KEEP BATTERY CHARGED WHILE USING THE NORCOLD 3-WAY ON 12V

dsatwork

I found this on another forum but if this guy is accurate, it answers a lot of questions and offers solutions.

The 7 Pin or 6 Pin Bargeman Supply "+12V" does not normally have sufficient voltage to charge Trailer Batteries. In modern vehicles, including the Tundra, the Alternator contains an electronic controller which adjusts output (Voltage, and therefore Amps) according to the measured "State of Charge" found via the "Sense" wire. For a short time after starting, the voltage WILL be sufficient to charge the batteries - but the "State of Charge" recovers pretty quickly, and the alternator reduces its voltage to a "float" level of 13.5 - 13.8V.

Even if all this voltage could be seen at the Trailer batteries, it's not enough to drive much current - and the batteries will not charge in a reasonable amount of time. But the situation at the Trailer batteries is even worse than that, for two reasons: Voltage Drop in the wiring, and lots of power being consumed by the refrigerator.

Typical RV refrigerators, built using heater-based "absorption" technology, consume 10-15A while running the DC Heater. While the refrigerator tries to draw this power, from both the Trailer batteries and the TV-Bargeman connection, the Voltage at the end of the wiring from the Tundra connection wiring by amounts which Internet "Voltage Drop Calculators" will estimate for you. "Voltage Drop" values of 5% and higher are not uncommon when the Fridge activates the heater. When the original "13.5V" drops below the Voltage available from the Trailer batteries, the Fridge will pull power from the Batteries instead:

They are being discharged, rather than charged.

The solutions to this problem all involve devices which can consume lots of Power from the Bargeman Connector (even at lower voltage) and convert to higher Output Voltage, capable of charging batteries. Ctek makes (one the "D250S"), and Redarc devices from Australia are very popular for solving this problem. The boxes install in the Trailer, not the TV. You could also build DIY, although multiple boxes would be involved: A Voltage Booster (a 12V->24V "boost" converter, with high current capabilities; A "smart" Solar charger, to convert the Voltage back down (so that the Trailer batteries are charged properly, and not overcharged); and a small pair of "12V" batteries wired in series, in the middle, to stabilize the high-frequency "PWM Mode" square wave demand profile which the Solar Controller will present to the upstream device.

Costs for DIY are (roughly) $60-80 for a nice, weatherproof converter; about $30 for the pair of batteries; and $40-60 for "half decent" Solar Controller. Costs for Ctek and Redarc devices are much higher, but they can also support the use of Solar Panels.

ScottG

Good post, @dsatwork. I've been pondering this since my drive home from NY. On that trip, just out of curiosity, I had put my plug-in voltmeter in the T/V (a Nissan Frontier). Much to my surprise, I noticed the exact variation in alternator voltage that you described. This occurs regardless of whether the trailer is hooked up or not.

Without knowing much about it, I hypothesized that truck's brain was controlling alternator output, and as a result possibly not feeding sufficient power to trailer battery, which in turn was picking up some of the load of keeping the fridge running.

I still arrived home with the T@B battery just south of 12.5V, but that was lower than where it was when we started the ~7.5 hour drive.

dsatwork

@ScottG If it's correct and my feeling is this guy is dead on. This would explain why some members, with what I would consider vehicles designed for towing or have larger amp systems can keep up and other can't.

Photomom

Hmmm.

dsatwork

Photomom said:

Trying to wrap my head around this - it sounds like the idea is to "trick" the car's alternator into continuing to supply the higher current output?

More like forcing it to

RollingBnB

My owners manual says if connected to a trailer turn on the lights, that will keep the ECM from turning down the alt in the tv. It works too. I can see the alt guage drop to 12v when on a long drive until I turn on the lights, then it jumps up to 13.5-14v.

dsatwork

RollingBnB said:

My owners manual says if connected to a trailer turn on the lights, that will keep the ECM from turning down the alt in the tv. It works too. I can see the alt guage drop to 12v when on a long drive until I turn on the lights, then it jumps up to 13.5-14v.

See now were making some real progress. We need to have best practice for towing your Tab and if we have it we should add that to it.

dsatwork

From the 2015 Chevy Silverado 1500 Owner's Manual
If charging a remote (non-vehicle) battery, press the Tow/Haul Mode button, if equipped, at the end of the shift lever. This will boost the vehicle system voltage and properly charge the battery. If the trailer is too light for Tow/Haul Mode, or the vehicle is not equipped with Tow/ Haul, turn on the headlamps as a second way to boost the vehicle system and charge the battery.

This guy adds some great information the context of the thread was a little different but he gets to the same conclusion.

