battery doesn't seem to be charging while driving

GibW · October 2019

On our TV, we need to have the headlights on to produce enough to charge the camper battery. Otherwise the alternator simply puts out the minimum needed for the TV. Sounds silly but our dealer tested it with a multimeter.... lights off only read 12.6. Lights on read 13.6. We keep the lights on when towing and it now keeps the battery charged and the refrigerator cold.

ChanW · October 2019

@GrandmasKid,

An adapter. I didn't know there was such a thing! Who makes it? How is it connected? Can I have a photo? Really curious... (Thanks!)

Sharon_is_SAM · October 2019

@GrandmasKid - these links may shed some light on your issue. I think that @JEB has a good point. The draw from the frig may be too much.

https://www.toyotanation.com/threads/is-there-an-alternator.254002/

http://www.elearnaid.com/whyis12voban.html

Well, here it says the trailer battery must be fully charged before towing. https://www.etrailer.com/question-36042.html

This link is about someone that uses a separate connection to charge their RV battery while in camp. http://www.rvitch.com/forum/index.php?action=printpage;topic=76149.0

https://www.etrailer.com/question-240636.html

GrandmasKid · October 2019

ChanW said:

@GrandmasKid,
An adapter. I didn't know there was such a thing! Who makes it? How is it connected? Can I have a photo? Really curious... (Thanks!)

Image: https://us.v-cdn.net/5021717/uploads/editor/bp/b67on1nljyo3.jpg

I
This may be where my problem is coming from.

ChanW · October 2019

@GrandmasKid, so it looks like (and I think you said) you have a separate 12v-supply wire that leads from your TV battery to the 9pin connector.

Two things are necessary with that 12 volt supply...

1 - the size of the wire - it should be 8 gauge minimum, to accommodate the draw that the 3way refrigerator demands on 12v (if I remember it's 11A).

2 - you also need a ground wire of the same gauge running back to the battery. There's likely to be too much resistance encountered if you only depend on a simple ground to the TV frame.

The large gauge is also needed if you're expecting to charge a highly discharged battery - which creates more draw on the system.

In either case though, you will probably need a higher output alternator, one that's intended to accommodate a camper. Our Tacoma, for example, without the 'tow package', does not put out a charge designed to charge a "house battery", such as the Tab's, even though we have a good size 12v charge line going to the 9pin.

GrandmasKid · October 2019

Sharon_is_SAM said:

@GrandmasKid - these links may shed some light on your issue. I think that @JEB has a good point. The draw from the frig may be too much.

https://www.toyotanation.com/threads/is-there-an-alternator.254002/

http://www.elearnaid.com/whyis12voban.html

Well, here it says the trailer battery must be fully charged before towing. https://www.etrailer.com/question-36042.html

This link is about someone that uses a separate connection to charge their RV battery while in camp. http://www.rvitch.com/forum/index.php?action=printpage;topic=76149.0

https://www.etrailer.com/question-240636.html

Sharon_is_Sam Thanks so much for these insightful articles. It gives me hope that someone thinks the Highlander Hybrid is the "ultimate tow vehicle." I'm thinking about taking my 4 pin to seven pin adapter apart to see if there's a loose connection in there, but I'm not going to do that until I get my alligator clips for my multimeter so I can do some more testing first. Thanks very much for your help.

GrandmasKid · October 2019

ChanW said:

@GrandmasKid, so it looks like (and I think you said) you have a separate 12v-supply wire that leads from your TV battery to the 9pin connector.
Two things are necessary with that 12 volt supply...
1 - the size of the wire - it should be 8 gauge minimum, to accommodate the draw that the 3way refrigerator demands on 12v (if I remember it's 11A).
2 - you also need a ground wire of the same gauge running back to the battery. There's likely to be too much resistance encountered if you only depend on a simple ground to the TV frame.
The large gauge is also needed if you're expecting to charge a highly discharged battery - which creates more draw on the system.
In either case though, you will probably need a higher output alternator, one that's intended to accommodate a camper. Our Tacoma, for example, without the 'tow package', does not put out a charge designed to charge a "house battery", such as the Tab's, even though we have a good size 12v charge line going to the 9pin.

ChanW- Thanks for your input. I don't know the gauge of my charge line wire installed by my T@B dealer, but it looks pretty thick. I suppose I do have a simple ground to the frame of the T@B trailer. I start out towing with both batteries charged all the way up but my house battery depletes pretty quickly with the frig running while I tow. I'm considering giving up on the Norcold and buying a good cooler to keep inside the TV, but I still want to charge the T@B battery enough so that it's full when I get to camp. Thanks for your help.

