TV Charging Battery

[Kirk's Keystone Outback.]

I have a 2013 F150 and a 2020 F250, both with the factory tow package. On several occasions I noticed that when I connect the TT umbilical cord to either truck, I don’t see a rise in battery voltage when the vehicle is running. I only started looking more closely after I connected a volt meter on the front of trailer.
Is it true that the tow vehicle is supposed to trickle charge the battery? If so, how can I prove it’s actually charging the battery? After performing a quick test today, I saw no rise in battery voltage with truck running.
Usually the trailer is connected to shore power while parked at home and reads 13.8, and holds between 12.8 and 13 vdc when unplugged.
Thanks in advance for any clarification.

[NH_Bulldog]

On my 2015 F150 I recall having to add a relay under the hood to get the charge function to work. On my 2022 F250 it just works with no alteration needed. I do know the truck has to be running, but I can’t say whether it needs to be in gear or not. What I can tell you is that after my last boondocking 2 night stay, the batteries were fully charged by the time we got to our next site after a day of driving.

[chuckster57]

Most Fords that I know of require a relay in the under hood fuse/relay center to activate the charge line. On my '94 the ignition has to be in the run position also, meaning the engine should be running.

Check your owners manuals for the right relay and which slot it goes in.

[Kirk's Keystone Outback.]

Originally Posted by NH_Bulldog

On my 2015 F150 I recall having to add a relay under the hood to get the charge function to work. On my 2022 F250 it just works with no alteration needed. I do know the truck has to be running, but I can’t say whether it needs to be in gear or not. What I can tell you is that after my last boondocking 2 night stay, the batteries were fully charged by the time we got to our next site after a day of driving.

I suppose that would be a good way to test it. I have a trip planned in April. I can try slightly discharging them and see if it recovers, but I’m only driving an hour and a half, but should still show something. My experiment today was with the F150, so I’ll pay a little more attention when I tow with the F250. Thanks for that information.

[Kirk's Keystone Outback.]

Originally Posted by chuckster57

Most Fords that I know of require a relay in the under hood fuse/relay center to activate the charge line. On my '94 the ignition has to be in the run position also, meaning the engine should be running.

Check your owners manuals for the right relay and which slot it goes in.

I knew I would get the right answers here.
My owners manual for 2013 F150 does not show a relay installed, so that answers that question. New question: Relay Part Number?
In my 2020 F250 manual, it does show a 30 amp fuse for Trailer Tow Battery Charge. So that’s good news. I’ll verify it’s actually working when able to swap trucks around.

Thanks for the quick responses, Chuck and Rob.

[Kirk's Keystone Outback.]

On another note relating to the charging system that I’ve been curious about:
Can the TV be connected and running at the same time when shore power is on and proving power without damaging the converter or alternator? My question is kinda related to a house generator providing power the same time the power lines are providing power, which is never good.
Is there a priority for power, shore over truck?

[JRTJH]

On F150's around 2010-2015 (maybe even today's models), Ford included a plastic bag in the glove compartment with a fuse and a relay to "enable trailer battery charging capability"... Some dealers installed the parts and threw the bag away, some left the bag in the glove box and left it up to the owner to install them, some took the bag and put it in the parts department with intent to sell it to the owner if they wanted the parts... So, no idea what the status of your parts might be.

That said, if the fuse and relay are not installed, your truck will not charge a trailer battery.

Here's what to look for: Under the hood is a "high voltage power distribution box"... Open that box and check for a relay in space #9 and a fuse in space #21 (not sure on your truck if it's space 21A or 21B).

Part numbers for the 2013 F150:
Relay: 8L8T-14B192-AA
Fuse: 6E5T-14A094-BA And these may have changed for different year trucks. The fuse is a 30 amp and the relay is available at AutoZone and NAPA as well as any Ford dealer.

If those are present and working, with the truck running, you should have 12 volt power to the 7 pin umbilical connector on the truck. (measure for 12 VDC between pins 1 and 4) Here is a diagram of the trailer end and the truck end of the 7 pin umbilical. Some trucks have a "interlock" to prevent trailer power with the truck in park. So you may have to put your truck in gear with the engine running to get power to the umbilical connector.

The wire to the umbilical Pins 1 and 4 are 16 Ga, so you won't get a lot of amperage to the battery. If the battery is "nearly dead" then after towing an hour or so, you're still going to have a "uncharged trailer battery"... It isn't going to be a "high capacity charging system" but better described as a "efficient trickle charger"... All day towing (8-10 hours) may show a significant charge increase, but you'll hardly notice a measurable change after a 1-2 hour tow.

[JRTJH]

Originally Posted by Kirk's Keystone Outback.

On another note relating to the charging system that I’ve been curious about:
Can the TV be connected and running at the same time when shore power is on and proving power without damaging the converter or alternator? My question is kinda related to a house generator providing power the same time the power lines are providing power, which is never good.
Is there a priority for power, shore over truck?

