I have a 75w baby, that plugs into the lighter with 1 port, a 350w that should be hooked direct to the battery but will run at a reduced rate when plugged into the lighter socket. Now I have a big dawg,

It runs up to 1.5 KW peak, and and 750 watt continuous. That should be good enough to power a small 110v electric compressor. and a 2gallon tank. Or at the least fire my Duwalt electric impact gun.

I am a little worried if I try to pull 1.5kw what if any issues could be created with the cars electrical system, it will be mounted direct to the battery inside the front compartment. Is the battery gonna go, Oh F*0K, is the alternator gonna scream in pain. I know if I run it at max duty, it'll probably drain the car battery in short order, but the car running can I can get enough amps out of my 100amp alternator. I am going to need to charge 2-3 laptops and a Projector (for posting movies on a white sheet, (camping)

I am thinking about grabbing a spare battery rigging up a quick down and dirty double battery setup. Simply put 2nd battery in trunk, running then parallel by using the top terminal of my main battery run and run two 3 ougt cables to the 2nd battery. Alternator will have a bit of strain but should get me through the weekend. I'll also be bringing 2 jumper boxes for emergency.

If I decide to install the 2nd battery long term, It will end up with relay closed system, So the battery can always charge, however the 2nd battery will have a relay to engage it only when the "crank" wire is powered up ensuring the car will always start.

Just to make it clear, I am doing it the cable to cable way for this weekend, then Will change it to properly installed dual battery solutions at a later. (battery isolator, larger double stud battery joints and replace all the lines with Ought 3 cables.

------------------
85GT Soon to be 87GT,93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.

You electrical system should be fine since the inverter will still only pull about 50 Amps from your battery. You will need to have the engine running to keep from draining the battery. As for the compressor, Inverters have an issue with inductive loads. They don't like them. With my 1500 watt inverter if I need to run a saw from it I have to also plug in a 40Watt Drop light to get the inverter to power the saw.

depends on the inverter, you should read the specs on what it will run. figure if you have a full 750 w continuous, you will draw about 70 amps at 13v, since most inverters are not much better than 80% efficient. Again consult the docs for it, they sometimes chart efficency vs draw.
They also draw more the lower the battery voltage, and will shut off below 11 or 10 v.
figure your draw for all the laptops, use the label on the ac adapter for the amperage draw, always figure worst case. ditto for the projector. laptops adapters can be from 65-95w draw depedning on the make and the state of the battery in the lappie. I don;t see a real big issue with the car running handling that, your compressor may spike the current but the second battery should keep the load off the alternator, which is what you really don't want to spike.

quote Originally posted by Capt Fiero: II am going to need to charge 2-3 laptops and a Projector (for posting movies on a white sheet, (camping)

are you going to do the portable drive in theater thing? like seen here make a portable drive-in theater!

Yep that was the plan, my dual battery is now mounted and runs perfect.

Now for the bad news I was supplying the laptop and a couple pre-release movies, however the guy with the projector has had to back down from coming, he did offer for me to pick up the machine and take it along, just not sure if I want to be responsible for something that expensive if something goes wrong, he uses it for his business doing presentations and such.

Now back to the dual battery.

I did this in my 88GT with an Optima in the stock location, dropped a heavy duty battery in the floor of the trunk, ran 3 ought cables from the new battery, up to the spare terminals on the Optima, (it has dual terminals.) So it made it so easy, just put 2 top terminals on the extra battery and 2 terminals on the other ends to attach to the optima. Everything works perfect the car starts great, and I should be good to go. I'll post pics of the wham bam 20 Min's install. Later, right now I got to get the trailer loaded so we can leave for the camping trip.

I just got back from driving it, I can tell the alternator is having a hard time charging the near dead deep cycle I added to the system, so I put it onto a rapid charge.
To add another whole new level, LOL, and a few of you are going to want to reach through the screen and smack me upside the head, I am running an under drive kit on the crank, the alternator is only spinning at 75% of normal. Which has been fine for the last few years even running the A/C

------------------
85GT Soon to be 87GT,93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.

Whew, we are back. Camping was for the most part good. I parked the car Friday, fired up the inverter, inflated our mattress, plugged in a light for a while, ran the Stereo for about 4hrs straight. Just to check, I jumped in, and it fired right up. So I shut it down. Next morning, radio back on, inverter to charge extra camera batteries, re-inflated the air mattress, charged up both radios, all 3 cell phones via the 12v car adapter to 5v USB adapter. Never even bothered to fire it up on Saturday. Sunday, morning, I jumped in hit the key and it spun the engine better than ever. I was very pleased. Hitched up the trailer and made the drive home, now its time to relax from the vacation, LOL.

------------------
85GT Soon to be 87GT,93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.

im more interested in how you set your portable drive in theater up im nerdy like that. the two batts is a pretty good solution for having to use that much power for an extened amount of time.

quote Originally posted by Capt Fiero: I just got back from driving it, I can tell the alternator is having a hard time charging the near dead deep cycle I added to the system, so I put it onto a rapid charge.

This is the main problem...the inverter is going to pull a lot of amps out of the battery 60- 70amps as indicated earlier. Even a deep discharge marine battery is going to last maybe 2 hours at the most and you would have to drive around all day to recharge it with the alternator. You are going to want to add an onboard a/c charger and plug in when you get home.

By the way, if you have two batteries to do it properly you need a battery isolator. If you just connect them in parallel, you are going to have issues because the weaker battery is going to drain power from the stronger battery. It's possible the weaker battery can even be over discharged and even go into reversal which is very bad.

[This message has been edited by jscott1 (edited 07-26-2009).]

Well I knew that as good as my Optima was it was not going to be enough. I did some quick brainstorming and said why the heck not. I grabbed the 3 ought welding cable I had left over from my remote mount battery in my 857GT. I grabbed 4 standard battery connectors and got to work. I put the 2 top post terminals on the AC Delco, then put one top post and one side post on the Optima as well as moved one of the stock ones to the top. This way I had no chance of accidentally hooking it up backwards. I dropped the battery in the base of the trunk. I was going to secure it with one of my universal battery hold down kits, however decided for the rather short time it would be in there, stacking camping gear beside it would suffice.

I am not sure if I am going to leave the cables in there or not. Having them in the trunk made it so much easier to quickly hoot the inverter up. I would have to get some cable boots. To cover up the ends, maybe make a small pocket to stuff them into.

The Delco battery was nearly dead when I first put it in, so I gave it a few hours charge on a battery charger, just to keep the load off of the alternator. I am running an under drive kit on the alternator, which spins it about 25% slower than stock. However in the end I am really pleased with it. The total combined cranking capacity of the 2 is 1250 cranking amps. Not sure if the gain is doubled or if it is kinda like sound, where 2 50db speakers don't equal 100db.

Note the battery cable is about 3 times the size and rating you need.

------------------
85GT Soon to be 87GT,93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.