Date: Sun, 29 Jul 2007 13:00:24 -0700
Reply-To: Michael Elliott <camping.elliott@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Michael Elliott <camping.elliott@GMAIL.COM>
Subject: Re: Deep Cycle Batteries
In-Reply-To: <000c01c7d1f6$40fe8310$0301a8c0@MASTERPC>
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Dennis Haynes typed:
> Of the battery choices out there, a conventional flooded cell will be the
> most tolerant of use and abuse and provide the longest life. Most of the
> 12 volt deep cycle batteries or beefed up starting batteries and still
> have short lives of one or 2 seasons. The golf cart batteries are a lot
> more tolerant of heavy use.
>
> Of the common, reasonable price brands, Trojans are probably the best.
> Best plates and a lot of active material in the plates. Yes there are
> better such as Rolls Surrette but bring money.
This is in agreement with what the designer at Blue Sky Energy
(http://www.blueskyenergyinc.com/) told me last week. Trojans, he said,
are "real" deep cycle batteries.
> AGM and Gel batteries is still emerging technologies and the advertising
> is a lot of hype.
I asked the engineer about one of the claims made of AGMs: namely that
they claim a higher charge efficiency (96%) as opposed to flooded cell
batteries (85% to 90%). Charge efficiency is a measure of how well the
battery converts charge energy into charge, not heat, so a higher number
means more rapid charging. He disagreed and said that one would be
hard-pressed to measure a significant difference between AGM and flooded
cell batteries. "Snake oil," is the phrase he used.
> For wiring and charging, the circuit needs to sized for both charging the
> battery and any load connected to it. This includes inverters. The GC-2
> will pull about 40 amps off the alternator during the bulk charge. Add you
> other loads. Best results will also be a direct line from the alternator.
> #6 gauge.
That's a good way. I have another view on the charging aspect of this,
though. If the wire is skinnier, then its resistance will limit the
initial flow of current into the battery. But as the battery comes up to
charge the current into it naturally drops so the resistance of the wire
becomes less of a factory. For many people, being able to deliver 40
amps into the battery for its first 15 minutes of charge might not be
worth stressing about when 20 amps will just add another 15 minutes to
the total charge time Of course, if one has a hefty bank of giant
batteries that are severely depleted and only a short time to charge
them, then giant alternators and garden hose-size wire may make a
significant difference in how quickly you can get them up to full
charge. But in our application, where the 100Ah group 27 battery is
usually about 20Ah low in the morning, we have plenty of time to charge
it up during the day, whether from solar or driving (stock alternator,
puts about 16 amps initially into a lowish battery through my 6-gauge
wire that runs from the starter battery. For us this is plenty.
> Also, you want a truly reliable relay. Most important that it
> disconects when expected. You want double break contacts like in those
> solenoid type cans. Not a small lighting relay.
Yup. Hate to wake up in the morning to find that my engine battery got
depleted along with the house battery because the relay's contacts fused
together.
--
Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
KG6RCR
