Wiring - Charging

[cico7]

I want input.....I want to put a battery on my popup camper and set up a charging point
in the back of the XK. This would allow me to plug the trailer into the XK and charge the
battery if I am not close to electricity.

The camper has an inverter now. I am going to add 2 batteries to it so I am looking for a
way to charge it.

I was just reading Adondo's reply on the Roof Rack lights so I hoped he or someone will
have input for a plug.

[hoaxci5]

I thought with 7 pin RV trailer connectors there was an aux wire that allowed the batteries in the RV to charge off the alt when the vehicle was running.

[Sal-XK]

I thought with 7 pin RV trailer connectors there was an aux wire that allowed the batteries in the RV to charge off the alt when the vehicle was running.

Really that would be cool. Ahww man now you got me thinking. But if there is no isolator installed then technically the RV battery could be allowed to drain the starter battery

[hoaxci5]

https://theultimatejeep.com/images/imported/2011/05/wire7_pintrailerplug14800x800-1.jpg

[hoaxci5]

I can't find a clear answer, but I believe that you are correct in that the 12+ is always hot meaning you could definitely kill your starting battery.

[Sal-XK]

I guess you could install an isolator after that plug to keep you starter battery from draining.

[cico7]

I guess you could install an isolator after that plug to keep you starter battery from draining.
I agree with that 100%. My first thought was a plug to charge the battery,
seperate from the tow wiring harness.

I would think I would need heavier wiring than a trailer plug which is about 14 -16 guage. The wire from your alternator to the battery is about 6g.

[IamJEEP]

I agree with that 100%. My first thought was a plug to charge the battery, seperate from the tow wiring harness.
I would think I would need heavier wiring than a trailer plug which is about 14 -16 guage. The wire from your alternator
to the battery is about 6g.

Yes but that's a short run from the alt to the bat. You would need to up-size the gauge to make up for the length if you want the same amount of amps to get back there. I'm thinking at least 4 gauge from the front to the back.

[hoaxci5]

I think with deep cycle batteries you want to charge them slowly, in which case there wouldn't be any reason to upgrade the wiring. Maybe just add a relay so that the 12+ on the 7 pin only has power when the ignition is on. (Can you do that with wires that connect two batteries?)

[Sal-XK]

I agree with that 100%. My first thought was a plug to charge the battery, seperate from the tow wiring harness.
I would think I would need heavier wiring than a trailer plug which is about 14 -16 guage. The wire from your alternator
to the battery is about 6g.

Not necessarily true you're not starting a motor or running a large electric motor like on a winch you're just charging a battery. So the smaller wire will do the job in fact maybe better then a larger one because it will charge slower instead of a hot charge. I would have to measure it but it a deep charge is considered 2amps or a trickle charge if you will but I'm guessing maybe get more amps out of it then that. Just some food for thought. Oh I can't measure the amps for you guys a blew the amp fuse in my meter :( and don't have any spares left.

[IamJEEP]

You are right but that 16 or 14 gauge wire will not charge that battery. You still need bigger wiring and an isolator. You would have to let the battery charge for a long time to get it fully charged. If you are using lights, fan, or whatever in that trailer that draws more than you are charging, the trickle charge will not be enough.

[hoaxci5]

Pretty good quick read on whats being discussed..
http://www.damouth.org/RVStuff/TrCharge.shtml

[Sal-XK]

a 14 gauge wire is rated at 15amps safely. I would think that would be enough to charge a battery?

[cico7]

Well, I never considered the 7 wire harness for providing power,
but after i read the various comments, I found a website e-trailer (http://www.etrailer.com/faq-wiring.aspx)
for a 7 wire diagram. They are using a 12 guage wire for the interior
lights or battery charger.

But like Sal suggested, need an isolator.

[cico7]

Oh I can't measure the amps for you guys a blew the amp fuse
in my meter :( and don't have any spares left.
Radio Shack or tinfoil.,

[IamJEEP]

Pretty good quick read on whats being discussed..
http://www.damouth.org/RVStuff/TrCharge.shtml

Bigger wires. =P

[IamJEEP]

a 14 gauge wire is rated at 15amps safely. I would think that would be enough to charge a battery?

Yes but how long are you willing to wait for that battery to charge?

[Sal-XK]

Radio Shack or tinfoil.,

I know I'm lazy


Bigger wires. =P

Yes bigger wires increases current and flow or amps and volts.


Yes but how long are you willing to wait for that battery to charge?

