How to - Export 12v DC to 120vAC power from LVB connection points

MarleysMME

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On a related note, has anyone checked into bi-directional chargers? I have seen a couple almost on the market, Wallbox Quasar being one of them. I installed a PV system on my house recently but the storage batteries are very expensive and on backorder for 6 months. This extremely limits the usability of power generated by the PV panels. I would like to use my MME as a home storage battery through a bi-directional charger. Any thoughts?

An ironic twist: most home storage batteries I have checked into run around $1600/kwh. At that rate, it's cheaper to buy a second MME and dedicate it to home power storage!
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dtbaker61

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160A is not for 100% duty cycle!
...
I'll quote the service manual here: "Depending on the vehicle and environmental conditions, the DCDC is capable of outputting up to 160 amps to the 12-volt battery."
To me that says 160A is for a very short time (seconds)
I haven't been able to find any Ford documentation on exactly what the limitations are of energy export and duty cycle from the provided 12v 'connection points'. If you have a source, please publish!

when I look at the circuits uncovered below the connection point.... there are 70, 70, 125 amp circuits fed by the bus feeding the 12v+ connection point. So, with a 265amp max draw by the car thru that bus.... I would hope that 160amps could be provided by the dcdc at a fairly high duty cycle under 'regular' conditions..... but I haven't seen any docs to that effect one way or the other.
https://www.macheforum.com/site/threads/12v-fuse-box-inside-tour-photos.5578/

In my case I expect continuous loads to be less than 500 watts, probably less than 200watts most of the time, even if I use it for emergency house backup.... with only occasional bumps to 1500 watts running a tea kettle for a few minutes, or possibly an inductive cooktop at 1200-1500 watts for 20-30 minutes while camping.
 
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dtbaker61

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On a related note, has anyone checked into bi-directional chargers? I have seen a couple almost on the market, Wallbox Quasar being one of them. I installed a PV system on my house recently but the storage batteries are very expensive and on backorder for 6 months. This extremely limits the usability of power generated by the PV panels. I would like to use my MME as a home storage battery through a bi-directional charger. Any thoughts?

An ironic twist: most home storage batteries I have checked into run around $1600/kwh. At that rate, it's cheaper to buy a second MME and dedicate it to home power storage!

whole-home backup is challenge indeed. With the MME we have lots of battery available, but as you can see from this thread, a fairly small straw to sip from. Hence my short-term goal for inexpensive access to 'emergency backup' power , camping, or job site power to recharge hand tools.

Having PV on your home actually complicates the backup picture, because if the system has a typical grid-tied Inverter and no batteries/charge control and transfer switch.... you do NOT want to wake up the PV with a backup generator! You have to disconnect from the Grid AND from the PV before connecting any Generator

For true 'whole home' backup, there are options.... some ac-coupled, some dc-coupled, but all expensive. most have batteries configured in 48V chunks. In theory it would be possible to re-charge the 48v bank from the MME 12 connection points, but the transfer would have to be throttled by the transformer so as not to exceed the MME limitation on export wattage.
 

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I’ll also add that you need to consider inverter efficiency because that will increase input current draw. At peak load a good inverter might only be 80% efficient, so if it’s outputting 1000W it will be drawing 1250W. If it’s only 60% efficient it will be drawing 1666W from the battery to output the same 1000W. You need to account for this inefficiency so you don’t overload your source.

Based on all this, I’m really going to recommend that folks use a 1200W inverter or less. Here is the model I recommend if you want to do this: https://samlexamerica.com/products/1000-watt-pure-sine-wave-inverter-ntx-1000-12/

Max continuous input is 100A, which is inline with what the DC/DC can output with a safe margin for peak loads up to 2000W. Look at the inverter specs and make sure the max rated input amp draw is less than 120A (75% of 160A) on whatever model you choose. Good design principles would dictate that the inverter should shut down on overload before ever reaching 160A input.
I’m curious, what is the difference between the model you referenced and their other 1000W one here: https://samlexamerica.com/products/1000-watt-pure-sine-wave-inverter-pst-1000f-12/
 

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dtbaker61

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That's the older model that's less efficient (85% vs 90%), but would work fine too. The new model is more compact and efficient.
samlex is 'pretty expensive' compared to others that are perfectly fine and reliable these days... especially for only occasional use in backup systems.

There are many options for decent pure sine inverter in the 1000w-3000w range is available for less than $350. I would use a 2500-3000 watt inverter to cover the temp spikes in power demand... knowing that we really don't want the continuous draw to exceed 1200 watts to be friendly to our on board dc-dc 'recharge' system.

I used a cheapo little 'Efergy classic' monitor to measure my background loads... and verified that my house loads hover around 200-300 watts most of the time, with only occasional spikes for appliances like coffeemaker, microwave, etc. so as long as I don't run appliances at the same time, this should not put much of a strain on the MME dc-dc.

I did get a chance to test this out over the weekend.... works great. I was just using jumper cables from MME to Inverter temporarily to test. I'll make up some nicer cables and connectors when I have time and put together a DIY thread at some point....

