inverter question

[Shomeyrwit]

I dont understand the complexities of this and cant decipher any other threads to answer this questin so


Say I have a nice mid level inverter, about 1500 watt continuous, and a nice optima deep cycle, and the only load is a device that draws .9 amp while running and say 5amps to start, said device runs maybe half of every hour, say it kicks on and off,,, 5 times,,,

1. How long will the battery run this before it's dead?

2. How much would a small solar panel help?

3. Will a twelve volt lead from the tow vehicle straight to the towed vehicle battery charge both batteries (i.e. a second pigtail)

4. the little 12v halogen lamps dont seem to draw much power but the idea of running one for even an hour seems like it would considerably drain a battery, am I overly concerned about that?


Your answers, patience and opinions are appreciated?

Thanks
S

[Shomeyrwit]

hmmmm any good guesses?

[Ken A Hood]

I can't help, but here's a link to a website.

INVERTERS http://www.phrannie.org/invert.html

BATTERIES http://www.phrannie.org/battery.html

[Dale M.]

Here is a few things to think about .

The 5 amp start up surge is instantaneous so that does not really figure in...

The .9 amp device running at 115 volt is about a 9 amp load on battery...

With an approximate 10:1 step up in voltage, you also have to multiply load at 10x ( or 9 amps)..

Depending in amp hour rate of battery (say 400 amp hour (which is 400 amps over 20 hours )) you can run device approximately 44 hours (400/9 = 44)before battery goes below useable voltage.

All calculations are approximate as there are other losses in inverter and appliance circuits not figured in here.

Yes you can parallel battery in tear with battery in tow vehicle to charge both batteries simultaneously. But I suggest a battery isolator device to protect both batteries from possible damage due to some unforeseen incident with batteries or charging circuit...

And here is yet another site with battery information.

http://www.uuhome.de/william.darden/

Now that I have stuck my neck out on this some one will come by and correct me, and you will have right answers...

Dale

[Shomeyrwit]

44 hours great scott, so assuming that a solar panel helps during the day, I run the car for awhile with the charge linked etc then I have to ask

Why would you spend all the money they want for a propane/elec fridge when you can buy a 110v fridge that draws only .9amp running for less than $200? (and tell me if someone is already doing this)

I was considering putting in a mini fridge and simply packing the freezer with the gel packs, run it till good and frozen then it should be good for a days worth of driving till plugged in again, ( I dont dry camp much) but in the process of searching for possible units I came across the fact that a lot of the new mini fridges draw very little power and can be mounted directly against the wall, which got me thinking

at any rate if no one comes on and tells me theres no way in heck it will work along with a compelling reason I'm gonna try it,, worst case scenario new beer fridge for the garage and a nicer inverter than origionally planned

speaking of which are small inverters more efficient?

[Dale M.]

The 44 hour figure is arbitrary (400Amp hour battery) .... I would have to know that exact amp hour rating of battery to give more accurate numbers... Also if appliance runs intermittent, then time would be extended......

This is description of Amp Hour Rating.....

Amp Hours

The Amp Hour rating tells you how much amperage is available when discharged evenly over a 20 hour period. The amp hour rating is cumulative, so in order to know how many constant amps the battery will output for 20 hours, you have to divide the amp hour rating by 20. Example: If a battery has an amp hour rating of 75, dividing by 20 = 3.75. Such a battery can carry a 3.75 amp load for 20 hours before dropping to 10.5 volts. (10.5 volts is the fully discharged level, at which point the battery needs to be recharged.) A battery with an amp hour rating of 55 will carry a 2.75 amp load for 20 hours before dropping to 10.5 volts.

Dale

[madjack]

Dale, I may have missed something but wouldn't a 400amphour battery be about the size of a house...are you sure you are not confusing that with cranking amps...the most AH I have seen packed into a group 27 deep cycle battery is around 115 AH in the heavy duty Trojans...even the big yellow top Optimas, dont carry but 75 AH....
madjack

[Dale M.]

Actually I pulled the 400 AH out of the air FOR EXAMPLE only....

Lets start over 75AH battery.... 9 amp load...about 8 hours.... OR if you want to go the 20 hour time line, the battery will maintain 3.75 amps output over 20 hours before it becomes technically "dead"...

Does this fit everybodies perspective better?

Dale

[madjack]

Dale, thanks for the clarification...I thought as much...especially as you are one of the knowledgeable members on electricuty....I just didn't want Showme to think he could go out and buy a 400AH battery
madjack

[Shomeyrwit]

thought that sounded rather large,


but you probably saved me from asking where they were

so will two batteries double this time?

[Chuck Craven]

Shomeyrwit
They make a 12 refer for campers in many sizes. There should be no problem running it off the tow vehicle when traveling. When at a campgrounds you can run it off a power supply from the 120v ac. That should save your battery for when you need it, when no AC available.
Halogen lamps are power hogs and heat generators, you can get LED lamps or lights with a little less Looms at vary low power consumption. You probably would not notice the difference in light level in the tear’s small space.
As to a solar panel you will need one that is ratted grater than the max load, if you want to charge the battery during the day. The solar panel will have to supply power to the refrigerator and still charge the battery. Else the battery will be discharging when the refrigerator is running and trying to recharge the battery when the refer is on it’s off cycle. A small solar panel will never be able to fully charge the battery.

Chuck

[Shomeyrwit]

i guess i should point out that I was under the impression that a refrigerator would drain a battery in two or three hours, my original plan was just to use coolers then i saw the price of 12v/propane fridges and was sure i was just going to use coolers
then came across the power ratings for the new small fridges and thought i must be mistaking because it seemed feasible to run one off an inverter between shore/generator power hook ups

thanks for all the info

[madjack]

shome...if the refer you are looking at, uses less than an amp and you had a 75AH batt, and the refer only ran half the time, you would end up with almosy 150 hrs of run time...HF sells a solar panel for a couple a three hundred bucks that will give you some usable solar power...also look in sdtripper2's index for more solar power info.....
madjack

[Sonetpro]

i guess i should point out that I was under the impression that a refrigerator would drain a battery in two or three hours, my original plan was just to use coolers then i saw the price of 12v/propane fridges and was sure i was just going to use coolers
then came across the power ratings for the new small fridges and thought i must be mistaking because it seemed feasible to run one off an inverter between shore/generator power hook ups

thanks for all the info

From your first post about running this refer with an inverter. I think your amperage is off.
It seems that you are refering to 120V power draw. The amperage will be higher running it through an inverter.
If you are figuring .9 amp at 120V that will be 9 amp at 12V and the 5 amp start will be 50 amp at 12V.
Regardless of the voltage the wattage will stay the same. 108 watts to run and 600 watts to start.
So yes, it will drain your battery in short order. Here is a good calculator to figure how long you battery's will last.

http://www.smartgauge.co.uk/calcs/peukert.xls

[madjack]

Steve...thanks, I guess I was having a major brain fart in my last post...120vac to 12vdc does indeed increase amperage by a factor of 10.......
madjack