Running accesories, dual/seperate battery required?

[Icemul]

I have seen several dual battery setups, all look nice. Here is my thing though, from what I can tell the dual batt setups allow the truck to use both batts for starting or for what ever power is needed. Correct?

I got a colman 12v cooler and an 800w inverter which I used on my trip. For the cooler I got a battery saver that shut off the cooler when the batt dropped below 12v. It was nice but I noticed if I didn't drive alot to recharge the batt, the cooler would only last a few hours before shutting off. The inverter worked on somethings, but I noticed it worked much better when the truck was running. Since the only time I would like the extra power is when I'm camping, I was wondering if there was a way to just put a second batt that was only used for the aux equipment, but charged by the altenator when the car is running. I just thought it might be cheaper then a dual setup??? Just trying to figure out what route I should take, just need more juice so my beverages of choice stay cold! :drink:

Any thoughts on what I should look into or do? Oh just FYI, I still have the stock batt.

[bulldog]

I have seen several dual battery setups, all look nice. Here is my thing though, from what I can tell the dual batt setups allow the truck to use both batts for starting or for what ever power is needed. Correct?

I got a colman 12v cooler and an 800w inverter which I used on my trip. For the cooler I got a battery saver that shut off the cooler when the batt dropped below 12v. It was nice but I noticed if I didn't drive alot to recharge the batt, the cooler would only last a few hours before shutting off. The inverter worked on somethings, but I noticed it worked much better when the truck was running. Since the only time I would like the extra power is when I'm camping, I was wondering if there was a way to just put a second batt that was only used for the aux equipment, but charged by the altenator when the car is running. I just thought it might be cheaper then a dual setup??? Just trying to figure out what route I should take, just need more juice so my beverages of choice stay cold! :drink:

Any thoughts on what I should look into or do? Oh just FYI, I still have the stock batt.

The dual batt setup I did, basically seperates the 2nd batt from the main system when you shut off the engine. This way you accesories running of the 2nd batt wont drain your main batt. Make sure to use a deep cycle batt though as they do get drained.

The advantage of having a seperator is that you can combine both batteries if needs be for starting when the main batt is down.

Read up on the operation of the seperator, when it connects and disconnects. It is pretty well described in this thread and in the write up.

See if that is what suites your needs or what you want it to do differently. I don't get what exactly you are looking for from your post.

[Teotwaki]

[QUOTE=Icemul]I........ The inverter worked on somethings, but I noticed it worked much better when the truck was running.......QUOTE]

I will bet that your inverter is at the end of some lengths of cable and that there is a significant drop. With the engine off put a load on the inverter and then measure the voltage at the battery and then at the inverter. The difference is due to the resistance of the cable and the amount of current drawn by the inverter. When the engine is running the voltage drop across the cable is about the same. It is just that you are starting with a higher voltage on the battery so that what is at the inverter is also higher (but still less).

Even with a 2nd battery you should see if you can run a larger set of cables to the inverter and fuse them appropriately for short circuits.

[Mikestang]

Could you also mount the 2nd battery in the rear cargo area? Assuming you use a sealed battery, or a sealed battery case w/vent tube, so the gasses don't accumulate in the cabin. If the majority of the 2nd battery use would be from items in the rear (fridge, etc.) it might not be a bad idea. Helps get the extra weight off the nose, too.

[Icemul]

Teo, I put it in the back right side panel, it fit perfect. The cable I used was 4ga with a 100amp fuse. I email the company and that is what they told me to use with their inverter for the 4runner. I havn't checked the voltage, but I'll have to get my hands on a volt meter and check that out.

[Teotwaki]

Teo, I put it in the back right side panel, it fit perfect. The cable I used was 4ga with a 100amp fuse. I email the company and that is what they told me to use with their inverter for the 4runner. I havn't checked the voltage, but I'll have to get my hands on a volt meter and check that out.

With 4 guage and the inverter at the back you may have a 15 foot run which is about 0.03 Ohms of resistance. If the inverter is under heavy load and not super efficient it may be that a 0.5 to 1 volt drop may make it unhappy. If you were running maybe 500 watts through the inverter it may well pull 60 amps at 12 volts so the voltage drop could be 60 x 0.03 = 1.8 volts.

When you get a chance to measure things let me know!

[bulldog]

With 4 guage and the inverter at the back you may have a 15 foot run which is about 0.03 Ohms of resistance. If the inverter is under heavy load and not super efficient it may be that a 0.5 to 1 volt drop may make it unhappy. If you were running maybe 500 watts through the inverter it may well pull 60 amps at 12 volts so the voltage drop could be 60 x 0.03 = 1.8 volts.

When you get a chance to measure things let me know!
Jim your ratings for the cable seems to be a bit pessimistic.

Here is a pretty good site to calculate voltage drop and also lists the ratings on the cables.

If there is a huge voltage drop with 4 ga cable, I would suspect poor connections or poor ground point first.

