Date: Fri, 25 Jan 2002 14:09:53 -0500
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: Shorten Aux Battery Recharge Time
In-Reply-To: <007901c1a5be$742a8f00$eb406620@sanjose.ibm.com>
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At 11:36 AM 1/25/2002, lchase wrote:
>I want to shorten the recharge time for a fully discharged Optima 750 Deep
>Cell Battery to around 2 hrs while driving.
>
>What if I power a 20amp smart charger (Made for Deep Cells) via my existing
>1000 watt inverter thru a switched circuit that allows the inverter to draw
>its needed power from the alternator while the engine is running. If my
>calculations are correct, a 20 amp charger should fully recharge this
>battery in around 2 hrs.
The Optima specs I see run about 55 amp-hours at C/20 rate. They seem to
be designating them by group now, so I don't know what corresponds to your
750. Anyhoo, I suggest you contact Optima for a charge regime that will
meet your specs. I'm pretty sure that a 20-amp charger won't put 60
amp-hours into a battery in two hours in this universe. <g> If (God
forbid) you're talking about sticking the charger on while the battery is
also hooked into the regular charging system, I have no advice beyond 1)
become an expert and 2) wear safety goggles. My gut feeling is that it's a
Really Bad Idea, but I don't have facts to back that up.
Unless you are willing to sacrifice performance to get 110vac charging
ability, you might do better looking at a smart regulator like the Next
Step http://www.amplepower.com/ which will charge the battery as fast as
the alternator allows (I think you can charge an Optima in an hour if
you're really serious about it), but you may need to supply extra cooling
to the alternator or use an alternator that is rated for
continuous-duty. I don't know specifically whether the Bosch will handle
continuous high-output operation but many (most?) automotive alternators won't.
Your vocabulary words for the day are "bulk stage," "absorption stage," and
"float stage."
> If the 1000 watt inverter uses too much power and
>puts too much extra load on the vehicle 12 volt system, I could dedicate a
>smaller inverter just for the Battery Charger and eliminate the need for a
>switch.
The 20-amp charger shouldn't draw more than ?300? watts -- the inverter
draws power based on what it's delivering.
david
--
David Beierl - Providence, RI
http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"
