Supercapacitor or light load startup to save inverter surging from welding/electric stove

[Brandon8792]

Hello!

So I already have a 12kw Growatt inverter all in one, and 2 300ah lifepo4 packs in parallel together.

I know the lithium doesn’t have an issue pushing the power and I know the inverter doesn’t. However, it seems to put strain on the inverter (in my opinion) when I turn the stove on; or say start a welder and then stop and then start and then stop…

I was going to add 240v super capacitor into the ac line set to try to eliminate the startup load on the inverter and instead let the inverter slowly/somewhat quickly charge the capacitors back up… I guess like a supercapacitor in an audio setup… however I know that’s dc and don’t really see how I’ll make that work…

My mini splits are soft start, so then I thought about a soft start for the whole house, but then idk if a welder or stove would even work that way… so I’m just mainly worried about lifespan on the inverter with things like this. It seems that wouldn’t be very good on the inverter… I know it seemed to really not be a fan of the welder, even though it didn’t pull near the max.

Let me know what I could do to try to limit it… even if you think it’s useless, I would feel more safe not putting such big startup strains on the inverter even with it being a transformer.

 

[A.Justice]

Your first step would be to grab an inrush current meter and find out exactly how much the inrush current is on those devices. It's hard to give any decent advice without knowing some numbers.

 

[Brandon8792]

Without buying an in rush current meter, I was able to find some information from the manufacturer.

The model 155 draws max 25.4 amps on 230V in MIG mode or, 5842 watts. It draws 26.7amps on 230V in stick mode or, 6141 watts.

This is an inverter based welder, and portable. It’s not anything big or crazy. But even if it was, I’m trying to find something that will be able to limit in rush current on everything, whether it’s big or smaller, so it can make work on the inverter easier… or better yet, something to go inbetween the line of the inverter to the main breaker box that will pull off of it first and not put such a big load on the inverter and instead a load on what’s inbetween (this is probably not going to work because the inverter will then just want to push power to charge that product up).

So as you can see I’m kind of conflicted on what could even be used to try to help make things easier for the inverter load… maybe this isn’t necessary, but I really feel the inverter didn’t like when a weld spark was started, stopped for maybe 1/4 of a second and then started right back… sounded like it made it buzz which went away but it seemed to piss it off so that’s why I’m even looking into this stuff

 

[bgflyguy]

It might be the DC side as well. Are you using 24v or 48v? Even if it's 48v, if you have bad connections or if one battery has substantially less resistance you could be seeing problems with your batteries.

Be sure to check all the connections under load.

 

[Brandon8792]

It might be the DC side as well. Are you using 24v or 48v? Even if it's 48v, if you have bad connections or if one battery has substantially less resistance you could be seeing problems with your batteries.

Be sure to check all the connections under load.

Never thought of that.

It is 48v yes. Batteries are in great health. Connections solid.

 

[mikejoconnor]

I've considered adding a super capacitor as well. I'm interested to see where this discussion goes.

 

[Hedges]

Problem could be the current waveform.
Inverters for 120/240VAC production produce sine wave voltage, expect sine wave current.
A switching power supply with poor power factor has just rectifier and capacitor front end. OK for some small loads. If your inverter welder is drawing multiple kW in the form of brief current spikes near peak of voltage waveform, that could be the problem.

Have a large AC motor you could connect and run (with no load on it)? That rotating mass might serve to "stiffen" the supply and take care of those burst of current. I've been meaning to measure current waveform of my VFD (for 2 HP pool pump) and then add a motor for similar reasons.

 

[toms]

Supercap will reduce discharge current from your battery, and eliminate AC ripple from an AC-DC charge source.

I use this system to allow a smaller battery to be used.

 

[CVdave]

Without buying an in rush current meter, I was able to find some information from the manufacturer.

The model 155 draws max 25.4 amps on 230V in MIG mode or, 5842 watts. It draws 26.7amps on 230V in stick mode or, 6141 watts.

