Is 7 pin trailer connector enough to charge house battery?

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Re: Is 7 pin trailer connector enough to charge house batter

Postby dancam » Fri Jan 13, 2017 11:21 am

I had found a better calculator, but try something like this. http://wiresizecalculator.net/#calc_goto
Do 3% line loss, 5% at the most i would say. And length your wire is from starting battery to trailer battery, not straight line distance.

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Re: Is 7 pin trailer connector enough to charge house batter

Postby facethewolf » Fri Jan 13, 2017 11:57 am

To Dale M. Thank you very much for the youtube tag clarification. Now I know.

To Dancam, that's an interesting idea, to put a VSR on the 7-pin for run of the mill charging, and then a manual disconnect on the Anderson plug (or any other plug) so that I can have extra juice to power the microwave oven temporarily.
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Re: Is 7 pin trailer connector enough to charge house batter

Postby dancam » Fri Jan 13, 2017 1:19 pm

You want to run a microwave oven off the vehicle battery? I dont think this will work well. I think your far better off installing a second battery in the trailer.
Your running an inverter for this microwave right? So ill guess a low wattage 1000 watt microwave, 85% efficiant inverter.
At 12v thats 83 amps, factor in inverter inefficiency is 100 amps draw. Your car battery will try to supply this to keep the voltage up.
Punch that into a wire size calculator for 25ft and your looking at 2/0 awg wire for a 5% voltage drop meaning your only getting 11.3 volts to the trailer battery. Thats 2/0 wire, not 2awg, so like half the thickness of your wrist... What voltage does your inverter shut off at?
What i am doing but have not completed yet is i am putting a 1500 watt inverter under the passenger seat in my tow vehicle. 1awg wire running the 9ft to it. And running 120v back to the trailer so i dont have huge line losses for things that take more power.

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Re: Is 7 pin trailer connector enough to charge house batter

Postby dancam » Fri Jan 13, 2017 1:47 pm

What is the problem your currently having that makes you want to do this? Is the inverter shutting off when you try to use the microwave?

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Re: Is 7 pin trailer connector enough to charge house batter

Postby facethewolf » Fri Jan 13, 2017 2:31 pm

I'm the kind of guy who tries to set up his stuff to be as flexible as possible. I try to figure what equipment I would need for EVERY possible situation. To be totally honest, all of this is theoretical at the moment because I want to TOTALLY plan out every jot and tiddle before spending a cent. I like the IDEA of being ABLE to run a microwave or some such high power device, though I'm not totally deadset on it. I like the idea of eating a (formerly) frozen pizza while boondocking. Of course the more situations I think of require more expensive stuff which just keeps building up the pricetag. Thus I'm also trying to decide what to buy immediately, and what to get later when I can afford it.

dancam wrote:What i am doing but have not completed yet is i am putting a 1500 watt inverter under the passenger seat in my tow vehicle. 1awg wire running the 9ft to it. And running 120v back to the trailer so i dont have huge line losses for things that take more power.


While I like the brilliance of putting the inverter next to the starter battery in order to turn 12 volts into 120 volts sooner, what's the difference between that and putting the inverter right next to the house battery? ARe you talking about having 2 inverters? and somehow synchronizing the AC so that the current from each adds up to power a high wattage device?
ANyways, thank you for the discussion.
Sincerely, Sean
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Re: Is 7 pin trailer connector enough to charge house batter

Postby dancam » Fri Jan 13, 2017 2:38 pm

facethewolf wrote:I'm the kind of guy who tries to set up his stuff to be as flexible as possible. I try to figure what equipment I would need for EVERY possible situation. To be totally honest, all of this is theoretical at the moment because I want to TOTALLY plan out every jot and tiddle before spending a cent. I like the IDEA of being ABLE to run a microwave or some such high power device, though I'm not totally deadset on it. I like the idea of eating a (formerly) frozen pizza while boondocking. Of course the more situations I think of require more expensive stuff which just keeps building up the pricetag. Thus I'm also trying to decide what to buy immediately, and what to get later when I can afford it.

dancam wrote:What i am doing but have not completed yet is i am putting a 1500 watt inverter under the passenger seat in my tow vehicle. 1awg wire running the 9ft to it. And running 120v back to the trailer so i dont have huge line losses for things that take more power.


