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Old 04-16-2016, 10:25 PM   #15
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Thanks to all who replied! Very thoughtful suggestions to my issue. I'll summarize below but first let me clarify a couple things. First, I do have an HD alternator of 180 amps. Second. I've done my current measurements ay the 7-way plug using an ammeter that shows the current tapering from 25a to about 3a over the first hour of drive time and the charge rate stays low for the rest of the drive unless I stop and restart the truck.

Here are your suggestions and my reaction:

1. Install an inverter on the truck and wire AC back to the 3-stage converter to charge the battery. An interesting take on the solution but doesn't seem to be too efficient to convert DC tonAC and back again. Also complex.

2. Dual voltage regulators driven off my HD alternator -- one to the truck and one to the trailer. My alternator has integrated regulator so don't think that'd work.

3. Use bigger cable to the coach batteries (twice suggested). I will try some tests to see if this will increase the charging rate but I don't think it'll help much.

4. Second alternator/regulator on truck (suggested twice). I like this solution but it would take a lot of re-engineering of the serpentine accessory belt on the engine.

5. Carry a generator (suggested 3 times). We're just not generator people.

6. Get an HD alternator. Already got one.

7. Get more solar. The idea I like the most. I'm not liking installing panels on our coach but thinking of gluing flexible panels on the topper of our truck. The coach is in the shade by choice but the truck could be in the sun and cabled a reasonable distance to the coach to augment our 120w portable solar. Solar on the truck might easily add 5-10 amps to the charge while driving in the sun.

8. Portable wind turbine. Interesting alternative often used by sailors. I think campsite winds to be less reliable than marine winds tho.

Thanks to everyone for your comments so far. I'm thinking more solar may be the answer.

John
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Old 04-17-2016, 09:24 AM   #16
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John, if you know any hard core racers or have dedicated race shops in your area check with them on how too mount and wire a second generator. There are companies that make everything you need for mounting a second independent alternator for powering a hauler/trailer. Pulleys, belts and mounts are available for most trucks. I am out of the loop but someone currently in the business should be able to help.
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Old 04-17-2016, 09:33 AM   #17
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Quote:
Originally Posted by crampshaw View Post
Thanks to everyone for your comments so far. I'm thinking more solar may be the answer.
John
More solar will help when there is sun. But on cloudy days or in shaded campsites, "more solar" will likely disappoint. For those inevitable situations, I suggest you get a lightweight, quiet 1000 watt Honda or Yamaha generator that has been converted to run on propane so you can hook up to your AS' propane supply. There is no need to carry gasoline and worry about gasoline residue in the carburetor. You only need to use and think about the generator when you need it. And if you don't, so much the better!
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Old 04-17-2016, 10:58 AM   #18
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I too use a cpap and have 2 6v batts. The simplest and cheapest solution I have found is a $220 1500 champion generator. Light weight, will run 8 hrs on 1 gal of gas, and run during the day while we are doing what ever occurs to us. It is not loud, (louder than a Honda), but thousands of $ less. If you aren't a automotive electrical specialist, you could run the risk of really messing up your TV. Labor costs alone to have this done would exceed the cost of a small gen. Remember, KISS. Keep It Simple S----d!
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Old 04-17-2016, 12:27 PM   #19
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You could run a bigger wire between the batteries on the pickup and the rv, maybe a second plug....I never seen a sensor in a battery cable, the regulator is built in the alternator.....
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Old 04-18-2016, 07:54 PM   #20
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dv to dc chargers

There are dc to dc chargers that address the issue of poor charging on the road. These chargers boost the voltage w dc to dc switching system. And they provide multilevel smart charging.

A 40A charger, Promariner 5504 is made for automatically charging house batteries on sailboats from the engine battery. Only issue is wiring between TV & trailer has to be large to carry 40A. About $325

A 7.5A charger, Powerstream 1212-15 is made for charging wheel chair batteries from a car or van. This can use the wiring in the 7-pin connector. Install in Airstream. About $200.

