Date: Tue, 21 Sep 2004 11:47:55 -0700
Reply-To: Vince S <gipsyflies@COMCAST.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Vince S <gipsyflies@COMCAST.NET>
Subject: Re: dual battery isolator / Optima Batteries
In-Reply-To: <BAY11-DAV27EyjWk9Ul0004fe12@hotmail.com>
Content-Type: text/plain; charset="US-ASCII"
Using stainless screw to bridge the gap is not the best solution.
Stainless steel is not exactly known for good electrical characteristic.
It has very high resistance. This is especially of a concern with the
staring battery. Starter draws upwards of hundred amps and the tiny
contact surface may get so hot that may even melts the lead around it. I
don't recommend performing the top posts removal of the Optima for the
starting battery due to such high current demand unless you can
reconstruct the gap with a very high power soldering iron.
Combining two batteries of exactly the same brand, model, and age may
work well in most situations but I won't preach it like a gospel. It is
not a recommendation any reputable battery manufacturer would recommend.
Why not just go with the Westfalia intended relay isolation for a house
battery and the starting battery? Simple, safe, and effective.
- Vince
http://gipsyflies.home.comcast.net
1989 Vanagon GL Camper
1993 Mazda Miata (for sale)
1996 Land Rover Discovery
2005 Mini Cooper S
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
Of Fin Beven
Sent: Tuesday, September 21, 2004 11:02 AM
To: vanagon@GERRY.VANAGON.COM
Subject: dual battery isolator / Optima Batteries
The simple solution is to just combine the two batteries. Use large Ga.
wire (2 ga, minimum). But I believe that it is important that the
batteries be identical. The result is ONE BIG BATTERY.
To complete the system, add a good volt meter. JC Whitney sells a LED
panel-mount voltmeter which seems reasonably accurate, and which can run
all night while using virtually zero amps. (I actually have an
on-off-on switch on mine, allowing it to operate when the ignition is
on, or directly from the batteries). It actually makes a rather nice
"night-light" at night.
The system is not idiot proof. It requires that you actually look at
the volt meter occasionally if you are using significant equipment (like
watching a DVD on a computer being powered by an inverter). Depending
on the particulars of your starting system, you should still be able to
safely start and re-charge with "at-rest" votage that has dropped to the
11.5 range.
Optima Batteries: This one is not for the faint-of-heart. I decided
that I would prefer to install them in the up-right position, but this
would involve cutting off the top-mounted terminals and attaching to the
side-mounted screw-in terminals. I looked at the renderings of the
Optima Batteries on their website. It appeared that the top-mounted
terminals were a solid piece, such that cutting them off should be no
problem.
Not So, at least not exactly.
When I cut off the negative terminal of the first of my two new "yellow
tops" I noticed that the terminal was, in fact, not quite solid. It was
as if there was an inner core (about 1/2 of the overall diameter) and an
outer ring. There was a very small gap between the core and the outer
ring. And I now had ZERO voltage at the screw-in terminals. After some
brief testing (this only seemed to matter on the NEGATIVE terminal) I
determined that there was insufficient contact beteen that inner core
and the outer ring. Believing that I may have destroyed the battery,
and further believing that I had little to lose, I screwed a #4 x
3/8ths" stainless steel pan-head/phillips head screw into that very
small gap between the core and the outer ring. This seemed to force the
inner core into better contact with the outer ring. Happy with by my
results, I inserted another screw along-side the first, just for good
measure. I then completed the same operation on the #2 battery.
After a week of camping in the Lake Tahoe / Blue Lakes area that ended
with snow on Saturday morning, I'm satisfied with the results, and with
the Optima Batteries. The installation looks like it was "meant-to-be",
and I detected no lack of voltage using the side terminals. This may be
especially so because I'm using the two batteries.
Fin Beven
'90 Carat, Custom Camping Conversion
Pasadena, CA
----- Original Message -----
From: Dennis Haynes<mailto:dhaynes@OPTONLINE.NET>
To: vanagon@GERRY.VANAGON.COM<mailto:vanagon@GERRY.VANAGON.COM>
Sent: Sunday, September 19, 2004 8:07 AM
Subject: Re: dual battery isolator
If not a defect, then either you are getting a false reading or the
advertising is misleading. I have seen regular isolators drop that
much
voltage but I was being conservative and my experience shows the 1.1
to
be normal until things really heat up. Anyway, thanks for proving some
of my points.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On
Behalf
Of Gnarlodious
Sent: Saturday, September 18, 2004 9:10 PM
To: vanagon@GERRY.VANAGON.COM<mailto:vanagon@GERRY.VANAGON.COM>
Subject: Re: dual battery isolator
Entity Dennis Haynes spoke thus:
From 23 Aug 2004
> after they get warm the actual voltage drop is closer to 1.1 volt.
Well, I just installed the Hellroaring model BIC-95150B and I am
dismayed to
se a 1.4 volt drop across the switch at ambient temperature.
At $174.45 for the high technology and much touted product this is
disappointing. The specs page didn't mention voltage drop. I'll try to
communicate with them about it during the week, maybe it's a defect.
-- Gnarlie
At 90 amps, the isolater is dissapating almost 100 watts. This is why
they
need heat sinks. You are paying for this power. Now, with this voltage
drop,
you are getting less than 13 volts to the batteries and accessories.
Ok,
so
now you can modify the regulator to increase the voltage or use a
remote
sense wire to compensate. At full load the limiting factor of an
alternators
capacity is its own resistance. Thus at full load, it is only slightly
more
than 50% efficient. Yes, 1/2 the power produced is given off as heat
in
the
alternator itself. That is why they have a big fan and they still get
hot.
So, we increase the voltage of the alternator by 1.1 volt so at 90
amps
the
alternator dissipates an additional 100 watts of heat. Can we say
shorter
life? So at full load, we are wasting ~200 watts of power due to the
use
of
the isolator. Under ideal conditions, 1 HP = 746 watts. Not that you
will
notice but we are wasting .26 HP here. The big issue here is the load
on
the
alternator.