Little inverter runs a fan better than my new 1100W??

[Mike90250]

... So when I calculate how much/long I can run is 10.5v where I can safely end...

10.5V is a safe and reliable way to destroy your batteries before you take them to the recycle center.
Voltage while the battery is active (charging or discharging) is not a reliable State Of Charge indicator. If you wait several hours, and then measure voltage, you can get a fair estimate.

BatteryServiceLife.jpgBattery_Volt_Chart.jpg

Inverters have a "low battery shutdown" not to protect the battery, but to protect the parts in the inverter, at 12.5V, for 300w, you pull about 30A DC, at 10.5V, you pull 34A, and as voltage drops, even more amps, and the internal components melt.

[Sunny Solar]

Sunking in the posters first post he said "he had a desk fan" Now unless the desk fan had 4ft blades and a 1/2 hp motor all your questions to him and the rest of your reply had less than 100% of nothing to do with why his fan was running slow.. How could you ever imagine there was even any possibility that the cables or the batteries were to small.???
FACT for a desktop fan of usual size will run off an inverter of just about the smallest available and only need a minimum sized battery to do so and anything resembling copper wire above the thickness of 3 human hairs would be adequate.

What Igave was the only reply that actually answered correctly the reason his desk fan was running slow.

The information you gave no matter how factual was not relevant to his question.

[Sunking]

10.5 volts is deder than ded!

1.75 volts per cell at rest is 100% DOD as Mike has pointed out.

[Sunking]

What Igave was the only reply that actually answered correctly the reason his desk fan was running slow.

OK John you told him to load up the inverter with more load. That being the case then the right answer is get rid of the cheap MSW 1000 watt inverter and get a good TSW inverter. Burning up more power to make it work is not a solution. its a band aid.

FWIW advising someone to use wire the size of 3 human hairs on a 1000 watt inverter is insane.

[inetdog]

FWIW advising someone to use wire the size of 3 human hairs on a 1000 watt inverter is insane.

It does make a nice low amperage fuse though. As long as you run it in a fireproof place.

[Sunny Solar]

THE POINT IS YOU SEEM TO MISS IS "HE WAS ONLY WANTING TO KNOW WHY HIS DESK FAN RAN SLOWER ON A 1000 W INVERTER COMPARED TO RUNNING ON A 400W INVERTER.. its not relevant the sensible use or otherwise of the 1000 w inverter it make no difference if he was asking about a 50000w inverter.
Anything better than wet string would carry enough current to power the fan that size..

That dear friends was his question. he wasn't asking if it was sensible or not to do it. .. OK ? it was just his learning experiment. You guys have never done a wasteful experiment or used something that was massive overkill for the job??

It no different if he was asking why his 50ton Mack truck uses more fuel to carry the weeks groceries home compared to his Honda Civic.He is not asking is it sensible to use a 50 ton Mack truck to carry the groceries.

[positiv4]

Indeed, I did not add the 1100w inverter to power the fan; it just happened to be what I grabbed to make sure the inverter worked out of the box. As it turns out, I have picked up some useful information along the way!

So calibrating working voltage to a quantified SOC would be a reliable way to know where I'm at with a voltmeter glance? Would varying loads affect that? That's the type of solution I was hoping for.

Thank you all so much for your replies

[inetdog]

Indeed, I did not add the 1100w inverter to power the fan; it just happened to be what I grabbed to make sure the inverter worked out of the box. As it turns out, I have picked up some useful information along the way!

So calibrating working voltage to a quantified SOC would be a reliable way to know where I'm at with a voltmeter glance? Would varying loads affect that? That's the type of solution I was hoping for.

Thank you all so much for your replies

There are three common types of AC voltmeters. One of them, the more expensive, is called a true RMS meter. RMS stands for Root Mean Square, which is a math shorthand for how it calculates a single voltage number for a constantly changing (AC) voltage.
It is a perfect representation of the amount of heat that waveform will produce into a resistive load (P= V²/R, where R is the resistance and V is the RMS voltage)
Another measure is the peak voltage, the maximum voltage of the waveform at the highest (and lowest) point in the cycle. This type of meter measures the peak but displays the nominal (RMS) voltage of a sine wave which has the same peak value.
A third, less common, is the average voltage. (For AC you would have to measure the average of the positive or negative half cycle separately, since the average DC voltage is zero.)
And again, that kind of meter would display the RMS voltage of a sine wave that had the same average value.

So, for any situation in which the waveform is not a sine wave (as in the Modified Square Wave or even (shudder) Square Wave), each of the three will read a different value.
That may lead you to believe that the "motor test" may be more useful than any of them. And indeed, for the purpose of running that particular motor it could be.
But for power supplies for electronics the peak value is most important and for heating appliances the RMS value is most important.
An MSW inverter will normally work fine for a heating appliance, but may cause problems for some motors and some electronics. Unfortunately, in the case of motors, trying to raise the voltage to get the same speed as with a sine wave is likely to damage the motor more than it is already being damaged by the MSW waveform.

Keep asking questions and learning!

[positiv4]

There are three common types of AC voltmeters.

Wow! That's a whole lot of stuff I didn't even know to think about!

My apologies for not quoting the original response I was addressing, but I was actually referring back to determining state of charge for my battery using a DC voltmeter connected to the battery. Sunking suggested using a hydrometer to calibrate voltage readings which, in the future, should allow me to know SOC by reading my volt display.

Thanks for the bonus AC voltmeter lesson!!

[inetdog]

Wow! That's a whole lot of stuff I didn't even know to think about!

My apologies for not quoting the original response I was addressing, but I was actually referring back to determining state of charge for my battery using a DC voltmeter connected to the battery. Sunking suggested using a hydrometer to calibrate voltage readings which, in the future, should allow me to know SOC by reading my volt display.

Thanks for the bonus AC voltmeter lesson!!

Just remember that your correlation between resting SG and SOC is only valid when the batteries are in fact resting (and have been for hours).
You need to add to your table of voltages the voltage readings with different values of load or charging current if you want to get even a rough idea while the batteries are in use. Fortunately you can collect a good number of voltage and current readings for every hydrometer measurement.
And don't treat those non-resting readings with the same degree of confidence as the SG readings themselves. They will change with the age of the batteries and the size of the wires to the point where your meter is reading.

Sunking gave you the short answer to get you started, and to stress the need for a hydrometer in the first place. There is a lot of additional learning you can pick up from old threads on the subject once you have gotten your hydrometer (temperature compensated please!)

[positiv4]

once you have gotten your hydrometer (temperature compensated please!)

Would this be adequate?

http://www.amazon.com/OTC-4619-Professional-Battery-Hydrometer/dp/B0050SFVHO/ref=cm_cr_pr_product_top

[positiv4]

...or this kind?

http://www.ezred.com/product/battery-hydrometer/

[inetdog]

...or this kind?

http://www.ezred.com/product/battery-hydrometer/

It looks like either one of those should work for you, but you can search the forum for "hydrometer" and get some specific recommendations and disrecommendations too.

[positiv4]

It looks like either one of those should work for you, but you can search the forum for "hydrometer" and get some specific recommendations and disrecommendations too.

Sounds good. The word hydrometer comes up on here A LOT! lol

Thanks

[SunEagle]

It does make a nice low amperage fuse though. As long as you run it in a fireproof place.

Actually the arrangement of thin wires in a fireproof tube is exactly how most "fuses" are built.