Date: Thu, 20 Sep 2012 20:18:14 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: [Nearly Off-Topic] Seeking Battery Switch
In-Reply-To: <505BAAA2.4080404@gmail.com>
Content-Type: text/plain; charset="US-ASCII"
You're really just adding complexity for almost no benefit. Use the smart
charger for your solar array since you may then have power for enough hours
for it to matter. Install a proper 110 volt charger such as one of the
progressive dynamic units for when the van is home or when shore power is
available. Do keep in mind that each time you "top off" (80-100%) the
battery you are doing a charge cycle which is limiting factor of battery
life.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Rocket J Squirrel
Sent: Thursday, September 20, 2012 7:46 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: [Nearly Off-Topic] Seeking Battery Switch
"Oh. I thought you were talking about running down the road using an
inverter to power a smart charger, and manually switching to it after
current monitoring to the house battery showed that bulk charge from the
engine alternator had diminished below the output of the AC-powered charger
(which would then go through its own bulk-finish-float sequence)."
Almost. I am using a smart charger but it takes 12VDC from the alternator as
input, not 120VAC from an inverter, though that would work, too. See
<http://www.powerstream.com/DCC.htm>
--
Jack "Rocket j Squirrel" Elliott
1984 Westfalia, auto trans,
Bend, Ore.
On 09/20/2012 03:43 PM, David Beierl wrote:
> At 05:03 PM 9/20/2012, Rocket J Squirrel wrote:
>> I have a little "smart charger" in the van which trickles the house
>> battery when I connect the side inlet to household AC power. But I
>> unplug the extension cord before starting the van, and turn off the
>> van before plugging in the extension cord.
>
> Oh. I thought you were talking about running down the road using an
> inverter to power a smart charger, and manually switching to it after
> current monitoring to the house battery showed that bulk charge from
> the engine alternator had diminished below the output of the
> AC-powered charger (which would then go through its own bulk-finish-float
sequence).
>
> If you're just concerned about paralleling the alternator and your
> AC-powered charger when the engine starts and automagically parallels
> your two batteries, I think you can probably stop worrying. The AC
> charger's bulk cutoff voltage will be higher than the alternator
> regulator setting, so it will continue charging until you unplug it.
> If the terminal voltage of the combined batteries rises above the
> alternator regulator setting, the alternator will reduce its field
> current or shut off entirely.*
>
> * A while back I did a little bench testing of one of the regulator
> units which indicated (to my surprise) that the regulator simply
> switches the field current on and off rather than modulating it. This
> keeps the regulator cool but generates a lot of hash on the B+ line
> (and I suspect is not ideal for battery longevity either).
>
> However, to be certain about this, ask the charger mfr. about it. If
> the charger has already shifted into float mode then the alternator
> might try to back-feed it, which it might or might not care about.
>
> If it's an issue, I suggest using a fancier (spdt/dpdt) relay on your
> paralleling arrangement. Common terminal to the house battery, NC to
> the AC charger, NO to the starter battery. Bypass diode between NC and
> common, in case unhooking the powered charger generates a spike (many
> chargers specify to connect the battery before plugging in the charger).
>
> Yrs,
> d
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