Elementary Question on basic charging - Page 2 - Fiberglass RV


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Old 07-26-2016, 05:18 AM   #15
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Name: Dick
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Hookiing 12volts from tv to converter

I just got a new Tow Vehicle tgat has a 7 & 4 pin trailer harness wired in at the factory
My trailer was set up for 4 so I gought a 20 foot 7 wire cable with molded in female connector . After figuring out what all the wires do I was able to tie the new cable in and leave the he 4 pin system in tack. i now have reverse lights!
My question is can I attatch the left over heavy gauge Black pos 12 volt wire to my Progressive Dynamics PD4045KA converter. it would be nice to charge on the road. The converter has its own 12 volt charger that runs off of shore power.
TV has a heavy duty alternator.
Where do I make the connection and do I need a switch to disable tgat circuit when pligged in to the power pole?
thanks
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Old 07-26-2016, 07:05 AM   #16
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Many Casita owners are not happy with the ability of the tow vehicle to charge the trailer battery while towing. DC loses a lot of power running thru 20' of 12 gauge wire to reach the Casita. Some owners upgrade the charging wire to 6 gauge but lots of work. YMMV.
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Old 07-26-2016, 07:12 AM   #17
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I'm with Tom on the trailer brakes. You dont say what size Casita this is. But I pull a 13' Scamp and would NOT be without trailer brakes!

On my Tow, I used the etrailer.com kit and I ran 10ga wire from the battery to my trailer connection. My trailer plug's black wire goes to the onboard battery- not the converter...probably works either way. My battery is on the tongue of my trailer. There is also fuses in the line as well... so keep that in mind.

Quote:
Originally Posted by BonesD View Post
I just got a new Tow Vehicle tgat has a 7 & 4 pin trailer harness wired in at the factory
My trailer was set up for 4 so I gought a 20 foot 7 wire cable with molded in female connector . After figuring out what all the wires do I was able to tie the new cable in and leave the he 4 pin system in tack. i now have reverse lights!
My question is can I attatch the left over heavy gauge Black pos 12 volt wire to my Progressive Dynamics PD4045KA converter. it would be nice to charge on the road. The converter has its own 12 volt charger that runs off of shore power.
TV has a heavy duty alternator.
Where do I make the connection and do I need a switch to disable tgat circuit when pligged in to the power pole?
thanks
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Old 07-26-2016, 07:32 AM   #18
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Bones, my tow vehicle +12 wire is connected to the trailer battery with a fuse nearby.

Realize any +12 point in your trailer wiring is the same as any other. Every +12 wire is connected to every other one.

Also realize proper battery charging is dependent on accurate voltage control. 0.5 volts is a big difference. Your trailer battery is relatively far from the TV alternator so there is going to be some voltage drop through the wire. That's why the fatter the wire the better and why sometimes TV charging doesn't work well.

Leaving the TV connected while the converter is plugged into 120 VAC means the converter will be charging your trailer battery and your TV battery in parallel. Probably won't hurt anything but won't charge your trailer battery as fast either. Pretty easy to just disconnect the seven pin plug when you set up camp and connect to shore power. Nearly always I have to disconnect the TV to level the trailer anyway.


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Old 07-26-2016, 08:12 AM   #19
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Originally Posted by MCDenny View Post
Bones, my tow vehicle +12 wire is connected to the trailer battery with a fuse nearby.

Realize any +12 point in your trailer wiring is the same as any other. Every +12 wire is connected to every other one.

Also realize proper battery charging is dependent on accurate voltage control. 0.5 volts is a big difference. Your trailer battery is relatively far from the TV alternator so there is going to be some voltage drop through the wire. That's why the fatter the wire the better and why sometimes TV charging doesn't work well.

Leaving the TV connected while the converter is plugged into 120 VAC means the converter will be charging your trailer battery and your TV battery in parallel. Probably won't hurt anything but won't charge your trailer battery as fast either. Pretty easy to just disconnect the seven pin plug when you set up camp and connect to shore power. Nearly always I have to disconnect the TV to level the trailer anyway.


Denny Wolfe
Wanderingourway.wordpress.com
If your tow vehicle has an isolation relay , leaving your trailer plugged into your TV has little affect. The factory charge wire in my truck is fused at 40 amps but because the AWG of the wire is so small , it can not deliver full amps at full voltage . I don't count on my TV doing much in the way of charging my trailer battery .
If I can keeps my trailer battery from depleting any further , I am satisfied . Somethings work better on paper than in actual use , and I believe this is a prime example !!
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Old 07-26-2016, 08:56 AM   #20
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Thanks for all the input. Its a !3 footer but had been gutted and has minimal accommodations' and very lightly built. Most of my stuff will be stored in the back of the Tundra. I don't have brakes, but do have a antiwar bar. Not the same but something anyway.
I like the idea of going straight to the tongue mounted battery as that would cut out a lot of wire going clear to the back to the converter. this should cut down on resistance and be more efficient. Sounds like it would just be best to run a new 10 gauge pair of wires straight to the battery like was recommended. Put in a good disconnect and I should be good to go.
Thank you all.
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Old 07-26-2016, 08:59 AM   #21
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... but do have a antiwar bar. ..

