Charging The Batteries From The TV While Running The Refrigerator On Battery

[Philip]

Hello Folks,

After an extended three month trip out west last spring/summer the only disturbing problem turned out to be that the batteries discharged while towing with the refrigerator running on batteries. Yes I know many campers run the refrigerator on propane while towing but I am one who is not comfortable operating that way. First, the waste heat when running on propane is more than on electric and I worry about venting this heat with the shell covering the vent. Second, I prefer to have the propane off when towing - call me a bit of a safety freak!

Since we most often prefer to camp in state/national forest or national park campgrounds which generally do not have electric, it is most important to have the batteries charged when we set up. We prefer these campgrounds since they are generally more beautiful and less congested/crowded.

After quite a bit of investigating I finally found a web site where a fellow described how he solved this TV charging problem. This solution was also confirmed in a good book titled "Wiring for 12 Volts" by the guru of 12 volt systems, in my opinion, David Smead. The solution is to increase the wire size considerably from the TV battery to the TM batteries. The reason the charging rate is so low with the factory plug connection is that the charging wire sizes are woefully small causing too much of a voltage drop from the TV battery to the TM batteries. Keep in mind that the only driving force to charge the TM batteries from the TV is the voltage difference from the TV to TM batteries - generally 2 volts or much less.

Before making any charging system changes, the TV charged the batteries on the order of 3 or 4 amps or much less. I have a Link Lite battery monitor to measure amps. With the refrigerator running the batteries went into discharge when connected to the TV.

After revamping the charging system the TV charges the TM batteries at anywhere from 50 to 25 amps depending on the charge state of the TM batteries. The TM batteries are always charged well with the refrigerator and refrigerator fan running on battery. Here is what I did. Run #2 gage wires from the positive and negative post on the TV battery back to a new two pole plug on the rear of the TV. Run #2 gage wires from the TM batteries to a two pole plug(which plugs into the new TV plug) on the TM. The plug should be a very high amp plug so any voltage drop over the plug is very small. I used welding cable for the wire as it is quite cheap and very flexable. Also be sure to put a fuse(I used a 100 amp fuse) in the line from the TV battery so the TV will be safe if you should get a short anywhere in the TV wireing.

That's it and it works great. I will also be able to charge the TM batteries from the TV when set up in a campground should I need to.

My TV is a 2005 Toyota 4Runner with a factory tow package. The alternator is 100 amp and still sees a light duty cycle.

I hope this helps others solve this problem.

Take care,

Phil Friess

[Wavery]

Originally Posted by Philip

Hello Folks,

After an extended three month trip out west last spring/summer the only disturbing problem turned out to be that the batteries discharged while towing with the refrigerator running on batteries. Yes I know many campers run the refrigerator on propane while towing but I am one who is not comfortable operating that way. First, the waste heat when running on propane is more than on electric and I worry about venting this heat with the shell covering the vent. Second, I prefer to have the propane off when towing - call me a bit of a safety freak!

Since we most often prefer to camp in state/national forest or national park campgrounds which generally do not have electric, it is most important to have the batteries charged when we set up. We prefer these campgrounds since they are generally more beautiful and less congested/crowded.

After quite a bit of investigating I finally found a web site where a fellow described how he solved this TV charging problem. This solution was also confirmed in a good book titled "Wiring for 12 Volts" by the guru of 12 volt systems, in my opinion, David Smead. The solution is to increase the wire size considerably from the TV battery to the TM batteries. The reason the charging rate is so low with the factory plug connection is that the charging wire sizes are woefully small causing too much of a voltage drop from the TV battery to the TM batteries. Keep in mind that the only driving force to charge the TM batteries from the TV is the voltage difference from the TV to TM batteries - generally 2 volts or much less.

Before making any charging system changes, the TV charged the batteries on the order of 3 or 4 amps or much less. I have a Link Lite battery monitor to measure amps. With the refrigerator running the batteries went into discharge when connected to the TV.

After revamping the charging system the TV charges the TM batteries at anywhere from 50 to 25 amps depending on the charge state of the TM batteries. The TM batteries are always charged well with the refrigerator and refrigerator fan running on battery. Here is what I did. Run #2 gage wires from the positive and negative post on the TV battery back to a new two pole plug on the rear of the TV. Run #2 gage wires from the TM batteries to a two pole plug(which plugs into the new TV plug) on the TM. The plug should be a very high amp plug so any voltage drop over the plug is very small. I used welding cable for the wire as it is quite cheap and very flexable. Also be sure to put a fuse(I used a 100 amp fuse) in the line from the TV battery so the TV will be safe if you should get a short anywhere in the TV wireing.

That's it and it works great. I will also be able to charge the TM batteries from the TV when set up in a campground should I need to.

My TV is a 2005 Toyota 4Runner with a factory tow package. The alternator is 100 amp and still sees a light duty cycle.

I hope this helps others solve this problem.

Take care,

Phil Friess

This issue has been brought up a few times on this forum. Most manufacturers use 10G 0r 12G wire for the hot lead for charging the trailer batteries. This is obviously problematic due to the voltage drop, that you describe, while charging batteries and running the fridge.

I have heard of people using 8G wire and having good results. 2G wire seems pretty extreme. It's expensive, hard to work with and heavy.

Glad that it works well for you. I hope that it is protected on both ends with a 40-60A fuse.

