Date:         Wed, 10 Mar 1999 17:27:26 -0800
Reply-To:     Davidson <wdavidson@THEGRID.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Davidson <wdavidson@THEGRID.NET>
Subject:      Auxiliary Battery Madness (looong)
Content-Type: text/plain; charset="iso-8859-1"

Volks,
Just thought I would share my research on auxiliary battery, switches, amps,
wire, fuses, etc.: Between this post and Harald's two posts (mentioned
below), I think a lot of things may become clearer about setting up and
auxiliary battery in a Vanagon. Enjoy the madness!

Thoughts on Connecting an Auxiliary Battery in the Vanagon:
March 1999

Disclaimer:
I am not an electrician or a mechanic. Nothing that follows is meant to be a
recommendation. I am only communicating the results that I have found on my
particular Vanagon and the conclusion that I have come to regarding those
results. My results may be flawed, my conclusions may be wrong, and/or your
vehicle may be different than mine. Wiring is nothing to play with; it can
cause fires and serious damage to your vehicle and its occupants. I
recommend that you employ the knowledge and skill of a competent mechanic
when making alterations to your vehicle.

Background:
About a year ago I decided I wanted to install an auxiliary battery in my 90
Westy Syncro. First, I had a Sure Power isolator installed by a mechanic. It
never worked properly. Then I discovered a write up on installing an
auxiliary battery at the vanagon.com web site. The basics of the article, as
my way over 40 memory allows, were that most of the later model vanagons
came equipped with a relay switch in the box under the driver's seat and
that all you had to do was to install the auxiliary battery between that
relay and the two wires that run to the fridge and other camper stuff. I
printed out the article, gave it to another mechanic, and he installed an
auxiliary battery per the directions in the article. I used this set up
during a six week camping trip to the Southwest, and it seemed to work fine.
Then in the past month or so this topic came up again on 'the list'. I
promoted the solution that had worked for me because it worked. But Harald
pointed out that the stock relay and wiring were inadequate for a safe
installation. There was a fair amount of constructive debate, and I realized
that there was much that I didn't know on this subject.  After delving into
the Bentley wiring diagrams, inspecting the stock wiring, reading a crash
course in Automotive Electrical Wiring by Haynes, consulting wire sizing
charts, measuring actual current draws, pondering time vs. amps fuse charts,
and considering many relevant posts to the list I have come to some
conclusions. I share some of that research and those conclusions below.
(This is more of a research article than a 'how to' article. For an
excellent 'how to' article on installing an auxiliary battery see Harald's
posts: Part 1 was under the heading: Re: Flash Alert! Dual Battery Relay
date 1/29/99 and Part 2 was under the heading:
Dual Battery Relay-Part 2 [long] date 1/31/99)

Switch Choices (pros and cons):

Manual Switch:
A manual switch is simple, and it is inexpensive. It simply connects or
disconnects the positive terminals of the starter and auxiliary batteries.
There are fewer things to go wrong with a manual switch. To charge the
auxiliary battery, you simply use it to connect the starter battery and the
auxiliary battery (close the circuit) after the engine is started and to
disconnect them (open the circuit) before or just after the engine is shut
off. The main problem with a manual switch is remembering. If you do not
close the circuit after the engine is started, then you will not be charging
the auxiliary battery. If you do not remember to open the circuit after the
engine is stopped, your appliances can drain the starter battery to the
point that it will not start the engine.

Relay:
A relay is generally used as a remote switch that can be set up to work
automatically. You don't have to remember to connect and disconnect the
starter and auxiliary batteries. That is done by a pair of actuator wires
that are 'live' only when the alternator operating. When these actuator
wires are live they force the contacts inside the relay that carry the
current between the two batteries to physically contact each other. This is
probably the most common non-manual switching device in the automotive
industry. Because of this I am inclined to believe it may be the most
reliable and most readily available. And they tend to be the cheapest.
The disadvantage of using a relay is that if it fails it could fail with the
contacts touching. If this happens you may not know about it, and your
appliances will drain both batteries leaving you unable to start the engine.

Solenoid:
A solenoid is very similar to a relay. Generally they are used as a remote
switch between the ignition and the starter, and they are designed to handle
much larger currents than relays.
It is my understanding that Solenoids have pretty much the same disadvantage
as a relay. In addition, since the contacts are larger in order to handle
larger currents (often over 160 amps compared to the typical automotive
relay rated at 30 or 40 amps), the actuator current must be larger in order
to move the contacts into place. There has been some concern expressed on
the list that the actuator circuit was not designed for and could be damaged
by this larger actuator current.