While I like the brilliance of putting the inverter next to the starter battery in order to turn 12 volts into 120 volts sooner, what's the difference between that and putting the inverter right next to the house battery? ARe you talking about having 2 inverters? and somehow synchronizing the AC so that the current from each adds up to power a high wattage device?
ANyways, thank you for the discussion.
Sincerely, Sean

I see. Inverter in camper right beside battery is better because it can be closer and use smaller wires than one in the tow vehicle.
Problem is when you want to also use tow vehicle starting battery to draw loads from. Then its no good to have in camper.
My situation i cant afford the weight and size of a decent battery and inverter in the trailer. So i will have a small 12v battery in the trailer and 1 inverter in the tow vehicle. Its also nice to have in the tv so i can charge laptops and cellphones but a tiny one that plugs into your cig lighter outlet would also do that.
I dont plan to run a microwave but we really like to have toast while camping :)

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Re: Is 7 pin trailer connector enough to charge house batter

Postby facethewolf » Fri Jan 13, 2017 3:04 pm

I see. Since your house battery is small, you want to attach the inverter to the large starter battery. That makes total sense.
Thank you very much for your input.
Sincerely, Sean
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Re: Is 7 pin trailer connector enough to charge house batter

Postby Socal Tom » Sun Jan 15, 2017 4:00 pm

dancam wrote:
facethewolf wrote:I'm the kind of guy who tries to set up his stuff to be as flexible as possible. I try to figure what equipment I would need for EVERY possible situation. To be totally honest, all of this is theoretical at the moment because I want to TOTALLY plan out every jot and tiddle before spending a cent. I like the IDEA of being ABLE to run a microwave or some such high power device, though I'm not totally deadset on it. I like the idea of eating a (formerly) frozen pizza while boondocking. Of course the more situations I think of require more expensive stuff which just keeps building up the pricetag. Thus I'm also trying to decide what to buy immediately, and what to get later when I can afford it.

dancam wrote:What i am doing but have not completed yet is i am putting a 1500 watt inverter under the passenger seat in my tow vehicle. 1awg wire running the 9ft to it. And running 120v back to the trailer so i dont have huge line losses for things that take more power.


While I like the brilliance of putting the inverter next to the starter battery in order to turn 12 volts into 120 volts sooner, what's the difference between that and putting the inverter right next to the house battery? ARe you talking about having 2 inverters? and somehow synchronizing the AC so that the current from each adds up to power a high wattage device?
ANyways, thank you for the discussion.
Sincerely, Sean

I see. Inverter in camper right beside battery is better because it can be closer and use smaller wires than one in the tow vehicle.
Problem is when you want to also use tow vehicle starting battery to draw loads from. Then its no good to have in camper.
My situation i cant afford the weight and size of a decent battery and inverter in the trailer. So i will have a small 12v battery in the trailer and 1 inverter in the tow vehicle. Its also nice to have in the tv so i can charge laptops and cellphones but a tiny one that plugs into your cig lighter outlet would also do that.
I dont plan to run a microwave but we really like to have toast while camping :)

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The main reason for having a seperate battery in the TD is so that the TV battery will still start the TV so you can go home. If you use the TV battery for recreational things with the engine off, you are taking a big risk.
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Re: Is 7 pin trailer connector enough to charge house batter

Postby facethewolf » Sun Jan 15, 2017 4:55 pm

Soooo many ways to spend money to get the most electricity into a trailer. :thinking:
Anyways. I have plenty of routes to consider.
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Re: Is 7 pin trailer connector enough to charge house batter

Postby Dale M. » Mon Jan 16, 2017 11:15 am

Just get battery big enough to do everything you want to do in trailer, install simple charge while towing concept.... Nothing complex.... Use KISS principle (Keep It simple Stupid)...

viewtopic.php?f=30&t=28620

The more complex you make it the more research you do the more you will tear your hair out....

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Re: Is 7 pin trailer connector enough to charge house batter

Postby Shadow Catcher » Mon Jan 16, 2017 10:52 pm

Most of our trailer battery charging is via solar but I am hooked up to the TV battery. I have jumper cables and Anderson 150A Power Pole connectors coming out of the trailer battery and a set of cables with the PP connector. If you want heavier cables as supplement the Power Pole connectors in tandem with the seven pin. (yes the 150A connector is over kill).
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Re: Is 7 pin trailer connector enough to charge house batter

Postby HotRod1 » Tue Jan 24, 2017 10:01 pm

The standard 7 wire has enough strength to charge your house battery when driving down the road. But, short trips do not work. You need to drive 2-4 hours. You will also need an alternator that puts out higher amps (usually), so you don't put a heavy load and blow the diodes in your alternator. Go look at the trailers at your local rv dealership, catch the repair techs when they aren't busy. Most are really good guys and will share their knowledge. The rv inverters/converters go both ways 12-120, 120-12 and have the trickle charge built in for the house battery. For toast I use a $5 Colman stainless steel fold up camp toaster. Walmart camping section. Image


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