A running truck connected to the trailer AND shore power providing a charge voltage via the converter/charger is not something that I'd do on a regular basis.

That said, it's also not something that would cause me to run as far as possible, dive in a ditch and cover my head to wait for the explosion....

It's not a "immediate damage will result" situation, and likely won't damage anything, but just like it's better to turn off water to a garden hose to stop the flow rather than fold the hose over on itself to stop the flow, doing it the "proper way" will keep your garden hose "round and not leaking at the fold" for a lot longer, and IMO, using or connecting one charging source at a time just seems like a better way to protect equipment...

As a sidenote, if the WFCO converter/charger "senses a charging voltage from the truck charging system" (usually 13.4 - 13.6 VDC, the converter/charger will reduce/stop the charging process and will revert to the "float mode" which is 13.2 VDC, so with the truck connected, your converter/charger will "essentially shut itself down"....

[markcee]

FYI...don't know when you are trying to measure voltage, but I believe I've also read on the f150forum.com that the brake pedal must be pushed before voltage is sent/detectable from Ford's integrated trailer brake controller (ITBC).

[Kirk's Keystone Outback.]

Originally Posted by JRTJH

A running truck connected to the trailer AND shore power providing a charge voltage via the converter/charger is not something that I'd do on a regular basis.

That said, it's also not something that would cause me to run as far as possible, dive in a ditch and cover my head to wait for the explosion....

It's not a "immediate damage will result" situation, and likely won't damage anything, but just like it's better to turn off water to a garden hose to stop the flow rather than fold the hose over on itself to stop the flow, doing it the "proper way" will keep your garden hose "round and not leaking at the fold" for a lot longer, and IMO, using or connecting one charging source at a time just seems like a better way to protect equipment...

As a sidenote, if the WFCO converter/charger "senses a charging voltage from the truck charging system" (usually 13.4 - 13.6 VDC, the converter/charger will reduce/stop the charging process and will revert to the "float mode" which is 13.2 VDC, so with the truck connected, your converter/charger will "essentially shut itself down"....

Thank you John for addressing both questions.
As soon as I read about the possibility of there being fuses and relays in the glove compartment, I couldn’t run to the truck fast enough to look, and guess what, there was a relay and a 30 amp fuse. I verified positions with the manual and you were 100% correct on position 9 and 21. Guess what, all systems are a go. Charging at 13 volts!!!

The contributors to this forum are nothing short of amazing.
Thanks to all who chimed in for a swift resolution.

[curtiscapk]

Wow this is why I love forums. We've had the new camper out twice. once to the local lake 20 miles from home. 2nd one was to our daughters 200 miles from home. on the second trip I noticed the camper battery was at half when we arrived at campsite. After plugging into shore power it charged back up. I wasn't thinking of the new DC fridge running on battery the whole trip there.

The old camper pulled nothing off battery during trips. My first f150 had some wires and fuses in a bag in the glovebox when I bought it which I put in my toolbox. (wasn't towing anything then) The bag sat there for 2.5 years until I had a blowout @ 70 MPH that sent me into the crossover cables and totaled the truck.

When I got the new (current) truck it had a relay and fuse in a bag. Well I put that in the other bag in my toolbox.
I assumed with the factory tow package everything would be correct on the 2013 f150. I was wrong! After reading this post I went out to the fuse box and while the fuse was there the relay wasn't!

Go to the bag and bingo! Instructions and everything else! 2 fuses 2 relays and wiring for a controller!

Thanks guys! We're going to Surfside Beach TX in 5 weeks, The battery would've been smoked running the fridge without a charge from TV. Along with the food we're taking!

[Kirk's Keystone Outback.]

Originally Posted by curtiscapk

Wow this is why I love forums. We've had the new camper out twice. once to the local lake 20 miles from home. 2nd one was to our daughters 200 miles from home. on the second trip I noticed the camper battery was at half when we arrived at campsite. After plugging into shore power it charged back up. I wasn't thinking of the new DC fridge running on battery the whole trip there.

The old camper pulled nothing off battery during trips. My first f150 had some wires and fuses in a bag in the glovebox when I bought it which I put in my toolbox. (wasn't towing anything then) The bag sat there for 2.5 years until I had a blowout @ 70 MPH that sent me into the crossover cables and totaled the truck.

When I got the new (current) truck it had a relay and fuse in a bag. Well I put that in the other bag in my toolbox.
I assumed with the factory tow package everything would be correct on the 2013 f150. I was wrong! After reading this post I went out to the fuse box and while the fuse was there the relay wasn't!

Go to the bag and bingo! Instructions and everything else! 2 fuses 2 relays and wiring for a controller!

Thanks guys! We're going to Surfside Beach TX in 5 weeks, The battery would've been smoked running the fridge without a charge from TV. Along with the food we're taking!

Being the original poster, I'm happy to know that this was also helpful to somebody else. Thanks for sharing your results.