It really does not matter how large a generator is, it cannot force more voltage through a resistive circuit than the circuit will allow. A 12 gauge wire, dependent upon it's length and manufacture, will usually allow up to 30 amps (approx) for a 20+ foot run. However, that is dependent upon the TV and trailer running 12 gauge wire; I would have to check schematics to find out the actual gauge used in production. (I can guess from inspection of my trailer wiring, it is not 12 gauge; more like 14.)

In addition, that circuit is fused, in most cases for trucks with a 30 amp fuse; therefore, regardless of the wire gauge and length or the stated max output of the generator, the max current through that circuit will be 30 amps. And since this is the max allowed for that circuit, you can figure out the actual max the circuit could draw under normal conditions is 25 amps (approx.) 

However, I will agree that the generator used on modern vehicles is more than just a trickle charger, but that charge rate is determined by a lot more than the regulator. From a GM operational perspective (however, I'll bet a lunch that all others are the same, just different acronyms), the regulator is controlled by a engine control module (ECM), or powertrain control module (PCM), depending on vehcle application) and the BCM. The BCM basically monitors the battery state of charge, and signals the ECM (or PCM) to increase or decrease gen output via the regulator circuitry. 

The BCM determines this via programmed algorithms and sensors that look at the battery state of charge, calculated temp (in some case actual battery temp) and battery amperage via a hall-effect amp sensor in the negative batt wire, and the driving condition. After the vehicle has been started, the BCM will usually signal for a higher output to bring the battery up to a set max charge; with most generators, this takes only a few minutes (provided it is not dead winter and it took quite a few cranks to fire up the engine). Once the full state is achieved, the BCM will signal the ECM (or PCM) to decrease output. (I'll add here that to save generators, the output state is not boosted to high but gradually rises; this saves the generator from the harsh high output increase in older vehicles without computer controlled regulators). 

Now, on a nice sunny summer day, after the battery is at full charge, the generator kicks down to a very low steady run state and the output drops considerably. This steady run state is just enough to keep the vehicle and all accessories up and running. This will cause the charge to the trailer batteries to drop to a trickle; unless, you turn on a large draw (such as headlights) which will cause the BCM to signal for a high output, and that higher output will cause an increase in the charge to all circuits that require the increase; including the trailer battery circuit. This should increase the charge state to the trailer battery to near max the circuit can handle.

In some vehicles, the tow-haul switch will also signal the BCM to increase the generator output (as well as change shift schedules, power curve, etc.)

Some examples....
Immediately after the engine is started the BCM will set a generator output voltage of 14.5V for a set 30 seconds. It will then determine what to set it at via the ECM and if a quick start on a fully charged battery, it will drop considerably.

Headlamps turned On, the BCM signals the ECM to set regulated voltage at 14.5 volts.

Normal drive mode, with headlamps off, tow-haul mode off, and estimated battery 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 amperes and greater than -8 amperes, and the battery state-of-charge is greater than or equal to 80 percent, regulated output will drop to 12.5 volts.

If you attach a large gauge jumper cables to the trailer directly from the battery, the BCM sees this as a drop in the TV battery charge and signals for a high output signal from the ECM; thus the generator goes up in output. (And I don't mean those skinny cables sold at walmart for 10.00. [:)])

From a GM owner's manual...
If charging a remote (non-vehicle)
battery, press the Tow/Haul Mode
button, if equipped, located at the
end of the shift lever. This will boost
the vehicle system voltage and
properly charge the battery. If the
trailer is too light for Tow/Haul
Mode, or the vehicle is not equipped
with Tow/Haul, turn on the headlamps as a second way to
boost the vehicle system and
charge the battery.

Again, I will repeat this information is based on late model GM vehicles, since that is what I am very familiar with from more than just a driver's perspective. And that perspective is I'm an old fart, retired after 18 years as an electrical service engineer from GM. However, sitting on some SAE committees with my fellow Ford, Chrysler, BMW, Honda, Toyota counter parts; all these systems basically work the same. Some might use the BCM as the main controller like GM; some might use the ECM (or whatever they call it) as the main controller, but the actual process of the charging systems across all mfgrs are basically the same. And I'll also state, yes, I call it a GENERATOR, while all others call it an ALTERNATOR. The word GENERATOR actually comes from an SAE standard (J1930) that required all auto manufactures who sold vehicles in the USA to use standard names and terms on what can be considered emission equipment and the GENERATOR is considered an emission part from the EPA's standpoint.

RollingBnB

So, what your saying is turn on the lights (which should be on anyway for safety)     

ScottG

Wow, I've been taken to school--great info!

