Wire a large inverter?

[dtbaker61]

Keep in mind inverter efficiency is less than 100%, so it will draw more power than it outputs. If you have a 1500W inverter that's 80% efficient, it will draw 156 amps at 1500W output continuous. Some cheaper inverters are only 70% efficient, more expensive ones are 90%+. That's why I would limit things to 1500W continuous or less.

Also you don't need to derate inverters. A good quality 1500W inverter will output 1500W all day long. Cheap China crap may not do so well.

I like the idea of a 1500W inverter because it will shut down on overload before the Mach-E's electrical system is maxed out. Kinda makes it almost impossible to overload.

the problem with small inverters is inductive loads.... power tools in particular if running directly. Fortunately, most people can get away with cordless tools and only have to run a battery charger.

This is why I usually use my 'portable power pack' that has a 1 kWhr 'buffer battery' to suck up the surge loads.

But, I am still thinking about putting a 1500watt under the back cover on the driver's side where there is a pretty big available space.

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[bbulkow]

the problem with small inverters is inductive loads.... power tools in particular if running directly. Fortunately, most people can get away with cordless tools and only have to run a battery charger.

This is why I usually use my 'portable power pack' that has a 1 kWhr 'buffer battery' to suck up the surge loads.

But, I am still thinking about putting a 1500watt under the back cover on the driver's side where there is a pretty big available space.

Yes, exactly. However, to my extraordinary disappointment, the 1kwh battery buffer I bought will not run any of my tools, despite being rated to 1800wh "surge". I chose poorly, apparently, and I've been looking for a "buffer for my buffer" (is there a small appliance with a capacitor that will smooth a 3 second 2x spike to a 9 second 30% spike? This would greatly improve the usefulness of my battery buffer). Therefore, more interest in a good inverter solution for the car as well.

The inverter I'm looking at is > 90% efficient and rated for 3 second 2x load. I don't intend to get burned by that particular failure.

There's what I would call an ecosystem sweet spot that starts at 1500w, because lots of US houses have circuits that are fused to 15A 110V, so manufacturers have a tendency to build within a (rough) 1500W envelope, even for aggressive power users like a sawzall. 1200w is conservative, but (given a 90% efficiency unit) 1500w seems the minimum I would go with. I own a 2kw gas generator for the same ecosystem reason, it's been very kind to me (eg, drives my 15A 110V restaurant grade espresso machine). Being stuck with a non-functional tool and a really big battery is a fresh memory and one I am not eager to repeat.

It should be possible to overload the 12v bus by running the inductive heater in the car and putting a large external load on. A person would have to be careful about the multiple users of a circuit. While I would expect that circuit to be fused at the source, I realize this case may have complexities around multiple sources.

The efficiency rating issue - where a 2000A will draw 175A - may push me to the 1500W unit. Still considering. Might look up where that fuse is located (any tips on that appreciated).

 

[dtbaker61]

Yes, exactly. However, to my extraordinary disappointment, the 1kwh battery buffer I bought will not run any of my tools, despite being rated to 1800wh "surge". I chose poorly, apparently, and I've been looking for a "buffer for my buffer" (is there a small appliance with a capacitor that will smooth a 3 second 2x spike to a 9 second 30% spike? This would greatly improve the usefulness of my battery buffer). Therefore, more interest in a good inverter solution for the car as well.

The inverter I'm looking at is > 90% efficient and rated for 3 second 2x load. I don't intend to get burned by that particular failure.

There's what I would call an ecosystem sweet spot that starts at 1500w, because lots of US houses have circuits that are fused to 15A 110V, so manufacturers have a tendency to build within a (rough) 1500W envelope, even for aggressive power users like a sawzall. 1200w is conservative, but (given a 90% efficiency unit) 1500w seems the minimum I would go with. I own a 2kw gas generator for the same ecosystem reason, it's been very kind to me (eg, drives my 15A 110V restaurant grade espresso machine). Being stuck with a non-functional tool and a really big battery is a fresh memory and one I am not eager to repeat.

It should be possible to overload the 12v bus by running the inductive heater in the car and putting a large external load on. A person would have to be careful about the multiple users of a circuit. While I would expect that circuit to be fused at the source, I realize this case may have complexities around multiple sources.

The efficiency rating issue - where a 2000A will draw 175A - may push me to the 1500W unit. Still considering. Might look up where that fuse is located (any tips on that appreciated).