Also it is bad to put an inverter in an enclosed space as they generate quite a bit of heat when they are heavily stressed.

Lastly an inverter will pretty much run any battery down in short order if fully stressed, especially if you have a battery saver inline that cuts off at 12V. A car abttery dips below 12V pretty quick when you run a load against it and over extended wires like JIm pointed out.

In most probability it is a combination of the above that causes your issue. Miek is onto something with a small second battery in the cargo area, especially if it is connected via a battery saver device that will disconnect it form the main battery. Make sure to get one that is a deep cycle device and enough capcity to drive the load for the period you need.

[bulldog]

With 4 guage and the inverter at the back you may have a 15 foot run which is about 0.03 Ohms of resistance. If the inverter is under heavy load and not super efficient it may be that a 0.5 to 1 volt drop may make it unhappy. If you were running maybe 500 watts through the inverter it may well pull 60 amps at 12 volts so the voltage drop could be 60 x 0.03 = 1.8 volts.

When you get a chance to measure things let me know!
Jim your ratings for the cable seems to be a bit pessimistic.

Here is a pretty good site to calculate voltage drop and also lists the ratings on the cables.
http://www.powerstream.com/Wire_Size.htm

If there is a huge voltage drop with 4 ga cable, I would suspect poor connections or poor ground point first.

Also it is bad to put an inverter in an enclosed space as they generate quite a bit of heat when they are heavily stressed.

Lastly an inverter will pretty much run any battery down in short order if fully stressed, especially if you have a battery saver inline that cuts off at 12V. A car abttery dips below 12V pretty quick when you run a load against it and over extended wires like JIm pointed out.

In most probability it is a combination of the above that causes your issue. Miek is onto something with a small second battery in the cargo area, especially if it is connected via a battery saver device that will disconnect it form the main battery. Make sure to get one that is a deep cycle device and enough capcity to drive the load for the period you need.

[Icemul]

If there is a huge voltage drop with 4 ga cable, I would suspect poor connections or poor ground point first.

Also it is bad to put an inverter in an enclosed space as they generate quite a bit of heat when they are heavily stressed.

I used all high quality connector and the ground should be good, I used on of these grounding terminals. (http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=263-623)

As for inverter generating heat, it sure does!!! Mine even has two fans, but I still put it in the back panel because I'll only run it with the cover off. There for its not enclosed when I use it. I'll take home a meter tonight and get the reading if it stops raining.

[Teotwaki]

I used all high quality connector and the ground should be good, I used on of these grounding terminals. (http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=263-623)

As for inverter generating heat, it sure does!!! Mine even has two fans, but I still put it in the back panel because I'll only run it with the cover off. There for its not enclosed when I use it. I'll take home a meter tonight and get the reading if it stops raining.

Very nice termination for the ground wires! Much better looking than a big old copper ground lug bolted to the floor. :)

All of that heat from the inverter is basically wasted energy due to the inefficiencies of the DC to AC conversion. Rather than pull off the cover you could add an intake grill and an exhaust fan to circulate air in there.

Anyhow, I think when Andries said "pessimistic" he was thinking "conservative" as I am optimistic that with a few measurements we'll have a full story. :bigok:

What I am hoping is that the inverter is not so sensitive that it can't handle a reasonable voltage drop across the 4 Guage. If you still have the inverter specifications it may spell out the voltage limits it can handle.

[Teotwaki]

With 4 guage and the inverter at the back you may have a 15 foot run which is about 0.03 Ohms of resistance. If the inverter is under heavy load and not super efficient it may be that a 0.5 to 1 volt drop may make it unhappy. If you were running maybe 500 watts through the inverter it may well pull 60 amps at 12 volts so the voltage drop could be 60 x 0.03 = 1.8 volts.

When you get a chance to measure things let me know!

I did go to the web site Andries listed and it shows 0.2485 Ohms per 1000 feet so that is 0.002485 ohms per foot. (It also said a maximum of 60 Amps so above that heat becomes a factor, the wire melts and you just invented a Fusible Link!)

For 15 feet that is 0.037275 Ohms. If the inverter is capable of delivering 800 Watts at 120VAC and let's give it an initial efficiency of 80% then for 800 watts out you have to pump 1000 watts in. My previous example used 500 out over 720 watts in so that was 69% efficient, probably a cheap Kragen inverter! At 80% it would be 625 watts in. Divided by 12 volts that is 52 Amps through the cable and 1.938 volt drop across. Now for 12.5 volts at the inverter you need the battery to be at 12.5 + 1.938 = 14.45 volts

For a 90% efficient inverter delivering 500 watts at 44.4 Amps and 12.5 volts you need the battery to be at 14.15 volts. We can see that inverter efficiency is important. That is also why airplanes use a higher voltage. The currents are lower and the wiring guage can be smaller.

It is fun to play with the numbers and with actual measurements you get a good feel for the performance.