Nissan apparently calls their version "Power Generation Variable Voltage Control" and from what little observation I've made it behaves exactly as you describe except that turning on the headlights (my standard practice when towing) does not kick the generator output up to 14.5 volts. If a strategy for increasing generator output exists on the Frontier, I've yet to find it.

I wonder what would happen if you disconnected the T@B battery and just let the fridge run off the T/V harness.*

* DISCLAIMER: I'm not advocating this approach, as it would also leave the breakaway brakes without power. Modifications would need to be made to the existing trailer in order to ensure the battery retained a direct connection to the brakes!

dsatwork

ScottG said:

Wow, I've been taken to school--great info!

Nissan apparently calls their version "Power Generation Variable Voltage Control" and from what little observation I've made it behaves exactly as you describe except that turning on the headlights (my standard practice when towing) does not kick the generator output up to 14.5 volts. If a strategy for increasing generator output exists on the Frontier, I've yet to find it.

I wonder what would happen if you disconnected the T@B battery and just let the fridge run off the T/V harness.*

* DISCLAIMER: I'm not advocating this approach, as it would also leave the breakaway brakes without power. Modifications would need to be made to the existing trailer in order to ensure the battery retained a direct connection to the brakes!

That would be interesting. There should be a way to test that out. I believe the Norcold installation manual tells you how to test for the proper voltage to the unit.

Connect the 12 volts DC supply (3-way and/or fan models only):

As the distance from the vehicle battery to the refrigerator increases, the correct AWG wire size and fuse size also increases. If the

wire size is too small for the distance, a voltage drop occurs. The voltage drop decreases the output of the system heater and causes

decreased cooling performance.

If you use an incorrect wire size and/or fuse size, electrical fire can result.

1. Determine the min. wire size and the max. fuse size to use:

- Measure the distance from the vehicle battery to the refrigerator:

! WARNING

! WARNING

! WARNING

Installation Manual 7

- If the distance is 0 - 20 feet, use a minimum of 12 AWG wire and a maximum 20 amp fuse.

- If the distance is more than 20 feet, use a minimum 10 AWG wire and a maximum 30 amp fuse.

- If the wire size is larger than the min. size, use the correct fuse per RVIA A119.2 standard or local codes.

The wire connections must be clean, tight and free of corrosion. If any of these items are not correct:

- A voltage drop to the refrigerator will occur.

- The voltage drop will reduce the cooling performance of the refrigerator.

The terminals for connecting the DC power supply are marked positive (+) and negative (-) on the terminal block of the refrigerator.

Make sure that:

- Each DC power supply wire is attached to the correct polarity terminal.

- The chassis or the vehicle frame is not used as one of the conductors.

- The DC power supply wires including the fuses are routed directly from the

battery to the refrigerator.

2. Connect the D.C. power supply wires:

- Attach a 1/4 inch female Quick Connect terminal to each DC power supply

wire.

- Push the positive (+) DC power wire onto the terminal block [219] tab with the

12V (+) mark. (See Art02583)

- Push the negative (-) DC power wire onto the terminal block [219] tab with the

12V (-) mark. (see Art02583)

- Make sure each DC power supply wire is on the correct polarity terminal.

TabberJohn

So is the gist of this your TV manual needs to indicate boost mode is supported for trailer hookup? Or can you just insert a voltmeter inside the T@B, turn on your headlights, and check for spike in voltage?

Here's the Ctek manuals page: http://smartercharger.com/manuals/
D250S instructions suggest you'd also want a SmartPass unit to power the refrigerator (consumer). That combo is in the $500 range.
Also notice a temperature sensor is attached to the house battery near the positive pole. Since TV boost has no way to monitor T@B battery temperature does mean the boost method can't perform the same functions as the Ctek combo?

dsatwork

@TabberJohn
So is the gist of this your TV manual needs to indicate boost mode is supported for trailer hookup?
It seems like that would be a good bet. 

Or can you just insert a voltmeter inside the T@B, turn on your headlights, and check for spike in voltage?
If it works, you should be able to see an increase when you turn on the lights.
However, @ScottG  says that he has tested and it doesn't work on his Frontier

Ratkity

So by accident, I've been boosting my alternator while driving hooked up? I always turn on my lights for safety and use the trailering mode (I have a 2015 GMC truck). Several times I've looked at the alt output while driving with the camper attached and it's been around 14.5V. I always check the transmission temp as well. I never ran the frig on 12V DC because it would freeze my food. The new camper's frig doesn't have a 12V mode. Running on propane, it's stayed lit while driving so far (no high wind conditions yet). 

