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#1 Pat and Ed

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Posted 23 January 2013 - 03:46 PM

Hi All,

Hope you all are avoiding the nasty weather up north!

Time for my expert's advice. We have a 38 foot fifth wheel. We have loved our new battery monitor (Thanks Jack!). And as I was told I am now watching the monitor even when I don't have to. When we're on the road we plug in to the bed of the truck. I know that when we're traveling some power is pulled from the fridge but doesn't the truck recharge the battery a bit too? We are at 100% battery when we leave and down to about 95% after five hours of driving.

It's not a big deal but I guess what I want to know is how much recharge to expect from the truck (If any).

Thanks and safe travels!

#2 DavidMc

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Posted 23 January 2013 - 04:21 PM

You could try an experiment -- related to the refrigerator.
This assumes you do not make any material changes to the system in the mean time.

The next time you start out -- Turn Off the refrigerator completely. Unless you are in-and-out of the refrigerator, constantly fanning the door, the refrigerator will retain it's coolness for four or five hours reasonably well.
Then -- if all things have otherwise been "left equal" -- see what the reading for your battery is at the end of that day's journey.

This could either tell you the refrigerator either --
1. demands more power than the truck-linked alternator is willing to supply (perhaps it is reducing its output because of other signals from within the truck), OR
2. has no impact on the outcome -- it is not a major player in your situation.

Edited by DavidMc, 23 January 2013 - 04:23 PM.


#3 David&Joanne

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Posted 23 January 2013 - 05:48 PM

Pat and Ed,
You might try checking to see if you have power from the truck to the tlr's cord. There is probably a 30 amp fuse under the hood of your truck.
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#4 Rif

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Posted 23 January 2013 - 07:06 PM

Pat and Ed,

Is this a standard RV type refrigerator or a household unit running on an inverter. If an RV type you should not see any usage to speak of. They draw very little power. If it is a household unit and you are relying on just the standard connection from the truck to supply power, being down to 95 percent on your batteries is not surprising. You will not normally get much of a charge from that connection. There is too much loss due to the size of the wire used and the length of the run.

Are you sure there is not another power load? Was the furnace left on?
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#5 Stanley P. Miller

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Posted 23 January 2013 - 07:08 PM

The truck to fiver wiring is about right for a propane fridge, way too light for any serious power draw.

Run a heavy wire from the alternator (best) or battery to a big fuse, then to a quick connector back in the bed. Run another heavy wire from the fiver batteries or your shunt if you have one to a big fuse and up to where it will reach the connector in the truck bed. You'll see a large improvement on power transfer with the right wire, check your distance and then use your "hoped for" amps to calculate the wire size. A 5% loss wouldn't be too bad since the power cost from the alternator is less than from solar where 2% is the usual loss factor you'd want.

Just fooling around? Pull the truck up to where you can use a good set thick jumper cables and see how the charging goes that way. Fast, easy and cheap way to see if the bigger wire solution is going to work for you.

If you don't fuse both ends of the wire I suggested above please send me snapshots of your rig before and after the fire. :-(

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#6 Kirk

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Posted 23 January 2013 - 08:01 PM

If an RV type you should not see any usage to speak of.

True, unless you happen to have one of those now rare, three way refrigerators which can operate from 12V-dc as well as 120V-ac and propane. In that case the standard truck wiring would not supply enough to keep the batteries charged.

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#7 Al Florida

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Posted 23 January 2013 - 08:12 PM

The standard 12V power wire in the truck to trailer cable is, if you are lucky, #12 wire. It could be #14 wire. To keep the batteries charged #8 is better. If you are intending to charge your trailer batteries, which have been depleted by lights, computers, furnace, etc, you need wire from the truck battery/alternator in the #4 to #6 range. If you have multiple batteries in the trailer you may need to go to #2 wire.

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#8 oscarvan

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Posted 24 January 2013 - 04:03 AM

FIRST.....

Make sure there IS a charge flowing from the TV to the trailer. When brand new my previous truck (Chevvy 2500HD) had a wire which needed to be connected at the vehicle electrical distribution panel (per owners manual) to get power to the appropriate pin in the 7 pin connector.

Sounds like you have a condition monitor installed (these are GOOD) soooo....

Note battery voltage before you connect to TV. (Something at or below 12.6v)

Connect to TV and start same.... You should now see something much higher.

If so....good, and then the draw discussion above is the next step. If not....there's your problem.

Edited by oscarvan, 24 January 2013 - 04:21 AM.