Yes I agree.. make love, not war
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Old 07-26-2016, 09:07 AM   #22
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The voltage drop of the charge line is always the difference between the two batteries and is independent of the wire gauge. What the wire size does determine is the charging current and thus in part how long the trailer battery will take to charge. No matter what size wire is present, sooner or later both batteries will reach the same voltage. Raz
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Old 07-26-2016, 09:42 AM   #23
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That would have been my guess. It may mot be in a full blown charge mode to the loss in wire capacity but anything is better than nothing . With shore power, and a generator this gives me a third option. Just about anything I can do to insure a succesful outing is a good investment.
Thank you
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Old 07-27-2016, 06:47 AM   #24
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Originally Posted by Tom Trostel View Post
Many Casita owners are not happy with the ability of the tow vehicle to charge the trailer battery while towing. DC loses a lot of power running thru 20' of 12 gauge wire to reach the Casita. Some owners upgrade the charging wire to 6 gauge but lots of work. YMMV.
Not to go off topic, but when you say this do you mean they upgrade the wire IN the TV or from the connector to the trailer's battery?

Thanks,
Dan

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Old 07-27-2016, 07:53 AM   #25
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Dan, I'm not a Casita owner but have read both Casita forums daily for 12 years. Some owners find that their tv charges the trailer battery fine. So many factors are involved; discharge state of trailer battery, output of the tv alternator, how long you drive, etc. Those that are not happy run larger gauge wire from under the hood thru or under the tv, with a cut-off, to get max charge to the trailer.
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Old 07-27-2016, 11:22 AM   #26
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Just to add to what Tom said, my factory wired Frontier will charge my trailer battery in about 3-4 hours. The charge line appears to be 14 ga but it might be 12 ga. This works for two reasons. My truck is the "work truck" model with minimal electrical demand and we run a small group 24 battery with just led lights, and the water pump for dishes and hand washing ( no shower).

If a battery is not charging fully, the problem is not due to voltage drop. Left long enough the battery will charge fully but since you don't want to spend you're afternoon riding around the campground a bigger charge line may help as it will increase the current and decrease the charging time. The next limiting factor is the alternator capacity and vehicle demand. For example I've found it takes longer to charge my battery if I drive with my lights on.

There are some situations, where folks have a large battery with high trailer demand and the charging system is just not up to the task. They either cut back demand, install a larger alternator, or in some cases add roof top solar Raz
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Old 07-27-2016, 12:31 PM   #27
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Originally Posted by Raz View Post
..

If a battery is not charging fully, the problem is not due to voltage drop. Left long enough the battery will charge fully ...
Q: Say I have a 100 AH lead acid battery that starts fully charged reading 13.6 volts, that I have discharged 25% and then has a voltage of 12.4 VDC. Say also that I have a charging system where the voltage at the battery is 10 volts (due to high resistance in the wiring or something else). Typical, how long will it take for the battery to be fully charged and back to 13.6 volts? Relating to your statement above, how long is long enough?
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Old 07-27-2016, 01:34 PM   #28
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Quote:
Originally Posted by gordon2 View Post
Q: Say I have a 100 AH lead acid battery that starts fully charged reading 13.6 volts, that I have discharged 25% and then has a voltage of 12.4 VDC. Say also that I have a charging system where the voltage at the battery is 10 volts (due to high resistance in the wiring or something else). Typical, how long will it take for the battery to be fully charged and back to 13.6 volts? Relating to your statement above, how long is long enough?
10 volts?The tow battery (alternator) must be greater that the trailer battery for charging to occur.

Suppose your tow is at 14 volts and your trailer battery is at 12 volts. Then the charging current is (14v - 12 v)/ the charge line resistance. If R charge line is 0.1 ohms you have an instaneous current of 20 amps but only if the tow system has 20 amps to spare. Typically with any source,, as you draw more current loading, a reduction in voltage, occurs. Example. Lights dim when a motor starts. Also, nothing is static. As the battery charges its voltage goes up. This will reduce the charging current. Lots of variables. How long will it take to charge your battery? Don't know. But by knowing your use you can make an educated guess.
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