N7SHG_Ham · October 2019

In that picture, does the wire beside the four way hook to something? There is no charge line in that four way, so you would need someway to hook the vehicle charge line to the trailer.

The discussion about wire gauge is worth paying attention to details too.

In the FB fourms this has been discussed lots. Basically the three way fridge can NOT be run on 12v even with working charge line without draining the tab battery, ghetto wiring will be worse than properly wired, but the physics of it in no case allows you to arrive with fully charged battery in the tab.

EDIT to add well there is a possible way, but it requires good proper wiring and a DC-DC charger in the Tab and that is still no guarantee, but goes a long way toward solving the issue.

Bayliss · October 2019

@GrandmasKid, I think you really should do yourself a big favor and get your tow vehicle properly wired for a 7-way plug, with proper sized wiring for the charge line. I think you will be glad you did and find it worth the cost to get it done.

GrandmasKid · October 2019

Bayliss said:

@GrandmasKid, I think you really should do yourself a big favor and get your tow vehicle properly wired for a 7-way plug, with proper sized wiring for the charge line. I think you will be glad you did and find it worth the cost to get it done.

Yes, The wire beside the 4 way connects to the charge line from the TV starter battery. Odly enough Toyota does not sell or install a seven post connector harness for this vehicle even though Toyota installed the hitch, so I got the T@B dealer to do it. I made the assumption that the dealer knew what they were doing. It has worked for 22K miles over the last two years but does not keep the house battery charged while running the refrigerator. Now I'm just trying to figure out if the charge line can work to keep the T@B battery charged without running the refrigerator.

N7SHG_Ham · October 2019

@GrandmasKid yes start with fridge off and see if that works.

Here is ultimate setup

https://www.adventurousway.com/blog/rv-electrical-upgrade-part-3-dc-charger-truck-12v-socket

ChanW · October 2019

@GrandmasKid, I'm interested to know how the hybrid does with charging output for a camper.

Let us know what you figure out!

GrandmasKid · October 2019

It's raining all day here so I'm not outside working on T@B electrics, but I have run across some interesting info. from someone using a Highlander Hybrid as a big efficient generator while they're camping!

https://www.popupexplorer.com/forum/index.php?topic=76149.0

ChanW · October 2019

@GrandmasKid, after thinking it over, (reading some of those links posted above), I think I may be wrong about running the negative 12v line all the way back to the battery...

From what others have written, it sounds as though the current sensing function of the 'smart alternator' might depend on the chassis-ground-return of the system. I suppose that, as long as you have a healthy vehicle ground system, your negative 12v would be fine going through the chassis ground.

But I don't think that your 4pin has a big enough ground wire coming off of it to provide a good path for higher amps though, so you might need to beef that ground wire up somehow.

The 4pin is intended as a supply for brake/turn/tail lights, which don't demand quite so much power...

Maybe someone with more knowledge of modern automotive charging systems can clarify...

GrandmasKid · October 2019

I wonder. I have an auxiliary power source in the rear of the TV (like a cigaret lighter socket). It's inside the car but close to the rear hatch. I wonder if current from it can be routed to the T@B battery. It's labeled 12v/120 watts. I think it's on a 20 amp fuse. If I did that would I need a controller of some sort to keep from overcharging the battery or perhaps a DC to DC charger? Those chargers are pretty pricey and I'm not sure how or where I would mount one. It's pretty obvious I'm a complete novice at solving electrical problems.

Ratkity · October 2019

My 2018 Ford truck's "hot" wire does not put out a charge until the 7-pin is connected and it detects a complete circuit. I found this out because I had my electric hitch set up to use the TV's battery to raise and lower the camper. Keep in mind, I no longer have a light T@B, but have a tiny toy hauler. The tongue weight is 540#. I got around this by connecting the hot wire to the headlight/running lights. I turn them on and have a hot wire.

The smart alternator in the truck boosts the amount of amperage when it senses a complete circuit. New trucks and SUVs seem to be going to this technology.

Unless you have an ARB cooler as a frig, turning on the 12V frig will not only leave you with a dead T@B battery, it'll leave you with a dead starter battery. I'm going to make an assumption that there's protection against draining the hybrid's main batteries. Putting a wire straight from your starter battery to the T@B battery is dangerous without putting protection against draining your TV's battery.

Please go to a place like UHaul and see how your TV can have a 7-pin installed. You may never have the amperage to charge your T@B battery, but you get backup lights and a tighter connection.

