Charging A Trailer Battery With A Small Gauge Wire - Electrical - DIY Chatroom Home Improvement Forum


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 04-05-2014, 10:56 AM   #1
Newbie
 
Join Date: Sep 2013
Posts: 13
Rewards Points: 10
Default

Charging a trailer battery with a small gauge wire


A common problem is that the charge wire from the tow vehicle is too small to adequately charge the battery in a travel trailer under tow. The problem is that due to the voltage drop in the wire itself, the voltage getting to the trailer battery is below a critical voltage threshold.

In order to push the charge rate up to, say, 10 amps, it would seem that one could use a DC-DC boost converter to boost the voltage to about 15 or 16 volts, then use an inexpensive solar charge controller to regulate the charge.

Any EEs or EE wannabees that can comment on feasibility.

Advertisement

Redbelly is offline   Reply With Quote
Old 04-05-2014, 10:58 AM   #2
Newbie
 
Join Date: Sep 2013
Posts: 13
Rewards Points: 10
Default

Charging a trailer battery with a small gauge wire


This is an example of a charge controller: http://www.ebay.com/itm/Solar-Panel-...item2c72472620

And this is an example of a small boost converter: http://www.ebay.com/itm/290934849599

Advertisement

Redbelly is offline   Reply With Quote
Old 04-05-2014, 12:22 PM   #3
Member
 
Join Date: Nov 2013
Location: Winnipeg, Canada
Posts: 1,122
Rewards Points: 1,360
Default

Charging a trailer battery with a small gauge wire


Quote:
Originally Posted by Redbelly View Post
A common problem is that the charge wire from the tow vehicle is too small to adequately charge the battery in a travel trailer under tow. The problem is that due to the voltage drop in the wire itself, the voltage getting to the trailer battery is below a critical voltage threshold.
Not really a voltage problem, but one more of current. You need thick cable and expensive connectors. Get yourself some welding cable/connectors and the problem is solved. Welder's trucks run 100's of feet of that stuff and don't suffer much in the way of current limitations.

If you don't want to deal with large sized cables however, then you're on the right track with upping the voltage. A larger voltage means less amps required for a given job, hence smaller cables required. However I would probably go with something a bit more standard than a 60 volt dc-dc converter (You would need a much bigger one than in your sample BTW). I would simply use an off-the-shelf 120VAC power inverter. Run 120 volts to the trailer, and then plug in a standard battery charger.
Bob Sanders is offline   Reply With Quote
Old 04-05-2014, 12:24 PM   #4
Master General ReEngineer
 
Bondo's Avatar
 
Join Date: Dec 2007
Location: Chaumont River, Ny.
Posts: 3,822
Rewards Points: 2,278
Default

Charging a trailer battery with a small gauge wire


Ayuh,... Seems it'd be alot easier to just run a 8ga. or 6ga. wire from the front of the tow unit, to the hitch, 'n plug into a like circuit on the wagon,...

Matter of fact, My pickup has twin 0ga. runnin' to the hitch, for that, 'n boostin' other vehicles from the back,...
Run my powered dolly leg off it too,...
Bondo is offline   Reply With Quote
Old 04-05-2014, 12:37 PM   #5
Member
 
Join Date: Nov 2013
Location: Winnipeg, Canada
Posts: 1,122
Rewards Points: 1,360
Default

Charging a trailer battery with a small gauge wire


Quote:
Originally Posted by Bondo View Post
Ayuh,... Seems it'd be alot easier to just run a 8ga. or 6ga. wire from the front of the tow unit, to the hitch, 'n plug into a like circuit on the wagon,...
Yup. Agree completely. A lot easier just running thicker cable.
Bob Sanders is offline   Reply With Quote
Old 04-05-2014, 12:53 PM   #6
Member
 
Oso954's Avatar
 
Join Date: Jun 2012
Location: Northern Calif.
Posts: 1,797
Rewards Points: 1,474
Default

Charging a trailer battery with a small gauge wire


Solar charge controllers are not made to regulate alternator/generator output, only PV panels.
If it is a combined solar/wind, it doesn't regulate the alternator output, it just dumps the excess power to a dump load.

I would expect the solar controller to burn out.
Oso954 is offline   Reply With Quote
Old 04-05-2014, 01:19 PM   #7
Newbie
 
Join Date: Sep 2013
Posts: 13
Rewards Points: 10
Default

Charging a trailer battery with a small gauge wire


Of course, one can install heavy cables. What I was looking for was a discussion of how to charge off a smaller wire. This is a commercial version of what I was hoping to build with off shelf components.

http://www.allbatterysalesandservice...fm/4,7750.html
Redbelly is offline   Reply With Quote
Old 04-05-2014, 03:00 PM   #8
Member
 
Oso954's Avatar
 
Join Date: Jun 2012
Location: Northern Calif.
Posts: 1,797
Rewards Points: 1,474
Default

Charging a trailer battery with a small gauge wire


Quote:
What I was looking for was a discussion of how to charge off a smaller wire.
That is too open ended. What size wires?

Your problem is probably your tow vehicle wiring, particularly if this is not a factory installed trailer connection.

What size wire is connecting the charge pin (aux power pin) to the tow vehicle battery ? If they picked up a source other than the battery, what is it and what size wire is feeding that source ? Also, what is the ground wire size and where did they connect it ?

