CT03911

I have searched here and a Tundra forum. I find conflicting information. Maybe one area here we can get on the same page.

I have a Tundra and a 24' Featherlight. The 7-pin connector recharges the battery backup for the trailer brakes. That unit actually has its own trickle charger.

That 12v wire continues into the trailer for ceiling 12v lights that only work when connected to the truck. So, like many, I want to add a battery to the trailer to power a winch, more lights, etc.

Here is where so many seem to disagree. How to charge the house battery???

The company I spoke with that sells isolators was pretty insistent that the thin wire 12v lead out of the 7-pin connector was not adaquate to recharge a trailer house battery.

They told me to install the isolator in the engine compartment and run an 8 gauge wire to the bumper. Using a single pole trailer plug run that power to the trailer with a single pole coiled power cable like this and connect to the house battery. They detailed where various breakers need to be.

I know Featherlight sells this setup. My trailer did not come with it and I cannot get Featherlite to call me back.

So, what are you guys using?? If Featherlight sells this setup, I am sure others do to. That must mean it is a good idea. Sounds like some are getting away with what must be a very slow charge off the 7-pin 12v wire or solar.

Yes, I do plan to also install 110ac shore power but usually at the tracks I go to there are few plugins and I may or may not want to park there just for power. Perhaps I will, for better power to interior lights, compressor etc but we'll see.

Obviously, the Tundra 7-pin 12v wire would eventually charge at least a partially discharged battery. With items like a winch and additional lights etc I am not sure I want all that on my Tundra's tow circuit 12v wire. Just because some make it work or it is the easy way is not the answer I am looking for. Is is a good idea really or should I go ahead with the extra effort of running an 8 guage wire from the truck to trailer?

007DT

I think I follow your question.. Here is how my Battery in my trailer is charged... Under my fron Cabinets I have a 110v outlet. I have a battery tender plugged into that outlet which is connected to the "House" battery. Anytime my trailer is either plugged in or if the generator is on that 110 outlet (And all others) is live thus keeping a nice trickle charge on the battery. (Battery powers: 12v lights, car wench, trailer wench)

CT03911

My question is if the 12v wire in the 7pin is really an adaquate or "best" charge source of 12v juice OR should I run a cable from the alternator back to the trailer etc etc? The forums have all kinds of answers.

Has anyone on this board had a professional electrician install a power source to a trailer battery??

Did they use the7-pin wire or rig up a more substantial separate 12v feed from the tow vehicle? (the way Featherlite does it and the way the pro selling the isolator told me to do it)

I understand it is easy if you are connected to 110 AC. I will not be very often and am not while driving.

Tom W

Or, another option: I have a solar panel on the roof of the trailer and I use it to charge the trailer battery. That way the battery is always charged regardless of if the truck is connected or not and I use the 12V lights as often as I want when I'm out working in it in the off season. I use a 15W solar panel that is designed to charge RVs. (My battery is also charged from the 7-pin as that is the way they designed it or I can charge it when I run the generator.)

KaiB

Why not bite the bullet one time.

Go ahead and wire your trailer up for 110vac, get a proper plug in charger and purchase a Honda EU2000i genset.

Best of all worlds.

Dan Jacobs

I also have solar panels on two of my trailers. Slicker then deer guts on a door ****

dgmark

You should have isolated battery power at your 7 pin connector at Pin 2, It is powerd through the sub battery relay. It only supplys power when the engine is running so you cannot drain the trucks battery. It is a normal feature of the truck if you have the trailer towing package. I have seen the 30 amp fuse left out at the factory, check the under hood fuse block and your owners manual the relay is also located at the under hood fuse block. It is a 30 amp rated circut, plenty of juice to charge the auxillery battery.

KaiB

Fact. Well written, thanks.

CT03911

dgmark you are the first guy to mention the 12v pin is isolated. No one on the Tundra forum ever suggested that. No one here either.

Why are guys using isolators then?

My 12v pin is working fine. The 2011 Tundra book and wiring diagram does say the "subb batt" is a 40amp fuse. It doesn't discuss it being isolated that I have found but does appear to be relayed off the ignition, easy enough to verify that.

Can I ask how you know this circuit is isolated or how I can check it? The only way I can think of is to connect it to the house battery (which I haven't installed yet) and load that down. If the truck battery is unaffected then it is isolated? Correct?

Sounds like great info guys. I am inclined to go the easy route and use the trailer 12v feed into a trickle charger, to the battery and then the winch etc.

I do like the solar comments Dan
I may look into that later too.

winders

http://woywoyautoelectrics.com.au/ba...tery-isolation

Scott

dgmark

The isolation comes from the relay, The relay is powerd with the ignition on through the ecm-Ig fuse (7.5 amps). A quick way to check it is to test for power at pin 2 with the ign on or engine running, when you turn the ignition off there should be no power at the pin. You can also remove the relay with the engine running or the key in run position to test that it is functioning, you will lose power when the relay is removed. You need this feature so you do not drain the battery on the truck when the engine is off and the trailer is hooked up. Remember you will have a battery on the trailer so all the high amp loads will be on that. The feed from pin 2 is only charging the battery. In the event you somehow overload the feed it will blow the sub battery fuse and protect the wire. The only way this could happen would be to run somthing like a winch with the trailer battery disconnected and with the trucks key in the run position. I wish i could post the wiring diagram for you but it is not in the right format.
You are correct it is a 40 amp fuse.

dgmark

Also, yes there is no "Isolation" when the engine is running or the key is on because the circut is live but this is really not a problum. there is plenty of protection built into the circut. If this is a concern dont run high amprage devices on the trailer with the key on. The isolators that are added go one step further and prevent any back flow from the trucks battery even when the circut is live, Yes it is an added layer of protection but I dont thik its nessesary for our uses.

CT03911

dgmark,

I have the Tundra tow wiring diagram. I see all the fuses and relays you mention.

I thought an isolator was a more complicated device than a relay. You are saying the "SUB BATT" relay is effectively an isolator.

It does so by protecting against battery drain because it is open with the key off.
Ok, got that part. Makes sense. Probably all I care about too but....

Does it also separate charging too, the other function of an isolator? The tow system wiring diagram I have does not show north of the "SUB BATT" fuse. I can't tell if the alternator feeds the "SUB BATT" fuse and main battery seperately.

Bottom line: if the trailer house battery is way low and I put the tow vehicle key on does the tow vehicle battery drop to balance the two or is it truely isolated?

Thanks

CT03911

dgmark,

You answered my question as I was typing it.

Ok. Got it. The Tundra, and presumably other makes, has some protection and probably will do a decent job charging a trailer house battery.

With the truck key off you can't discharge the truck battery anyways.

It does sound as if I had a fully discharged trailer batttery and THEN turned on the truck key to start it, the starting battery would try to equalize with the trailer battery.

I will either add an isolator then or just be careful to not discharge the trailer too much before trying to start the truck.

A solar panel or shore power solves all this.
Thanks.
Dennnis

dgmark

Go solar thats what I have on mine, works great. Also if the battery is dead just start the truck before hooking up the trailer.