Hi all!
When I get my truck, I am planning on installing a Cobra 1,500W inverter somewhere in the engine compartment. Has anybody done this? Any write ups? Anything to think about?
I want to use it to charge our trailer batteries when camping - sort of as an emergency backup. Of course, the engine would be running, and I'd install a 12V ON/OFF switch. What I'd be doing is using the 110V output of the inverter to connect the trailer to as charging through the 7 pin harness is not very effective; all you get is sort of a trickle charge I believe.
I'd expect about a absolute max 650W draw out of the inverter, with losses maybe 800 - 1000W on the input side. At 12V from the battery / alternator, that would be under 80Amps. It looks like the F150 alternator is rated at 155 Amp, 2100 Watt/220 Amp, 3000 Watt; not sure why there are two numbers (idle / running maybe???), but both numbers would be ok for the job. Especially since the real draw would be likely significantly lower than the 80A I assumed as worst case.
As I expect to use that only as an emergency backup - maybe once or twice a year when dry camping - I would like to avoid the extra cost, weight and hassle of a generator.

Thanks for any input on this! Feasible or not? What do you think?

 

I have a 600w pure sine wave inverter under my passenger seat to run my kids xbox 360 and whatever else that I may need in a jam.

 

Interesting! What gauge wire did you run to the battery? What fuse? How did you route the wires?
Any details you don't mind mentioning, I am interested.
Yes, pure sine is the ideal thing, but for the trailer charger / power center, I'd hope the mod sine is ok.

Thanks a lot!

 

With a 10 ga lead from the 7 pin, you should be seeing more than a trickle charge, and if what you are looking for is an emergency back up, wouldn't it be simpler to forget the inverter and just run a second fused charge line from your truck battery to a dedicated receptacle on the back for your trailer battery?

Check with an amp meter first as you may be surprised how many amps it will deliver. A modified sine wave will power your trailer converter, but an engine bay is not the environment I would choose for an inverter install.

good luck,

Steve

 

Steve, thanks a lot. Several good points you are making.
Hmmm, I think you are right, a few measurements of currents and charging voltage levels will not hurt. Of course, measuring the actual currents is not all that simple without the right equipment (shunt R & precision volt meter). But the charge voltages may do it.
I'll do that. What's the concerns about mounting an inverter in the engine bay? Fumes plus the possibility of sparks? I've been wondering about that myself also ....

 

Clamp meter will give you amperage in less than a minute.

Inverters are heat sensitive and mounting them in an engine bay is not recommended. I think what you are going to find is the output from your converter will be no more and likely less than a decent charge line from you truck battery with considerably more complexity and cost due given the inverter.

I know you maybe thinking the output from your converter will be its rating in charging your battery, but I can tell you from experience it will not be close.

Steve

 

Sure, I would take pictures but my foot is currently broken and I have 5 pins hanging out. lol. I used 4ga wire from lowes and ran it through the existing rubber grommet in the passenger side firewall. I used an audio in-line fuse like you can get from wally world.

I then routed it through the door floor door track thingy (sorry I am on my meds) and came out through the carpet slit near the floor heater vent. It was an easy run except it was a tight squeeze through the fire wall. I hope this helps. I had an 800 watt inverter in my f350 that was ran pretty much the same way but I used it all the time because I had two alts and batts.

 

Ok, where to start:
First, the Cobra inverter, like most of the cheap truck-stop inverters, is a piece of junk. "Modified sine wave" means there might be one step at zero on the way to Vmin or Vmax.
See: Solar power - Pure/true vs modified sine waves and inverters as an example

Real inverters are made by companies like Xantrex/Trace, Samlex, etc.

I have a 600-watt Samlex pure-sine inverter under one of my rear seats to power equipment in the vehicle. I'm running a second battery in the rear with 1/0ga. power from an isolation solenoid up front. Power from the master distribution panel is 4ga via a 100-amp breaker and high-current relay (to allow remote control from the front switch panel). At least a portion of the power distribution can be seen here:
http://www.tvsjr.com/truck/8_back.jpg

Inverters are temperature sensitive - most larger units are forced-air cooled via fans. They are also typically not designed for under-hood use. The unit needs to be installed inside the cab, climate-controlled.

You should review the installation manual:
https://cobra.com/Manuals/CPI1575_MANL.pdf

Cobra says 40C/105F as a maximum temperature for this unit. Engine bay temperatures will exceed this in seconds after startup, causing either damage to the unit or (if it's equipped) a thermal shutdown.

