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actual capacity of an inverter

Daddy Tanuki

Emperor Of Solar
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so in another thread a member was commenting on his inability to power a chop saw with a solark 12K. i have been using the magnum 2012 (2000 watt 12 volt LF inverter) in my camper all the time to power my chop saw while i was building my shop. this was repeated cuts on 100x100x4.2 (4x4x3/16") steel beams.

currently I am running two of the 4448's in parallel. what are other members results running these 12k, 16k, and supposed 18k HF inverters?

i mena if a 12k inverter cannot start a 14" chop saw then is it really 12k? it seems to me its not even 2k.

thoughts, complaints, gripes?
 
The solark 12K was only rated for 8 KW of output, later updated to 9 kilowatts. However it is very protective of its output and whilst I'm sure the electronics could probably take the surge the firmware won't let it.
I don't doubt it could run an 8 kilowatt load for 24 hours no problem but it is not a serger.
 
Yeah I have yet to find the limit of my 4k/24v LF inverter. I used it while building the cabin so we had a table saw, skill saw, miter saw, angle grinder and a few milwaukee batteries charging at any given time. It also powers my 120v/50ft deep well and the fridge. Never a hiccup.
Quite frankly if i dont add any sort of resistive heating like water heater or baseboard heat i dont think ill ever max it out.
Im a bit stuck in my ways but HF inverters are not attractive to me. They remind me of Ford putting a 13,500lb tow rating on an F150, i just mumble to myself "yeah right..." 😅
 
Until you have all the facts in hand it is hard to say if the problem is the inverter or the load placed on it. 14 inch chop saws can have widely different horse powered motors. Inverters can be wired improperly or be supplied by inadequate battery capacity. On the face of it I am inclined to think it is not the fault of the inverter. This is based on running all kind of things off my HF AIO's of much less rating than a 12kW unit has. For instance I have not found anything that plugs into a normal 15A 120vAC outlet that my 3kW AIO's will not start and operate.
 
I really haven't seen anyone post about any well known inverters that weren't able to meet their ratings. But some of the no name units have been known to release the smoke, when pushed to their limits.
The only issue here was that someone assumed that Sol-Ark named their inverters by their output. Which is completely understandable. But it's not the case.
It's just deceptive marketing used by Sol-Ark and EG4.
With those two brands, you can't go by the names. You have to look at the actual specs.
 
Most AC motors have a large spin up surge current that can be 4 to 6 times the run current that has a time duration of about half a second. It is also very inductive during startup meaning the peak sinewave current lags the peak sinewave voltage by close to 90 degrees phase shift. This causes a very poor power factor (0.2 to 0.4) during startup.

The inductive reactance causes the motor to draw more peak current. Part of peak current is inductively stored during part of the sinewave cycle and given back up to AC supply source during other part of sinewave cycle. This is a reverse power flow back to AC source during a portion of the AC cycle.

Reactive power factor copy.png

HF inverters don't like poor power factor, reactive loads that spits back power during a portion of the sinewave. It causes feedback control stability issues on battery to HV DC converter. They typically start to have problems with stability for an inductive load power factor less than 0.75.

LF inverters' large, heavy, low frequency transformers can support overload current with low power factor, inductive loads, better. LF inverters are inherently bi-directional capable in power flow and just pushes the partial sinewave cycle inductive return current back to batteries. (Yes, there can be charging battery current push back for a portion of AC cycle). The inherent, instant bi-directional power flow change capability also make LF inverters much better choice for AC coupling of PV GT inverters.

HF inverters may specify a peak surge current but say nothing about allowable time duration or spec something like 1 to 10 milliseconds. Such short surge duration time allowance is fairly useless for starting up an AC motor.

SolArk and Deye have a large bank of HV DC storage capacitor that helps supply surge current and keep battery to HV DC converter stable at a lower load power factor, but still unable to support very low power factor, high current, loads less than 0.5 to 0.6.

