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
>
>