Read more by google search. I am in process of installing the Powerstream unit now.
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Old 04-19-2016, 10:28 AM   #21
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Quote:
Originally Posted by tjdonahoe View Post
You could run a bigger wire between the batteries on the pickup and the rv, maybe a second plug....I never seen a sensor in a battery cable, the regulator is built in the alternator.....
The size of the stock wires from the alternator of the TV to the trailer batteries are generally woefully inadequate. There are plenty of voltage loss spreadsheets on the internet to estimate what the actual losses are. Remember, on a DC line the actual line length on the calculations must be doubled, since the DC current must actually travel through both lines.

Below are the pics showing my "fix" to the problem. Note that the high amperage delivered to the trailer batteries MAY not be optimum for your setup.
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Old 04-19-2016, 12:06 PM   #22
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I would suggest you contact "Shacksman" here on the forums. He runs a setup that I think would take care of your problem. It's easy to install and use.

Enjoy,
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Old 04-20-2016, 01:29 PM   #23
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GM Charge Circut Description

OK - There have been a lot of suggestions made, but before you go crazy you might want to know exactly how the factory system actually work.

below is a partial pdf copy of pages 9-1693 & 9-1694 of the factory service manual



Engine Electrical 9-1693
Body Control Module (BCM)
The body control module (BCM) is
a GMLAN device. It

Communicates with the engine control module (ECM)
land
the instrument panel cluster (IPC) for electrical

power management (EPM) operation. The BCM
•determines the output of the generator and sends the
•formation to the ECM for control of the generator
field control circuit. It monitors the generator field duty
cycle signal circuit information sent from the ECM
takes
control of the generator. It monitors a battery

[current sensor, the battery positive voltage circuit, and
•Estimated battery temperature to determine battery
[state of charge (SOC). The BCM sends idle boost
requests to the ECM.
•Battery Current Sensor
The battery current sensor is a serviceable component
fiat is connected to the negative battery cable at
I tie battery. The battery current sensor is a 3-wire hall
I elect current sensor. The battery current sensor
monitors the battery current. It directly inputs to the
BCM. It creates a 5 volt pulse width modulation (PWM)
I signal of 128 Hz with a duty cycle of 0-100 percent.
Normal duty cycle is between 5-95 percent. Between
0-5 percent and 95-100 percent are for diagnostic
I purposes.
Engine Control Module (ECM)
The ECM directly controls the generator field control
I circuit input to the generator. The ECM receives
| control decisions based on messages from the BCM.
It monitors the generators generator field duty
cycle signal circuit and sends the information to
the BCM.
Instrument Panel Cluster (IPC)

