F150 inverter and RV charge line

[AC0GV]

I am hitting the road this week and will be thinking about two projects as I travel.
#1) Has anyone replaced the stock (under seat) Ford inverter with a pure sign wave unit? What did you use? I’m told the stock unit is more of a modified square wave then sign wave.
#2) I would like to boost the 12 volt line to the RV up to more like 14 VDC to better charge the battery, not just run things. 12 VDC will NOT charge a 12 volt battery but I’m not sure where to mount the device.

[Raspy]

Originally Posted by AC0GV

I am hitting the road this week and will be thinking about two projects as I travel.
#1) Has anyone replaced the stock (under seat) Ford inverter with a pure sign wave unit? What did you use? I’m told the stock unit is more of a modified square wave then sign wave.
#2) I would like to boost the 12 volt line to the RV up to more like 14 VDC to better charge the battery, not just run things. 12 VDC will NOT charge a 12 volt battery but I’m not sure where to mount the device.

12 Volts is a category, it doesn't mean the voltage is 12. My F250 Tremor runs at a constant 14.5 volts the entire time it is running, and it charges the trailer batteries just fine through my Anderson plug with #4 wire to the rear bumper. Don't count on the seven pin hot wire to do much. If you want real trailer charging, run a new circuit just for that purpose. An Anderson plug is ideal for this. See the included pic of the plug on the rear bumper:

[Raspy]

Originally Posted by AC0GV

I am hitting the road this week and will be thinking about two projects as I travel.
#1) Has anyone replaced the stock (under seat) Ford inverter with a pure sign wave unit? What did you use? I’m told the stock unit is more of a modified square wave then sign wave.

Just out of curiosity, is there something you want to run that the modified square wave inverter is not compatible with?

[AC0GV]

Originally Posted by Raspy

Just out of curiosity, is there something you want to run that the modified square wave inverter is not compatible with?

,, some chargers fail when plugged into non sine waves. Many contractors will not allow their tools to be charged with a square wave. Also some home entertainment equipment will buss when run on a low quality inverter.

The problem is that than no one MAKES a high quality 400 - 500 watt inverter.

[AC0GV]

Originally Posted by Raspy

12 Volts is a category, it doesn't mean the voltage is 12. My F250 Tremor runs at a constant 14.5 volts the entire time it is running, and it charges the trailer batteries just fine through my Anderson plug with #4 wire to the rear bumper. Don't count on the seven pin hot wire to do much. If you want real trailer charging, run a new circuit just for that purpose. An Anderson plug is ideal for this. See the included pic of the plug on the rear bumper:

Because the 12 volt in the 7 pin is very regulated. (and I already have a small Anderson on the RV for the solar panel.)

[Raspy]

Originally Posted by AC0GV

Because the 12 volt in the 7 pin is very regulated. (and I already have a small Anderson on the RV for the solar panel.)

The seven pin 12v line is very low amps. Add an Anderson, as shown, to plug your trailer into and feed the trailer with 14.5 volts directly to the house battery. The Anderson connects to the truck battery with only a circuit breaker. I've been charging my trailer that way for a long time. Works fine.

You mentioned that the Ford inverter was a modified square wave. That means it is not a true square wave. Have you actually had any trouble with it? I've been running with older square wave inverters for a long time and never had any trouble with anything. The microwave might make more noise, but the phone and laptop don't seem to mind it at all. I'm just wondering if you have actually had a problem or not. It's hard to imagine that Ford would install an inverter that nobody could use, or one that would ruin anything plugged into it. The one in my F250 works just fine.

[AC0GV]

Originally Posted by Raspy

The seven pin 12v line is very low amps. Add an Anderson, as shown, to plug your trailer into and feed the trailer with 14.5 volts directly to the house battery. The Anderson connects to the truck battery with only a circuit breaker. I've been charging my trailer that way for a long time. Works fine.