The longer it takes the better the charge and the happier the battery. I'm assuming that a deep cycle battery would be going on the trailer since it would be used to operate stuff and not start stuff. So I would be willing to wait you don't want to hot charge a deep cycle.

[IamJEEP]

I researched a bit online and according to a couple of RV forums, 12g wire at 10amps of charge is all you need for a trailer battery. So I would say you can use the trailer 7 wire to charge you trailer battery with no issues.

Sal, I agree that a deep cycle would be the ideal battery here. Trickle charge is the way to go, but I think you would need a battery monitor to stop charging when full.

[Sal-XK]

I always go back and read this when I talk about this kind of stuff or I'm planning any work with electricity. It always jars the cobwebs loose.
Ohm's Law Defined

Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance. One ohm is the resistance value through which one volt will maintain a current of one ampere.
( I ) Current is what flows on a wire or conductor. Current is measured in (A) amperes or amps.

( E ) Voltage is the difference in electrical potential between two points in a circuit. It's the push or pressure behind current flow through a circuit, and is measured in (V) volts.

( R ) Resistance determines how much current will flow through a component. Resistors are used to control voltage and current levels. The higher the resistance, the smaller the amount of current is allowed to flow. Resistance is measured in ohms.

( P ) Power is the amount of current times the voltage level at a given point measured in wattage or watts.

V = I x R
I = V / R
R = V / I

[Sal-XK]

I researched a bit online and according to a couple of RV forums, 12g wire at 10amps of charge is all you need for a trailer battery. So I would say you can use the trailer 7 wire to charge you trailer battery with no issues.

Sal, I agree that a deep cycle would be the ideal battery here. Trickle charge is the way to go, but I think you would need a battery monitor to stop charging when full.

I think a proper battery charger would be the way to go to protect the trailer battery. That should work both ways protecting the starting battery as well and you can skip the isolator then as well.

[cico7]

Deep cycle batteries need a slower charge, but I don't want to take all day to charge the battery.
If your'e driving a ways you can get a full charge. The wire size should not regulate the charge.
I need an isolator and more research.

[Sal-XK]

Well, when I replace my fuse I can measure the amps and volts coming out of that wire and we can do the math an figure out a charge rate from that.

[cico7]

I think a proper battery charger would be the way to go to protect the trailer battery. That should work both ways protecting the starting battery as well and you can skip the isolator then as well.
The regulator will keep it from over charging and I can disconnect the charging wire if I
think it will be an extended time period. But it would put out a higher rate of charge.
The charger idea is good, but can you find a battery charger that runs off a battery?

I am enjoying this discussion and everyone's input on this.
Beauty rest is in great need. Great Great need at this point.
So I must retire for the evening.

Hoaxci5, IamJeep, Sal, thank you very much. I will continue tomorrow.

[IamJEEP]

WAKE UP!!!!!!!!!!!!!

Morning all, I could'nt stay up any longer so I crashed for the night.

I read somewhere (too many sites to remember) there is a battery tender that runs off of the vehicle battery and switches off with the ignition. So, it only charges when the vehicle is turned on (or keyed on). I think it was like $110 or so and had all the fetures you would need. I'll look for it today during lunch.

[IamJEEP]

Question:

Hi, Have converted from 4 pin to 7 and everything is working fine. Question is, is all I need is #10 wire and inline circuit breaker? Do I have to do anything at the fuse block on the Fj? and Will the in-line circuit breaker prevent my truck battery from being run down? or do I need something to prevent drainage?

asked by: dana



Expert Reply:

You have it figured out. You will need an appropriate length of 10 Gauge Wire, item # 10-1-1, and a 40 amp circuit breaker, item # PK54540, to provide 12 volt power to the trailer connector at the rear of your FJ. This will provide a maintenance charge to the trailer battery while towing the trailer. You will not need to make any changes at the fuse block on your vehicle. The 12 Volt power wire connects to the number 4 position inside your 7-way connector, see the photo in the trailer wiring diagrams FAQ linked here.

The power wire is connected from the trailer connector to the Auxilliary side of the circuit breaker and from the Battery side of the circuit breaker to the positive terminal of the vehicle battery. You should remove the ground cable from the vehicle battery before connecting the power wire from the circuit breaker.

The inline circuit breaker will protect the vehicle and trailer from any type of short circuit or power surge that may occur, but will not isolate the battery from the trailer connection when the the trailer is connected to the vehicle. Most people simply unplug the trailer from the back of the vehicle when they get to their camping destination, to keep the vehicle battery from being discharged.

