Electrical

Sebastian

Learned more about Alde, now need to know more about electrical.  Will my T@B CS-S 2015 battery receive charge from my TV while I'm driving? Recently while I was parked for short while and the T@B was hooked up, my auto battery was drained.  There was nothing on/using power while I was parked.  Battery in Subie is 1yr old and recently tested. Battery in T@B is deep cycle ~4 yrs old and recently charged, but doesn't seem to hold or take a charge.
TV 2011 Sabaru Forester

ScottG

@Sabastian, the short answer is yes. A properly wired tow vehicle will provide 12V power to the camper through the 7-pin connector.

Most, but not all, vehicles cut the power to this circuit when the vehicle is turned off. I don't know about Subarus particularly, but it sounds like yours does not.

Your T@B battery is almost certainly toast and needs to be replaced. There is phantom drain in a typical 2015 T@B, though I would not expect that to drain your car battery in such a short time. However, a very dead T@B battery could possibly draw the life out of your car battery pretty quickly.

Cbusguy

@ScottG properly might be a matter of what the user needs,  sounds like Sebastians rig is wire for on all the time.    Mine  trailer 12 volt wire for on and off with the ignition key,  to minimize the chance of a dead tow vehicle battery.   

But highlights the point that everyone needs to understand how their rig is wired.

Marceline

I agree with Scott. It sounds like your vehicle is wired with an unswitched 12v line to the 7pin connector. The trailer battery keeps drawing on your vehicle battery while parked. Mine also works like this. So if my trailer battery is low or I’m running the fridge I disconnect if I’m parked for more than a couple of minutes. 

Sharon_is_SAM

@Sebastian, a battery not holding a charge is a good sign that you need a new battery.  Like our minivan, it sounds like your charge line coming off your TV battery does not turn off with the ignition, resulting in your TV battery drain.  As Scott said, in addition to towing with the 2 way frig, there are other phantom power drains that will draw down your TaB and TV battery.  After you replace your TaB battery you will benefit from a TaB battery cut off switch.

Bayliss

@ScottG , in your earlier post your wrote, "Most, but not all, vehicles cut the power to this circuit when the ignition is not off."   Did you mean to say, ". . . when the ignition is off?"

What is the best (easiest) way to determine if your 7-pin is actually charging the camper battery, and whether it is doing that only when the TV ignition is "on"?  I was told that my 7-pin does charge the camper battery, and that it disconnects when the ignition on the TV is off (so as not to drain the TV battery), but I would like to independently confirm that.  Thanks!  (Greg)

N7SHG_Ham

@Bayliss check your plug on the back of the TV with a voltmeter, you should be able to determine if the charge line is hot all the time or just with the key on. Wired "properly" the key should control a relay which will carry the actual current from the battery to the camper. Pins 2 and 4 are the two to check between with the meter, that should be the charge line and the ground. If that always shows 12v then you know it is wired through key to be hot only with ignition on.

ScottG

Bayliss said:

@ScottG , in your earlier post your wrote, "Most, but not all, vehicles cut the power to this circuit when the ignition is not off."   Did you mean to say, ". . . when the ignition is off?"

What is the best (easiest) way to determine if your 7-pin is actually charging the camper battery, and whether it is doing that only when the TV ignition is "on"?  I was told that mine does, and that it disconnects when the ignition on the TV is off, but I would like to independently confirm that.  Thanks!  (Greg)

@Bayless, you are correct! I think I combined "off" and "not on" in my brain, and, well, you can see how that worked out. I've edited my comment and I thank you for catching it.  :-) 

You should be able to check your T/V by putting a multimeter across the 12V charge pin and the ground pin at the 7-pin receptacle (the function of each pin is usually labelled on the receptacle cap or some other nearby location). If your vehicle has a switched line there should be voltage when the ignition switch is on but not when it is off.

Alternatively, if multimeters aren't your thing, just disconnect your T@B battery, plug your trailer pigtail into your vehicle, and turn on a light or some other obvious device in the camper. If your line is switched, the light should turn on and off along with your ignition.