I have build and used both 1500 and 3000 watt pure sine inverter + battery packages, and use the MME 12v export basically just as a charger. you will need a 3000 watt inverter to start a typical 120vAC powertool and 4000 or even 6000watt to start a 1 horse (750watts running) compressor or ac unit.

 

[bbulkow]

I have build and used both 1500 and 3000 watt pure sine inverter + battery packages, and use the MME 12v export basically just as a charger. you will need a 3000 watt inverter to start a typical 120vAC powertool and 4000 or even 6000watt to start a 1 horse (750watts running) compressor or ac unit.

3000W? So it's pulling 6000W during its surge? Wow.

Or would a 1500W with a 3000W 3 second surge rating do it, generally? (or 2000 with 2x...)

 

[tarheelluv]

I connect my inverter with very heavy-duty alligator clamps to the areas noted on these drawings.

 

[dtbaker61]

3000W? So it's pulling 6000W during its surge? Wow.

Or would a 1500W with a 3000W 3 second surge rating do it, generally? (or 2000 with 2x...)

an old compressor or rv ac unit with 1 hp motor will not start with a small inverter.... inductive motors can pull 8x their run load at start unless they have modern soft start

 

[dtbaker61]

I connect my inverter with very heavy-duty alligator clamps to the areas noted on these drawings.

alligator clamps don't have much surface area in contact.... ok for temp use, but not extended high current. much better to install d-rings at posts, perhaps with suitable big Anderson disconnects rated for 150a

 

[bbulkow]

an old compressor or rv ac unit with 1 hp motor will not start with a small inverter.... inductive motors can pull 8x their run load at start unless they have modern soft start

Well.

I think you've convinced me to measure load with the handful of tools I have and see what they draw before buying inverters.

I also find myself thinking - but - there's a breaker on my home circuits. I might have a 10A motor based appliance with 7A 110v steady state, but if it's pulling 50A, on a 15A rated circuit without blowing the breaker, it better be for a short period.

This implies there's a spec for breakers. Some number of seconds over amp is OK, with some limit. A casual search hasn't found the spec yet, but it's got to be out there. Having an inverter (or the inverter on a battery device) match that same spec would give the best compatibility. All of the tools I have don't trip breakers.

I have also greatly upped my supply of battery based tools after this excursion. It could be I just lean into that; it seems the modern way, go device by device replacing as I need.

More research required, down the rabbit hole.

[ Of course agree about connectors, alligator clips at these power levels are temporary. I've always found Andersons annoying, but will figure something out. There's got to be a more standard DC plug format that's easier to use than Andersons. ]

 

[dtbaker61]

Well.

I think you've convinced me to measure load with the handful of tools I have and see what they draw before buying inverters.

you will need a really good multimeter capable of capturing and displaying 'in-rush current'. The start-up current is required less than a second before settling to load wattage.

I can tell you for a fact that a 1500 watt, and even a 3000watt inverter cannot successfully 'start' even a small 120v table saw or 1hp air compressor. Also will not start an old 1hp RV air conditioner that will run on 120v-30a shore power. Believe me, I've tested.

You will need at least a 6000watt pure-sine inverter to start these kinds of loads, and would be wise to put at least 1- 12v-100ah battery in between as a buffer for the MME dc-dc converter.

There are some really great inverters out there, but not many 12v-6000watt ones. The cheapest one If found is WZRELB
https://www.amazon.com/WZRELB-6000W-10000W-120VAC-Inverter/dp/B07ZBHSCWS/ref=sr_1_5?

I also find myself thinking - but - there's a breaker on my home circuits. I might have a 10A motor based appliance with 7A 110v steady state, but if it's pulling 50A, on a 15A rated circuit without blowing the breaker, it better be for a short period.

exactly.
branch circuit breakers are NOT instant blow, so a grid-tied system sucks up the surge no problem. resi breakers overload duration is a combination of overload current, and time.

Surge current from inductive motors lasts less than a second, so it doesn't blow a household breaker unless the RUN current exceeds the breaker capacity.

There's got to be a more standard DC plug format that's easier to use than Andersons. ]

It's not easy to find DC plugs or disconnects for more than 40amps.... no matter what you find, you do NOT want to connect or disconnect under load! DC arcs are Loooong, and will pit or weld contacts if you make or break connection under load.

 

[bbulkow]

you will need a really good multimeter capable of capturing and displaying 'in-rush current'. The start-up current is required less than a second before settling to load wattage.

I can tell you for a fact that a 1500 watt, and even a 3000watt inverter cannot successfully 'start' even a small 120v table saw or 1hp air compressor.

