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### Topic: Battery inverter question (Read 760 times)previous topic - next topic

#### tjones9163

##### Oct 23, 2018, 02:27 amLast Edit: Oct 23, 2018, 02:29 am by tjones9163
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.

#### DVDdoug

#1
##### Oct 23, 2018, 02:56 am
Quote
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.

Quote
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.

Quote
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.

#### tjones9163

#2
##### Oct 23, 2018, 03:13 am
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.
Thanks for response and help DVDdoug!

#### mauried

#3
##### Oct 23, 2018, 03:18 am
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 .

#### tjones9163

#4
##### Oct 23, 2018, 03:48 am
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 .

I will try that. Thank you.

#### TomGeorge

#5
##### Oct 23, 2018, 03:58 am
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..
Everything runs on smoke, let the smoke out, it stops running....

#### tjones9163

#6
##### Oct 23, 2018, 04:25 am
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

#### raschemmel

#7
##### Oct 23, 2018, 05:44 amLast Edit: Oct 23, 2018, 05:44 am by raschemmel
If you have any welder cable that should work better than your car battery cables.

lugs
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

#### tjones9163

#8
##### Oct 24, 2018, 02:10 am
If you have any welder cable that should work better than your car battery cables.

lugs
If you have any welder cable that should work better than your car battery cables.

lugs
If you have any welder cable that should work better than your car battery cables.

lugs
Im sorry, that is what i am actually using

#### MorganS

#9
##### Oct 24, 2018, 02:22 am
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.
"The problem is in the code you didn't post."

#### MarkT

#10
##### Oct 24, 2018, 12:44 pm
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.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

#### raschemmel

#11
##### Oct 24, 2018, 04:40 pm
Quote
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.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

#### tjones9163

#12
##### Oct 25, 2018, 02:29 am
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?)

#### tjones9163

#13
##### Oct 25, 2018, 02:38 am
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?

#### raschemmel

#14
##### Oct 25, 2018, 02:51 am
Quote
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:

Quote
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.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

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