Inverter and battery sizing to power my camper microwave

[LaneW]

So, I am getting all sorts of misinformation on this and hope someone can give me correct scoop.

I am planning to replace my LA battery in my truck camper with two, 100 ah Lithium batts (probably SOK). I also need to install an inverter, really just to run my microwave. It’s a 900 watt MW that draws 1350 w according to the manual. Looking at a couple of 2000 watt pure sine inverters. But I am getting conflicting info, even from the manufacturers, as to whether two 100ah lithiums and a 2000 w inverter will be adequate to run the microwave .

Does anyone have definitive information on this question, or can you point me to a truly reliable source for answers?

Thanks in advance!

[StirCrazy]

otrfun wrote:

StirCrazy wrote:
ok so here are the specs. once again renogy customer service was quick and efficient. so there is two specs one for max power (4000watts) and one for overload protection. so it will handle the max power (4000watts) for 5 seconds and if it hits a overload conditions that will trip the inverter to protect it with in 40milli seconds.

You didn't state the model number. I would assume that's for the Renogy low-frequency 2000 watt inverter which costs about $600 and weighs about 50 lbs., right? That toroidal coil, which helps provide all the inrush current, makes for a heavy unit. Specs for most of these 2000 watt low-frequency inverters are somewhat similar in terms of their power/duration specs.

The high-frequency Renogy 2000 watt inverter, which costs about $300 and weighs 12 lbs. only has a 4000 watt peak rating as far as I can tell. My guess, the peak rating means it will only output 4000 watts for 20-40 milliseconds. Not enough time to produce much inrush current. I believe this is the unit the OP was looking at purchasing.

The Xantrex 2000 watt Freedom X inverter, which I believe is also a high-frequency unit (at 15 lbs.), will output 4000 watts >2 sec. Xantrex states specifically it's very effective for starting motors. That's an awesome spec for a high-frequency inverter.

no, it is thier one that is on sale for 369 cdn right now and includes battery cables and a remot control

2000W 12V Pure Sine Wave Inverter
SKU: RNG-INVT-2000-12V-P2-CA

Steve

[3_tons]

5 sec seems a uber robust number for a lower price point HF inverter - I’d need to see the spec to believe it - JMHO

3 tons

[otrfun]

StirCrazy wrote:
ok so here are the specs. once again renogy customer service was quick and efficient. so there is two specs one for max power (4000watts) and one for overload protection. so it will handle the max power (4000watts) for 5 seconds and if it hits a overload conditions that will trip the inverter to protect it with in 40milli seconds.

You didn't state the model number. I would assume that's for the Renogy low-frequency 2000 watt inverter which costs about $600 and weighs about 50 lbs., right? That toroidal coil, which helps provide all the inrush current, makes for a heavy unit. Specs for most of these 2000 watt low-frequency inverters are somewhat similar in terms of their power/duration specs.

The high-frequency Renogy 2000 watt inverter, which costs about $300 and weighs 12 lbs. only has a 4000 watt peak rating as far as I can tell. My guess, the peak rating means it will only output 4000 watts for 20-40 milliseconds. Not enough time to produce much inrush current. I believe this is the unit the OP was looking at purchasing.

The Xantrex 2000 watt Freedom X inverter, which I believe is also a high-frequency unit (at 15 lbs.), will output 4000 watts >2 sec. Xantrex states specifically it's very effective for starting motors. That's an awesome spec for a high-frequency inverter.

[StirCrazy]

otrfun wrote:

theoldwizard1 wrote:
On refrigeration equipment you might find "locked rotor amperage" (LRA) which would be worse than normal inrush current.

Sorry, have to respectfully disagree. One cannot be any "worse" or better than the other since they both, more or less, describe the same thing.

Air conditioner manufacturers use LRA to quantify the inrush current drawn by the compressor motor at its rated voltage when the rotor is kept stationary. Or, put another way, LRA quantifies the inrush current necessary to place a stationary or locked rotor in a compressor motor in motion.

theoldwizard1 wrote:
No manufacturer specs their in rush current.

Agree, it's not very common for manufacturers to use the term inrush current when providing specs for their products. The primary reason is because inrush current is a general descriptor for a short, momentary burst (or inrush) of current. The time/duration for measuring inrush current can vary for RV a/c compressors and small household motors as opposed to large commercial equipment.

Inrush current, in terms of starting RV a/c compressors and smaller consumer-type AC motors, is typically measured in less than a second. A Fluke or Amprobe inrush current capable clamp-on ammeter bears this out because it provides inrush current results in less than second. The time/duration for the inrush current analysis is less than a second, but obviously much longer than what's required for a peak reading.

With that being said . . . if an inverter or inverter generator manufacturer specifies current and time/duration at multiple power levels, one can use this data to approximate inrush current performance. For example, a 2000 watt inverter (with a 2000 watt "continuous" power rating) that also has a 4000 watt *peak* power rating will probably provide minimal inrush current. A 2000 watt inverter that can also output 4000 watts for 1-2 seconds should provide excellent inrush current. A 2000 watt inverter that is capable of producing 4000 watts for 5-10 seconds (and/or 6000 watts for 1-2 seconds) should provide outstanding inrush current.

