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Camper
/ Trailer Application Notes
 When it comes to RV or trailer camping, the usage on your
battery differs substantially from that of your vehicle primary
starting battery. When you set up for camp, you need
lights, power for your water pump, maybe a fan, radio, or TV etc...
You operate these during times when the engine is not
running. During this time, your RV battery slowly empties
its charge. With your trailer or RV battery connected to
your charging system, your starting battery will share the current to
your loads. The problem is, your starting battery was never
designed to perform in this manner and, as a result, will fail early in
its expected life. The other problem is a little more
serious. You may be enjoying your stay so much that you
stay put for a while. Eventually you may run out of battery
charge, leaving you stranded without starting
power!
People have utilized many different ways to save your
starting battery from this annoying situation. They have
used diode isolators, relays with switches, relays wired to ignition
circuits or accessory circuits, high current switches, or
automatic mechanical combiners. Each of these methods
have their own advantages and disadvantages. Some are more
complex than others. Now, you have the choice of using a
system with more advantages than ever
before! The Hellroaring BIC-95150B
and BIC-95300B Battery Isolator/Combiners
are the best solution on the market today.
RV Starting Battery Isolation
For motorhome types with high output alternators and
large house loads while operating, consider the RV starting battery
isolation technique as a simple solution to multiple use
batteries. With this setup, a high output alternator can supply
maximum charge current to large house battery banks. All
batteries receive proper alternator voltage from an internally sensed
alternator due to the very low ON resistance of the BIC-95150B (less
than 0.004 ohms). Since there is no diode drop, the starting
battery stays fully charged. Electrical loads on either battery
will not draw from the other. If you choose this method, we
recommend that you contact our technical
support staff at our sales email for assistance.
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Basic Auxiliary Battery & Trailer
Application
For most applications, (i.e. slide-in
camper, trailer, RV's with required continuous loads under 50 amps on
the auxiliary side during engine operation, etc...) consider the basic Auxiliary Battery setup. Because it is so simple, it has become one of our most popular setups! Your primary objective is to
prevent your starting battery from draining while you consume
power from your house (deep cycle) battery. (Don't be fooled by low cost battery disconnect
devices as a solution.)
You also want your house battery to obtain full charge as
quickly as practical while operating your vehicle. With the
BIC-95150B installed as shown below, you will obtain those two
objectives! The BIC-95150B has very little resistance (less
than 0.004 ohms) when ON during charging and it automatically isolates
the two batteries when charge voltage  stops, even if your alternator
fails. This setup is NOT for Full Backup starting. But, if desired, you will have the ability to combine the
batteries manually for a starting boost (i.e. the main
battery must still supply substantial cranking current such as cranking slowly, or almost turning over). The BIC
has no mechanical moving parts to degrade or wear out! For those
on a budget and who want the simplest installation,
the BIC-95150B basic Auxiliary setup makes an excellent choice for full
charging without the voltage drop or bulky physical size associated
with diode isolators! Works great for alternators sensed at the
alternator output (i.e. internal sense or single wire alternator.)
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Trailer / Camper mounted battery isolation
Although the BIC's can be mounted in a camper or trailer, we recommend mounting a BIC-95150B in the Tow vehicle instead for best performance.
With a Hellroaring BIC-95150A, you can
install it in the camper itself. There is no need to alter the tow
vehicle alternator system. Since the BIC-95150A is basically a DC Solid
State Relay, like what others may call a battery separator, it has integrated control electronics designed for dual
battery systems, and it does not require ratings based on the
alternator, like a diode isolator does. This is because it never receives all of
the alternator output. Rather, the BIC rating need
only be higher than the maximum continuous current expected in the
camper charge line. And then, you normally protect it and the
wiring by installing an in-line fuse or circuit breaker, where we recommend 50 or 60A rating with 8 AWG wire.
We aim to limit the peak demand to the Auxiliary battery to about 60 to 80A and average under about 50A by recommending a minimum length of 20 feet total length of not larger than 8 AWG, or 6 AWG if your length exceeds 35 feet. This also provides a good margin, well within the BIC-95150A continuous
capability of 95 amps. For those applications where even more continuous current
is required, the BIC's can be wired in parallel for double or more
capability.
One key point about mounting in the camper rather than the tow vehicle: You can expect reduced performance, i.e. reduced charge rate, due to factory tow harness charge wires being long and small prior to reaching the BIC mounted in the camper. This may, at times of higher demand, see the voltage dropped across that long charge line and sufficient resistance exists in that input path, the BIC will sense that drop in voltage and go into a cycling mode which would effectively reduce your charge rate by about half. That is, unless you run an external Sense wire from the BIC sense terminal, through a spare pin or other connector to the truck, and back towards and connects near the main battery or alternator end. This way the BIC will not sense the voltage drop across the small and long factory tow harness wire.
