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Date:         Thu, 30 Sep 2004 21:13:05 -0700
Reply-To:     Rocket J Squirrel <j.michael.elliott@ADELPHIA.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Rocket J Squirrel <j.michael.elliott@ADELPHIA.NET>
Subject:      Re: Monitoring aux battery charging?
In-Reply-To:  <6.1.2.0.2.20040930121204.04a970a0@pop1.attglobal.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Fortunately Mellow Yellow and I are not at sea for months at a time, and a failed battery will not sink us. So a first-order approximation of battery charge should suffice, I reckon. Today I picked up an good old school round analog ammeter with a +60-0--60 scale. Wired it in series with the aux battery's (+) terminal. Negative readings big enough to deflect the meter will indicate that I am pulling a lot of current out of the battery, so I should back off on the power consumption. And during charging, high positive current will show that the battery is absorbing a lot of current while it charges up from a partially discharged condition. The current should taper off as the battery reaches full charge. All I need to do is make sure that the engine is revved enough to make the alternator's voltage regulator regulate and watch the meter. A digital voltmeter connected to the aux battery will let me monitor alternator voltage when the engine is running and the aux battery is connected to the main battery. And when the engine is off and the aux battery disconnects from the main, the voltmeter will let me keep an eye on how much reserve the aux battery has. Optima does not recommend letting this Yellow Top discharge below 10.5 volts.

That's my plan, it's a good one, and I'm sticking to it.

-- Mike "Rocket J Squirrel" Elliott 71 Type 2: the Wonderbus 84 Westphalia: "Mellow Yellow (The Electrical Banana)" KG6RCR

David Beierl wrote:

> 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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