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Old 09-16-2019, 08:17 PM   #1
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Trailer batteries not charging while travelling?

I need some help please.
my knowledge of 12v DC is just basic so I may have this wrong.
But my trailer batteries do not seem to be charging while I am travelling. Last long trip resulted in the trailer batteries discharged. I replaced them and now am checking the electrical connections. The trailer batteries are reading 12.5 v with vehicle on or off, same reading on tow vehicle battery. Checked continuity on the 12v line through the tow vehicle to trailer connection and got the same reading from end to end. turned the headlights on in the tow vehicle and battery showed 13.5 v, but trailer batteries still showed 12.5v. Should the trailer batteries have shown the same voltage as the tow vehicle battery?
My connection for the 12v to the trailer is right off the tow vehicle batteries positive post.
Am I testing this right way??
Woody
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Old 09-16-2019, 08:24 PM   #2
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What position is the battery disconnect switch in while you're towing/testing?
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Old 09-16-2019, 08:49 PM   #3
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My truck does not appreciably charge my trailer when towing. I think that is pretty typical. Lots of wire and voltage drop and the alternator is seeing the TV batteries which are fully charged. Is this the first time you have tried this? I know others report charging while driving but for me it has not happened with either of the two TV I have used.
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Old 09-17-2019, 12:06 AM   #4
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Your 2000 Excella is probably wired like my 2001 Safari and 2002 Classic. If so it has a rotary mechanical switch called a "Kill Switch", not a USE/STORE switch like the newer trailers. The "Kill Switch" disconnects the trailer distribution panel from all power sources. The vehicle charge line is always connected to the batteries as is the converter.

Your tow vehicle, however may not be equipped to charge your batteries. My F-150 was missing a relay that had to be plugged into the fuse panel to activate the line, and then would only put voltage on the wire when the engine was running. When new, the relay was in the glove box but it got lost with one of the previous owners. I had to buy and install one. My Ram, however, has the line activated all the time, but there is a fuse.

Check your tow vehicle manual to see if there is a fuse or relay or both and make sure they are installed. I think you should see some elevation of the trailer battery voltage with the tow vehicle engine running but, as others have mentioned, it probably is not sufficient to make up for more than a little use while camping. You will probably have to have solar or a generator if you plan on camping more than a day or so without shore power.

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Old 09-17-2019, 01:19 PM   #5
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My gmc sierra 2018 outputs 12v to the trailer but very minimal amperage. New computers regulate the alternator.
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Old 09-17-2019, 07:27 PM   #6
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Quote:
Originally Posted by overlander63 View Post
What position is the battery disconnect switch in while you're towing/testing?
Thanks for your reply. I usually tow with the disconnect switch in the "off" position. But this shouldn't make any difference whether it is off or on unless I was running 12v stuff which I don't think that I was. Lights, fans, etc. were all "off". Running, brake, turn signals lights all run off the tow vehicle. The refrigerator was definitely off because it was 5 degrees F and I was concerned about everything freezing.
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Old 09-17-2019, 07:53 PM   #7
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Quote:
Originally Posted by Al and Missy View Post
Your 2000 Excella is probably wired like my 2001 Safari and 2002 Classic. If so it has a rotary mechanical switch called a "Kill Switch", not a USE/STORE switch like the newer trailers. The "Kill Switch" disconnects the trailer distribution panel from all power sources. The vehicle charge line is always connected to the batteries as is the converter.

Your tow vehicle, however may not be equipped to charge your batteries. My F-150 was missing a relay that had to be plugged into the fuse panel to activate the line, and then would only put voltage on the wire when the engine was running. When new, the relay was in the glove box but it got lost with one of the previous owners. I had to buy and install one. My Ram, however, has the line activated all the time, but there is a fuse.

Check your tow vehicle manual to see if there is a fuse or relay or both and make sure they are installed. I think you should see some elevation of the trailer battery voltage with the tow vehicle engine running but, as others have mentioned, it probably is not sufficient to make up for more than a little use while camping. You will probably have to have solar or a generator if you plan on camping more than a day or so without shore power.

Al
Thanks Al for your reply. The charge and Brake controller wires are connected to 12v battery post on the tow vehicle. Each have their own breaker.
The kill switch only affects the 12v circuits in the trailer. Takes care of everything except for the propane detector.
The vehicle charge line is always connected to the trailer batteries. Goes into a 12v buss protected by breakers. The vehicle ground wire connects to the trailer negative buss bar.
This is my 4th A/S trailer and I have never had solar panels with the trailer batteries holding their charge.
Woody
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Old 09-17-2019, 08:22 PM   #8
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Some new info

Talked to the service rep at our A/S dealer today and he also has a background with vehicle maintenance. When I turned on the headlights on the tow vehicle it shouldn't and didn't have any change in the trailer batteries voltage. Suggested I repeat the test and put the trailer ceiling lights and fans on. Tried this and had the same readings on the trailer and vehicle batteries. (Kill switch was on.) The trailer batteries should have felt the drain and absorbed a charge from the vehicle.
When I do this testing, I do not have the trailer hooked onto the vehicle. But the umbilical cord from vehicle to trailer are connected. I'm wondering now if the ground wire from the vehicle is somehow disconnected. Would that not account for the trailer battery readings not changing when a load was put on the trailers??? I'll check out the ground wire tomorrow.
The trailer brakes (electric/hydraulic) get their 12v from the tow vehicle. Anyone know how the vehicle's and trailer's batteries don't charge simultaneously. How does the vehicle generator not overcharge either the vehicle or trailer batteries????
Any more suggestions?
Woody
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Old 09-17-2019, 08:39 PM   #9
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Question Tow vehicle MUST charge the trailer brakes.