On the trailer what are those two wire sizes and what is the amphour capacity of the battery(s) you are attempting to charge ?
Oso954 is offline   Reply With Quote
Old 04-05-2014, 03:44 PM   #9
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,457
Rewards Points: 4,560
Default

Charging a trailer battery with a small gauge wire


Quote:
Originally Posted by Redbelly View Post
Of course, one can install heavy cables. What I was looking for was a discussion of how to charge off a smaller wire. This is a commercial version of what I was hoping to build with off shelf components.

http://www.allbatterysalesandservice...fm/4,7750.html
You would still need at least a 10 gauge wire.
__________________
When posting in certain forums, knowing your location will help others give better feedback/advice/solutions to your questions.
beenthere is offline   Reply With Quote
Old 04-05-2014, 03:48 PM   #10
Semi-Pro Electro-Geek
 
Join Date: Jul 2009
Location: Arizona, USA
Posts: 2,570
Rewards Points: 2,036
Default

Charging a trailer battery with a small gauge wire


Quote:
Originally Posted by Redbelly View Post
Of course, one can install heavy cables. What I was looking for was a discussion of how to charge off a smaller wire. This is a commercial version of what I was hoping to build with off shelf components.

http://www.allbatterysalesandservice...fm/4,7750.html
That device is basically what you're proposing, but in one unit. It's probably a pure boost converter, operating in current mode with a setpoint dependent on the output voltage. It pushes a constant current to the charging battery until it reaches float voltage. You could do it the way you're describing, but it can probably be done without using the PV charge controller. Just use a DC-DC converter that will accept 8-14V in, and provide carefully regulated 13.8V output with a peak current limit.
__________________
I am a lawyer, but not your lawyer. And who cares anyways? We're here to talk construction. This is DIY advice, not legal advice.
mpoulton is offline   Reply With Quote
Old 04-05-2014, 04:32 PM   #11
Newbie
 
Join Date: Sep 2013
Posts: 13
Rewards Points: 10
Default

Charging a trailer battery with a small gauge wire


Quote:
Originally Posted by Oso954 View Post
That is too open ended. What size wires?

Your problem is probably your tow vehicle wiring, particularly if this is not a factory installed trailer connection.

What size wire is connecting the charge pin (aux power pin) to the tow vehicle battery ? If they picked up a source other than the battery, what is it and what size wire is feeding that source ? Also, what is the ground wire size and where did they connect it ?

On the trailer what are those two wire sizes and what is the amphour capacity of the battery(s) you are attempting to charge ?
The question is hypothetical, though this is a common problem, particularly with DIY installed charging wires. It is exacerbated when trying to run the trailer's refrigerator on 12 volts while under tow. A concrete example would be a Dodge truck that comes wired with 14 gauge charging wire as part of the tow package (Ford and GM use 10 gauge). If the battery is in the back of the trailer you have 17 feet of wire under the truck and another 25 feet (or more) under the trailer. So a minimum of 42 feet, assuming the chassis ground has near zero resistance. That would be 0.11 ohms for the wire. At ten amps, that is 1.1 volts drop in the wire. That is enough to reduce the charge rate significantly.
Redbelly is offline   Reply With Quote
Old 04-05-2014, 04:33 PM   #12
Newbie
 
Join Date: Sep 2013
Posts: 13
Rewards Points: 10
Default

Charging a trailer battery with a small gauge wire


Quote:
Originally Posted by beenthere View Post
You would still need at least a 10 gauge wire.
A 14 gauge wire is good for 15 amps, with respect to current carrying capacity. Assuming you are stuck with this wire, the question is how to compensate.
Redbelly is offline   Reply With Quote
Old 04-05-2014, 04:41 PM   #13
Newbie
 
Join Date: Sep 2013
Posts: 13
Rewards Points: 10
Default

Charging a trailer battery with a small gauge wire


Quote:
Originally Posted by mpoulton View Post
That device is basically what you're proposing, but in one unit. It's probably a pure boost converter, operating in current mode with a setpoint dependent on the output voltage. It pushes a constant current to the charging battery until it reaches float voltage. You could do it the way you're describing, but it can probably be done without using the PV charge controller. Just use a DC-DC converter that will accept 8-14V in, and provide carefully regulated 13.8V output with a peak current limit.
But wouldn't you want a higher voltage during the boost phase, tapering down to a lower voltage for the float phase? I believe that the multistage output is a common feature of the PV controllers. If the voltage was constant, but too low it would charge slowly (the basic problem) and if it was set too high, it would boil the battery.
See chart: http://www.westmarine.com/WestAdviso...attery-Charger
Redbelly is offline   Reply With Quote
Old 04-05-2014, 05:00 PM   #14
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,457
Rewards Points: 4,560
Default

Charging a trailer battery with a small gauge wire


Quote:
Originally Posted by Redbelly View Post
A 14 gauge wire is good for 15 amps, with respect to current carrying capacity. Assuming you are stuck with this wire, the question is how to compensate.
Look at the install instruction for that booster. Tells you you need 10 gauge.
__________________
When posting in certain forums, knowing your location will help others give better feedback/advice/solutions to your questions.
beenthere is offline   Reply With Quote
Old 04-05-2014, 05:17 PM   #15
Member
 
Oso954's Avatar
 
Join Date: Jun 2012
Location: Northern Calif.
Posts: 1,797
Rewards Points: 1,474
Default

Charging a trailer battery with a small gauge wire


Quote:
a Dodge truck that comes wired with 14 gauge
Simply run a 10 gauge from battery+ to the aux power pin of the trailer connector.

Advertisement

Oso954 is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Charging battery while using it vs charging till empty will this affect battery life? jratftcc Electrical 2 04-01-2013 11:41 PM
Wire gauge for 80 amp continues load diyguy41 Electrical 20 11-28-2012 01:30 PM
Can 14 gauge wire be used on 20 amp circuit? diyer111 Electrical 9 08-13-2012 11:14 AM
Wire Gauge for 30A RV Outlet (long span) jayne1986 Electrical 24 02-20-2011 09:18 PM
What wire gauge for plumbing ground? bob22 Electrical 4 04-04-2010 08:01 PM




Top of Page | View New Posts