DC power inverter wiring questions.

My wife bought me a 5000 watt DC inverter for my truck. My goal is to mount it into one of the compartments of my trucks' service body. I've spent a week so far, researching the best way to hook this up. I wind up with more questions than answers. I have also searched the forum, but have not found what I'm looking for. I originaly thought I would wire it from one of my truck batteries. It is recommended though, that I use 4/0 battery cable. Only problem is that 4/0 cable is anywhere from $10 to $16 per foot. Even only needing about 10 feet, which will really be 20 feet, is going to be expensive. I would rather just buy a deep cycle battery, and mount that in the compartment with the inverter. Question though, could I run a separate wire from my alternator to keep this battery charged? Any other thoughts or suggestions? Thanks. John.

 

Why such a large inverter? 5000 watts will be pulling more than 400 amperes from the battery and unless you plan on filling the bed of the truck with 8D (or larger) deep cycle batteries you would kill any normal-sized automobile battery in a few minutes.

To answer this question: The answer is yes, but. You would need a device known as a charge divider to do it properly but a large silicon rectifier diode would also work, more or less.

 

If you need that much power, get a generator.

Otherwise as said above, if you use a lot of power from a car/truck battery, you will drain it and then the car/truck will not start!

When non-vehicle running power is needed from a truck, typically a 2nd battery is installed. Then you use power from that. Then the first battery is reserved for starting and running the truck. So you can run down the 2nd battery, but your truck will still start.

Then there is quite a bit to designing such a system with fuses, relays, proper size wires, etc. Here is one diagram...
http://www.kozmafamily.net/wp-conten...250_AuxBat.png

And here is a DC wire size chart. Protect wires with appropriate fuses...
Wire Gauge Amps Ratings for 12 volt Automotive Systems

 

A 5,000 watt inverter should not be run off a single battery. It should have its own separate bank of identical deep-cycle batteries.

Two of the biggest 6-volt golf cart batteries you can find, wired in series, is the minimum. Four would be better (two sets of two in series, and the sets wired in parallel).

A battery isolator allows the alternator to charge the auxiliary bank without draining the starting battery. It will automatically charge both the starting battery and the aux bank when the engine is running. When the engine is not running it will disconnect the starting battery from the aux bank.

On the other hand, you might not use the 5,000 watt inverter at its rated power all the time. What will the inverter be used for?

 

Keep in mind, this inverter will draw 500Amps at full load. You're going to need to paralell some 4/0 to run your inverter.

You will need a bay of Deep cycles to power this.

 

I think the original size was a typo. Hopefully the O/P will come back and let us know.

(Or maybe he is out looking for forklift batteries.)

 

It's not a typo. It's 5000 watts. That's why I posted. I'm not an expert, but I know there are experts like you guys to put me on the right path. I do have a Generator, But It can be a pain to load and unload, after every job. It weights about 300lbs. An inverter would be nice, because it could just stay in my truck. It would be used mainly for power tools. Reality is that I would need about 2000 watts, at any given time.

 

What kind of power tools? Do you use more then one at a time?

On the other side you may want to see if you can get a higher then standard alternator for your truck. Thirty plus years ago I remember being told emergency vehicles had special high output alternators. Maybe thats still true and you can get one to fit your truck.

 

At any given time, I may be usng a rotary hammer drill, sawzall, angle grinder, circular saw, and some times, 1000w halogen lights. The tools are used one at a time, but occasionally in conjunction with the halogen lights. I can get up to a 350 amp alternator that will fit my truck. I also found a battery isolator that would handle up to 500 amps.

 

Sounds like you are on the right track.

 

I would look at the long term cost of this. And that is the initial cost as well as the amount of fuel used to provide power.

Seems to me a generator would use a lot less fuel than a truck running.

And instead of figuring all that out and needing to be a math wiz, you could just look at what big corporations do (they like to save money!). Around here they have generators in their trucks. Perhaps cheaper in the long run to buy a separate generator for the truck?

Also look at recreational vehicles like motor homes. These also have generators to power things. (Instead of running the vehicle motor to provide power.)

 

I see the light. The long term cost would be north of $1500, not to mention having to maintain a bank of batteries. For that money, there are decent generators on Ebay. But, that's why I come here, and ask these questions. Thanks for good advice everyone.

 

Don't forget the battery charger. Even with an upgraded alternator the truck wouldn't be able to fully charge the aux bank during short runs from home to the job site and back. You would also need a multi-stage heavy duty charger and let it run all night.

There also may be business tax advantages to buying the genny. Fuel costs are deductible, but it's difficult to justify a deduction for the electricity costs of recharging a bank of batteries on your residential utility account.

Speaking of fuel costs, a 5,000 watt genny will use quite a bit more fuel than a 3,000. Since you only use one power tool at a time (1500 watts) with a 1,000 light, you could save on both the original investment and long-term fuel.