Finally finished my charging cable mod from TV alt/battery direct to camper batterys for dry camping...I did a small charge today and checked voltages only. My clamp on amp meter was not working... I will post back with amps and how long it takes to recharge from 12 volts to fully charged...These are the anderson like connectors I got cheap on amazon. total about $40 bucks. I had to cut the ends and solder on a 3/8" ring to connect to battery. The other side was fine. I connected the other to a 50 amp resettable breaker.. These are 6 gauge.Also note my truck has a 105 amp alt. I want to limit the amps out why I used 50 amp breakers. Truck runs alone at about 20 amps. So it should not do more then 70 when charging.I may change the breakers to 40 or 30 amperes...New battery studs/side mount with 3/8" extension. 50 amp breaker on pos side with bracket. Got these breakers from e trailer...50 amp breaker with bracket.Keep it rolled up in a void near firewall..Camper side. 8ft rolls up nice and stores in left side box.. Note 50 amp breaker on this end too on pos side right batt.... Dont need no short or fires...Connected to TV.....This is the voltage I am getting at my home made meter. I tied into 12v wires that are in the wall for the tank/battery monitor. so its not right from the convertor.Notice 14.32 volts. I gave a charge when batterys were down to 12.4.So the truck puts out over 14 volts.And this is at the batterys.. 14.47 volts from my alternator... Cant get any better then this.. IMO I should be able to recharge my batterys when boondocking in a few hours...Any one what to share what I can do better or criticism let me know please...Hope this helps others that may want to try this mod...Again I will get amp readings soon...

You can probably estimate the amperage going through the #6 wire by measuring the miliamps voltage drop across the 6' length of the #6 wire. Put one lead on the battery terminal for the truck, and the other on the battery lead for the trailer. If you get a 0.001 volt drop and the ohms are 0.03, you can use math to estimate the amperage flow through that wire.Chances are that amperage and milivolt drop across the wire will be about the same. Most clamp on amp meters are only rated at AC amperage, because it influxes 60 times a second, and the meters can pick this up. DC clamp on meters are much more rare, and the Amprobe one that I bought cost $375 a few years back. Now I hear that Sears sells a clamp on DC meter that only costs about $85.It looks like you used the right things to get this project done. It should quickly fill your battery. However know that while the engine is at idle, there is not a lot of oil flow (volume) to the upper end of the valve train. So while you might not think it will do any damage to idle the engine for a hour, it can. Ford says not to idle their diesel trucks, even while hitching up the truck to the trailer. The gas trucks can handle more idling, but still it is not 'good' for them. That said, you can plug in your truck to the trailer for say 10 minutes, and some of the truck's battery power will go into the trailer. Then a short run of the truck will provide max amperage from the alternator. 10 minutes at 130 amps will provide 2 amp hours per minute, or upwards of 20 amp hours in 10 minutes. Your RV will consume 35 amp hours per day to just run the propane detector and CO detector, and refrigerator. Add lights to this, and it will be around 50 AH daily. You might also consider a solar panel. SunElec.comYou can get a 100 watt solar panel that will also produce about 30 amp hours per day in full sun. Two advantages is that the solar panels shade the roof, and help it not get so warm inside.Have fun camping!Fred.

Good luck... I wouldn't do it as this breaks rule #1 - "Never mess with the truck systems. This is the only way to get home..."Depending on your DC current demand by how large your battery bank is you could easily demand an additional 50-100 DC AMPS from your truck alternator system during the charge cycle and this may be over what the truck alternator can produce. That could result in "game over" for the truck alternator.. My 255AH battery bank will demand around 53AMPS DC current when first hit with 14.4VDC. This starts tapering back and in 30 minutes or so it will be down to around 8AMPS DC CURRENT.Also idling your truck motor for three to four hours is probably not all that great on your truck motor.I charge my 50% charge state trailer batteries with the on-board converter/charger being run by my 2kW Honda Generator setup using a RV30A-15A long adapter. This will get my batteries back up to their 90% charge state in around three hours of generator run time. Then I am good for the next day/night run off of the batteries.Battery science says if your want to fully charge your batteries using 14.4VDC it will take right at 12 hours if you are able to produce 17-20AMPs of DC Current per battery in your bank...Lets us know how you make out... Not saying it will not work out for you just something I would not put my truck alternator on the line. This alternator system is only designed to charge a single 12VDC START battery.just sayingRoy Ken

So you're planning on leaving the truck run for hours and hours during the day? Doesn't sound so economical to me...