Bayliss

Perfect, @ScottG .  Your second option was what I was going to try, but I wasn't sure if that would be definitive, because I know I am sending power to the camper since the exterior lights work (although, I suppose they are on separate circuits, particularly the charge line.)  I do have a multimeter, so I will try that first since my TV is at my house, but the camper is in storage.  And thank you too, @N7SHG_Ham for identifying the pins to check.  I think I have a chart that shows that as well.  Thank you both very much for the quick responses.  (Greg)

Bayliss

@ScottG and @N7SHG_Ham - - that worked........."Houston, we have power!"  (Or, put another way, no power when the TV ignition switch is turned off.)  Thanks again!  (Greg)

ScottG

You're welcome, @Bayless. You are correct about the trailer running lights being on different circuits. Here's the pigtail connections at the forward junction box:

Pins 2, 3, and 4 from the left (unlabelled) I believe are the running/turn/brake lights. They connect directly back to--and are powered by--different circuits on the tow vehicle.

Pin 6 from the left (the one with the labels) connects the tow vehicle's 12V charge line to the T@B battery, converter, and breakaway brakes. Therefore, if you disconnect the T@B battery the tow vehicle will be the only source of power to the converter.

Bayliss

Thanks, @ScottG - - the labeled photograph and added description are very helpful.  I will cut and paste your post for future reference.  I have more notes on my T@B than I ever had for any other RV I have owned.  Crazy, but nice to have to refer to when I need it.  This forum is a wealth of information thanks to all the contributors who share their knowledge.  I even learn from the trials and tribulations of others and how everyone works together to find a solution. 

pthomas745

@Bayliss you can also bookmark this thread.  If you haven't done it before, way over to the right next to the "Electrical" header is a "blank star."  Click the star, it turns yellow, and you can use "My Bookmarks" from the menu on the left side of the page to find it again.

BrianZ

The 7-way power line on our 2005 Sienna van appears to be wired directly to the battery, with a 30-amp breaker on the positive line near the TV battery.  I got 12V with a voltmeter at the TV 7-way socket when the car was parked/engine off/locked.

Sebastian

Thank you all.  I feel better just knowing this and being able to refer to it (it's a lot of knowledge for a beginner me).  I'm so glad we have this forum.  
Sebastian

ScottG

I hear ya' @Sabastian. It's a dish best digested in small bites. Just wait 'till you start thinking about adding a solar panel!  ;-)

BrianZ

This discussion is a good reminder for me that turning off the T@B's battery isolation switch will not protect our TV battery from a potential power drain, and we must therefor pull the the 7-way plug to protect the TV battery if there is anything extra left running like a frig.  

That said, I am currently testing the rate of discharge of our T@B's battery due to background electronics left running (not counting television which now has a power switch to turn off power supply), and it's not very much.  After 5 days so far, here's our battery status:

It appears we are using 250 milliamps or 6AH per day.  Surprisingly, we are still at 91% state of charge, I presume due to the Peukert effect.  The "time remaining" is apparently not reliable, since it started at 10 days and is still there.  It also appears we could last significantly longer than 10 days, but based on the Amp-hour usage, I'm not sure how accurate the SOC is either, unless that Peukert effect is really large at this slow discharge rate.  Our battery is 150 AH.

Sharon_is_SAM

@BrianZ, we do not bother unplugging our 7 pin or isolating the battery.  With the ARB, the draw is so low, we don't worry when just stopping for lunch.  We have a 150 amp AGM, too.

klenger

I did some testing this weekend to see how much charge current the tow vehicle (Jeep Wrangler) furnishes to the T@B when towing.  I have a battery monitor, so checking the charge current amounted to simply reading the display.  Hooked up the Jeep to the T@B in the driveway, had the DW rev the engine to about 2,000 RPM, and checked the charge current.  Was I surprised to find that the Jeep not only DID NOT provide any charge current when connected, it actually was drawing about 300 MA from the T@B.  

