear to me
>>how fast the engine needs to run, nor how long it needs to run, to bring
>>the aux battery back to fully-charged status.
>
>I had similar questions, since I had to run my engine to
>recharge my aux battery while camping 3 days and running
>my computer via an inverter. Idling for 30+ minutes
>appeared to charge it back up--this by watching the
>voltage level in the system. (Of course, max voltage
>depends on the temp of the battery.) I hadn't run my
>aux down very much--the inverter was very sensitive to
>the voltage and quit when it started to drop a little.
I feel like the voice crying in the wilderness here...but one more try:
getting the most out of lead-acid batteries doesn't come cheap, and you can
pay different ways. Lots of money is one way -- go to somebody involved in
off-grid living with significant battery power, or go to an experienced
long-distance cruiser with similar inclinations; or to the serious RV
voyagers; or to the guy who runs amplepower.com. Hand over a thousand
bucks and say "Make it work for me" -- it will. You may have to come up
with another $500 -- or worse -- to get your baby back, and you may have to
actually read some equipment manuals and pay a certain amount of attention
to consumption and maintenance schedules, but if you correctly stated your
requirements you'll have a setup that will make you smile.
The second extreme is lots of understanding and an obsessive, fanatical
attention to detail, plus a hydrometer and a sensitive voltmeter and a
whacking great rheostat, or some carefully chosen light bulbs if you're
*truly* cheap. People sailing across oceans tend to have plenty of time
for this...you may not.
And the third is to balance the money and the understanding and the
attention -- you can trade money against attention and (somewhat)
understanding, understanding and attention against money, longevity against
weight and first cost...it's going to be $300 or more for a voltage
regulator, $xxx for one or more batteries of the right size and
construction, and likely a fair chunk for a marine-type continuous-duty
alternator or some forced-air cooling for the existing one. You can swap
some moderate attention against a few hundred for a fancy charge-management
box, and you can save a good chunk of weight by deciding to discharge your
battery below the 50% mark -- at a large cost in longevity and lifetime $$.
In return for any of the above you'll get a system that supplies the power
you need at a minimum expense in gasoline and noise and engine
wear-and-tear, and ultimately a minimum expense for batteries. I use the
third method on Scamp -- I've got 300 amp-hours of nominal capacity which I
elect to draw down to about 25% instead of stopping at 50%. I have a
nominally 35-amp alternator that will deliver 30 once it's warm, needs the
Atomic 4 to run about 1400 rpm to do it. That's a bit of a kluge, with the
right pulleys I think it could do the job at 1000 rpm which would be a lot
quieter. And I have the cheapest regulator that Ample Power makes; it cost
$300 and it does *exactly* what it claims to, which is to stuff charge into
those batteries as fast as the alternator can deliver it, until the
batteries say "enough" -- and then make a token attempt to fill the
remaining 15% with a timed tapering-rate charge that shuts off after an
hour. I can be fairly lavish with the juice in utter silence for 3-4 days
-- and then charge for a solid eight hours, with the ammeter sitting on 30
amps for about seven of them. A $25 rheostat would do as well, except I'm
way too absent-minded to rely on myself to keep watch over it.
That's if you're serious. The dividing line between even-a-little-serious
and not-hardly-serious IMO is the regulator. You can maybe make a
convincing case to be somewhat serious with a starting battery like the
Optima that's rated for 50 discharge cycles to 10%. But without going to
either manual control or a full three-stage smart regulator you're going to
be just where I used to be on Scamp, charging and charging and charging at
five or ten amps, and never actually getting the suckers charged at all,
and then having to replace them too soon because they wouldn't *take* a
charge. I was in the land of I Wish for about 25 years too long.
That being said, in the Westy I have a normal starting battery and the
stock regulator and a 10-amp charger and a hundred-foot extension
cord. Our main cabin light is an 11-watt CF reflector bulb in a clip-on
gooseneck lamp. (looks like a narrow-angle PAR lamp, I've never seen
another exactly like it) that draws an amp and change through an
inverter. We're not usually more than 24 hours away from 110vac...it works
for us. And the battery lasts about half as long as it should, even so.
cheers,
david
--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage," '85 GL "Poor Relation"
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