[bulldog]

Jim, you are off with a decimal place in your math ;)

0.2485 Ohm per 1000 ft is 0.0002485 per ft and 0.0037275 Ohm for 15ft. That would mean with a 90A load it would have a drop of 0.34V with perfect connections. I would budget for 0.5V drop.

90A is probably a good number to use for max load on an 800W inverter that is any good (75% efficient). The thing with most inverters are that they draw more current as the voltage drops to maintain the output, they do however have over current and low voltage protection.

I stand by the battery saver and drop in battery voltage below 12V with load that kicks out the inverter. Most abtteries will easily drop below 12V when you put a 90A load on them and then engine is not running. Put a voltmeter on it and turn on the highbeams and see what you get on the battery terminals. On the 4R the High and low beams with rear/park lights in total is 250W or so, so basically a 20A load. Even with that most batteries will dip below 12V.

BTW the site I listed has a calbulator to calculate vlatge drop over a length of wire to make things easy. ;)

[Icemul]

I didn't get a chance to check the voltage last night, it rained like crazy, so I'll have to get them tonight. But in the mean time I just thought I'd post the specs on the inverter I got. Its nothing special, but its worked so far.

Specifications:

· Continuous output power: 800 Watts

· Surge power capability (peak power): 2000 Watts

· dc input / operating voltage: 10 to 15 Volts · Output voltage: 120 Volts ac

· Output wave form: modified sine wave

· Output frequency: 60 Hz

· Battery low voltage alarm: 10.5 +/- 0.5 Volts

· Battery low voltage shutdown: 10.0 +/- 0.5 Volts

· No load current: < 0.95 Amps

· Full load efficiency: 90%

· 1/3 load efficiency: 95%

· No load minimum operating temperature: -15 degrees Celsius

· Full load maximum operating temperature: 55 +/- 5 degrees Celsius (automatic shutdown)

· AC Output Socket Type: dual Type 2 -3 prong

· High input voltage protection: 15V

· Low input voltage shutdown: 10V

· Internal fuse protection

· Product size (L x W x H): 10.25”X 6.5”X 2.5” · Weight: 3.7 lbs

[Teotwaki]

Jim, you are off with a decimal place in your math ;)

0.2485 Ohm per 1000 ft is 0.0002485 per ft and 0.0037275 Ohm for 15ft. That would mean with a 90A load it would have a drop of 0.34V with perfect connections. I would budget for 0.5V drop.

90A is probably a good number to use for max load on an 800W inverter that is any good (75% efficient). The thing with most inverters are that they draw more current as the voltage drops to maintain the output, they do however have over current and low voltage protection.

I stand by the battery saver and drop in battery voltage below 12V with load that kicks out the inverter. Most abtteries will easily drop below 12V when you put a 90A load on them and then engine is not running. Put a voltmeter on it and turn on the highbeams and see what you get on the battery terminals. On the 4R the High and low beams with rear/park lights in total is 250W or so, so basically a 20A load. Even with that most batteries will dip below 12V.

BTW the site I listed has a calbulator to calculate vlatge drop over a length of wire to make things easy. ;)

crap, crap, crap.... :mecry: teach me to do things longhand.

Looks like from the posted specs the inverter is around 90%.

[Icemul]

Here are some pics of the inverter.

Pic of the inverter in the back compartment
http://img85.imageshack.us/img85/9684/img0788hs5.jpg

http://img85.imageshack.us/img85/1431/img0789sq5.jpg

This is where I drilled the holes to bring the wires into the compartment to hook up the inverters.
http://img85.imageshack.us/img85/1026/img0792ye9.jpg

http://img85.imageshack.us/img85/8710/img0793je7.jpg

With this battery connector I was able to use the stock terminal, I didn't have to cut it.
http://img85.imageshack.us/img85/4714/img0795ok4.jpg

[Icemul]

Alright I put the volt meter to the car. Here are the results.

Car off-
Battery: 13.0
at the inverter: 12.9

Car on-
Battery: 13.62
at the inverter: 13.61

Car on, inveter on with load-
Battery: 13.59
at the inverters: 13.55

[bulldog]

Alright I put the volt meter to the car. Here are the results.

Car off-
Battery: 13.0
at the inverter: 12.9

Car on-
Battery: 13.62
at the inverter: 13.61

Car on, inveter on-
Battery: 13.59
at the inverters: 13.55
Are these with the inverter running at load? Or just inverter on?

[bulldog]

Where did you bet that abttery terminal for the Pos connector? I would like to get one for my 4Runner as the pos terminal I got would allow for the stock connector to just bolt on. DOes it have 2 additional points, so I can put in my winch and second battery connctor as well?

[Icemul]

I got the connector at www.partsexpress.com (http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=263-677)

I had to cut off the little wings off on the battery terminal, but then it fit fine.

As for the loads, the first 2 were just the inverter. The last one is at load.