Slightly OT ~ For electronics guys on 120v Power Inverter

[BRENT in 10-uh-C]

I am wanting to install a 3000 watt 12 volt-to-120 volt power inverter in my Hauler to use to power two 500 watt flood halogen lamps and one flourescent two-bulb lamp inside. My question is how do I determine how long a battery(s) will last running continuously with a 1500 watt draw?

For example, if my 12v deep-cycle battery had the following specs:
105 amp hours rate,
575 CCA at 0 degrees,
42 minutes @ 75 amps ...or 205 minutes at 25 amps,

--what are these numbers telling me based on what my load needs to be? TIA!!




.

[Kevin in NJ]

Depends on the inverter input requirements. The 3000 watts is what it can output. Usually there are some loss so you would expect more energy needed to run the device.

Here is a link to a place that will calculate how long a battery might last:

inverter FAQ

If you plan on extended run times I would steer you to a pair of golf car batteries. A good pair of golf car batteries can run a motorhome at Hershey without needing a charge. That includes running heat, tv and laptop. We usually get a pair of good used batteries off a pile cause we know someone in the business.

[Big D]

Those numbers are telling you about the battery... You have only listed the battery's output and total load the inverter can handle.... nothing about the inverters input requirements. But Let's start with output side--- 3000 watts @ 120 VAC is 25 Amps. Let's say for a start that the inverter is of fair grade and has 90% eff rating.. that would mean it needs somewhere near 3400 watts@120 VAC.. ANYWAY--- most likely it's got several stages and will not run at that level.. For 90% eff and use for 1040 watts (both lights and 40 watt total flour) I would guess about 2.5 hours total time.. of course that would be hard on your battery and charging system as that would be completely dead.. I would recommend if you are going to have all that on, you start your rig. If you are going to be running a small light and fan should be ok for several hours on battery power.
Hope it helps out.. D

[MikeK]

1500 watts @12V = a whopping 125amp draw.
If the inverter is 88% efficient, you need even more, 125/.88= 142 amps.


You cannot draw a deep cycle battery much below 65% at that rate without significant voltage fall-off that would affect inverter performance.

65% of 105amp-hours = 68 usable amp-hours.

68/142 = .48 hours, about 29 minutes.

[Tom Wesenberg]

Over the years I've purchased five 110 volt inverters ranging from 80 watts to 800 watts. The 80 watt is the best and does it' job well and will actually put out 80 watts with no cooling fan. The best part is it cost $5 at a flea market. The other 4 inverters have a cooling fan and only put out about a third of their rated CONTINUOUS output. My 400 watt has a surge rating of 800 watt, but will only light a 100 watt light bulb and anything more will trip the circuit breaker. My 300 watt has the low power light lit unless the engine is running, but it will still put out the 100 watts to light the light bulb. It also trips OFF if I try anything more than 100 watts.

Since I mainly want to run my shaver and computor I'm OK with these, but the rating is a JOKE. Last summer I could have bought a new 2000 watt at a garage sale for $15, but I passed because I was sure I'd be lucky to get 600 watts out of it.

A 1000 watt (900 watt really) Honda generator, like the EU 1000i is a very nice quiet power source.

[BRENT in 10-uh-C]

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Thanks guys. Based on the concensus, two batteries would give me one hour of service time with the lights which should be ample time to do what I need. I might also add that the engine uses 2 batteries for electrical serviced by two 105 amp alternators. Before we did the "swap" in this thing (engine, trans., computers, steering column, instrumentation, etc.) , the powerplant saw service in an ambulance which was decommissioned after 5 years of service which one alternator serviced the emergency apparatus and the other took care of the vehicle needs. This thing has miles of wiring (pic below) and 3 computer systems that were integrated into the truck. It has done extremely well after all the bugs were worked out and is meeting my needs well.

Thanks again for your help.

[MikeK]

[QUOTE=BRENT in 10-uh-C;208934]

Thanks guys... This thing has miles of wiring (pic below) and 3 computer systems ... Thanks again for your help.

And guys on this forum have trouble with Model A wiring!