If you intend to install such a unit, all wiring should be at least 120% of the unit's maximum operating load. The unit is specified for 1500 watts maximum output at 83% efficiency, with a minimum input voltage of 10.4VDC. So... 1500 / 0.83 = 1807 watts input / 10.4 VDC = 173.772A * 1.2 (safety factor) = 208.52A. You will need to run 4/0ga. wire to make this run without excessive voltage drop (voltage drop leads to heating of the conductor, and ultimately a fire).

Neither the alternator nor the battery will sustain this load for long.

Now, all this being said, why do you want to convert 12V-->115VAC-->12V? Notice that 83% efficiency factor above... you'll see something similar (though slightly better) on the 115VAC-->12V conversion. So, you'll be giving away about 40% of your available energy as heat (heat that you have to deal with).

The factory trailer connector, with the relay and fuse installed, is limited to 30A. This should be sufficient to keep your trailer batteries charged under light to moderate loads. If you're intending to run your microwave, TV, computers, etc., then you need to look at a generator. The Honda EU-series generators are very nice, light, and quiet... and you can likely buy an EU2000 for what the inverter, cabling, fusing, etc. will cost. And, you put the runtime on a small, $1K generator - not a $35K-$50K truck.

If you choose to run from battery and want to charge off the truck... might I suggest putting the nose of the truck toward the trailer and employing a pair of jumper cables? It would be a whole lot less work, and must cheaper.

I speak with a bit of experience on in-vehicle wiring... this is the front half of the equipment console in my 09 F150:
http://www.tvsjr.com/truck/12_running.jpg

 

I agree with all your points and they parallel my own experince installing and servicing inverters. I was operating under the assumption the OP was searching for a more elegant solution that jumpers, but they certainly would serve purpose. Working with inverters, I tend to be less enthusiastic about their use. To me a proper inverter system means multiple batteries, large expensive fuses, and cables capable of moving serious amperage.

Steve

 

Holy smokes, tvsjr, you sure have a lot of experience routing inside the truck! That pic is impressive.
Thanks for all the replies! I am glad I posted here, lots of good input. For one, the engine bay is out, you convinced me, no question. Need to think more about the rest. The good thing about having an inverter is being able to also charge the laptop, and other small stuff.
And yes, in an emergency situation, as set of good jumper cables should do the job, agreed. Maybe I tried to "over-engineer" this.

Again: thanks, and now back to the planning / drawing board!
What an an amazing message board!

 

Yeah, Steve, I was looking for something a bit more "elegant", with a few side benefits (like plugging in the laptop or other small stuff).
You guys convinced me though. May just get that set of good jumper cables for emergencies (when the awning won't retract or the tongue won't move), and a small inverter with a cigarette lighter plug for really small things.

 

tvsjr, just looked again at the pic, and now I have to ask: what's all the electronics for? Looks like a bunch of CB radios, no?

 

I picked up a cheap cigarette model inverter at Best Buy that works fine for my laptop and similar.

Steve

 

If you want something more elegant, take a look at the Anderson Powerpole connectors. These are made in sizes from 15A to 600A - you'll commonly see them on electric golf carts and fork lifts. The 150A models should work nicely for your application. Consider installing a pigtail with one pair of connectors under the hood, and a matching connector on the trailer, with a jumper of appropriate length (again, think about current demand vs. length).

I've seen this done for vehicles that were frequently used for jump-starting purposes (courtesy patrol, etc.). A connector was installed under the hood, with the cable being a Powerpole on one end and jumper cables on the other. Hook the two jumpers up to the dead battery, then plug in to the service vehicle. The Powerpoles are enclosed so any arcing is contained inside, and the connection is away from the battery to eliminate the threat of explosion/fire from any gasses that might be present around the battery.

Again, you're putting a lot of strain on a $35K+ truck and a $300-$500 alternator. You still might be better served with a small generator... the small Hondas are very quiet and easy to maintain!

Radios, yes. CBs, no.

 

Can anybody help me out with what kind of isolator/coil relay to mount under the hood between the battery and a 1000w invertor I'm going to put in. Plan is to mount it (the solinoid) behind the battery on my dads F150 (2010). Already have the invertor mounted under the back seat to the floor. But striking out finding an isolator/coil solinoid type relay between battery and inverter.

Thanks for you help.
Sam