Date: Mon, 1 Feb 1999 14:55:43 -0800
Reply-To: harald_nancy <harald_nancy@EARTHLINK.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: harald_nancy <harald_nancy@EARTHLINK.NET>
Subject: Re: Dual Battery Relay - Part 2 (long)
Content-Type: text/plain; charset=ISO-8859-1
Hi Volks,
Bill wrote:
1.>The $62 VW relay that you mentioned, how many amps is it rated for?
>And is it a Bosch? I wonder because my FLAPS has a 40 amp 4 post Bosch
relay
>for about $8.00.
1) My opinion:
There was no way to find out the rating of the
VW relay, except to order it.
And even then one probably would not know
the rating.
But I guess one could match it with something
that looks similar. I am not a specialist on relays.
Some friendly listmembers seem to do ok with
heavy duty headlight relays.
If one wants the max, I can
only recommend to get the VW relay. Since it is proven
to work with the relay trigger circuit.
(Maybe a "Interstate battery shop" has more
selection on battery relays).
There are 40 amp relays for $2.99 with a plastic
cover, and relays with the same rating for 5 times
as much. All I can say, don't be too cheap.
I would get a relay with a metal housing with 2 screw on
terminals for the # 8 wire.
2.Bill wrote:
>It is interesting to me that in some of the previous posts discussing
>the wire size and relay amp ratings, it was mentioned that a drained
>auxiliary battery could draw the total potential output of the alternator.
I
>believe that would be 90 amps. I had a short talk with a tech guy at
Optima
>the other day and he confirmed this possibility. If that is the case, I'm
>wondering why we are messing around with 40 amp relays and fuse/breakers?
2) My opinion:
A #8 wire is rated for 50 amp charging for a distance of 15'
(according to Sure Power company)
So with the #8 wire, one could install a 50 amp relay and
a 50 amp breaker safely.
But remember VW uses a smaller 6.0 mm wire for the same purpose.
That is why I don't think they figured on 50 amp for the aux.
battery. The vanagon alternator doesn't seem all that vicious.
How many amps go into the aux. battery in this application?
I think the most maybe 30 amp. (?)
The engine has to be running for the alternator to
charge. That means the fuel pump, fuel injection,
ignition etc all use quite a bit.
Also you are always charging 2 batteries at the
same time.
And the regulator still senses the main battery.
Basically the aux. batt. is hooked up to the
main battery, not directly to the alternator.(?)
I am mostly concerned about the relay trigger
circuit. I would not want to overload it, with
a too heavy "industrial" type of relay.
Personally, I would rather that the breaker
shuts off once in awhile than risk overloading
the trigger wires with too big a relay.
And as you once said, a deep
cycle should not be charged too fast anyway.
My main concern is not to damage anything that is stock,
in this case, the wiring harness with the trigger wires.
Bill wrote:
>3. seems that in some places you mention 'breaker' and in some places
>'fuse'. Can you or anyone comment on the relative virtues of the two in
this
>auxiliary battery application?
3) My opinion
The main difference betwen a fuse and a breaker:
The fuse burns out, and has to be replaced.
If the breaker is an automatic reset, it will cool down
and reset itself. You won't even know it ever went off.
4.Bill wrote:
>I did notice that Sure Power uses a 50 amp
>circuit breaker (auto reset I believe) in the kit that they sell. I'm not
>sure how even a 50 amp breaker would work in the event of a drained
>auxiliary battery and a 90 amp current. It is also interesting to me that
>they put their 50 amp breaker between the auxiliary battery and the
>isolator. I don't understand what they are trying to protect. (Perhaps the
>#8 wire?)
4) My opinion:
I use a 40 amp breaker with the batt. isolator
and the Optima deep cycle.
You are right, Sure Power says to install a 50amp
breaker, but I put in a 40 amp, because the
shop was out of 50 amp breakers.
With the isolator setup, there is the
possibility that the optima could get most of the
output of the alternator if it is hungry.
Even though I don't think the breaker ever went off.
Even with a discharged auxiliary battery. I have never
noticed any wild fluctuations on the voltage gauge on my
dash. Also if there should be a spike sometimes, its ok for
the breaker to shut off, and reset itself within a few minutes.
I thought the reason for the breaker
on the isolator setup is to protect the "deep cycle" battery.
They only recommend a breaker to the auxiliary battery,
never to the main battery.
Harald
90 westy
