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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??
Comments: To: pickle vanagon <greenvanagon@gmail.com>
In-Reply-To:  <91c8f9760903181353w6cc1261cq82f57be754850e60@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed

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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