Diagrams for a LF inverter battery current profile:
Inverter power factor waveform.png
 
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I have heard the Midnite Rosie can surge quite well for an HF inverter. They say 8400va for 30 seconds and max surge of 15000va but as mentioned above, they dont spec the duration for the 15k max... They just say "surge up to 3x its rating" (which is contrary to the spec sheet of 15k max) or "starting a 11kw 120v load on imbalanced legs is a cake walk" or something to that effect. Being a 7kw rated split phase inverter thats still pretty good. Id really like to try one out but i cant bring myself to decommission my current system that works flawlessly.

@Brucey have you loaded that Rosie up yet?
 
I ran a magnum 4448 for 14 years, it powered everything i threw at it.
I know 2 friends upgraded to solarks, one had an outback system the other had a magnum, both have overload problems to this day.
My opinion with HF inverters is you need to go bigger then a LF inverter to get the same performance
 
I have heard the Midnite Rosie can surge quite well for an HF inverter. They say 8400va for 30 seconds and max surge of 15000va but as mentioned above, they dont spec the duration for the 15k max... They just say "surge up to 3x its rating" (which is contrary to the spec sheet of 15k max) or "starting a 11kw 120v load on imbalanced legs is a cake walk" or something to that effect. Being a 7kw rated split phase inverter thats still pretty good. Id really like to try one out but i cant bring myself to decommission my current system that works flawlessly.

@Brucey have you loaded that Rosie up yet?
Not yet been working on adding more panels to deal with potato winter production. Mostly been on grid. Also working on getting solar assistant working with it (added to beta last week).
 
As I understand it, the 12k is a bit of an outlier on the naming convention.

Sol-Ark 8k outputs 8k continuous
Sol-Ark 12k outputs 9k continuous
Sol-Ark 15k outputs 15k continuous

According to their spec sheets.

That said, powering out on a chop saw could easily be a battery issue. Too little battery to support the startup surge.

Either way, I'm glad I went with the 15k. My theory is that the marketing team got the best of the engineers on the 12k, and that somehow reverted on the 15k (likely due to complaints). Who knows what happens in the background at these companies...
 
I have had a Solark 12k and currently have a Solark 15k. There was nothing 120v that would shut down my 12k, including 120v welders and 120v air compressors.

I do know a while back there was a problem with many SolArks that the firmware was programmed too sensitive to surges (like mentioned above), and an update fixed a lot of it. I kept mine up to date and never had a problem.

There's too many variables between people's systems (like also mentioned above) to say for sure that the equipment had a physical problem.
 
I have the Growatt SPF in both 6k and 12k. The warden used to occasionally cause an overload fault on the 6k but the 12k remains undefeated. I don't know for sure but doesn't that big heavy transformer allow a certain amount of overload on one leg to get assistance from the other?
 
OK so the solark 12k is only an 8k inverter, with low surge capability and even at that it can't keep up with a 2k LF inverter? regarding battery and cables for the inverters... remember how big of a cable it takes for a real 2kW inverter at 12 volts? yeah... if two 12 volt agm's with 500 watss of solar can power a chopsaw and a solark 12 K cannot there is something wrong somewhere... anyway was just curious if anybody had actually loaded or sued used one of them and managed to actually get nameplate from it

edit: sorry dyslexia kicked in as usual, ignore the typo's please.
 
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Miter saws use DC brushed motors that have low inductance and behave like a short circuit at stall. I measured 170A peak from one. Some inverters clip AC voltage output to maintain output current and can start this kind of saw. Some inverters are designed to trip immediately. Seems like EG4 and Solark line of inverters are tuned to trip rather than clip voltage. A small firmware tweak could fix that.
20241026_204126_resized1-jpg.252208
 
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In my case it was 100% the Solark 12K inverter and the firmware is fully up to date. I swapped it for a sungold power SP6548 (yes I know that are rated for 6500w output) and it handled the same equipment with no problem at all on the same battery.
I've never even thought what I'm throwing at the 18 kpv, it just does it.
By the way I'm not slagging my Solark 12k, I think it is a very fine inverter it just errs on the side of caution and that's all right.
 