Golden_HVAC wrote:It looks like you used the right things to get this project done. It should quickly fill your battery. However know that while the engine is at idle, there is not a lot of oil flow (volume) to the upper end of the valve train. So while you might not think it will do any damage to idle the engine for a hour, it can. Ford says not to idle their diesel trucks, even while hitching up the truck to the trailer. The gas trucks can handle more idling, but still it is not 'good' for them. That said, you can plug in your truck to the trailer for say 10 minutes, and some of the truck's battery power will go into the trailer. Then a short run of the truck will provide max amperage from the alternator. 10 minutes at 130 amps will provide 2 amp hours per minute, or upwards of 20 amp hours in 10 minutes. Your RV will consume 35 amp hours per day to just run the propane detector and CO detector, and refrigerator. Add lights to this, and it will be around 50 AH daily. Fred.I have two duracell 75 ah batterys... No way am I using 35 ah a day IMO... Like I said I have 50 amp breakers that will limit charge from the alt... Again I have 105 amp alt.My lights are all led with a draw of .7 amps per light.Cars and trucks idle all the time in traffic so I dont know what damage is possible I can do to my motor...This is a gasser...

Charging with TV alternator... Mod with pics...

scrubjaysnest
Explorer
Apr 21, 2015
We have used a similar system for over a decade although we only charge the batts when moving the camper between CG's. I used solid state isolator, manual reset breakers under hood and auto reset at the camper. Batteries are fully charged in 3 to 4 hours at highway speeds. 15.5 volts into the isolator 14.8 volts at the batteries. The last was measured with the truck in tow/haul, headlights on and refrig on dc. Truck was at idle. Truck batt charge line was up graded to 8 awg with 8 awg in parallel through a 2nd connector. When at the camp site we use solar to charge the batts. Some CG's with a no generator rule will also not let you idle the truck as a FWIW.

4/21/2015 update:
Had to move the camper today so did a recheck, batts were at 90% or 12.77volts, cranked the truck put in tow/haul and lights on at idle. Again 15.5 volts into the isolator with 14.8 volts out and 50 amps to the cranking battery. Once this tapered off isolator switched output to trailer batts and had 14 amps to the trailer batteries. Refrig was off and with the trailer closed up there is no way to measure the voltage at the batteries. Another minor mod in the works maybe.

Remote breaker box at the camper

Under hood breaker box and battery isolator
gijoecam
Explorer
Mar 31, 2015
My only concern with your setup is the length of the wires inder the hood... There's a lot of exposed cord length draped across 'stuff' and the insulation on the wires can chafe through over time. Shorted wires can do a LOT of damage at far less than 50A without tripping a breaker. My dad's Jeep almost caught fire in our garage thanks to the winch cables doing just that.

I'd look at using an Andersen connector securely fastened in a fixed location. out of the way with a dust cover on it to keep the grime out. I use them as a main battery disconnect on our camper, and have been quite happy with them. They also provide a quick means of powering other 'stuff' from the camper if needed. I've considered using a similar setup to yours in a pinch if necessary, but I personally wouldn't make it my primary means of charging. It's just plain inefficient, and if I needed to do it more than a couple times a year, I'd be looking at a genset.
lawrosa
Explorer
Mar 30, 2015
bandit86 wrote:
I thought of this for when im driving, but for boondocking I want a generator. Most generators, say a 2000 watt Honda only put out 8-10 amps dc,

That is an unregulated connection. Why would you consider using it? You would just cook the batterys.

so get a large and I mean large 50 amp battery charger and run it off the generator. I have seen the 200/40/20/2 die hard battery chargers designed to start a dead car bit never had a chance to see at what voltage they charge at. one of those would be almost perfect if one could limit charging voltage to 14.5

Well you can buy your 1000 buck gen and the car charger and test it and let us know .. I did my set up for less then 60 bucks.

Always wondered why generators aren't made a hogh current 14.5 volt output, but then one can build one of these;
http://www.energymatters.com.au/honda-12v-25hp-55amp-battery-charger-with-digital-ampmeter-p-273.html

Why build one? And how much is that? All it is , is an alternator with a honda motor driving it..

I already have one. Its a 4.3 liter vortec V6 with a 105 amp alt...

EDited, if you have a generator all you need is a small welding unit that does dc, or a mig welder. To the whip need to add a large capacitor to clean out the rectified ac into a good dc, then a solar controller to limit output to something a battery can take.

Dont want to weld, most rv converters can do very high currents, about 50 amps dc, its basically a 12v power supply. 150 bucks. Wire into generator and hook all dc outputs to the battery. Probably easiest fix, no need to reinvent the wheel. Maybe even tap into your rv converter you already have, and using a breaker give full dc power to the bbatteries

Sounds complicated. Ill stick with my set up. Thanks for the feedback, but it dont help much IMO...
bandit86
Explorer
Mar 30, 2015
I thought of this for when im driving, but for boondocking I want a generator. Most generators, say a 2000 watt Honda only put out 8-10 amps dc, so get a large and I mean large 50 amp battery charger and run it off the generator. I have seen the 200/40/20/2 die hard battery chargers designed to start a dead car bit never had a chance to see at what voltage they charge at. one of those would be almost perfect if one could limit charging voltage to 14.5

Always wondered why generators aren't made a hogh current 14.5 volt output, but then one can build one of these;
http://www.energymatters.com.au/honda-12v-25hp-55amp-battery-charger-with-digital-ampmeter-p-273.html

EDited, if you have a generator all you need is a small welding unit that does dc, or a mig welder. To the whip need to add a large capacitor to clean out the rectified ac into a good dc, then a solar controller to limit output to something a battery can take.

