Date: Wed, 18 Mar 2009 12:06:46 -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: <49C13E6D.5040905@cox.net>
Content-Type: text/plain; charset=UTF-8; format=flowed
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
>