Isolator:
These are the square or rectangular boxes with colorful fins. It is my vague
understanding that isolators do not connect the two batteries. They are a
solid state device that directs charging power from the alternator to the
each of the batteries independently depending on whether each battery needs
a charge or not.
It is my opinion that the main disadvantage of the isolator for the Vanagon
owner is that there have been many anecdotal reports that it is difficult to
get the isolator to work correctly with the Vanagon. Even the tech support
person at Sure Power said this to me. (I think this is because the Vanagon
alternators put out less voltage than the typical American vehicle and there
is also a voltage drop across the isolator, thus not leaving enough voltage
to activate the solid state switch. I think.) That being as it may, Harald
has reported that he prefers the isolator and it seems to work fine in his
vanagon.

Another disadvantage is that this device is larger, making it harder to find
a place for it. And it should not be installed in a hot environment (the
fins are meant to dissipate internal heat). Also, according to Bob
Livingston (RV Repair & Maintenance Manual, p. 1.20), other problems that
can be caused by the isolator include: 1) a shorted diode can cause the
battery(s) to overcharge or boil (I think this is because the isolator
essentially replaces the stock voltage regulator.) 2) an open diode can
cause one battery not to charge or both batteries to go dead, and 3) a
defective diode can cause low battery voltage.

Battery Combiner:
This device is offered at West Marine (a boating supply store), and the
device has the West Marine name on it. It measures about 4 x 4 x 3 inches,
and I believe this too is a solid state device. As I understand it from
reading the box, the Battery Combiner combines the starter and auxiliary
batteries while they are charging (above 13.1 volts) and isolates the two
batteries when the are discharging (below 12.8 volts). Unlike the isolator,
West Marine claims that there is no voltage drop across the Battery
Combiner. There are two models, one rated at 50 amps and one rated at 150
amps.
The disadvantage of the Battery Combiner is that it is relatively new and
unknown. I haven't read or heard any independent review or anecdotal
evidence regarding this product. It also concerns me that it takes 13.1
volts to activate the device. My experience in measuring the voltage output
of the alternator at my battery is that it goes down very close to the 13.1
volts and is known to vary considerably.

Amps Measured:

Relays/Solenoid actuator amps:
The purpose of this test was to determine amperage draw of the actuator
circuits for various relay & solenoid options. The idea was to avoid
choosing a relay or solenoid with significantly higher amperage draw than
the stock relay and the associated higher risk of damaging the actuator
circuit.

30 amp Bosch relay:   180 mA
75 amp Bosch relay:   245 mA ($17 from Alternative  Energy)
160 amp Tekonsha solenoid:  750 mA (Sold at Camping World)
(All tested with digital ammeter in line with one of the actuator wires in
my 90 Westy Syncro.)

I do not know for certain the amp rating of the stock 'battery cut-out
relays' (Weekenders only) or the 'fridge cut-out relays' (Full Camper). But
I did see a Wolfsberg Weekender in a junk yard that had obviously been set
up with an auxiliary battery. The 'battery cut-out relay' looked original.
It was a 30 amp Bosch relay.

 Auxiliary Battery Amperage draw:
The purpose of this test was to determine maximum amperage draw of the
auxiliary battery circuit (including appliances) in order to choose the
battery switch hardware and to size the wire running between the batteries.

 Test 1: (Aux Battery run down to 8.3 volts under 2 amp load; 9.7v no load;
Starter Battery 12.6v)

Aux Batt only:     surge to 25 A;    steady at 20 A
Aux Batt + 12v fridge + 2 - 1 amp lights:  surge to 45/50 A;  steady at 35 A

Test 2: (Aux Battery discharged to 2.5 volts under  2 amp load; 4.3 V no
load; Starter Battery 12.6 v)

Aux Batt + 12v fridge + 2 - 1 amp lights:  surge to or above 75A;  steady at
30 to 45 A
                 (radiator fan on and off)

(All tests were done with the engine running and the starter battery and the
auxiliary battery connected in parallel with #4 wire. The positive
connection was manually switched to start the test. All the amp measurements
were with an inexpensive analog inductive ammeter that measured a maximum of
75 amps. My guess is that they can be considered accurate to + or - 10% or
so. The surge amps lasted only a fraction of a second. Ambient temperature
was about 60 F.)