If the trailer ever separates from the tow vehicle ( sure hope never), the umbilical cord separates and the breakaway switch is activated forcing the trailer brakes to lock up. At that time, the trailer brakes must get their power from the trailer batteries. So the tow vehicle must keep the trailer batteries charged while going down the road or the brakes will never work.
Wishful thinking or fact????
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Old 09-17-2019, 10:14 PM   #10
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Quote:
Originally Posted by woodytwo View Post
If the trailer ever separates from the tow vehicle ( sure hope never), the umbilical cord separates and the breakaway switch is activated forcing the trailer brakes to lock up. At that time, the trailer brakes must get their power from the trailer batteries. So the tow vehicle must keep the trailer batteries charged while going down the road or the brakes will never work.
Wishful thinking or fact????
Woody
I drove my Safari 25 and F150 for a year withiut the TV charge line working. Unless you are running the air conditioner from an inverter, have bad batteries, or have boondocked your batteries dead there shouldn't be enough drain to affect the trailer brakes.

Al
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Old 09-18-2019, 02:56 PM   #11
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Woody what is your tow vehicle? As Seabloom mentioned it might that the a computer is controlling output from the alternator. And the minimal loads you put on the trailer aren't enough pull from the TV batteries to cause the alternator to kick in. Do you have a DC clamp meter so that you can monitor 12v loads? That might be useful.
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Old 09-19-2019, 12:04 PM   #12
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The TV bases charging on the battery in TV only. The TV charging system only sees the trailer battery as a small extra load when it needs charging, like having lights on. If the TV battery isn't low you would be lucky to get 10 amps of charging in a best case scenario with a stock setup.

With my Chevy without using tow/haul mode once TV battery is charged the running voltage drops below 13v (as designed) which would pretty much result in no trailer battery charging.
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Old 09-19-2019, 01:48 PM   #13
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If you are running the fridge on 12V, that will suck a battery dry in no time at all.



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Old 09-20-2019, 11:21 AM   #14
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Quote:
Originally Posted by Wazbro View Post
The TV bases charging on the battery in TV only. The TV charging system only sees the trailer battery as a small extra load when it needs charging, like having lights on. If the TV battery isn't low you would be lucky to get 10 amps of charging in a best case scenario with a stock setup.

With my Chevy without using tow/haul mode once TV battery is charged the running voltage drops below 13v (as designed) which would pretty much result in no trailer battery charging.
I beginning to believe from yours and others who have replied that my trailer batteries at the most get "maintained" as opposed to "charged". So if I travel with the "kill switch" off, the only draw on those trailer batteries should be items like the propane detector. And if the trailer batteries started the trip fully charged, I should arrive at the end of the day with them almost fully charged.

So either those batteries will not hold their charge or I have a phantom draw somewhere.

Since I have a set of new batteries, I will forget about this issue for now and see how the next trip (3 weeks at the end of the month) works out.

Thanks to all input received to date. Your time and thoughts were all appreciated.

Woody
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Old 09-20-2019, 02:29 PM   #15
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Aren't all the running lights, brakes, etc. also running off the batteries when you tow?

I would suggest confirming that your tow vehicle IS charging the batteries correctly, when you are on the road. That is the basic design of the system. Postponing its full and complete implementation may be penny-wise and pound-foolish IMO.

Have a good weekend and trip.

Peter
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Old 09-20-2019, 02:53 PM   #16
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I did not think so, although I would have to look at the schematic again. Whatever is on in the trailer is a load, like the propane detector and if you have the Store switch Off, only that, if it is ON, whatever else is on like the subwoofer, control circuits for the refrig, etc. But the running lights are off the 7 way, not the battery. The brakes are also off the battery.
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Old 09-21-2019, 05:49 AM   #17
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Good suggestions, Larry. If the trailer running lights are fed from the 7-way connector, this is one more reason to dig deeper IMO, and to figure out why the tow vehicle does not appear to be charging the trailer batteries completely.

On a trip, the trailer brakes alone could start to drain the trailer batteries fairly quickly IMO, if I have understood you correctly.

Thanks,

Peter
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Old 09-21-2019, 06:13 AM   #18
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I would want to see if there is 12 vdc at the charging wire, as measured at the 7 way on the bumper and in the trailer. While I can think of scenarios where it might not charge the batteries, I would expect that if there is 12 vdc then it will operate the brakes, with or without a battery. The battery would come into play if the trailer disconnects from the TV, the brakes engage, and the only power would be the battery.
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Old 09-21-2019, 06:16 AM   #19
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I think that earlier parts of this thread deal with that issue, but I have not read it all. Gonna bow out here.

Good luck, Woody.

Peter

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Old 09-25-2019, 07:06 PM   #20
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Thumbs up There is light a the end of the tunnel!

Went back to this problem today. And I think that I am finally on to finding where the problem originates. There were 3 wires connected to the positive buss bar at the front of the trailer. These wires were not shown in the owners manual schematic. Traced these to the front of the "A" frame where they were capped off. I also had a look at the umbilical cord where it enters the trailer and the charge and ground wires were missing.
I am now thinking that the previous owner (2 years ago) had wired in connections of some kind to accommodate a generator(?) and in the process had used the charge and ground wires for something. I did notice that 2 or 3 wires were capped off.

So I'll have a thorough look into this A frame wiring tomorrow and see what else I find. To date all that I have found has indicated to me that both the charge and ground wires from the umbilical cord were dead. I think maybe I am about to find out why.
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