Date: Mon, 15 Mar 2004 11:23:17 -0800
Reply-To: David Marshall <vanagon@VOLKSWAGEN.ORG>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Marshall <vanagon@VOLKSWAGEN.ORG>
Subject: Re: more on problems with second battery
In-Reply-To: <4055F93F.2C7BA274@earthlink.net>
Content-Type: text/plain; charset="US-ASCII"
Mark and the list...
I've been looking at this whole second battery isolator / relay thing. I
agree that a relay is the way to go as opposed to a diode based isolator. A
good 40A relay should suffice for the secondary battery or if you are going
to be running LOTS of current while the vehicle is running a pair of 40A
relays would be more than over kill.
It seems to me that the circuitry to these dedicated 2nd battery charging
relays is overly complex. I've seen some systems that want the tach or W
terminal signal to trigger the relay or a manually operated relay. What is
wrong with a 'simple' $9.95 relay wired like this:
30 Alternator or 1st Battery Positive pole
85 0.3 BAR oil pressure switch
86 looped back to the 30 terminal
87 Positive terminal of the 2nd battery
This is what I am going to do in my TriStar with it's second battery which
will be used for the HF/VHF radio system which can be set to operate like a
repeater when I am away from the vehicle. The only time the 0.3BAR switch
goes to ground is when the motor is running and the oil pressure is above
0.3BAR. If the motor is running and the oil press is below 0.3BAR you have
other things to worry about! When the 0.3BAR switch goes to ground, the
relay closes and the two batteries and alternator are connected together
thus starting the 2nd battery to charge. The relay(s) can be mounted in the
engine compartment with a nice chunk of 8ga cable running from the relay(s)
to the 2nd battery.
I think this solution is simple, costs much less that $70 and you can build
it yourself in about 1h.
David Marshall
Fast Forward Automotive Inc.
4356 Quesnel-Hixon Road
Quesnel BC Canada V2J 6Z3
http://www.fastforward.ca mailto:sales@fastforward.ca
Phone: (250) 992 7775 FAX: (250) 992 1160
- Vanagon Accessories and Engine Conversions
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-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com]On Behalf
Of mark drillock
Sent: March 15, 2004 10:43 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: more on problems with second battery
Joy, the Separator is small enough to mount in the compartment with the
second battery. The relay is even smaller.
I recently purchased a SurePower Separator 1315 for $70 plus tax.
The Separator is the simplest solution as far as hooking it up.
The relay is almost as simple.
The Isolator is the most involved of the options, and most people should
avoid it on Vanagons.
For the record, the Separator IS A RELAY!!
The Separator is also a solenoid. For our purposes here the 2 things are
the same. Sure Power takes an off the shelf industrial relay and adds a
'smart module' to it. The 'smart module' can tell when the relay should
be activated and does so automatically to charge the batteries. You can
accomplish much the same thing with just the industrial relay. The Hella
kit is not a good idea as it has an inadequate charging rate for typical
uses though that can be compensated for by leaving the fridge connected
to the main battery as is.
The Separator and relay is nothing more than a remote control switch. A
manual switch would do the same job if you could always remember to turn
it on and off at the right times.
Isolators can work fine when properly installed. So do separators,
relays, solenoids, switches, whatever.
Mark
Joy Hecht wrote:
>
> Thanks very much to everyone who provided all the details on our problems
> with the isolator.
>
> It looks like there are two reasonable choices open:
>
> - Exchange the Sure Power isolator for a Sure Power separator and
install
> that. I don't know how much the separator costs - I assume it's in the
same
> range as the isolator ($70). It sounds from some of the emails like it
may
> be easier to install, because we can do it between the two batteries and
> don't have to rewire to the alternator, but I'm not sure if I've got that
> right.
>
> - Return the isolator (the RV place said if it's in good shape, which it
> should be, they'll give me most of my money back) and buy the Hella relay
> kit that Busdepot sells for $20. Some people have sworn by the Hella kit,
> others have said the separator would be better.
>
> I'd appreciate anyone's knowledge of pros and cons of the two options,
> particularly regarding:
>
> - ease of installation - what we have to be able to access to wire it,
> whether we can use the setup we already organized - Optima battery in its
> hole, separator or relay in the cabinet under the sink, wires running
under
> the carpets from batteries to sink), and
>
> - performance - does one setup or the other have significantly better
> power management characteristics or less waste or not recharge fully
enough
> or other things?
>
> And another question - I now have some understanding of what a diode is,
and
> therefore what an isolator does. If anyone could explain to me - on about
> the level of a high school shop course - how relays and separators work,
I'd
> appreciate it!
>
> Oh, and for all who said I need the Bentley - yes, yes, I'm ordering it
> today.
>
> Joy
>
>
