Hello, I am further trying to understand batteries and my question is, today at work(lighting film sets), I was using a 12v battery and a 2000w inverter, not a pure sine wave but modified square wave works fine for powering tungsten bulbs, and I am able to power up to 650w lamps but anything higher than that the inverter will start beeping and then say "EOC" message which means error overcurrent.
But it will power 650w lamp for a while. I understand how voltage and current works but I don't understand too much when it comes to how a battery is discharged.
My 12v battery read 12.2 volts, which it should be 12.6 and above, so that could be why i would get that EOC message.
My questions are when it says EOC does that mean that when I try a higher watts lamp like a 1000watts it says EOC because I'm pulling more current because the voltage remains roughly the same, voltage x amps= watts?
My next question is when I am running a lamp off the inverter, how does the actual battery get discharged? Does it depend on the amount of current I am pulling and what i am really asking is what is the relationship of voltage and current in a discharging battery, as the current drains the voltage also drops? Maybe for my setup next time I should try a fully charged 12v battery if you guys think that might help run a 1000w lamp?
I have also seen youtube channels like Greatscott, were they say some companies make false advertisements of how many watts an inverter can handle (sometimes even up to half) and the one I was using didn't look the greatest.
And just so no one yells at me, I do actually plan to implement some sort of RF device and Arduino that can read the voltage of the battery leads and transmit to a receiver that I will have, to know when the battery will die if i am somewhere else on set.
2000w inverter, not a pure sine wave but modified square wave works fine for powering tungsten bulbs, and I am able to power up to 650w lamps but anything higher than that the inverter will start beeping and then say "EOC" message which means error overcurrent.
I'd say they are "fudging" the specs! Incandescent lamps do draw additional current when cold, but I would expect the inverter to handle that.
My 12v battery read 12.2 volts, which it should be 12.6 and above, so that could be why i would get that EOC message.
That shouldn't be a big problem. The battery is only "fully charged" for a very short time and as it discharges the voltage will drop. Ideally, the voltage would remain constant until the battery dies (like a gas tank running out of gas) and real batteries try to maintain fairly-constant voltage over most of the charge-life, but they are not perfect.
And, a good boost converter (or inverter) should work with reduced voltage so it should extract the most from the battery.
because I'm pulling more current because the voltage remains roughly the same, voltage x amps= watts?
It's probably something like 90% efficient so with the 650W lamp you could be pulling something more than 700W from the battery. That would be about 60 Amps on the battery-side.
DVDdoug:
I'd say they are "fudging" the specs! Incandescent lamps do draw additional current when cold, but I would expect the inverter to handle that.
That shouldn't be a big problem. The battery is only "fully charged" for a very short time and as it discharges the voltage will drop. Ideally, the voltage would remain constant until the battery dies (like a gas tank running out of gas) and real batteries try to maintain fairly-constant voltage over most of the charge-life, but they are not perfect.
And, a good boost converter (or inverter) should work with reduced voltage so it should extract the most from the battery.
It's probably something like 90% efficient so with the 650W lamp you could be pulling something more than 700W from the battery. That would be about 60 Amps on the battery-side.
Measure the voltage right on the inverter terminals when running the lamp.
650W is at least 54 amps, and will be a bit higher on account of the Inverters efficiency.
Some of the cheaper inverters shut down on low input volts, at around 11V .
mauried:
Measure the voltage right on the inverter terminals when running the lamp.
650W is at least 54 amps, and will be a bit higher on account of the Inverters efficiency.
Some of the cheaper inverters shut down on low input volts, at around 11V .
TomGeorge:
Hi,
What are you using for leads from the battery to the inverter?
What is your battery?
Have you monitored the battery voltage as you load up the inverter?
Thanks.. Tom..
Thank you for response Tom.
I don't have the battery in front of me but it is an Everest 12v deep cycle, I am using standard 12v car battery jumpers less than 2 ft long.
and tomorrow I will measure under load.
Thanks again
DVDdoug:
It's probably something like 90% efficient so with the 650W lamp you could be pulling something more than 700W from the battery. That would be about 60 Amps on the battery-side.
This is the right way to do the calculation.
Consider what happens as the battery voltage drops: the output power is constant so the inverter must draw more current because of the lower voltage. Eventually it will draw more current than the inverter's input stage can handle. So even though the battery is not flat and the output is not overloaded, the input has reached its limit and it must shut down.
That is why it is difficult to place just one power figure on the label: the actual capacity varies depending on the characteristics of the supply and the load.
650W of quartz halogen will pull about 5kW initially when the filaments are cold, if you can sequence
the lamps switch-on you may be able to get more from the inverter if its cutting out due to
switch-on surge.
Mains lamp filaments heat up a lot quicker than low voltage bulbs due to smaller thermal mass, but
for a short time the current pulled is nearly ten times the steady state value for all efficient (ie high
temperature) tungsten lamps.
650W of quartz halogen will pull about 5kW initially when the filaments are cold, if you can sequence
the lamps switch-on you may be able to get more from the inverter if its cutting out due to
switch-on surge.
