Date: Sat, 28 Jul 2007 09:52:21 -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: CDN Tire: Two 6 volt vs One 12 volt battery question
In-Reply-To: <283416.87244.qm@web43138.mail.sp1.yahoo.com>
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There are trade-offs.
The links your provided take me to a log-in page where my USA-style zip
code is not accepted.
So I can't comment on those batteries. But I can offer these possibly
useful thoughts.
1. The ampere/hour ratings of the batteries are not given at the same
discharge rate. The 6V battery is rated at 6 hours discharge (golf cart
usage) while the 12V battery is rated at 100 hours. Typical ratings for
batteries being sold into the solar market are given at the 20-hour
discharge rate. So apples to oranges, almost. One can make guesses if he
knew more about the batteries, which I don't.
2. The 12V battery is an AGM. For longest life they want care when
charging to avoid damage. If you plan to connect them to a wall charger
and let them sit, then make sure it is designed for AGMs which want a
three-stage charging cycle: bring battery up to about 14V by dumping
current into it ("bulk" charge stage), choke back current as needed to
hold voltage for about two hours (absorption stage), then drop voltage
to manufacturer's recommend "float" voltage. This is less critical for
flooded batteries, like the 12V one, which can be held at the same
voltage for float as for absorption w/o damage as long as you keep an
eye on the electrolyte levels and add distilled water as needed to
replace any that has fizzed out. For less muss and fuss, three-stage
charging can be a good idea for flooded batteries. Flooded batteries
also want occasional "equalization" to make sure that all the cells in
the battery are providing the same voltage. This is something that some
chargers and our solar controller can be told to do. More here:
http://www.bigginhill.co.uk/batteries.htm
Though. The difference between a two stage and three stage controller
when using AGMs is probably not worrying about if you use your battery
like we use our non-AGM battery, where the battery gets charge taken out
every morning before getting charged up during the day. Daily cycling
with a two-stage charger apparently isn't a problem for AGMs, although
battery mfgrs may differ; this mainly because they are thinking about
wall chargers that will keep the battery at 14V 24 hours a day, and will
damage an AGM.
More tradeoffs. Your alternator + 1315 probably won't take the battery
up to its full absorption voltage, so it won't get baked, but it won't
get quite as fully charged as a good solar controller or two- or
three-stage charger can take it. In my application I see that we run
about 10Ah short of fully charged when I use the alternator to charge
the battery when compared to a good charge from the solar controller.
For me, if I was choosing between the two, and since you are
contemplating using your alternator for charge (at first) and want a few
days of use between charges, I'd go with two golf cart batteries if they
are of good quality. My opinion only, and one that is not as informed as
others, but better than many.
--
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
Malcolm Stebbins typed:
> Having read the post regarding Canadian Tire's battery sale, CDN Tire has 2 batteries that seem to
> be what I want/need:
>
> http://www.canadiantire.ca/browse/product_detail.jsp?FOLDER%3C%3Efolder_id=1408474396673605&bmUID=1185573901792&PRODUCT%3C%3Eprd_id=845524443277145&assortment=primary&fromSearch=true
> and
> http://www.canadiantire.ca/browse/product_detail.jsp?FOLDER%3C%3Efolder_id=1408474396673605&PRODUCT%3C%3Eprd_id=845524443290779&bmUID=1185574219890&assortment=primary&fromSearch=true
>
> If your browser breaks up those URLs, The specs are:
>
> 6 volt: $85 CDN - Features
>
> * Deep-cycle 6 V battery can be used with solar panels as a source for stored energy when used
>
> in conjunction with inverters
> * 390 minutes of reserve capacity (at 25 amps)
> * 150 Amp Hours (at 6 hours)
> * Also fits golf cart applications
> * 6-month manufacturer's warranty
> * 6-month free replacement
>
> 12 Volt:; $213 CDN Features
>
> * Renewable energy deep cycle battery
> * 12V sealed AGM (Absorbed Glass Mat) deep cycle lead acid battery
> * Designed to be used with Xantrex PowerHub 1800 (11-1877) or as part of any battery bank for
> a
> renewable energy system
> * 100 ah at 100 hour rate
>
>
> I know VERY little about electricity. but I do know that 2, 6 volts can = 12 volts.
>
> So which is "better"? My intended application/use is:
>
> Battery under rear seat (so no space limitations), to power all stock interior lights and my
> lap-top through an inverter, but NOT the Dometic fridge; I have a top loading Waeco compressor
> type fridge that draws, on average (at 70 Deg F) 1 amp per hour. I figure that 3 to 4 days of NOT
> running the van (to charge the batteries) will be about all I'll need.
>
> I also plan to maybe add a solar panel to the top of my van, maybe a 2 or 3 amp panel.
>
> I also have a SurePower 1315 and I called them and they said their unit would not care if it sees
> One 12 volt or Two 6-volt batteries.
> Cost is really NOT a factor, (but 2x$85 = $170, or $213) I want the best, more reliable, and
> longest running set-up.
>
> So which is "better".................... I fear the answer will be "There are trade-offs...."
>
> Malcolm (who barely understands watts = amps x volts, AC vs DC etc.)
>
>
>
>
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