Cool information!! Thanks.

jkjenn

I find the alternator output on the Grand Cherokee disappointing but I always wonder if the fact that I am charging my phone and a tablet, and sometimes a GZ battery have anything to do with that.

dsatwork

I just tested our 2016 Kia Sorento and found the voltage was 14.31 while at idle or at 2000 rpm with the lights on or off..14.31 didn't matter whether the car was just started had driven 30 miles on the freeway....still 14.31. Not really sure what that means other than it's consistently pretty high. In theory the car was designed to tow, so maybe they thought that through. Also found out today that the alternator is 130 amps which also isn't too bad. 

ScottG

I made a few more observations this weekend on my 2015 Frontier. When I was running the lights, vent fan, and wipers, the generator/alternator output seemed to stay at ~14.2V. Otherwise it would tend to drop to the 13.2-13.3V range for extended periods. In summary, I still haven't found a reliable way to force the voltage to stay at >14V.

While I understand how higher voltage is needed to push a charge back into a battery, I'm still a little fuzzy on how generator wattage comes into play here when trying to run the fridge on DC. Even if the voltage is high, couldn't insufficient current (amperage) from the T/V force the fridge to struggle and potentially not operate properly without tapping into the T@B battery?

Even with a sufficiently robust generator, peak wattage is usually only achieved at RPMs well exceeding those at typical cruising speed. It seems to me that to run that darn fridge properly you need sufficient voltage and wattage from the generator, but--especially when one considers how much computer control occurs in modern vehicles--figuring out the relationship is exceeding my pay grade. Insights anybody?

ChanW

@ScottG, I'm thinking that yes the current output needs to stay up in order for the TV to be able to provide enough juice for the Tab. If the current output of the TV is insufficient, it's indicated by a low voltage reading. Thinking Ohm's Law.

Just a guess on my part.

Sharon_is_SAM

We had 10 gauge wire installed for our 7 pin battery charge line in our minivan.  We have not had a problem maintaining our ARB and battery during travel.  I think it must make a difference.  The alternator output is 150 amp.

ScottG

@ChanW, good point. Something to consider while we ruminate on the topic.

@SAM, I'm not familiar with ARBs, but don't they demand much less power than 3-way models? Did you use the ARB and have problems before installing the 10g wire?

I can't easily tell what the size of the battery charge line on my Nissan OEM harness is, but it might be worth investigating. I should add that when I'm not running the fridge and the T@B's converter is disconnected, my battery charges just fine while enroute.

Sharon_is_SAM

The ARB does draw less power, but we even started it while driving and we had no problems.  We had the 10 gauge from the outset.

Ratkity

The ARB draws significantly less amount of power and has a thermostat. I also have the wireless temp monitor and the insulation made for the Arb. Man, that thing is efficient. It is a great way to keep things cool while traveling. No worries about alternator power or propane flame not staying lit. Just my experience. I've also used it as a freezer and hauled ice cream desserts to a picnic. w00t! The powah of da ARB!

lapowers57

I drove for 10 hours last weekend with my fridge set for 12 volt.  When I stopped I found the battery at about 9.5 volts.  We turned off the fridge and drove for another two hours at this point the battery was at 12.2.   I ran the fridge on propane for the night and then ran for two hours with the fridge off, then two hours with the fridge on 12 volt and then an hour with the fridge off.  This got me to the campground with the battery reading about 12.5 volts.  The car can charge the battery but not with the load of the fridge.  Until I find a better way I will probably travel 2 on and 2 off making sure I run for at least one hour off before reaching the campground.  

The typical voltage regulator on a car runs at a high output for a short time then quickly tails off to a trickle charge.  On our sailboat we were able to change the regulator out for one that had a better charging profile.  I have wondered if these were available for cars.

ScottG

lapowers57 said:

...
The typical voltage regulator on a car runs at a high output for a short time then quickly tails off to a trickle charge.  On our sailboat we were able to change the regulator out for one that had a better charging profile.  I have wondered if these were available for cars.

Good question, but probably more complicated than it sounds. My impression (based on limited research) is that the variable voltage regulator is typically part of  the generator, and is ultimately controlled by the vehicle's computer. Sounds like a lot of integration that would make a simple swap-out unlikely. 

jason330i

dsatwork said:

I just tested our 2016 Kia Sorento and found the voltage was 14.31 while at idle or at 2000 rpm with the lights on or off..14.31 didn't matter whether the car was just started had driven 30 miles on the freeway....still 14.31. Not really sure what that means other than it's consistently pretty high. In theory the car was designed to tow, so maybe they thought that through. Also found out today that the alternator is 130 amps which also isn't too bad. 