Super Max is a 2012 Chevvy 3500 Crew Cab Dual Rear Wheels.....Duramax Diesel and Allison 6 Speed. Max takes care of TWO RV's:......"Yertle" our 2012 Lance 1191 Truck Camper for short missions, and "The Castle" a 2013 Heartland Cyclone 4100 King HD for our longer vacations.

#9 Pat and Ed

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Posted 25 January 2013 - 10:24 AM

FIRST.....

Make sure there IS a charge flowing from the TV to the trailer. When brand new my previous truck (Chevvy 2500HD) had a wire which needed to be connected at the vehicle electrical distribution panel (per owners manual) to get power to the appropriate pin in the 7 pin connector.

Sounds like you have a condition monitor installed (these are GOOD) soooo....

Note battery voltage before you connect to TV. (Something at or below 12.6v)

Connect to TV and start same.... You should now see something much higher.

If so....good, and then the draw discussion above is the next step. If not....there's your problem.


We found out that there was nothing coming from the TV. Blown fuse. Problem fixed! Hubby says that this is the third time he's had to replace the fuse though. So now we need to find out what the deal is with that.

Thanks for all you help!

#10 Kirk

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Posted 25 January 2013 - 12:34 PM

. So now we need to find out what the deal is with that.


It probably simply means that you are trying to supply more than the fuse is rated for because of the needs to fully charge the RV batteries. The fuse most likely is sized based upon the wire size that it supplies. You can either replace that wire with a heavier one and then go to a larger fuse, appropriate for the wire size chosen, or you may want to simply run a completely new wire and use an "in-line" fuse holder. Even so, you still need to size the fuse by the wire gauge that is chosen. The fuse is there because the wire size can only carry so many amperes and drawing too much would melt the insulation and could cause a fire. Since this only seems to happen occasionally, that is most likely the problem.

What size is the fuse and how large is the wire to the RV power plug?
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#11 Stanley P. Miller

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Posted 25 January 2013 - 01:13 PM

Several cheap/easy options to avoid new wiring:

Replace the fuse with a "slow blow" version to see if it is a current spike causing the blowing.

Replace the fuse with a circuit breaker module, possibly one that does automatic resets.

-------

Is it the fuse at the truck end or the fiver end of the wire that is blowing?

Do you have the same size wire on the truck end and the fiver end of the charging circuit? You might only need to update the wire on one side if the other is larger and not being a problem.

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#12 oscarvan

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Posted 26 January 2013 - 01:07 AM

I agree with the learned gentlemen above. However, comma, pause, after a lifetime of occasionally frying things here and there I have learned to make SURE that the fuse wasn't actually doing it's job. IE, check that there is no short of any kind. Multi meters are your friends.
Super Max is a 2012 Chevvy 3500 Crew Cab Dual Rear Wheels.....Duramax Diesel and Allison 6 Speed. Max takes care of TWO RV's:......"Yertle" our 2012 Lance 1191 Truck Camper for short missions, and "The Castle" a 2013 Heartland Cyclone 4100 King HD for our longer vacations.

#13 Pat and Ed

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Posted 26 January 2013 - 11:37 AM

I agree with the learned gentlemen above. However, comma, pause, after a lifetime of occasionally frying things here and there I have learned to make SURE that the fuse wasn't actually doing it's job. IE, check that there is no short of any kind. Multi meters are your friends.



Thanks for the suggestion. As I said previously we are both novices in this process. Any suggestions on where to check for possible shorts? In the truck? In the fifth? Any input you have on the best way to check will be appreciated!

Thanks!

#14 Stanley P. Miller

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Posted 26 January 2013 - 05:35 PM

Checking for a constant short is easy for one of you, not so good for the other, since it will blow your fuse every time. You just make or buy a pigtail light socket and stick an incandescent bulb in it (no LED one will work as well) and put it in place of the blown fuse. Disconnect the wire at the end opposite your light bulb thingie. The bulb will light up as the short draws power and one of you can sit in a comfy spot with a nice cup of coffee while the other moves along the wire from one end to the other wiggling it around. At some point the wiggler will cause the light to go out, the sitter hollers "you got it" and goes back inside for more coffee and a couple hands of Free-cell solitaire while the wiggler deals with the short.

At least that is how I recall the process last short I had to deal with.

The same thing can sometimes help with an intermittent short too, worth a try before you start cutting open the wire looms to actually look at the wires. In that case since the silly thing won't be shorted the light will be out. The wiggler does the same thing but the sitter watches for the light to go on instead of off.