If it has PV / grid to support it, otherwise it's 12KW; 6 per leg.
Yes, In theory. I do think that is just spec'd for the worst-case battery scenario. Will report back if I test beyond 12k off-grid, and at night.

Lt.Dan's experience with 120v loads lends credence to a firmware problem, or to people running things without a good battery. While I'm sure you ran enough battery Quattro, I'm not sure everyone does. For example, our Sol-Ark 15k's can push approx. 24,000 watts for a 10 second peak load (again spec sheet numbers). You need a pretty dang big battery to support that. I used 6 server rack batteries as a minimum when setting up my system in an attempt to avoid the battery bottleneck.

Simple realities and mathematical limits are not something everyone takes into account.
 
OK so the solark 12k is only an 8k inverter, with low surge capability and even at that it can't keep up with a 2k LF inverter? regarding battery and cables for the inverters... remember how big of a cable it takes for a real 2kW inverter at 12 volts? yeah... if two 12 volt agm's with 500 watss of solar can power a chopsaw and a solark 12 K cannot there is something wrong somewhere... anyway was just curious if anybody had actually loaded or sued one of them and managed to actually get nameplate from it
If you find that interesting, you are going to love the EG4 naming conventions! I do agree that the 12k is not named decently. I also think one person's example is not a great example since there are so many variables.
 
Miter saws use DC brushed motors that have low inductance and behave like a short circuit at stall. I measured 170A peak from one. Some inverters clip AC voltage output to maintain output current and can start this kind of saw. Some inverters are designed to trip immediately. Seems like EG4 and Solark line of inverters are tuned to trip rather than clip voltage. A small firmware tweak could fix that.
20241026_204126_resized1-jpg.252208
I think this could be seen also as deliberate design choice. On larger system run with 18k solark there would be possibly whole lot equipment experiencing brown-outs if the inverter has sort of "soft start" or active output limiting. Faulting to overcurrent shut-off tells the end user that the connected equipment is behaving "badly" and drawing excess current instead of whole household experiencing reoccuring brownouts and even possible equipment failures.
Having said that I'd think I would rather have inverter that starts the motor even if it supplies wrong voltage instead of shutting off.
 
I have the Growatt SPF in both 6k and 12k. The warden used to occasionally cause an overload fault on the 6k but the 12k remains undefeated. I don't know for sure but doesn't that big heavy transformer allow a certain amount of overload on one leg to get assistance from the other?
Sort of, but not exactly that.
The inverter creates single phase, and the transformer turns it into split-phase.
So, both legs of output are coming from the same input. Leg imbalance is only seen at the transformer output, and has no affect on the inverter itself.
 
Sort of, but not exactly that.
The inverter creates single phase, and the transformer turns it into split-phase.
So, both legs of output are coming from the same input. Leg imbalance is only seen at the transformer output, and has no affect on the inverter itself.
So it's not a pair of 6k inverters but actually one 12k inverter?
 
Faulting to overcurrent shut-off tells the end user that the connected equipment is behaving "badly" and drawing excess current instead of whole household experiencing reoccuring brownouts and even possible equipment failures.
Having said that I'd think I would rather have inverter that starts the motor even if it supplies wrong voltage instead of shutting off.
connected equipment is behaving badly? no the connected inverter is behaving badly. sorry AC motors been around longer than HF chinesium inverters... if the old american designed inverters can do it then there is something wrong with the chinese inverters as they cannot....

that or like everything that comes out of china its a lie and its not a 12k or even an 8k inverter inside of the case but lets be kind and call it a crappy 2kw inverter. and that would be closed to the truth.

it seems to me that the solark line is a line of craptastic junk with highly inflated output number in other words it only hit these numbers when lightening strikes the unit and gives it a boost.
 

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