Date: Wed, 18 Mar 2009 15:06:22 -0700
Reply-To: Rocket J Squirrel <camping.elliott@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Rocket J Squirrel <camping.elliott@GMAIL.COM>
Subject: Re: Problem with Stancor 120-901 relay??
In-Reply-To: <91c8f9760903181353w6cc1261cq82f57be754850e60@mail.gmail.com>
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On 3/18/2009 1:53 PM pickle vanagon wrote:
> Then again, maybe a good choice would be to wire a 2ohm resistor inline
> with the coil on the 901. This should move its operating range up to
> 10.1v-14.9v, which is probably perfect. (Current draw would be around
> .67amp.) Can anybody imagine a problem with such a setup?
I don't see one. A series resistor is a perfectly acceptable way to soak
up extra voltage. Get one rated to handle the power, preferably a nice 5W
aluminum-bodied one that can be easily bolted to something. Other than the
(vanishingly slight) reduction in reliability caused by two additional
solder joints and one component, you're good to go!
--
Mike "Rocket J Squirrel" Elliott
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
Bend, OR
KG6RCR
On 3/18/2009 1:53 PM pickle vanagon wrote:
> As I posted earlier, the 15v version is rated to come online so long as
> the coil voltage is at least 11.25 volts, so 11.8 would have been plenty
> (even allowing for some further voltage drop before the coil). Same
> with the starting assist feature: a battery worth getting assistance
> from should have at least 11.25 volts of power, no?
>
> As a fringe benefit, the 902's coil will draw slightly less current (.6
> vs .8 amps) due to the greater coil resistance.
>
> Comparing the two versions, the 901 has an operating range of 9v-13.2v,
> while the 902 has an operating range of 11.25v-16.5v.
> I agree that the optimum range would be somewhere between these two, but
> given that this is the choice, it seems like going over 13.2v could be
> more of a common thing then dropping below 11.25v (especially when the
> alternator is running!).
>
> Then again, maybe a good choice would be to wire a 2ohm resistor inline
> with the coil on the 901. This should move its operating range up to
> 10.1v-14.9v, which is probably perfect. (Current draw would be around
> .67amp.) Can anybody imagine a problem with such a setup?
>
> -Wes
>
>
>
> On Wed, Mar 18, 2009 at 3:06 PM, Rocket J Squirrel
> <camping.elliott@gmail.com <mailto:camping.elliott@gmail.com>> wrote:
>
> Mark has come up with a couple of caveats worth considering.
>
> When I was relocating from SoCal to Bend last August I arose early one
> morning in a motel, well before dawn, to begin the second leg of my
> flight
> from California. Driving in the darkness I noticed that the battery
> voltage meter I have plugged into the cigarette lighter was reading darn
> low: like 11.8 volts.
>
> I began to fret that the alternator was failing. But a second thought
> occurred: the Vanagon's skinny wires in association with headlight draw
> and the heavy current that my aux battery's Powerstream 12V > 12V
> charger
> draws when it needs to bring up a partially-discharged house battery
> (kept
> the Norcold reefer on all night long in the desert heat -- sourdough
> starter wanted to be kept cold) all combined to reduce the voltage
> at the
> dash and, presumably, at the coil of the Stancor relay used to
> connect the
> Powerstream to the engine battery. I tested my theory by briefly turning
> off the headlights and the voltage climbed to a more reasonable number.
>
> If the relay had been the one with the higher-voltage coil it might not
> have pulled in, and my aux battery would not have received any charging
> until daybreak and the headlights had been turned off. Which might have
> been okay anyway.
>
> That said, I wish I could have been able to see the voltage at the
> engine
> battery -- it may not have been receiving much, if any, charging
> current.
>
> As for bridging the two batteries for starting if the engine battery had
> weakened, well, I pull the coil voltage from the aux battery which I
> expect would have a better charge than the engine battery else I'd not
> need to bridge them. However, when I installed the Powerstream I
> forgot to
> rewire things. Now flipping the switch with the bridge relay open does
> nothing as it tries to get voltage from the input of the Powerstream to
> power the coil. And there's no way voltage from the house battery could
> make its way backwards through the Powerstream to charge the engine
> battery anyway.
>
> Kinda overlooked that. Need to fix it. Gimmie a welding iron.
>
> --
>
> Mike "Rocket J Squirrel" Elliott
> 84 Westfalia: Mellow Yellow ("The Electrical Banana")
> 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
> Bend, OR
> KG6RCR
>
>
>
> On 3/18/2009 11:33 AM mark drillock wrote:
>
> Neither coil voltage offering is ideal for Vanagon use. There are
> various reasons to choose one over the other but it all comes
> down to
> trade-offs. The actual voltage seen by the relay coil will
> depend on how
> you wire the control circuit for the relay coil.
>
> I agree that typical use of the relay in a Vanagon could be
> expected to
> subject the 12v relay coil to in excess of the 110% spec.
> Probably 115%.
> How often this will occur would vary by application. This has not
> resulted in any known failures of the 8 or so I have installed
> in the
> last 12 years.
>
> Selection of the 15 volt coil version complicates the use of the
> relay
> to connect the aux battery to the main battery for starting assist
> should the main battery be low. Some people don't care about such a
> feature but I want it available
>
> My typical installation of the 120-901 is in Westys, where I use the
> output of the stock fridge relay to control the Stancor relay
> mounted in
> the driver's side battery box. The voltage at the fridge relay
> when the
> fridge is running on 12 volts can be down at the 11 volt range
> depending
> on other loads.
>
> In installations where there is no fridge relay I use the output
> of the
> X circuit relay from the dash wiring to trigger the Stancor relay.
>
> Incidentally, SurePower uses that relay with the 12v coil in their
> 1314/1315 Battery Separator products.
>
>
>
> Mark
>
>
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