I believe you.

Yes, I'll have to look at my fluke and see exactly what it supports. It's a solid high end model, I'd expect some kind of setting to capture and hold a peak, and I don't remember a setting like that, so maybe it does, maybe it doesn't. Down the rabbit hole.

Were the inverters you tested promising 3 second surge support? Because a 2,000W promising 3s 2x would seem to cover a lot of ground (although not all the way to table saw). I also get it about voltage sag on the small 12v.

I'll probably sniff around the solar connectors. I've just started fooling with large panels, but they seem to have screw-style connectors rated for high voltage & current.

 

[dtbaker61]

I believe you.

Yes, I'll have to look at my fluke and see exactly what it supports. It's a solid high end model, I'd expect some kind of setting to capture and hold a peak, and I don't remember a setting like that, so maybe it does, maybe it doesn't. Down the rabbit hole.

Were the inverters you tested promising 3 second surge support? Because a 2,000W promising 3s 2x would seem to cover a lot of ground (although not all the way to table saw). I also get it about voltage sag on the small 12v.

inexpensive 'transformerless' inverters cannot handle inductive motor starts very well at all. If you get a 'good' transformer inverter/charger with 3kw capacity like a Magnasine or AIMS, then the size, weight and cost is higher than a cheaper 6000watt like the WZRELB

but go ahead poke around , see what you come up with!

For construction site powertools up to 1hp, I am betting you are going to end up with: 6000 watt inverter, 2x-12v-100ah batteries, 2awg wire with d-rings to MME 12v connections, Anderson connector in the middle.

....speaking of work.... I gotta go.

 

[Neandrewthal]

I also find myself thinking - but - there's a breaker on my home circuits. I might have a 10A motor based appliance with 7A 110v steady state, but if it's pulling 50A, on a 15A rated circuit without blowing the breaker, it better be for a short period.

This implies there's a spec for breakers. Some number of seconds over amp is OK, with some limit. A casual search hasn't found the spec yet, but it's got to be out there. Having an inverter (or the inverter on a battery device) match that same spec would give the best compatibility. All of the tools I have don't trip breakers.

The terminology you're looking for for home circuit breakers is the "trip curve" or "time-current curve." See attached. Short version is that a residential breaker will allow 6-7X the rating for a few seconds, which sure seems like a lot! More interesting to me is that they can allow 2x for an entire minute or more.

 

[ChasingCoral]

You could also consider switching to a vehicle with 9.6 kW of available onboard power in 110v and 220v outlets:
https://www.ford.com/trucks/f150/f150-lightning/

 

[bbulkow]

The terminology you're looking for for home circuit breakers is the "trip curve" or "time-current curve." See attached. Short version is that a residential breaker will allow 6-7X the rating for a few seconds, which sure seems like a lot! More interesting to me is that they can allow 2x for an entire minute or more.

Excellent, data curves. I see 2x crossing at about 10 seconds, 1 minute is hard to read because it's a log curve but I'd guess 20%. Had no idea the curve was so wide.

That certainly does push me to a high quality 2,000W inverter, which will *maybe* allow a few more plug-in tools than currently survive. I have few 1hp tools. The numbers I see on fairly high quality inverters are specified as 2x for 3 seconds minimum. 4,000W is 2.4x of 15a 110v, but 3 seconds is not 10 seconds by a long shot.

I don't think I'm *that* serious about all this, I don't want a huge truck just because of one inverter issue. I'll buy more battery powered tools and rig myself our for more charging instead.

 

[dtbaker61]

Excellent, data curves. I see 2x crossing at about 10 seconds, 1 minute is hard to read because it's a log curve but I'd guess 20%. Had no idea the curve was so wide.

That certainly does push me to a high quality 2,000W inverter, which will *maybe* allow a few more plug-in tools than currently survive. I have few 1hp tools. The numbers I see on fairly high quality inverters are specified as 2x for 3 seconds minimum. 4,000W is 2.4x of 15a 110v, but 3 seconds is not 10 seconds by a long shot.

I don't think I'm *that* serious about all this, I don't want a huge truck just because of one inverter issue. I'll buy more battery powered tools and rig myself our for more charging instead.

the new 40v cordless tools are pretty damn good. Get matching brand tools (milwaulkee good by expensive, or Hercules are surprisingly good), two batteries, and one 120v charger.... charge one battery while you work the other and swap batteries all day long charged from MME via 1500watt inverter.

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