We do offer the Tow Ready Battery Isolation Solenoid, item # TR118665, which will shut down the connection from the vehicle battery to the trailer connector when the vehicle ignition is off. It would be a good idea to install the battery isolator if you plan to leave the trailer connected to the vehicle for extended periods, when the vehicle is not running. The isolator also installs inline with the power wire to the trailer connector. You will need a switched ignition source to attach to the 12 volt source on the isolator and the isolator needs to be mounted to the vehicle chassis for a ground connection.

expert reply by: Bob G

I quoted eTrailer.com here 'cause I thought this would help. Just ignore the fact that they are talking about an FJ, LOL...

PS: If I've violated any rules by doing this, please advise and I'll delete.

[cico7]

<Insert Joke/>
She was an avid gardener, and she got carried away purchasing shrubbery one day.
You might say she had all her money tied up in hedge funds.

She would have a safer portfolio is she didn't place all her money into such a garden-variety investment.

Though Hedge funds are dirt cheap

[cico7]

So a man walks into a bar:
Bartender says "what will you have?"
Man says to bartender "give me a Bin Laden"
The bartender asks "a Bin Laden; what's that?
The man replies "two shots and a splash of water"

[Sal-XK]

^^^^^^^^^^^^^^ now thats funny

The 14 gauge has the current to charge a battery (more then a trickle charge at 15amps) I'm just not convinced it cant until I know what the flow is threw that wire then I will know what the watts are and then make a good decision. I will add that jeep put that there to charge a trailer battery which is pretty good evidence the flow or volts will be there to charge the batter.

[cico7]

American Wire Gauge (http://www.powerstream.com/Wire_Size.htm) instructional program

Claculator (http://www.powerstream.com/Wire_Size.htm)


https://theultimatejeep.com/notfound.png



643

[Sal-XK]

Well both my meters have the amp fuse blown LOL. so off to the sore to get some fuses.

[IamJEEP]

Well both my meters have the amp fuse blown LOL. so off to the sore to get some fuses.

You should pick up a meter manual while you are at it!!! LMCAO!!! Sorry bro, I had to.

[IamJEEP]

I guess the question here is............How long will it take to charge the battery with a 14g wire VS a 12/10g wire? Also, Cico mentioned he did not want to wait to charge so, a deep cycle is out of the question here ($0.02).

[Sal-XK]

You should pick up a meter manual while you are at it!!! LMCAO!!! Sorry bro, I had to.

LOL funny bro, A manual won't help my issue any. forgetting its hooked and turning the key to on does it every time.


I guess the question here is............How long will it take to charge the battery with a 14g wire VS a 12/10g wire? Also, Cico mentioned he did not want to wait to charge so, a deep cycle is out of the question here ($0.02).

Well don't go to autozone for replacement fuses. They sell the meter but not the fuse???? I picked up a glass fast reacting 20A we'll see how that works:(

[IamJEEP]

Un-named source.......

"If you feel the need for speed, and you are willing to spend more money, you can buy a larger charger. But don't expect to be able to pump 50 amps into the battery and have it fully charged in one hour. Fast charging a battery for extended periods will harm the battery. Automotive batteries are designed to handle very large currents for only short periods of time for engine cranking. If a high current is forced in or out for an extended period of time, the battery will overheat and suffer internal damage. Better chargers commonly have capability to run a 15 amp charging rate. An important feature of the larger capacity automatic charger is that it may be able to maintain something close to the rated current until the battery is nearly fully charged. Then when it's finished it can shut off suddenly and not overcharge the battery. As such a 15 amp automatic charger may be able to fully charge a flat battery in as little as 3 or 4 hours"


They are talking about battery chargers you can buy from auto stores but, it fits in this topic (I believe).

[IamJEEP]

LOL funny bro, A manual won't help my issue any. forgetting its hooked and turning the key to on does it every time.

Ah yes, been there done that. Lol....

[Sal-XK]

https://theultimatejeep.com/images/imported/2011/05/Pin20out20trailer20wiring-1.jpg

[Sal-XK]

LMAO hahahahah well, blew another fuse glad I bought a pack. 32amps at that trailer connection. Yes 32amps so the wire gauge must be bigger then 14gauge. Also the key must be on or there is no power to that connection. Now I have a rated 20amp meter the fuse blew sitting on 32amps which took to long to blow IMO so I'm glad I was using my spare\back up meter :) I hope this helps out at 32amps your good to charge a battery for sure. I was only getting 10v but I have to confirm that with my other meter now LOL.