You mentioned that the Ford inverter was a modified square wave. That means it is not a true square wave. Have you actually had any trouble with it? I've been running with older square wave inverters for a long time and never had any trouble with anything. The microwave might make more noise, but the phone and laptop don't seem to mind it at all. I'm just wondering if you have actually had a problem or not. It's hard to imagine that Ford would install an inverter that nobody could use, or one that would ruin anything plugged into it. The one in my F250 works just fine.

But I have looked at the waveform that others have recorded. It is not smooth.
Do you unplug the fuse to the 12 volt line in the seven pin when you run the other charge line?

[CarlD]

I have the 1000 watt version of this inverter and it works great. This one is 400 watts.

https://wagan.com/collections/power-...s/pureline-400

[Raspy]

Originally Posted by AC0GV

Do you unplug the fuse to the 12 volt line in the seven pin when you run the other charge line?

The 12v line in the seven pin pigtail is not connected in my trailer. The truck plug has 12 volts, but that wire is not connected on the trailer side. I don't think it would hurt anything if it was, but I want much more amperage than it will provide, and my system it is not designed to use that wire.

You may be overthinking all of this.

[AlanKilian]

Originally Posted by AC0GV

The problem is that than no one MAKES a high quality 400 - 500 watt inverter.

I'm not an inverter user, but are you saying all of these inverters for sale are low quality?

https://www.amazon.com/500-watt-pure...+wave+inverter

I mean this US$50 one has 2,600 ratings and 92% of them are 4 or 5 stars.
Someone even posted oscilloscope screenshots of the output waveform!
https://www.amazon.com/BESTEK-300Wat...0916476&sr=8-1

[CarlD]

One thing to be aware of if you use an dedicated line like Raspy has is a means to disconnect it from the truck when the truck is turned off or you risk discharging the truck battery. There are different methods to implement this. Here are 2 for example: 1. unplug the Anderson connector. 2. Install a relay with the coil connected to the 7 pin connector trailer feed wire (this is what I have).

[Raspy]

Originally Posted by CarlD

One thing to be aware of if you use an dedicated line like Raspy has is a means to disconnect it from the truck when the truck is turned off or you risk discharging the truck battery. There are different methods to implement this. Here are 2 for example: 1. unplug the Anderson connector. 2. Install a relay with the coil connected to the 7 pin connector trailer feed wire (this is what I have).

This is an important consideration.

I'm pretty casual about it, but do disconnect if we are staying for more than one night. The relay that is controlled by the seven pin hot, is a good idea, but I don't think my Ram ever shuts off that hot lead. Never used it on the F250.

If you have solar, the trailer will charge the truck through the Anderson too, if needed. Or, if you have a suitcase solar, it can plug directly into the truck Anderson if needed. Either the trailer Anderson, or the truck Anderson can be used to run a compressor, or electric hydraulic jack too. Very useful.

I used to charge the trailer, while camping, with jumper cables from the truck. Then I had a ranger come by and tell me I could not do that in the park. Huh? The Anderson is the same thing, but doesn't look the same.

[John in Michigan]

Kenneth, here is a REDARC article on how to charge auxiliary batteries when your vehicle has a smart alternator, as most newer vehicles do.

https://redarcelectronics.com/blogs/...ut-alternators

REDARC is not the only company that produces good quality DC to DC chargers. DIYsolarforum has a good thread dealing with dc to dc chargers, including a table here:

https://diysolarforum.com/threads/dc...cussion.17211/

[Darwin Maring]

What equipment do you want to use that is so sensitive that a normal inverter will not work?