One important thing to note is that because the MME LVB is so small, the voltage sag under loads is pretty significant.... unless the MME is 'on' so the internal dc-dc and HV battery are supporting the loads rather than the little LVB.

My system happens to have a couple batteries on the shelf to use for short outages, which are kept charged by standalone Solar (just one panel and charge controller)... The idea would be to have enough energy available for a couple hours whether MME was 'home' or not, and then use the MME for long-term backup if and when needed.

Interesting note is that since the MME provides energy at 13.5 volts, it will not only flow thru the Inverter, but also charge the batteries on the shelf! With the batteries on the shelf at 12.6-12.8, the 'natural' dc-dc charge rate from voltage difference is right around 7 amps without any additional charge control needed, so the 'shelf batteries' will get a charge while the MME is connected as a side benfit.

Ford Mustang Mach-E How to - Export 12v DC to 120vAC power from LVB connection points EV to 12v to invertor


Ford Mustang Mach-E How to - Export 12v DC to 120vAC power from LVB connection points bbu backfeed house
 
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ericNdfw

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ericNdfw

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dtbaker61, I went ahead and just ordered what looks like a similar one you have in your picture.

https://smile.amazon.com/WZRELB-Inv...pply/dp/B07HQ38J1S?ref_=ast_sto_dp&th=1&psc=1

Am interested to hear what cabling you decide on long term. I likely will just use good quality jumper cables for any emergencies we might have but would be nice to have dedicated wiring.

UPDATE: That link isn't showing the same one for some reason, it's a 2500W 12V model.
Ford Mustang Mach-E How to - Export 12v DC to 120vAC power from LVB connection points 1637104054595
 
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dtbaker61

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dtbaker61, I went ahead and just ordered what looks like a similar one you have in your picture.

https://smile.amazon.com/WZRELB-Inv...pply/dp/B07HQ38J1S?ref_=ast_sto_dp&th=1&psc=1

Am interested to hear what cabling you decide on long term. I likely will just use good quality jumper cables for any emergencies we might have but would be nice to have dedicated wiring.

UPDATE: That link isn't showing the same one for some reason, it's a 2500W 12V model.
Ford Mustang Mach-E How to - Export 12v DC to 120vAC power from LVB connection points 1637104054595
I usually try to get the 3000watt one just for the extra cushion on peak power. I've had good luck with a number of these units.... probably installed 10 over the last year for people as garage 'generators'. I like them in part because they have 2 built in outlets for charging power tools, etc in the garage 'all the time'.... but the terminal connection you can wire a custom outlet/plug to that is rated for full 30amps.

This is key for 'whole home emergency backup'. I hardwire a 30amp outlet at the Inverter, and make up a cord with a 30amp 110 plug on one end, and a regular NEMA 14-50 plug on the other with a jumper between legs so you can energize BOTH legs of your service with 110v (in phase, so no 240v loads will work). The cord can ONLY be used to backfeed, and ONLY after the home is disconnected from the Grid by turning off the Main breaker, and all other 240v breakers, including grid-tied Solar backfeed if you have it.

on the DC side I dont like jumper cable alligator clips... not enough contact, and slip off too easily. I will probably put d-rings on both ends for 'permanent' mount on the Mache connection points and Inverter DC input, and 'Anderson plug' in the middle for easy and secure connection. Project for another day.... which I'll document better in the future after I modify my Frunk access.
 

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I usually try to get the 3000watt one just for the extra cushion on peak power.
I'm only needing a few items to run on it so I hoping 2500w will be okay.
In winter:
* 1 Refrigerator
* Home networking equipment (if an outage lasts beyond the 2 hour UPS I already have on it)
* Charging up phones

In summer, add a couple of box fans and possibly will rotate in an additional refrigerator and freezer I have in the garage (not sure I could power all 3 at same time)
 
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dtbaker61

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I'm only needing a few items to run on it so I hoping 2500w will be okay.
In winter:
* 1 Refrigerator
* Home networking equipment (if an outage lasts beyond the 2 hour UPS I already have on it)
* Charging up phones

In summer, add a couple of box fans and possibly will rotate in an additional refrigerator and freezer I have in the garage (not sure I could power all 3 at same time)

2500w peak should be fine for what you describe.

If you are curious to see more exactly, you can get an inexpensive, easy to install monitor like the Efergy 'classic' (about $120). comes with two CT clamps you put on the 'hot' L1, L2 coming in from the grid.... and it will display/record current/kWhr.

Installation does require pulling off the 'deadfront' on your service enclosure, so you *should* turn off your 'main' while installing, wear gloves, and be careful working in there, The 'line-side' conductor lugs are live even when the main breaker is off !

I put the clamps on my 'main' grid conductors one evening, and verified that my peak load, with refrigerator running, TV, etc was just under 500 watts. Microwave bumped that up another 900, but obviously just while running. I have NG heat and hot water, so the flue fan and circ pumps can pull about 200 watts when running..... my peak was under 2000 watts, averages around 300, and drops as low as 150 in the middle of the night.

I have Solar.... so the backfeed from Solar throws metering net consumption with Efergy for a loop since the CTs they use can't tell the direction of the current. Since my net metering is measured and reported on my utility Bill, I moved the Efergy CTs to my 240v charge outlet circuit L1, L2. Now I can see specifically what I am putting out to the EV charger under normal circumstances on a daily basis.... and I could 'zero' and record how much I extract from MME if I were using it as a Generator.
 