[ShrimpBurrito]

Sounds great, Phil. But with that size wire, you may want to double check that you are not charging your batteries at too high of a current. From what I have read, it seems you should not be charging a battery in excess of a C/10 rate. The C/10 rate is a charging current in amps equal to 1/10th of the battery's capacity in Ah. So with 2 large Trojan T-105s, weighing together about 130 lbs and a combined capacity of 225 Ah, they should never be charged any faster than ~23 amps. The battery that came with your TM probably has a capacity of ~80 Ah, so it's max charging rate would be 8 amps. Charging too fast for any significant length of time can generate excessive heat, cause the electrolyte to boil and the case to crack (which will cause the electrolyte to spill everywhere), and cause hydrogen off-gassing, which is obviously a major safety hazard.

Also note that your current setup is not ignition protected. That means that anytime your TM and TV are connected, your TM will draw current from your TV, even with the engine off. That could very quickly kill your TV battery and leave you stranded.

And as Wayne suggested, you should have TWO fuses in that wire -- one close to each of the TM and TV batteries.

I had the same exact concerns and thoughts as you, and here's my solution:
http://www.trailmanorowners.com/foru...ad.php?t=10587

Dave

I’m one of those that replaced both TV and TM wiring with 8ga. With the refrig. on 12v, my MorningStar batt monitor shows a slight discharge at idle. At 1200 RPM or more it shows a good charge, depending on the state of the battery. On the last four trips we made, I checked the batteries at the start and end of each run, they always had more charge when I arrived at my destination than when I started out. I can’t argue that 2ga would be better than 8ga but I think that if I were to do it again I would go with 6ga at the most. I only replaced the pos wire and use the hitch for ground. With everything hooked up, I jumped the TM & TV batteries with a length of welding cable and couldn’t see any improvement so I just stayed with only replacing the pos wire. The length of the TV and TM model would have to be considered. There is a good calculator near the bottom of this site to determine what size wire should be used.

http://www.powerstream.com/Wire_Size.htm?nowritefs

Ed

[Bill]

Philip -

Wow! What a job! You really wrapped it up and tied it with a bow!

I did the same thing in 2006 - see Post #22 in this thread.
http://www.trailmanorowners.com/foru...ead.php?t=4909
Rather than using really really heavy wire, like #2 or #4, I went to Lowes and bought a 50-foot 10-gauge extension cord (it was cheaper than 10-gauge wire), cut off the plug and socket, and threw them away. I then wired up both ends of this cord as you described, cut it at the tow vehicle bumper, and put in an ordinary boat-trailer plug and socket. As has been noted, you need a circuit breaker or fuse on both ends, so I did that, and I also put an isolator relay in the tow vehicle. The whole thing worked like a champ!

I'm sure I didn't get as much charge current as you get, but I decided that if the TM battery maintains a few amps of positive charge current with the refrig and fan running, all would be fine. And it was - I never had another problem.

I made the job harder than it had to be by running the wire inside the tow vehicle, under the carpets and in existing wire channels. I wouldn't do that again. But other than that, the job was a complete success, not too expensive, and not too difficult.

Bill

fwiw, both my 2002 Chevy 1500HD and 2008 GMC 2500HD seem to have adequate wiring.

But, I never tow for more than 5 hours in a single day, and usually between 3 and 4 hours.

I have never measured a drop in battery voltage. I have never been disappointed.

If I had a TriMetric meter or equivalent I may be able to measure otherwise, but I just have not installed one.

I also have never looked to see what size wire they use. I do know it has a 30 amp fuse.

[Philip]

Originally Posted by harveyrv

This issue has been brought up a few times on this forum. Most manufacturers use 10G 0r 12G wire for the hot lead for charging the trailer batteries. This is obviously problematic due to the voltage drop, that you describe, while charging batteries and running the fridge.

I have heard of people using 8G wire and having good results. 2G wire seems pretty extreme. It's expensive, hard to work with and heavy.

Glad that it works well for you. I hope that it is protected on both ends with a 40-60A fuse.

Carolyn & Wayne,

I forgot to say I have fused the plugs on both the TV & TM as you recommend.

Although 2G sounds like overkill, I used it to get maximum charging since I want the batteries to be full up when I get to my site. As mentioned, I most often go to sites without electric and want to get my normal ten days(at least) out of my batteries before needing a charge. I have no problem getting this out of the 420AH total battery capacity I have installed(two 210AH lifeline batteries). I also can use the high charging rate to charge the batteries with the TV when at a no electric site should I need to. The TV becomes my generator - much quieter and no additional equipment.

The 2G wire is welding cable which is very fine strands and almost as flexable as a noodle. On the internet you can get it for approx. $1.50/foot. I needed 86 feet. You also need a lug crimper to attach the end connections which I already have.

Happy camping and take care,

Phil

[Philip]

Originally Posted by ShrimpBurrito

Also note that your current setup is not ignition protected. That means that anytime your TM and TV are connected, your TM will draw current from your TV, even with the engine off. That could very quickly kill your TV battery and leave you stranded.

Dave

Hello Dave,

You are right, I know I have to remember to unplug the TV from the TM whan I stop for any time. At my charging rate I could swiftly discharge my TV battery.

Phil

[Philip]

Originally Posted by Bill

I made the job harder than it had to be by running the wire inside the tow vehicle, under the carpets and in existing wire channels. I wouldn't do that again. But other than that, the job was a complete success, not too expensive, and not too difficult.

Bill

Hello Bill,

I ran the TV wire down along the frame to the rear of the TV - generally following the brake line tubes to assure that the wire was never on a moving part. Not such a big job. Probably much easier than your path but hindsight is always 20-20.

Phil

[ShrimpBurrito]

Phil - Well with that kind of battery capacity, you will be fine. I would have chosen your route with those beasts. Where do you have them mounted? Do you have any pics by any chance?

Dave