[Raspy]

Originally Posted by John in Michigan

Kenneth, here is a REDARC article on how to charge auxiliary batteries when your vehicle has a smart alternator, as most newer vehicles do.

https://redarcelectronics.com/blogs/...ut-alternators

REDARC is not the only company that produces good quality DC to DC chargers. DIYsolarforum has a good thread dealing with dc to dc chargers, including a table here:

https://diysolarforum.com/threads/dc...cussion.17211/

I charged my (4) 100 AH gel batteries in my trailer, directly from the smart charger in my Ram for over a year. No DC-DC converter. Just an Anderson plug fed by #6 wires from the battery. The alternator does not go to "float" until it senses that the batteries are charged. The alternator is watching the truck batteries, and the trailer batteries are a load placed directly on one of the truck batteries. This may not be the perfect system, but it certainly works well and is simple. A DC-DC charger, placed in the trailer, will prevent power from flowing back toward the truck, and it prevents the truck batteries from draining by not coming on until the voltage is high enough. Not being able to feed power back out of the trailer batteries means you cannot run other equipment from that plug, and it means you have to work around that problem in order to program the controller. The last one I had anything to do with, the owner could not program the controller because it would not feed power out the Anderson on the trailer. Even the RV shop could not make it work. So I suggested that the system was not defective, and to plug it into the truck to program it. Worked perfectly. This after hours of several people trying to figure it out! Sometimes simple is way better.

[parmm]

Get a good 12 VDC to 12 VDC battery charger (around $250) to run off you tow vehicle's 12 volt system and mount the charger near your trailer's battery bank.

[Raspy]

Originally Posted by parmm

Get a good 12 VDC to 12 VDC battery charger (around $250) to run off you tow vehicle's 12 volt system and mount the charger near your trailer's battery bank.

OK, and how do you power it? And why not do it the simpler way? Please be more specific and tell us why.

[Raz]

Most alternators run at about 14 volts. Most smart chargers start at 14.4 volts. My 1985 Napa 2 stage charger runs at about 13.8 volts. They all seem to work just fine. The term "smart" is a misnomer. With a "smart" charger, rather than use an analog compare circuit (like in my Napa), the control decisions are done in software. It's as "smart" as the person who programmed it. In the case of tow vehicle charging, the regulator has been replaced by the on board ECM controlling the output. Not surprising as there is so much electrical demand on even the simplest vehicle. With all due respect to John in Michigan, the REDARC article posted reads like a sale brochure; present a problem and provide a solution. The implication is that if the negative lead on your battery has circuitry then you need their product. My Nissan has current sense circuitry on the negative lead. If my alternator wasn't capable of charging my trailer battery then why would Nissan include a charge line in the factory installed trailer wiring?

The charge line connects the alternator (energy source) to the trailer battery. The charging current is

Icharge= (Vtow - V trailer)/ Rchargeline

Increase Vtow, the alternator output, you increase the charging current. Decrease the charge line resistance, bigger wire, same thing. Both are only true up to the limits of the alternator. If your alternator has already reached its maximum output then you need a bigger alternator. Many vehicles with a tow rating only provide wiring for trailer lights (4 pin). It could very well be that the folks who designed the vehicle thought adding a charge line was not a good idea!

Finally, consider this. A DC to DC converter will increase Vtow and thus increases the charging current. Power = Voltage x Current. Since the power goes up on the output, conservation of energy requires the power to go up on the input. But if the alternator is already at maximum capacity, there is no place for that power to come from. As such, I see no benefit in a DC to DC converter. What am I missing?

[CarlD]

Raz, You are not missing anything except an adequate alternator! Wire size or a DC-DC charger current setting will determine the charge rate.

A LFP battery, however, needs a DC-DC charger or CV/CC power supply because lead acid and LFP voltage levels are different.

[John in Michigan]

To the OP's battery charging question, every situation is different. How big is the battery bank? Lead acid or lithium? How many feet (EDIT: how many feet of actual wire) from the alternator to the battery bank? When using a DC to DC charger (or just a charging wire), determine the peak current needed while charging your battery bank. Is the wire gauge sufficient to carry the amperage? For example, a Victron Orion Tr Smart Charger Isolated 12/12-30 DC to DC charger may draw 40 amps or more while charging a battery bank.

Also, use your multi-meter and monitor charging current, etc.