Starter Amperage off Main Battery:
With the intention of using the auxiliary battery as a back-up starter
battery (without having to use jumper cables), the purpose of this test was
to determine the amperage draw of the starter in order to size the wire
between the batteries and the fuses at both positive terminals.

surge to 300 A; rebound to 125 A
(measured at + post) (total about 1/2 second)
(average maybe 150  to 175 amps)

Well, the measurements do not have digital accuracy, but I think they help
zero in on the appropriate sizing of wire, fuses, relays, etc.

My Personal Data Conclusions (Opinions):
I think Test 1 shows how marginal using the stock wiring and relay can be.
Typically I would run my Auxiliary Battery (Optima) down to 10.5 volts with
my lap top computer. 10.5 volts is about the lower limit for many
appliances. Then when I left camp I would switch the fridge over to 12 volt
and start the engine. So I must have been drawing between 20 and 30 amps
(the fridge is 7.5 amps) over about a # 13 wire (2.5 mm sq in Bentley) and
through a 30 amp relay. (My stock "fridge cut out relay"[Bentley term for
the Westfalia relay] was replaced with a 30 amp Bosch relay and I don't know
what the amp rating of the original "fridge cut out relay" was. If it was
less than 30 amps then Test 1 would show it to be less than marginal.)

And I think Test 2 shows what would happen if I left some interior lights
and/or the fridge on 12 volts by accident over night. Surging to 75 amps and
a steady draw of 40 amps would make the stock 2.5 mm sq wiring and relay (30
amp or less?) of the Westfalia woefully inadequate. Even upgrading to a  40
amp relay with the Weekender #10 wiring (6.0 mm sq in Bentley) would be
marginal. (The Weekender relay is called a "auxiliary battery cut out relay"
in the Bentley. It is apparently a 30 amp relay as that is what I observed
in a Weekender wreck at a junk yard.)

I decided to upgrade my auxiliary battery charging circuit so that it would
have a margin of safety even if I made the mistake of leaving appliances on
overnight to find a deeply discharged auxiliary battery in the morning. From
the data above and wire sizing charts I decided that I would use a minimum
of #8 wire and a relay rated over 40 amps. And then I decided that if I used
#4 wire I could use my auxiliary battery as a starter battery in the event
that my starter battery died. This larger wire would also allow my auxiliary
battery to charge faster than with # 8 wire.

My Personal Choices:

Switch:
As outlined above, the various switches all have there advantages and
disadvantages. I wanted a switch that would fit in the auxiliary battery
compartment with my Optima battery, and I wanted something simple and
dependable. I felt that narrowed my choice down to the relay or the
solenoid. I went for the Bosch 75 amp relay (part # 0 332 002 150) over the
solenoid because its actuator circuit draws only 245 mA, much closer to the
180 mA draw of the stock 30 amp relay than the solenoid.
As you can see from the wiring schematic below, I installed the relay as a
bypass of the Hella (#87181) 100 amp manual switch (West Marine # 598375).
(Or, depending on how you look at it, I installed the Hella manual switch as
a bypass of the relay and Bussmann Maxi fuse.) I used # 6 wire for the
fuse/relay 'bypass' because the lengths were short and it is easier to work
with in the limited space. Even #8 wire would have been adequate for the
fuse/relay 'bypass' since the #4 wire is only required for using the
Auxiliary Battery as a starter battery. One of the nice things about this 75
amp Bosch relay is that it has screw terminals… perfect for #8 or #6 wire.
(You just don't find spade connectors for these larger size wires.)

Wire:
# 4 starter battery + terminal to Hella manual switch
# 4 Hella manual switch to auxiliary battery + terminal
# 4 auxiliary battery - terminal to metal battery box
# 6 starter battery side of Hella manual switch thru Maxi Fuse holder to 75
amp Bosch relay
# 6 Bosch relay to auxiliary battery side of Hella manual switch
(Anchor Marine wire is MUCH more flexible in these larger sizes and nicer to
work with in the small spaces of the battery box.)

Fuses:
I special ordered the Bussmann Maxi Blade Fuse (Max-60) through Kragen and
installed it between starter battery side of Hella manual switch and Bosch
relay (Installed in HHX In-Line Fuse holder for Maxi Fuses, #6 lead wires).