Thanks for the info. What voltage level (on the T@b) do you usually see after a long drive with the fridge set to battery?

I recently did a 5 hour drive, in 100+ deg temps, up a mountain and when I got to camp, my T@b battery voltage was at 13.1V.

dsatwork

jason330i said:

dsatwork said:

I just tested our 2016 Kia Sorento and found the voltage was 14.31 while at idle or at 2000 rpm with the lights on or off..14.31 didn't matter whether the car was just started had driven 30 miles on the freeway....still 14.31. Not really sure what that means other than it's consistently pretty high. In theory the car was designed to tow, so maybe they thought that through. Also found out today that the alternator is 130 amps which also isn't too bad. 

Thanks for the info. What voltage level (on the T@b) do you usually see after a long drive with the fridge set to battery?

I recently did a 5 hour drive, in 100+ deg temps, up a mountain and when I got to camp, my T@b battery voltage was at 13.1V.

Wow, I'm not seeing that kind much for sure. Maybe 12.7v at the best usually about 12.5 what size is your battery bank? Is it a single 24group 12v typically 80ah? I have two 100ah AGM so I'm not really keeping up that well.

jason330i

dsatwork said:

jason330i said:

dsatwork said:

I just tested our 2016 Kia Sorento and found the voltage was 14.31 while at idle or at 2000 rpm with the lights on or off..14.31 didn't matter whether the car was just started had driven 30 miles on the freeway....still 14.31. Not really sure what that means other than it's consistently pretty high. In theory the car was designed to tow, so maybe they thought that through. Also found out today that the alternator is 130 amps which also isn't too bad. 

Thanks for the info. What voltage level (on the T@b) do you usually see after a long drive with the fridge set to battery?

I recently did a 5 hour drive, in 100+ deg temps, up a mountain and when I got to camp, my T@b battery voltage was at 13.1V.

Wow, I'm not seeing that kind much for sure. Maybe 12.7v at the best usually about 12.5 what size is your battery bank? Is it a single 24group 12v typically 80ah? I have two 100ah AGM so I'm not really keeping up that well.

Actually, it was probably lower than that. When I got to camp, I plugged into shore power, did some stuff, then checked my battery level.  So my number is probably not accurate. But sounds like I should expect under 13v.

My battery is the original battery my dealer gave me.

dsatwork

@jason330i The only way to accurately measure your battery is after it's been disconnected from the 12v charge coming from the car and before you connect to shore power, let it settle for about 30 minutes before you check you voltage at the seelevel. Shore power or checking to soon after charging will skew the results.

ScottG

My battery (105ah group 27) settled in at just below 12.5V after ~8hrs of driving with the fridge on DC. I was careful to turn the fridge off if I stopped for anything longer than the time it takes to get gas.

Normally the battery settles at a fully charged 12.7-12.8V after extended driving.

dsatwork

ScottG said:

My battery (105ah group 27) settled in at just below 12.5V after ~8hrs of driving with the fridge on DC. I was careful to turn the fridge off if I stopped for anything longer than the time it takes to get gas.

Normally the battery settles at a fully charged 12.7-12.8V after extended driving.

Thanks @ScottG Given that I feel better about my results.

MuttonChops

Great forum thread.

As noted most newer vehicles have some type of Variable Alternator Output Control to help boost overall MPG. The chart below shows this working in different tow vehicle electrical load configurations. For those of us with more visual minds.

Chevy Colorado. Recording voltmeter at 7-pin reading every 20 seconds, no trailer.
Vehicle first driven to nearly fully charge battery and force lower voltage output mode.  Since 13.6 is below a battery charging voltage I did not drive long enough to force the worse case low range voltage below 13.1.

Vehicle Reference Information:

In GMC Canyon/Colorado mid-size trucks if the vehicle battery is sensed to be fully charged than Fuel Economy Mode turns-on with Battery Charge / Alternator output controlled at 12.5 to 13.1 VDC. Well below the level needed to charge a trailer battery via the 7-Pin connector V+Battery circuit.

GMC overrides the Fuel Economy Mode if headlights are turned on or the Tow/Haul Mode feature is turned on. Tow/Haul changes transmission shift points, default maximum gear in 'L' transmission mode, and alternator output. Tow/Haul voltage output range is 13.9 to 14.5 VDC.

+12V wire to 7-pin is 10 AWG and directly connected to Battery via a 30 Amp fuse. +12V stays on when vehicle is not running.

In my limited load test it seems Tow/Haul does a better job of stepping up the voltage than just having the headlight on. Having an actual trailer battery load may cause the vehicle computer to increase the voltage more.