Remember the amperage for a non-hybrid vehicle that is sending a charge to the camper battery is a trickle charge. You cannot charge the battery in 2-hrs or 12-hrs from 50% depletion. You need an overnight charge without any loads. Keep in mind that you have phantom power in your camper that the T@B battery is trying to keep up with. The solar charger is the same. It's a trickle charge. If you use 15% of your battery overnight or the day before, then your solar could top off your battery nicely. It may also keep up with the phantom power drain if you stop off for lunch somewhere.

GrandmasKid · November 2019

Finally I've figured out that my problem was that 4way flat to seven way round adapter that I showed a picture of (see above). It was corroded internally but worked intermittently until it failed completely. It has been kept outside over the last two years and 22K miles with a few trips to the salt air of Florida. I've bought a new one and now everything is working well. I'll keep the new adapter out of the weather when I'm not towing. Is it a good idea to put some dielectric grease on the contacts? I haven't had time to evaluate the trickle charge to the trailer battery. I'll let you know. Thanks for all the advice.

Horigan · November 2019

GrandmasKid said:

... 4pin flat to 7 blade adapter.

Yes, dielectric grease on the contacts is a good idea. I spray Corrosion-X myself, including inside the 7-way plug.

ChanW · November 2019

Glad to hear it was 'simple'!

Sharon_is_SAM · November 2019

Please keep us posted. It will be nice to have some history of a hybrid TV charging ability.

GrandmasKid · November 2019

Just evaluated my Hybrid Highlander/T@B Outback electrical situation as best I can without taking a road trip. Since I got a new 4 way flat to 7 way round adapter that seems to have solved my problem. Without having the Norcold frig on the voltage on the camper battery jumped from 12.7V to 13.5V so I'm getting a charge to the battery, With the frig turned on the voltage dropped back down to 12.7V so I don't know if the charge can keep up with the amperage demands of the Norcold. I think the amperage supply problem is not with the tow vehicle (TV). I suspect the wiring of the adapter can only handle so much amperage. The charge line from TV battery appears to be about 10 gauge but the ground wire from the adapter is looks a little thinner, perhaps 12 gauge. Also there are connectors and I don't know how many amps they can carry. I need to plan a road trip, perhaps a dive trip to the Florida Keys, to further evaluate running the Norcold while towing. I'm not too worried about depleting the T@B battery as on the last long trip I depleted the AGM T@B to 35% and I don't think I hurt it as it seems to accept and keep its charge ok. I'll certainly monitor that battery closely as I drive and let you know how it goes. Happy camping!

N7SHG_Ham · November 2019

@GrandmasKid I think your issues will continue with your wiring setup. No way to nicely say your wiring setup is about as amatuer as I have ever seen. That adapter and depending on the ground in the four pin just is going to be a continuous issue. The ground wire in the four pin was meant as return path for the exterior trailer lights only and is way undersized for the current you need to charge and run the three way fridge on battery.

You mentioned someplace up above about no current was measured with your new meter. Did you read instructions about measuring current? You need to have the meter in series with the load to measure current, voltage is measured in parallel so you might of not been using the meter properly?

It is a bit of a chore to wire in a seven pin properly if your TV didn't come that way and I am assuming it didn't? Also, you should have the charge line via an ignition on relay so it only gets power when the TV is running, this will avoid killing your TV battery when the TV is not running and the trailer is plugged to TV.

GrandmasKid · November 2019

The wiring setup was originally installed by the dealer that sold me the T@B new in 2017. I did make the assumption they knew what they were doing. The charge line is fine directly from the TV battery with a circuit breaker in the line. The new adapter has a separate ground wire and I ran a ground wire from it to the frame of the TV. That ground wire is 10 gauge solid copper and shoud handle the amperage just fine. The grounding for the charge is not going through the 4way flat. Yes I read the instructions on how to use the multimeter but have not used it to measure the current through the new adapter yet. The current through the old corroded adapter was next to nothing. My Toyota Highlander Hybrid has a hitch installed by Toyota but Toyota does not sell or install a seven way harness for that vehicle so the only option to tow a T@B with that vehicle is by using a 4way to 7blade adapter for the lights. For the charge line that is separate from the lighting. I'm happy that the lights are working well and the charge line is delivering good voltage to the T@B battery. It's still a question as to whether the charge line can keep up with the high demand of the Norcold refrigerator, which I hear is about 13 amps.