This is an inverter based welder, and portable. It’s not anything big or crazy. But even if it was, I’m trying to find something that will be able to limit in rush current on everything, whether it’s big or smaller, so it can make work on the inverter easier… or better yet, something to go inbetween the line of the inverter to the main breaker box that will pull off of it first and not put such a big load on the inverter and instead a load on what’s inbetween (this is probably not going to work because the inverter will then just want to push power to charge that product up).

So as you can see I’m kind of conflicted on what could even be used to try to help make things easier for the inverter load… maybe this isn’t necessary, but I really feel the inverter didn’t like when a weld spark was started, stopped for maybe 1/4 of a second and then started right back… sounded like it made it buzz which went away but it seemed to piss it off so that’s why I’m even looking into this stuff

I would run a generator for the welder

 

[Brandon8792]

I would run a generator for the welder

I would, but the whole point of me overbuilding the system, is so id never have to be dependant on a generator, gas anything. Just the solar.

 

[mikejoconnor]

I would, but the whole point of me overbuilding the system, is so id never have to be dependant on a generator, gas anything. Just the solar.

Well then the obvious solution here is to convert the generator to run on ethanol, grow some corn, and use the excess solar in the summer to distill the ethanol. Problem solved.

 

[Quattrohead]

I think anyone running a welder on an inverter is nuts, seems like a good way to kill them. And WTF is a super capacitor connected to AC ?

 

[Hedges]

Motor-generator would be a good way to isolate welder. Or a motor-generator welder.

 

[MurphyGuy]

Why would a stove produce a surge current? Is this an induction stove or just a normal heating element?

Also, and you should double check on this, but I think inverter type welders have their own surge storage built right into them..

How far is your battery bank from the inverter and what size wire are you running?

 

[Hedges]

Also, and you should double check on this, but I think inverter type welders have their own surge storage built right into them..

But likely a horrible power factor.
Simple rectifier/capacitor front end? But putting out multiple kW, not just 250W like my laptop supply?

 

[MurphyGuy]

But likely a horrible power factor.
Simple rectifier/capacitor front end? But putting out multiple kW, not just 250W like my laptop supply?

I have a Millermatic 251.. Its a very large welder for residential uses, small by commercial or industrial standards. when welding heavy 1/4 inch plate for pressure applications, I draw around 7.5kW.. but such welding is pretty rare. Most home owners weld sheet metal.. 11ga, 14ga plate, angle iron, etc. I probably draw around 2.5 kW when welding thin metals, or roughly the equivalent of a 240 volt hot water heater element.

I think the key statement here is that his stove causes the unit to act up.. and unless there's something about his stove I'm not aware of, resistive loads don't have an in-rush current.. In fact, its just the opposite if my experience with running my toaster on a cheap inverter is any indication. It seems that a sloppy sine wave is more likely to reduce power at the element than make it run hotter.

This leaves me thinking that something in his system is having a problem keeping up with the specs listed on the inverters.. I figure the battery cables are a good place to start, then dig into the delivery specifications of his battery bank..

Your motor idea is a good one. I ran a 3 phase system from a residential 240 supply using a 15hp rotary phase converter. The more pumps and motors we had turned on, the smoother things ran. That third leg was never happy until it had the company of another 3phase motor running. None of our servo controllers would act right until at least one pump was turned on.

 

[Hedges]

Your motor idea is a good one. I ran a 3 phase system from a residential 240 supply using a 15hp rotary phase converter. The more pumps and motors we had turned on, the smoother things ran. That third leg was never happy until it had the company of another 3phase motor running. None of our servo controllers would act right until at least one pump was turned on.

I just tried a 1.5 HP sprinkler pump (induction motor) at the other end of house while running 2 HP 3-phase pool pump. It still showed the huge brief current spike each cycle. But inconclusive/confusing other behavior, spikes when I compare to resistive heater load seemed opposite polarity.