Hope this helps.

ok so here are the specs. once again renogy customer service was quick and efficient. so there is two specs one for max power (4000watts) and one for overload protection. so it will handle the max power (4000watts) for 5 seconds and if it hits a overload conditions that will trip the inverter to protect it with in 40milli seconds.

[otrfun]

pianotuna wrote:
I can tell you that inrush on a 1000 watt psw inverter is high enough to blow a 30 amp fuse. And that is with no load. DAMHIK

I believe you're talking about the current encountered on the INPUT of the inverter when it's connected to a power source without first precharging the inverter caps with a resistor.

Yup, been there, done that--lol!

Note: This is not to be confused with the inrush current produced on the OUTPUT of the inverter---which is the topic currently being discussed.

[otrfun]

theoldwizard1 wrote:
On refrigeration equipment you might find "locked rotor amperage" (LRA) which would be worse than normal inrush current.

Sorry, have to respectfully disagree. One cannot be any "worse" or better than the other since they both, more or less, describe the same thing.

Air conditioner manufacturers use LRA to quantify the inrush current drawn by the compressor motor at its rated voltage when the rotor is kept stationary. Or, put another way, LRA quantifies the inrush current necessary to place a stationary or locked rotor in a compressor motor in motion.

theoldwizard1 wrote:
No manufacturer specs their in rush current.

Agree, it's not very common for manufacturers to use the term inrush current when providing specs for their products. The primary reason is because inrush current is a general descriptor for a short, momentary burst (or inrush) of current. The time/duration for measuring inrush current can vary for RV a/c compressors and small household motors as opposed to large commercial equipment.

Inrush current, in terms of starting RV a/c compressors and smaller consumer-type AC motors, is typically measured in less than a second. A Fluke or Amprobe inrush current capable clamp-on ammeter bears this out because it provides inrush current results in less than second. The time/duration for the inrush current analysis is less than a second, but obviously much longer than what's required for a peak reading.

With that being said . . . if an inverter or inverter generator manufacturer specifies current and time/duration at multiple power levels, one can use this data to approximate inrush current performance. For example, a 2000 watt inverter (with a 2000 watt "continuous" power rating) that also has a 4000 watt *peak* power rating will probably provide minimal inrush current. A 2000 watt inverter that can also output 4000 watts for 1-2 seconds should provide excellent inrush current. A 2000 watt inverter that is capable of producing 4000 watts for 5-10 seconds (and/or 6000 watts for 1-2 seconds) should provide outstanding inrush current.

Hope this helps.

[StirCrazy]

StirCrazy wrote:

otrfun wrote:

StirCrazy wrote:

otrfun wrote:


IMO the most important takeaway when discussing inrush, starting, peak, or surge, current is the following: unless a specific time or duration (or testing standard/protocol) is specified for any given current rating, the current rating provides little insight into how the device will perform in the realworld.

I do agree the lack of companies putting this in there advertising makes things a little more difficult. personaly I have never been met with any issues when I email the company and ask for that information.

You mentioned the Renogy 2000w PSW inverter. Very popular unit. Always wondered what time/duration they used for their peak rating. Did you happen to get this info?

not yet. I was actualy going to email them and see after what you said the other day. hang on I'll email them now and let you know. I have a go power 2000watt inverter in the 5th wheel and it has never had an issue running anything. I think it actualy started my ac once by accident haha.. but I am looking at the renogy for the camper.

Steve

[StirCrazy]

otrfun wrote:

StirCrazy wrote:

otrfun wrote:


IMO the most important takeaway when discussing inrush, starting, peak, or surge, current is the following: unless a specific time or duration (or testing standard/protocol) is specified for any given current rating, the current rating provides little insight into how the device will perform in the realworld.

I do agree the lack of companies putting this in there advertising makes things a little more difficult. personaly I have never been met with any issues when I email the company and ask for that information.

You mentioned the Renogy 2000w PSW inverter. Very popular unit. Always wondered what time/duration they used for their peak rating. Did you happen to get this info?

not yet. I was actualy going to email them and see after what you said the other day. hang on I'll email them now and let you know.

Steve

[3_tons]

Checking the reviews on the Renogy site I found at least two fellas that say they use the 2000w PSW to run microwaves, coffee makers and resistance heaters, but don’t say what oven wattage, nor is a duration spec provided…On their other 2000w PSW inverter-charger they do list the duration at 1 sec which comes up a bit short compared to the 5sec on my ProSine 2000w PSW, but 1 sec sounds about right at that price point… If you think about a 60 cycle waveform, 1 sec would likely be sufficient for a smaller sized microwave, but in my mind doubtful for an inductive motor load like a compressor - JMO

https://www.renogy.com/2000w-12v-pure-sine-wave-inverter/

3 tons

Upon edit, a same rating, like-kind Aims inverter list surge at 4000w/duration at 40ms - I wouldn’t be surprised if they came out if the same Wuhan factory…

https://www.aimscorp.net/documents/PWRI200012120S%20022222.pdf

[pianotuna]

I can tell you that inrush on a 1000 watt psw inverter is high enough to blow a 30 amp fuse. And that is with no load. DAMHIK

[theoldwizard1]

LaneW wrote:
You folks are very helpful, thanks. I do get it about wiring and will plan to discard what comes with an inverter and oversize the cabling.