Michigan_Mike · November 2019

GrandmasKid said:

I have a seperate charge line from the TV starter battery to the rear of the car that comes out next to the 4 pin flat receptacle. From there the charge line connects to an adapter for the seven blade adapter. I'm in the process of following that further but I need some aligator clip leads that should be here in a couple of days. Maybe there's a fault on the adapter. I should know soon. Thanks for your help.

As Verna noted above, your trailer battery WILL NOT be charging as your vehicle has a 4-pin adapter. You need to have a 7-pin harness wired into your tow vehicle and eliminate the 4-wire hookup (along with a dedicated charge line) to allow the vehicle to charge up your trailer battery. 👍🏻

N7SHG_Ham · November 2019

None of your photos showed both a positive and negative wire from the adapter to the tow vehicle, you can understand why folks trying to help may have suggestions that are already implemented.

If you can access FB, read this thread paying attention to what Bob Peloquin has to say. He actually tows with a Highlander Hybrid, BUT I don't know if he has shared how his is wired?

https://www.facebook.com/groups/24931511064/permalink/10156170036021065/

Verna · November 2019

@GrandmasKid, I hope you realize we are looking out for your best interest. The last 3 of us who have commented about your need for a 7 pin plug on your Highlander together have decades of experience in both electricity and 12 to 52V DC voltage.

Please believe we would never send you on a wild goose chase. We want the best T@Bbing experience for you without puzzling failures hindering you from have the fun camping that you should have.

GrandmasKid · November 2019

I do appreciate all the comments and advice and am very glad this forum exist for us nonprofessionals. There are no seven way harnesses available for my vehicle. Only a four way harness exist, thus the need for an adapter for the lighting to the seven way plug and a separate charge and ground line to the 7 way plug. I'll let folks know how it works out. I think it should be fine and better than what the dealer installed. Understand that what the dealer installed worked for two years and 22K miles before it failed from corrosion. It just was not charging enough to keep up with the refrigerator which I see is a common problem with tow vehicles which don't have a "tow package." Happy camping.

Marceline · November 2019

GrandmasKid said:

My Toyota Highlander Hybrid has a hitch installed by Toyota but Toyota does not sell or install a seven way harness for that vehicle so the only option to tow a T@B with that vehicle is by using a 4way to 7blade adapter for the lights.

Just because Toyota doesn’t sell it doesn’t mean that it doesn’t exist.

Here’s a discussion on eTrailer about how to wire a 7pin on a Highlander

(https://www.etrailer.com/question-9034.html). I’m not sure if there’s any difference if it’s a hybrid model. But I’ve found the folks at eTrailer to be very responsive and I think they’ll help you assemble the right kit to get the job done correctly.

I think the kind of adapter that you’ve been using should really be viewed as a temporary measure and not a permanent solution.

PS. What are you using for a brake controller?

GrandmasKid · November 2019

There is a difference between the hybrid and non-hybrid. The hybrid models are only rated to tow up to 3,000 pounds and the gas models to 5000 pounds mostly due to the lighter duty CV transmission I think. I'll look again but I don't believe anyone sells a 7way harness for my Highlander Hybrid, and I have looked at Etrailer. The hybrid doesn't have a traditional alternator but instead uses a controller that controlls the charge from the big drive battery bank to the starter battery and the wiring for the harness is different between the two types of Highlanders. I think that my new setup will be fine as long as I keep the contacts protected. I’ll let you know.

Marceline · November 2019

GrandmasKid said:

There is a difference between the hybrid and non-hybrid. The hybrid models are only rated to tow up to 3,000 pounds and the gas models to 5000 pounds mostly due to the lighter duty CV transmission I think. I'll look again but I don't believe anyone sells a 7way harness for my Highlander Hybrid, and I have looked at Etrailer. The hybrid doesn't have a traditional alternator but instead uses a controller that controlls the charge from the big drive battery bank to the starter battery and the wiring for the harness is different between the two types of Highlanders. I think that my new setup will be fine as long as I keep the contacts protected. I’ll let you know.

Unlike other online merchants, I’ve found the people at eTrailer to be pretty knowledgeable. I think that it would be worth your while to read the info at the link I posted above and then contact them with your hybrid-specific questions. The 4-pin to 7-pin hardwire adapter that they sell (https://www.etrailer.com/p-ETBC7.html) isn’t Toyota-specific, but I bet that you can install it on your vehicle (here’s info about installing it in a 2017 Highlander Hybrid: https://www.etrailer.com/question-368132.html).

Are you using a wireless brake controller?

battery doesn't seem to be charging while driving

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