The IPC provides a means of customer notification in
case of a failure and a voltmeter. There are 2 means
of notification, a charge indicator and the driver
information center (DIG) SERVICE BATTERY
CHARGING SYSTEM message.
Charging System Operation
The purpose of the charging system is to maintain the
battery charge and vehicle loads. There are 6 modes
of operation and they include:
• Battery Sulfation Mode
• Charge Mode
• Fuel Economy Mode
• Headlamp Mode
• Start Up Mode
• Voltage Reduction Mode
The engine control module (ECM) controls the
generator through the generator turn on signal. It
monitors the generator performance though the
generator field duty cycle signal circuit. The signal
is a 5 volt pulse width modulation (PWM) signal
of 128 Hz with a duty cycle of 0-100 percent.
Normal duty cycle is between 5-95 percent.
Between 0-5 percent and 95-100 percent are for
diagnostic purposes.
The following table shows the commanded duty cycle
and output voltage of the generator:
Commanded Duty Cycle
10%
20%
30%
40%
50%
60%
70%
80%
90%
Generator Output Voltage
11 V
11.56V
12.12V
12.68V
13.25V
13.81 V
14.37V
14.94V
15.5V
The generator provides a feedback signal of the
generator voltage output through the generator field
duty cycle signal circuit to the ECM. This information is
sent to the body control module (BCM). The signal is a
5 volt PWM signal of 128 Hz with a duty cycle of
0-100 percent. Normal duty cycle is between
5-99 percent. Between 0-5 percent and 100 percent
are for diagnostic purposes.
Battery Sulfation Mode
The BCM will enter this mode when the interpreted
generator output voltage is less than 13.2 volts
for 45 minutes. When this condition exists the BCM
will enter Charge Mode for 2-3 minutes. The BCM will
then determine which mode to enter depending on
voltage requirements.
Charge Mode
The BCM will enter Charge Mode when ever one of
the following conditions are met.
• The wipers are ON for more than 3 seconds.
• The GMLAN Climate Control Voltage Boost Mode
Request is true, as sensed by the HVAC control
head. High speed cooling fan, rear defogger
and HVAC high speed blower operation can cause
the BCM to enter the Charge Mode.
• The estimated battery temperature is less than
0°C (32°F).
• Battery state of charge is less than 80 percent.
• Vehicle speed is greater than 145 km/h (90 mph)
• Current sensor fault exists
• System voltage was determined to be below
12.56 volts
• Tow/Haul mode is enabled
When any one of these conditions is met, the system
will set targeted generator output voltage to a
charging voltage between 13.9-15.5 volts, depending
on the battery state of charge and estimated battery
temperature.
Fuel Economy Mode
The BCM will enter Fuel Economy Mode when the
ambient air temperature is at least 0°C (32°F) but less
than or equal to 80°C (176°F), the calculated battery
current is less than 15 amps and greater than -8 amps,
and the battery state of charge (SOC) is greater than or
equal to 80 percent. Its targeted generator output
voltage is the open circuit voltage of the battery and can
be between 12.5-13.1 volts. The BCM will exit this
mode and enter Charge Mode when any of the
conditions described above are present.
2009 -
Headlamp Mode
The BCM will enter Headlamp Mode when the
headlamps are ON. Voltage will be regulated between
13.9-14.5 volts
Start Up Mode
When the engine is started the BCM sets a targeted
generator output voltage of 14.3 volts for 30 seconds.
Voltage Reduction Mode
The BCM will enter Voltage Reduction Mode when the
calculated battery temperature is above 0°C (32°F).
The calculated battery current is less than 1 amp and
greater than -7 amps, and the generator field duty
cycle is less than 99 percent. Its targeted generator
output voltage is 13 volts. The BCM will exit this mode
once the criteria are met for Charge Mode.
Auxiliary Battery Charging (TP2)
The auxiliary battery provision (TP2) can be used to
supply electrical power to additional equipment that the
customer may choose to add, such as a slide-in
camper or trailer, without discharging the vehicles
primary battery. The auxiliary battery relay closes when
the engine is running, in order to allow the generator
to charge the auxiliary battery. The relay opens
when the engine is off, so that the accessories will not
discharge the vehicles primary battery, which is
used for engine starting. If the vehicle is equipped with
an auxiliary battery, the relay will be located on the
driver's side of the vehicle, next to the underhood
electrical center. Generally, a fuse should not be used
in the STUD 1 Fuse 70 position of the underhood
fuse block, if the vehicle is equipped with an auxiliary
battery. A plastic plug may be installed in this
position instead of a fuse. If a fuse is installed in this
position, the accessories will discharge the primary
battery in addition to the auxiliary battery.
Instrument Panel Cluster (IPC)
Operation
Charge Indicator Operation
The instrument panel cluster (IPC) illuminates the
charge indicator and displays a warning message in
the driver information center (DIG) when the one or
more of the following occurs:
• The engine control module (ECM) detects that the
generator output is less than 11 volts or greater
than 16 volts. The IPC receives a GMLAN
message from the ECM requesting illumination.
• The BCM determines that the system voltage is
less than 11 volts or greater than 16 volts.
'
• The IPC receives a GMLAN message from
body control module (BCM) indicating there is
a system voltage range concern.
• The IPC performs the displays test at the start)
each ignition cycle. The indicator illuminates
fa*i