Two Blue Sea Systems 150 amp Mega Fuses (bolt-in high current, time lag
fuse) to protect the #4 wire connecting the two batteries in the event of
catastrophic grounding (If the #4 wire grounds it will draw current from
BOTH batteries!). (I intentionally fused this on the low end for using the
auxiliary battery as a starter battery because it will be seldom used, and I
want to have the quickest fuse burn out in the event of grounding.) One is
bolted to auxiliary battery + terminal and # 4 wire that runs to Hella
manual switch.
The other one is bolted to starter battery + terminal lug tightening bolt
and # 4 wire that runs to Hella manual switch. (Bussmann shows a time lag
fuse designed for battery cables on its web site. It is about the same size
and style as the Blue Sea Systems Mega Fuse. I would have chosen this ABI
fuse, but it will not be in production until around the beginning of the
year 2000. You will then be able to order it from your FLAPS… just order and
ABI 100 or ABI 125… etc for 100 or 125 amp rating. But you really need to
study the time/amp chart on the web page to make an intelligent decision.
Same with Blue Sea.)

Battery:
Optima Deep Cycle (yellow top w side posts). This is the largest deep cycle
battery that will fit (on its side) in the auxiliary battery box under the
driver's seat. I don't have to worry about it giving off poison fumes since
it is sealed. I laid it on its side (top posts pointing forward), and had to
cut two notches (one for each top post) in the curved metal plate at the top
forward part of the battery box. Also cut two notches in the hinged lid of
the battery box…. One for each of the side post bolts… just to prevent
contact of the side post bolts with the metal lid. I taped over these
notches with black duct tape, and it is hardly noticeable. I made a couple
of wooden wedges to hold the battery in snuggly. Also lined the battery box
with thin plastic to prevent any of those many wires from accidentally
grounding.

Wiring Schematic:
(In case this doesn't line up in email format, just line up numbers 1 thru 9
at the left hand margin. Dashed lines and slashes indicate wire pathways,
periods are used only as spacers to keep things aligned.)

1….. #4 ---- Metal Battery Box
2…… \
3……./
4……(-)
5……Optima (+)  ---- #4 ---- Hella Manual Switch ---- #4 ---- + Start Battery
6………………………………..\………………./
7……………………………….#6……………..#6
8………………………………. /……………….\
9……………………Bosch relay ----- #6 ----- Maxi Fuse

Basically, you can think of this as a manual switch set-up with a relay by
pass for automatic operation.
The large #4 wire and the manual switch allow me to us the auxiliary battery
to supply the large amperage needed to jump start the starter battery in the
event that it fails. It also allows me to charge the auxiliary battery
through the manual switch in the event that the relay by pass fails.

Specialty Parts Sources:

Alternative Energy Engineering, orders: 800-777-6609, tech support:
800-800-0624,
 www.alt-energy.com
[quality wire, large size wire connectors, 75 amp Bosch relay, 'Battery
Switch' solenoid]

Camping World, 800-626-5944, www.campingworld.com [Tekonsha 'Battery Switch'
Solenoid]

West Marine/E&B Marine Supplies, 800-262-8464, www.westmarine.com
[quality marine wire, large size wire connectors, Battery Combiner, Hella
manual battery switch, inexpensive large wire connector crimper (#6 to 4/0)]

Information Sources:

Battery Specifications & tech support (size, amp storage capacity, cranking
amps,
charging time, etc.)
Optima, 303-340-7440, www.optimabatteries.com

Fuse Products & time vs. amps charts:
Bussman, www.bussman.com

General Automotive Electrical:
Haynes Automotive Electrical Manual, Haynes Publishing Group 1989.
[available at most automotive parts stores]

Isolators vs. Solenoids:
RV Repair & Maintenance Manual, Trailer Life Books, Third Edition, 1998,
Bob Livingston. [available at Camping World]

Vanagon Wiring Diagrams:
Volkswagen Vanagon Official Factory Repair Manual 1980 > 1991, Robert
Bentley, July 15, 1991. [available at VW dealers]

Wire Sizing:
 Alternative Energy Engineering: charts at www.alt-energy.com
 Haynes Automotive Electrical Manual: charts on page 67
        West Marine 1999 Catalogue: page 402