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2500w peak should be fine for what you describe.

If you are curious to see more exactly, you can get an inexpensive, easy to install monitor like the Efergy 'classic' (about $120). comes with two CT clamps you put on the 'hot' L1, L2 coming in from the grid.... and it will display/record current/kWhr.

Installation does require pulling off the 'deadfront' on your service enclosure, so you *should* turn off your 'main' while installing, wear gloves, and be careful working in there, The 'line-side' conductor lugs are live even when the main breaker is off !

I put the clamps on my 'main' grid conductors one evening, and verified that my peak load, with refrigerator running, TV, etc was just under 500 watts. Microwave bumped that up another 900, but obviously just while running. I have NG heat and hot water, so the flue fan and circ pumps can pull about 200 watts when running..... my peak was under 2000 watts, averages around 300, and drops as low as 150 in the middle of the night.

I have Solar.... so the backfeed from Solar throws metering net consumption with Efergy for a loop since the CTs they use can't tell the direction of the current. Since my net metering is measured and reported on my utility Bill, I moved the Efergy CTs to my 240v charge outlet circuit L1, L2. Now I can see specifically what I am putting out to the EV charger under normal circumstances on a daily basis.... and I could 'zero' and record how much I extract from MME if I were using it as a Generator.
I only plan on plugging the few items in via a pair of extension cords to the unit directly as needed, not wiring into the panel.
 
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dtbaker61

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I only plan on plugging the few items in via a pair of extension cords to the unit directly as needed, not wiring into the panel.
that's certainly an easy way to power up key appliances as needed.... but most people look for a way to keep the refrigerator running without having to move it to plug in an extension cord. ;)

The reason I suggest a custom male-male cord to backfeed from EV Inverter into your EV outlet, is that makes it super easy to energize ALL the 120v circuits in the house without running an extension cord from garage to multiple points of use, or needing to move appliances like the refrigerator to get to the plug.

If you have a hardwired EV charger, with no 240v outlet handy in a nearby Laundry room, you could make TWO male-male 120v extension cords, and run them from the Inverter 120v outlets to the nearest 120v outlets that are on your L1, L2 'legs' to accomplish the same thing in energizing all your 120v circuits....

Keep in mind that if you are backfeeding to any outlet, you MUST turn off your 'main' and all 240v circuit breakers first!
 

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that's certainly an easy way to power up key appliances as needed.... but most people look for a way to keep the refrigerator running without having to move it to plug in an extension cord. ;)

The reason I suggest a custom male-male cord to backfeed from EV Inverter into your EV outlet, is that makes it super easy to energize ALL the 120v circuits in the house without running an extension cord from garage to multiple points of use, or needing to move appliances like the refrigerator to get to the plug.

If you have a hardwired EV charger, with no 240v outlet handy in a nearby Laundry room, you could make TWO male-male 120v extension cords, and run them from the Inverter 120v outlets to the nearest 120v outlets that are on your L1, L2 'legs' to accomplish the same thing in energizing all your 120v circuits....

Keep in mind that if you are backfeeding to any outlet, you MUST turn off your 'main' and all 240v circuit breakers first!
I am getting an inverter and will build a custom cord to reach a 240 outlet as described on this thread. Thanks for all the great info @dtbaker61!
However, instead of making a male-male extension cord to backfeed the outlet, I plan to hang a male pigtail off the inverter and then the extension cord can have the traditional ends on it. Seems like less of a chance of a male-male extension cord being used improperly in another application.

Let me know if this is a worse idea for some reason.
 
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dtbaker61

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I am getting an inverter and will build a custom cord to reach a 240 outlet as described on this thread. Thanks for all the great info @dtbaker61!
However, instead of making a male-male extension cord to backfeed the outlet, I plan to hang a male pigtail off the inverter and then the extension cord can have the traditional ends on it. Seems like less of a chance of a male-male extension cord being used improperly in another application.

Let me know if this is a worse idea for some reason.

not a good idea to have the male prongs exposed 'all the time'. The prongs will be 'hot' if you flip on the Inverter accidentally, or plug tools etc into the built in 120v outlets on the front.

You could get a spare female plug end, and not add any wiring, to use it as a 'prong cover' when you are not backfeeding.

This is why I decided to hardwire a 30a 120v F outlet from the inverter, and then a M-M 120v cord only used when backfeeding; to avoid 'hot' prongs exposed when I was using the regular outlets as I do for my rechargable tool batteries in the garage.

The 'terminal' output on these inverters is rated for 30a, the outlets are 15a.... so for backfeeding the house you should use the terminal connection from the Inverter for backfeed to house.

You COULD get an oven or dryer 240v 'pigtail' and hard wire it.... and avoid the work of taking apart the 240v male if you combine the L1 L2 at the terminal end. You will not be able to run any 240 loads, because the L1/L2 will be in-phase.... but it would energize both legs for 120 loads and you wouldn't have to take apart the 240v M plug end to add a jumper.
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