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#15 oscarvan

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Posted 28 January 2013 - 09:00 AM

Checking for a constant short is easy for one of you, not so good for the other, since it will blow your fuse every time. You just make or buy a pigtail light socket and stick an incandescent bulb in it (no LED one will work as well) and put it in place of the blown fuse. Disconnect the wire at the end opposite your light bulb thingie. The bulb will light up as the short draws power and one of you can sit in a comfy spot with a nice cup of coffee while the other moves along the wire from one end to the other wiggling it around. At some point the wiggler will cause the light to go out, the sitter hollers "you got it" and goes back inside for more coffee and a couple hands of Free-cell solitaire while the wiggler deals with the short.

At least that is how I recall the process last short I had to deal with.

The same thing can sometimes help with an intermittent short too, worth a try before you start cutting open the wire looms to actually look at the wires. In that case since the silly thing won't be shorted the light will be out. The wiggler does the same thing but the sitter watches for the light to go on instead of off.


If you're on your own a radio can be the "sitter".

Edited by oscarvan, 28 January 2013 - 02:06 PM.

Super Max is a 2012 Chevvy 3500 Crew Cab Dual Rear Wheels.....Duramax Diesel and Allison 6 Speed. Max takes care of TWO RV's:......"Yertle" our 2012 Lance 1191 Truck Camper for short missions, and "The Castle" a 2013 Heartland Cyclone 4100 King HD for our longer vacations.

#16 Kirk

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Posted 28 January 2013 - 09:21 AM

An intermittant short is a possible cause, but replacing the wire with one that is of heavier gauge will correct that as well. Doing as Stanly suggests and putting in a "slow blow" fuse will not endanger frying anything in the system, so long as you make sure that the new fuse has a rating that is no greater than the present one or perhaps just a little bit below the present one. You have not said what the value of the original fuse was? When replacing the original fuse, did you just pick one with the same number rating or did you also match the letters that follow the number of amps? Those letters do have meaning and if the circuit is near the limit of the fuse, those letters can make a difference in how well it works.

What is the amp rating of the present fuse?

Do you own a meter and know how to use it? If you do, simply measure from the load side of the fuse holder to the chassis ground on the truck without the RV connected and with the fuse removed. It should read near to the maximum of the scale on your meeter when set to ohms. I would expect to see at least 5K ohms if there is no problem in the wiring . Once you do that, go to the RV and lift the positive battery cable and then read from the charge wire of the RV plug to the trailer chassis. It should also read at least as high a resistance.

Edited by Kirk, 28 January 2013 - 09:25 AM.

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#17 Pat and Ed

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Posted 28 January 2013 - 10:41 AM

An intermittant short is a possible cause, but replacing the wire with one that is of heavier gauge will correct that as well. Doing as Stanly suggests and putting in a "slow blow" fuse will not endanger frying anything in the system, so long as you make sure that the new fuse has a rating that is no greater than the present one or perhaps just a little bit below the present one. You have not said what the value of the original fuse was? When replacing the original fuse, did you just pick one with the same number rating or did you also match the letters that follow the number of amps? Those letters do have meaning and if the circuit is near the limit of the fuse, those letters can make a difference in how well it works.

What is the amp rating of the present fuse?

Do you own a meter and know how to use it? If you do, simply measure from the load side of the fuse holder to the chassis ground on the truck without the RV connected and with the fuse removed. It should read near to the maximum of the scale on your meeter when set to ohms. I would expect to see at least 5K ohms if there is no problem in the wiring . Once you do that, go to the RV and lift the positive battery cable and then read from the charge wire of the RV plug to the trailer chassis. It should also read at least as high a resistance.


The fuse is a 30 amp. We are on the road now. When we plugged in before we left the battery monitor said the truck was charging the battery.

We plugged the fifth into a different plug. We two plugs; one in the bed of the truck and one near the license plate. We usually plug in the bed, today we're using the one near the.license plate. Maybe thats the problem

Thanks for all your help!

#18 Kirk

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Posted 28 January 2013 - 01:02 PM

Either plug is a real possibility, whether in use or not. I would take a hard look at both and make sure that the one at the bumper area isn't full of dirt and road debris. Since both of them are connected to the same wire harness, it is possible for one not in use to cause the problem.

Good travelin !...............Kirk
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Full-time 11+ years...... Now seasonal travelers again.
Kirk & Pam's Great RV Adventure
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