You can sequence the halogen loads using contactors rated for the load current. Make a panel with toggle switches on it to switch the contactor coils individually so you can sequence them. Run the halogen current
through contactor contacts. This way you can bring up 10 halogens individually, so you won't overload the
inverter.
MorganS:
This is the right way to do the calculation.
Consider what happens as the battery voltage drops: the output power is constant so the inverter must draw more current because of the lower voltage. Eventually it will draw more current than the inverter's input stage can handle. So even though the battery is not flat and the output is not overloaded, the input has reached its limit and it must shut down.
That is why it is difficult to place just one power figure on the label: the actual capacity varies depending on the characteristics of the supply and the load.
couldn't of asked for a better explanation!!
Thank you to everyone also responding, this answer really resonates with what I was thinking.
(did we just become best friends?)
raschemmel:
You can sequence the halogen loads using contactors rated for the load current. Make a panel with toggle switches on it to switch the contactor coils individually so you can sequence them. Run the halogen current
through contactor contacts. This way you can bring up 10 halogens individually, so you won't overload the
inverter.
I'm trying to visualize what you are explaining but still don't understand?
I'm trying to visualize what you are explaining but still don't understand?
I somehow got the impression that there was more than one halogen powered by the inverter:
and I am able to power up to 650w lamps but anything higher than that the inverter will start beeping and then say "EOC" message which means error overcurrent.
does not the 's' at the end of 'lamp' imply more than one ?
Are you not saying that when you turn on ALL the lamps (more than 650W) the inverter faults out ?
Did you imply anywhere in your post that you are ramping up the load by switching on one 'lamp' at a time , as opposed to powering them all at the same time ?
There is an assumption made here that the root cause is inrush current due to excessive load due to an excessive number of lamps being energized simultaneously , rather than being ramped up gradually by
having each lamp controlled by it's own switch , which in fact is a toggle switch for the coil current of a contactor rated for one lamp load. The panel having 'n' toggle switches for 'n' lamps.
raschemmel:
I somehow got the impression that there was more than one halogen powered by the inverter:
does not the 's' at the end of 'lamp' imply more than one ?
Are you not saying that when you turn on ALL the lamps (more than 650W) the inverter faults out ?
Did you imply anywhere in your post that you are ramping up the load by switching on one 'lamp' at a time , as opposed to powering them all at the same time ?
There is an assumption made here that the root cause is inrush current due to excessive load due to an excessive number of lamps being energized simultaneously , rather than being ramped up gradually by
having each lamp controlled by it's own switch , which in fact is a toggle switch for the coil current of a contactor rated for one lamp load. The panel having 'n' toggle switches for 'n' lamps.
Thank you for the response, I actually only meant one at a time, but sometimes i will switch out a lamp for a higher or lower wattage depending on the scenario. The lamps we use are very high in wattage, I meant one 650w light and this is considered a very small light compared to when-when we use an 18,000 w HMI bulbs to light up an entire street at nighttime.
I do now understand what you were trying to explain. But for the most part, we only use small single lights for stuff like shooting a "car scence" and sticking the inverer and battery in the back seat.
Is there a space constraint ?
You can add current inrush power resistors connected to the N.O. contacts of a contactor driven by a timed relay with a 3 sec time delay so when you energize the lamps, the relay is enerized at the same time, switching the current inrush 1000W 1 ohm resistors (or 10 ohm) IN SERIES with the load. At the end of the
3 seconds the relay turns off , deenergizes the contactor and the connects the inverter directly to the lamps
via the N.C. contacts of the contactor. We used something similar for very high currents at a company I worked at. It's up to you if you want to reverse the logic and have the resistors connected to the N.C. contacts. Obviously the inverter is connected to both the resistors and the contact without the resistors
but there is only one current path at any point in time, either through the resistors or bypassing them.
The resistors are sometimes replaced with inductors for inductive loads.
My 12v battery read 12.2 volts, which it should be 12.6 and above, so that could be why i would get that EOC message.
I'm not a mechanic but that sounds low. Is the alternater recharging the battery while the lamps are on or are you running them straight off the battery ? To be frank, I never heard of any vehicle drawing that much current so on general principles, I would have to say that when the battery manufacturer designed the battery, they never in their wildest dreams imaged some bloke driving that much current off the one
battery. Don't Off-Road vehicles have more than one battery to power the high power driving lights for
night driving ? Normal autos don't have super bright 100,000 candle power driving lights. I honestly think you need to add at least one more battery to cut the battery load in half. As far as the inverter
performance, you can easily test that by hooking up multiple batteries in parallel to power the inverter and see if you get the same fault. You could borrow a couple of batteries from other vehicles for the test.
you can jumper two more cars to your battery with two sets of jumper cables to see if the inverter works
or gives the same fault.
Whats the AH rating of the battery and how are you charging it ?
Deep cycle batteries normally need to be 2 stage charged, ie around 1 - 2 hours at 14.4 V then trickle charged at 13.2 - 13.6 V .
Its normally written on the batteries label what the charging requirements are.