[Sal-XK]

Ok so we have 32amps at 12.40 volts for battery charging at the plug. I confirmed the volts with my good meter.

[IamJEEP]

Ok so we have 32amps at 12.40 volts for battery charging at the plug. I confirmed the volts with my good meter.

That is plenty enough to charge the trailer battery. You must have a 10 or 12 gauge wire for that many amps, tho.

So Cico, you will need at least a 14g +12vdc feed off of your main battery (w/ a relay for switched operation) to a 7 pin harness. Done!

Correct me if I'm wrong, anyone.......

[IamJEEP]

Sal, are you using a "multi meter"? You should'nt be blowing fuses if you are, just change the range up one notch.

Unless you started the Jeep again with it hooked up..LOL.

[Sal-XK]

Sal, are you using a "multi meter"? You should'nt be blowing fuses if you are, just change the range up one notch.

Unless you started the Jeep again with it hooked up..LOL.

Yes I am but the max amperage is fused at 20amps. So when I hold it on anything pushing more then 20amps the fuse blows can't do anything about that and you can't put a bigger fuse in or you will melt something else in the meter. I didn't start it LOL but I had to have the key turned to the on position to get power to the plug. I'll drop another fuse in the bad boy and recheck the readings.

[IamJEEP]

Yes I am but the max amperage is fused at 20amps. So when I hold it on anything pushing more then 20amps the fuse blows can't do anything about that and you can't put a bigger fuse in or you will melt something else in the meter. I didn't start it LOL but I had to have the key turned to the on position to get power to the plug. I'll drop another fuse in the bad boy and recheck the readings.

Interesting...............I have a Fluke 77 and have kept it hooked up to the alternator output for long durations and have never blown the fuse. According to the manu specs, it's only rated at 10amps DC. 1000v DC.

Am I missing something here?

[Sal-XK]

Yes first I'm jealous I haven't owned a fluke in some years now :( Second as long as you are not measuring AMPS you will be fine. You can measure 250v 50amp feed all day but as soon as you move your lead to the amp terminal and turn the switch to amps it will pop.

[cico7]

I guess the question here is............How long will it take to charge the battery with a 14g wire VS a 12/10g wire? Also, Cico mentioned he did not want to wait to charge so, a deep cycle is out of the question here ($0.02).


..... but I don't want to take all day to charge the battery All day. If I am out and about and then need to charge the trailer battery, I dont want to have it plugged in with the engine running several hours. What I will do is run a 10gauge wire to the back with an isolator so it doesnt back charge or drain the main.

I have a back up plan, I bought a 1000w generator. https://theultimatejeep.com/images/imported/2011/04/20110420_080008_165-1.jpg

[cico7]

....but as soon as you move your lead to the amp terminal and turn the switch to amps it will pop.
Then don't do that. Didn't they teach you that in Meter Manual school?

[Sal-XK]

Then don't do that. Didn't they teach you that in Meter Manual school?

Funny, but then how do I measure the amps then? I guess I could use one of those fancy formulas to calculate the amps but its easier to change fuses when I pop them. LOL Sweet generator by the way. I don't think you need the 10 gauge wire because thats probably whats already in there. at 30+amps measured its plenty to charge a battery. I would run 10 gauge from the bumper back to the trailer and have an isolator on that.

[hoaxci5]

Get a solar setup, if you get the right size panel you should be able to run for days if not weeks without ever having to worry about recharging..

[superacerc]

If you know the voltage(easy) and check the ohms(easy) you know the amps. voltage/ohms = amps. Ohms will probably be below 1.
Watts are amps x volts fyi. Easy to check how many amps a light will pull. If you buy a 50 watt light and you know with the car running you have 13.4 volts - 50/13.4 = 3.74amps. If the car was off and you only had 12 volts it would be more amperage 50/12 = 4.1amps.
With my 4, 55 watt (wussy) offroad lights on my rack the amperage is (not including resistance from the length of 10gauge wire) (55w/13.4v)x4 = 16.41 with the engine on and (55w/12v)x4 = 18.33 with the engine off.

[cico7]

What i ended up doing is getting a heavy plug with lighter type attachmentl. Ran 10ga wire
to the front, followed the existing wiring harness. I add this plug. This is a low draw system,
not starting or trying to fast charge the battery.

Right now, this is my wifes old battery. I will replace with 2 storage type batteries.

https://theultimatejeep.com/images/imported/2011/07/20110726_080650_507-1.jpg