A DC-DC charger is a must !

If you have not purchased the inverter, look at inverter/charger/automatic transfer switch. Remove your old converter. Wire the DC fuse panel directly to the battery (large fuse at the battery). Shore power cord directly to the inverter/charger input. Out out goes directly to the A/C breaker panel.

LaneW wrote:
But how do I find out about the inrush current matter? That's a bit concerning to me. I want to do all of this once only and get it right the first time.

No manufacturer specs their in rush current. On refrigeration equipment you might find "locked rotor amperage" (LRA) which would be worse than normal inrush current.

[LaneW]

otrfun wrote:

StirCrazy wrote:

otrfun wrote:


IMO the most important takeaway when discussing inrush, starting, peak, or surge, current is the following: unless a specific time or duration (or testing standard/protocol) is specified for any given current rating, the current rating provides little insight into how the device will perform in the realworld.

I do agree the lack of companies putting this in there advertising makes things a little more difficult. personaly I have never been met with any issues when I email the company and ask for that information.

You mentioned the Renogy 2000w PSW inverter. Very popular unit. Always wondered what time/duration they used for their peak rating. Did you happen to get this info?

No, I have not been able find that information - and would like to.

[otrfun]

StirCrazy wrote:

otrfun wrote:


IMO the most important takeaway when discussing inrush, starting, peak, or surge, current is the following: unless a specific time or duration (or testing standard/protocol) is specified for any given current rating, the current rating provides little insight into how the device will perform in the realworld.

I do agree the lack of companies putting this in there advertising makes things a little more difficult. personaly I have never been met with any issues when I email the company and ask for that information.

You mentioned the Renogy 2000w PSW inverter. Very popular unit. Always wondered what time/duration they used for their peak rating. Did you happen to get this info?

[StirCrazy]

otrfun wrote:


IMO the most important takeaway when discussing inrush, starting, peak, or surge, current is the following: unless a specific time or duration (or testing standard/protocol) is specified for any given current rating, the current rating provides little insight into how the device will perform in the realworld.

I do agree the lack of companies putting this in there advertising makes things a little more difficult. personaly I have never been met with any issues when I email the company and ask for that information.

[otrfun]

StirCrazy wrote:

otrfun wrote:
. . . Choosing a capable 2000w inverter is important. Not all 2000w inverters are created equal. Although most inverters can supply their continuous current rating, many fall short providing suitable amounts of inrush current. Inrush current is necessary to successfully start a/c units and microwaves. Unfortunately, very few manufacturers provide inrush current specs for their inverters.
Good luck!

inrush and starting current are the same, just different names depending on the type of equipment. in rush covers any time a electric componant temporatly draws more power when you turn it on, in a motor it is generaly called starting current. every inverter I have seen lists this as peak power. and its usaly a couple K watts above the rated output. for example the renogy is a 2000 watt inverter continious with a peak of 4000 watts that will handle anything on a rv but maby not two large power users at once.

Steve

IMO starting current is just a colloquial term to sometimes describe inrush current and not related to any particular type of equipment. Also, peak current is very different from inrush current (see last paragraph).

IMO the most important takeaway when discussing inrush, starting, peak, or surge, current is the following: unless a specific time or duration (or testing standard/protocol) is specified for any given current rating, the current rating provides little insight into how the device will perform in the realworld.

For instance, I could claim a 12vdc/120vac inverter has 2000 watts (16.6a) of continuous output. Notice I specified current AND time/duration (continuous). This is 100% useable data that translates into realworld performance. I could also claim this same inverter produces 4000 watts (33a) of surge or peak output. However, if I don't specify a time or duration it's a meaningless claim in terms of realworld performance. If I claimed it could produce 33a for, say, a few milliseconds, then that 33a is completely useless. Not enough time/duration to help start an a/c compressor or motor. Now, if I claimed it could produce 33a for almost a second (or longer), that's a huge deal in terms of realworld performance---exactly what an a/c compressor or motor needs to sucessfully start. Time/duration is everything in this context.

I've found the following to be generally true for consumer grade inverters and inverter generators: There is no standardized time/duration for a surge rating. Depending on manufacturer, it can range from a fraction of a second to as long as 30 min. A surge rating can be useful *IF* a specific time/duration is specified. IMO peak current is more of a marketing ploy because the time/duration for peak current (1 or 2 cycles) is too short to be of much use in a realworld environment. Time/duration for inrush current is much, much longer (approaching a second). Assuming sufficient current, this is exactly the time/duration necessary to successfully start an a/c compressor or motor.