My paralleling a rotating motor didn't seem to help with the VFD front end.

But motor-generator isolation should do it.

I've run (or at least spun) a 3-phase motor-generator welder with 240VAC, after first spinning it with 24VDC on the welding circuit.

 

[stok]

slightly off topic but concerns welding from a inverter none the less.
I have a 3kw meanwell TS3000 224, 24v to 240v inverter with 2 banks of 8s 120ah cells each with a 60a bms (225a peak) and a 7s 120ah lion pack with a 60a ( ??a peak) bms that powers my house(gas cooking, heating and gas geysers) I have a fairly old +- late 80's stick welder with info plate removed so i do not know the input power, it is adjustable for 40, 55, 65, 80, 100, 140 amps, with my setup I can do a lot of welding I usually use 100a welding current, and i have used 140 also without my inverter or bmses disconnecting. Also have 2kw pv feeding two victron smartsolar 100/50 scc's. The only time i have ever experienced my inverter tripping on overload is when we use the eclectic kettle and microwave at the same time, or the hairdryer( still do not understand why my wife need a 2600w hair dryer)

recently I used it extensively to build burglar bars and security gates for my house, gates used 22mm round bar and 5mm flatbar, burglar bars I used 12mm round bar. Not really continuous welding more like welding 5cm beads every 5 minutes or so.

the past days I experimented with headway 40152 cells, 9 in series seems to give a nice arc distance but it dumps alot of amps into the weld, DCEP it burns a hole in everything thinner that 5mm before you have time to spread the weld pool, DCEN slightly more controllable but you have to move FAST.

I would like to regulate the dc amps from the headway cells to about 100a, do any of you have a idea how I can achieve this in a purely DIY way?
a 0.28 OHM resistor in series seems like it will work, but how do I make one that can withstand the short circuit amps delivered by a 2p9s headway pack I am unsure of the short circuit amps of these cells according to data sheet they do 225amps peak.

 

[mrzed001]

Hello!

So I already have a 12kw Growatt inverter all in one, and 2 300ah lifepo4 packs in parallel together.

I know the lithium doesn’t have an issue pushing the power and I know the inverter doesn’t. However, it seems to put strain on the inverter (in my opinion) when I turn the stove on; or say start a welder and then stop and then start and then stop…

I was going to add 240v super capacitor into the ac line set to try to eliminate the startup load on the inverter and instead let the inverter slowly/somewhat quickly charge the capacitors back up… I guess like a supercapacitor in an audio setup… however I know that’s dc and don’t really see how I’ll make that work…

My mini splits are soft start, so then I thought about a soft start for the whole house, but then idk if a welder or stove would even work that way… so I’m just mainly worried about lifespan on the inverter with things like this. It seems that wouldn’t be very good on the inverter… I know it seemed to really not be a fan of the welder, even though it didn’t pull near the max.

Let me know what I could do to try to limit it… even if you think it’s useless, I would feel more safe not putting such big startup strains on the inverter even with it being a transformer.

When you start a big load maybe lights goes darker for a sec? Check that AC (and DC) cables are strong enough and no bad connection.

I do not think it is possible to soft start the whole house
But you can soft start separate equipments. Soft starter/VFD for pump, electric motors.

And best to use equipment with inverter already in it.
Inverter AC, washing machine, dishwasher, pump, welder ... no inrush, no problem.

The real joke is that theoretically equipments with inverter can run even directly from DC. Like a PC/server/freezer too.

 

[120vjohn]

DC battery seems to deal with your inrush currents, 12kw inverter is enough for one appliance at a time, problems occurs in worst situations of same time start.
Pay attention at inrush reactive power, it can be mostly reactive than active.
IF you use a hi voltage battery some appliances can directly powered, as electronics and lighting.
My battery is 120vdc directly compatible with common appliances, even in Europe with 230v standard, but I power them on inverters dc bus at 310vdc.