Dont want to weld, most rv converters can do very high currents, about 50 amps dc, its basically a 12v power supply. 150 bucks. Wire into generator and hook all dc outputs to the battery. Probably easiest fix, no need to reinvent the wheel. Maybe even tap into your rv converter you already have, and using a breaker give full dc power to the bbatteries
lawrosa
Explorer
Mar 29, 2015
pianotuna wrote:
Hi,

Thanks for the data. It is quite amazing how fast the amps going into the battery bank drop off.

Fully charged for me is when there is less than one amp going into the bank.

You may want to improve the wiring on the house bank to be like the image below.

Yes I do have the house bank wired like that with all 6 gauge...
pianotuna
Nomad III
Mar 29, 2015
Hi,

Thanks for the data. It is quite amazing how fast the amps going into the battery bank drop off.

Fully charged for me is when there is less than one amp going into the bank.

You may want to improve the wiring on the house bank to be like the image below.
lawrosa
Explorer
Mar 29, 2015
OK here is chart kind of...

To power the truck and a fully charged truck battery required about 2 amps from the alternator.

I drained camper batterys down to 12.3 volts

5pm start

amps 57
volts at camper batterys 13.99
alt temp 148f

5:20

amps 22.4
volts at camper batterys 13.93
alt temp 188f

5:40

amps 19.5
volts at camper batterys 14.05
alt temp 187f

6:00

amps 13.4
volts at camper batterys 14.02
alt temp 176f

6:20

amps 11.3
volts at camper batterys 14.09
alt temp 171f

6:40

amps 8
volts at camper batterys 14.20
alt temp 159f

7:00

amps 5.8
volts at camper batterys 14.22
alt temp 160f

7:20

amps 4.9
volts at camper batterys 14.33
alt temp 155f

7:40

amps 4
volts at camper batterys 14.34
alt temp 154f

Note: I could have probably stopped here as batterys were most likely charged.

8:00

amps 3.2
volts at camper batterys 14.34
alt temp 154f

9:00

amps 2.7
volts at camper batterys 14.39
alt temp 154f

9:10

After running the furnace for 10 minutes to take off the surface charge, I took a final volt reading.

12.85 volts at battery.

In summary without using amp meter or anything else when camping I will charge until volts get up to the 14.3 mark and stop there more or less... This will be with my volt meter I have in the camper..

Although I always carry my multimeter with me and the hydrometer...
lawrosa
Explorer
Mar 29, 2015
pianotuna wrote:
Hi,

Thanks for posting the information gathered from your test.

It is normal for a 50 amp breaker to NOT open immediately when the rating is exceeded. My wiring is rated for 60 amps, so when I replaced the fuses with breakers I used 50 amp ones.

Did you happen to measure the voltage at the alternator and voltage at the house batteries just after beginning the testing?

I'd love to see the every twenty minutes data in a table.

I will put something together later or tomorrow.

I think volts at alt and battery would be similar to what I was reading at the campers batterys as 6 gauge wire would have no loss @ 12 ft of cable IMO..
pianotuna
Nomad III
Mar 29, 2015
Hi,

Thanks for posting the information gathered from your test.

It is normal for a 50 amp breaker to NOT open immediately when the rating is exceeded. My wiring is rated for 60 amps, so when I replaced the fuses with breakers I used 50 amp ones.

Did you happen to measure the voltage at the alternator and voltage at the house batteries just after beginning the testing?

I'd love to see the every twenty minutes data in a table.
John___Angela
Explorer
Mar 29, 2015
lawrosa wrote:
Also a note. These are two new battery's.. I found it very hard to kill them throughout the day. I had every light on in the camper, fan for oven vent on, tv on through invertor, and heater on.

I also have an 7 pin plug with a fuse that connects the two pins togther so I can sit with the campers running lights on.

Basically I was pulling about 7 amps. It would of taken 10 hours to kill the batterys...

I guess what I am saying is I dont have enough hi draw items to kill the batterys quickly...

I hope this helps the people out there that may want to try this themselves.. I urge you all to make sure you fuse both ends of the cables. If not bad bad things can happen...

Let me know if there are any questions I can answer with anything I missed...

Excellent report. Thank you. Like I say, we have been doing it for years and it works excleently for us. Ours is on a V10 ford based class C motorhome but execution is almost the same. We had to use longer cables so the gauge is thicker but same idea. I have no place to pack a generator or the fuel for it. As far as noise from the v10, I guarantee our v10 is quieter than any generator of any make. I can hear a 2800 onan start from the other end of a campground. I can't hear my v10 in the next camp site.