For this reason, and because most customers do not have a spare wire to use or don't want to deal with adding a new wire in the tow vehicle, we would recommend mounting the BIC under the hood of the tow vehicle instead for BEST performance. And, in this case, the BIC-95150B provides the simplest and cleanest installation. The BIC-95150A has the external sense terminal and requires and external sense resistor and TVS diodes mounted externally on the terminals. The BIC-95150B has all that built in internally for a cleaner installation, but does not have the ability to run the separate sense line. So, again the BIC-95150B is best mounted in the tow vehicle under the hood.
With this setup, you can connect your
trailer to the tow vehicle and leave it connected for as long as you
want. The trailer loads will not drain your vehicle
battery. If your tow vehicle is already equipped with a
towing package, you should have a charge wire available near the
trailer hitch. However, if your factory charge wire is smaller than 10 AWG, and If you have sufficient alternator capability, you
can increase your peak and average charge rates by upgrading the charge wire to 8 AWG, or 6
AWG if your length exceeds 35 feet from the BIC.
With the AC charger connected as in the
diagram, you will charge your camper battery only. If you connect
it to terminal "A" instead, then you will charge the vehicle battery
also.
Diagram to be updated...
Tow Vehicle Backup Battery System
If you like to disconnect your trailer and drive around
to enjoy the scenery, you will not have your trailer loads to worry
about. But, suppose that, while you are out and about, your
alternator fails. They always seems to fail at the most
inopportune time. You may not notice the problem until it
is too late and your engine dies or will not start. You may
be parked 20 miles from nowhere, walk back to your vehicle after a nice
afternoon fishing, and find your vehicle unable to crank.
It sure would be nice to have a spare battery at a time like
this. Then consider the Basic Backup Battery setup
illustrated below. With this setup you have an emergency
backup battery that is always fully charged, even when you disconnect
your trailer and your alternator quits.
If you look closely at why you need an isolation system
anyway, you will discover that it is for one primary reason. That
is; to have the ability to start
and operate your engine when you have inadvertently
drained your starting battery. Most people only
foresee the possibility that their house loads will drain the starting
battery. Because they aren't aware of other possibilities,
their focus goes toward preventing that condition only. We
believe that you should not limit your security to only one of the
possible ways to drain you starting battery. When you spend time
in the field, you should cover all likely possibilities, including
alternator failure. Those who connect relays to your
ignition system obtain a false sense of
security. If their alternator unknowingly fails,
their vehicle will continue to operate until both batteries are
drained. All the while they believed that their backup
battery was being charged! Our BIC units will protect a
spare backup battery from discharge due to either draining your
house/trailer battery, if your alternator quits, or even if your main battery
effectively gets disconnected due to
corrosion!
Consider this installation suggestion:
Suppose you install a super combination deep
cycle/starting battery such as an Optima Yellow top as your starting
battery (It is rated for deep cycle use, yet it has plenty of cranking
power - 750 CCA.) Then install, in your vehicle, a regular
starting battery as a spare backup battery isolated
with a Hellroaring BIC-95300B configured for high current.
With this setup, you don't need isolation to your
trailer or house battery. You will always have a spare
capable of cranking your engine! If your house loads drain
your starting (deep cycle) battery, you can, with the simple flip of a micro-switch,
crank your gasoline engine (You will need two
units in parallel and two Backup batteries for a Diesel
Engine that requires two main batteries.) An added benefit to this system is that you will gain
battery capacity by the amount of your main battery.
This will add life span to your batteries because you will not need to
discharge either one as deeply than as with a single
battery. With this setup, you will need less circuit
breakers, less hardware, less space, and will receive more security.
Sure, there may be less expensive individual isolation
products available. But, none stack up
to all the benefits that the BIC-95300B is capable of.
After considering all the parts and labor needed to perform the same
functions, We believe this setup is one of the simplest, most
convenient to use, most reliable, most economical and practical system
available for a Backup Start application, and the BIC-95150B is the best for an Auxiliary or Camper battery application.
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Here is one very nice benefit from this
setup. If you use your tow vehicle in cold climates, then
you can have double the
cranking power when you need it the most as the temperature drops to
below -10F. There is no need to even get out of the vehicle
nor open the hood! Simply flip a micro-switch on the
dashboard and you are on your way! We believe that this is one
of the very best setups available!
With this setup, we believe that you do not need
isolation between the trailer battery and main battery for two
reasons. 1) You will have the backup starting capability, and 2)
The trailer battery usually is not connected all the time.
However, if you feel you must have isolation here in addition to having
the backup capability, it is very simple to add a BIC-95150B between
the alternator and trailer battery or in the trailer itself as described above.
If your application is extreme such that you want
multiple and different isolated batteries/loads, you can add a
BIC-95150B for each Auxiliary battery bank in addition to the BIC-95300B with a
backup battery.
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