Note that I have a single Battleborn 100 AH lithium battery, 200 watt lithium solar charger, and 30 amp lithium converter.  The battery voltage w/o the Jeep connected was about 13.3 VDC and pretty much stayed at that voltage when the Jeep was connected.  

Next, I checked the Jeep's DC voltage with the engine running (using the Jeep's built in display) and found that the alternator/battery voltage was only 12.7 VDC with the engine running.  I confirmed the voltage with a digital meter.  

So it appears that if my lithium battery is reasonably charged, the Jeep does not charge the T@B battery at all, and in-fact slightly discharges the T@B's battery when towing.  

Based on this information, I made a wiring modification, adding a fuse between the T@B 7-way charge wire and the T@B battery.  I left the fuse out, since the tow vehicle wasn't charging the T@B anyway.   Should some situation arise where the T@B lithium battery voltage is very low (below 12.7 VDC, I can simply insert a fuse and then use the tow vehicle to charge the T@B battery. 

I was a bit surprised to see such a low charge voltage from the Jeep, but maybe this is a new trend in automotive design.  I don't think there is anything wrong with the Jeep since it starts and runs just fine.  

So, I will rely on the solar and converter (lithium spec) to do all the T@B battery charging, and a Honda EU2200i generator (if I can ever buy one).  I have always believed the charging a towable TV battery from the tow vehicle is a loosing proposition, but this experiment (with my setup) confirmed it for me.

Awca12a

For reasons related to voltage drop, alternator size and the small AWG wires used in the harness, the Vast majority of tow vehicles can’t charge your TT battery to any degree while driving.  At best, it can float charge the battery and keep up with parasitic losses which is something.  

dsfdogs

@klenger I have researched the BB lithium, and still plan to get it, but after reading about the TV draw from the lithium you experienced...could I have read somwhere the two batteries try to balance each other and because the lithium is a higher voltage, it's drawn down?? Sure seems like it would be a problem for everyone. I may very well be wrong, but thought I'd throw it out there for the smarties.

Sharon_is_SAM

@klenger, did you check the Jeep voltage with your headlights on?  Have you partially discharged your lithium battery and then measured?  

Also, contrary to Awca12a, we installed a 10 gauge charge wire and ground wire and have had no problem recharging our TaB battery.  Definitely more than a trickle charger.

jkjenn

I cannot speak to the newer JK or JL, but my Grand Cherokee seems to use "smart" technology when it comes to how it handles power distribution. Its priority is the tow vehicle and then the trailer. Sadly, Jeep's alternators are under-sized for towing. They seem to only put the higher amp alternator in the WK2 SRT.

@klenger forgive me if posted and I missed it, but did you replace the standard converter with one meant for charging lithium? I am also wondering if a minimum amp input is required to charge a lithium and if there is some sort of protection to keep the battery from being hurt by too low of a charge input?

Lastly, it never hurts to check the fuses in your TV.

BrianZ

@klenger, I was wondering about your new fuse arrangement and whether your automatic brakes would still receive power from your T@B battery in case of an emergency disconnect from the TV if that fuse was not in place?  

PS:
Our TV charge line goes directly to the TV battery & is hot all the time.  Before leaving our campground last fall, with engine idling & rooftop solar connected, our partially discharged T@B battery was receiving 6A from the car & 5A from solar - as I had shown at the bottom of this page..
http://tabforum.nucamprv.com/#/discussion/3847/what-battery-should-i-upgrade-to
I presume our TV battery was getting around 14+ volts from the alternator in order to be sending that much current, but no I had no measurements.  Will have to look closer next time & look at higher RPMs.  We may have been able to run our frig without propane, but never tried it.

Cbusguy

Battle born has a built in battery management system and is touted as a drop in lead acid replacement,   so in theory you should be good.   with that said, Most folks I know that use it still use the victron battery protection system to protect from over voltage and over discharge.    The batterys are just too expensive and fragile to not run some sort of automatic protection.   I believe they have a 10 year warranty,  but I hate the screwing around with a warranty claim.

