Date: Wed, 18 Mar 2009 16:53:48 -0400
Reply-To: pickle vanagon <greenvanagon@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: pickle vanagon <greenvanagon@GMAIL.COM>
Subject: Re: Problem with Stancor 120-901 relay??
In-Reply-To: <49C14646.8020307@gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
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> 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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