approximately 3 seconds.
• The ignition is ON, with the engine OFF.
Battery Voltage Gauge Operation
The IPC displays the system voltage as received 'r
the BCM over the GMLAN serial data circuit. If
there is no communication with the BCM then the
gauge will indicate minimum.
This vehicle is equipped with a regulated voltage
control (RVC) system. This system turns off the
generator when it is not required in order to improve
fuel economy. The generator will turn back on
when additional voltage is required. This will cause •
voltmeter to fluctuate between 12 and 14 volts as
opposed to non-regulated systems which usually
maintain a more consistent reading of 14 volts. The
fluctuation with the RVC system is normal system
operation and NO repairs should be attempted.
SERVICE BATTERY CHARGING SYSTEM
The BCM and the ECM will send a GMLAN mess
to the DIG for the SERVICE BATTERY CHARGING
SYSTEM message to be displayed. It is command
ON when a charging system DTC is a current
DTC. The message is turned OFF when the condition
for clearing the DTC have been met.
Electrical Power Management
Description and Operation
Electrical Power Management
The electrical power management (EPM) is used to
monitor and control the charging system and alert *
driver of possible problems within the charging
system. The EPM system makes the most efficient
use of the generator output, improves the battery i
of charge (SOC), extends battery life.
The idle boost operation is a means of improving
generator performance during a low voltage or
low battery SOC condition.
Idle boost is activated in incremental steps, idle
boost 1 must be active before idle boost 2 can be
active. The criteria used by the body control
module (BCM) to regulate EPM are outlined below.
I
Function
Idle Boost 1 Start
Idle Boost 1 Start
Idle Boost 1 Start
Battery Temperature
Calculation
Less Than-15°C
(+5°F)
_
Battery Voltage
Calculation
Less Than 13V
Less Than 10.9 V
Amp-hour Calculation
Battery has a net loss
greater than 0.6 AH
Action Taken
First level idle boos I
requested
First level idle boost I
requested
First level idle boost
requested
2009 -



thus you can raise the charge voltage by doing any of the things listed such as pushing tow/haul button.

VicH
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Old 04-23-2016, 10:54 AM   #24
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Tow Mode is the answer for now

Thanks to all those posting suggestions to help my charging issue.

Especially Vich who posted part of the GM shop manual. After reading it, I tried a few thing on last Thursday's tow.

Headlights nor AC seemed to move the charging system out of economy mode that does no trailer battery charging. But Tow Mode always moved the charging to a higher voltage mode. I'll have to test the amps, but the voltage as read on the voltmeter looks better.

So I'll bee using Tow Mode to get better charging.

John
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Old 05-20-2016, 09:09 AM   #25
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Join Date: May 2016
Posts: 8
As has been stated the wiring to the trailer batts is way too small to do any real charging. It also is probably current limited by the computers I doubt in this day and age it's going straight from battery to battery.

If it were me, I would run a separate 2 or 4 gauge wire from the engine battery, through a battery combiner, and then to the house batteries with some sort of disconnect in between to unhook. You'd also need an equally sized ground connecting the truck to the trailer. I assume the trailer hitch would probably provide this i'm not too sure on trailer grounding)

Once that's done the combiner will do it's job and connect the two batteries every time there is charging (ie when running) and disconnect when not charging.

This would essentially allow the batteries to equalize, draining the engine battery and charging the house batteries. The alternator would then see the engine batt voltage dropping and apply more charge current.

This would run probably 100 bucks in good wire and 50 bucks for a 120A combiner and you're in business. This is how my motorhome is setup and it will pull 80 amps from the alternator when the house batts are low. A very simple and effective setup.
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