Like sharon I upgraded my truck wiring to much heavier than standard and my alternator to a 250 amp, or somewhere thereabouts,   to specifically charge the trailer batterys while traveling.   Still trying to decide if a battery isolator is a good idea.....

Sharon_is_SAM

@Cbusguy, We considered having an isolation relay installed in our TV, but in the end, as long as we do not turn the battery switch off, there is enough amperage between both batteries to not deplete either one of them.  Certainly more than enough to not worry with a lunch stop.  Now, that is with a 150 amp TaB battery and a low draw ARB.  YMMV running a 3 way frig on DC or even a 2 way.  Also, no need to remember to turn the switch back on before towing.

Cbusguy

@Sharon_is_SAM what I was looking at was a bit more than a switch.   Here is a link.    It Electric Isolates each battery even while charging.     Big sigh,  not sure if it is necessary or not.

Sharon_is_SAM

@Cbusguy, I see.  That is different than an auto isolation relay switch.  Not sure anyone has done that here on the forum.

Cbusguy

@Sharon_is_SAM I used one on my jeep to Isolate the starting battery from the winch and lighting electrical system.     That winch would draw 500 amps under load and could stall the motor. 

I have already installed a contiuous duty relay that it tied to the vehicle ignition to turn the trailer circuit off with the key,   But I still worry about a highly discharged battery sucking the TV battery dry even with my high amperage alternator.....probably me just being paranoid.   But luck favors the prepared.

klenger

Thanks for all the comments regarding my post above.  I believe my situation is somewhat specific to my installation with the lithium battery and lithium spec'd solar controller and converter (Progressive Dynamics PD9130LV), which tends to run at higher voltage than a lead acid or AGM battery.  By adding the fuse holder, I can very simply elect to install the fuse and restore tow vehicle charging or not as I learn more.  I will do some more experimenting when actually towing and with and without the refrigerator on DC.

Regrading the breakaway switch wiring, I made sure that the brake system is powered from the T@B battery regardless of the tow vehicle charge wire connection.   

For those interested in my (highly modified) wiring, goto http://www.klenger.net/wiring-diagrams.html and click on the "Owner Modified" wiring diagram button.  The tow vehicle wiring is on sheet 1. 

On a side note, I finally had a chance to boondock with this setup last weekend.  Note that I have a 150 watt sine wave inverter and have switched out the TV to a 120 VAC model from Best Buy (works great).  Running the inverter, TV, one or more lights, and the Alde (at night), total battery draw was around 3+ amps.  By the next morning, my battery capacity was down to around 80% and the 200 watt solar charged the battery back to 100% by 11:00 AM and kept the battery at 100% till the sunset.  I am very impressed with the efficiency of the systems in the T@B.  On previous full size RVs I've had, the same loads would draw 10-25 amps DC.

I also looked at the battery isolation device linked above.  From my brief review, it appears that you would need to install the device in the tow vehicle's electrical system to fully benefit from its design.  It appears that the intended use is for motor homes that have split electrical systems for chassis and coach power.  It may still help if installed inline inline with the tow vehicle charge wire in the T@B wiring but don't know enough about it to know in advance.  I do believe that a simple diode would not help much because the 0.6 VDC drop would render the tow vehicle charge voltage ineffective.   

Hope I'm not hijacking this thread too much. 

ScottG

Thanks for the info, @klenger. I'm no guru on the finer physics of batteries, but I do believe that two connected batteries in different states of charge will try to equalize. In that light, your issue makes sense.

I'm also under the impression that most modern vehicles incorporate voltage output control on their generators (apparently we have gone back to that term now...). My Frontier certainly does; very rarely do I see an output of the old standard 14.4V, and frequently it's coughing up less than 13V. While some vehicles allow you to trick the generator into upping its output by turning on the lights, this does not work on mine.