How much 12v power can we pull continuously thru 12v connections from HV battery?

[dtbaker61]

You've contradicted yourself here. I think the latter is correct and you will not need to have the Mach E on to keep running 12v power off the battery access jump points and the dc-dc system should keep it topped up. There's only one way to find out for sure.

This would be different that doing this same operation on my Leaf. The Leaf definitely has to be turned on to keep the 12v battery topped up.

I don't KNOW that the MME checks 12v when 'off' since it apparently shuts down all the parasitic 12v loads it can once the car is turned 'off'. I am only guessing that it checks once in a while to take care of the LV battery when MME is parked for 'long periods'.

For my purposes, knowing that I want to run significant 12v loads while parked, I am GUESSING I'll have to leave MME turned on so that main contactors stay closed, dc-dc is powered up, etc.

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[louibluey]

I don't KNOW that the MME checks 12v when 'off' since it apparently shuts down all the parasitic 12v loads it can once the car is turned 'off'. I am only guessing that it checks once in a while to take care of the LV battery when MME is parked for 'long periods'.

For my purposes, knowing that I want to run significant 12v loads while parked, I am GUESSING I'll have to leave MME turned on so that main contactors stay closed, dc-dc is powered up, etc.

If Dan can get to 75A to 100A continuous load on the 12V bus, I think the DC-DC converter will either be running 100% duty cycle, or it will be operating at a very high duty cycle. I think MME will need to be ON (and getting it to stay ON for hours will be another issue for later, if it works).

 

[ChasingCoral]

I don't KNOW that the MME checks 12v when 'off' since it apparently shuts down all the parasitic 12v loads it can once the car is turned 'off'. I am only guessing that it checks once in a while to take care of the LV battery when MME is parked for 'long periods'.

For my purposes, knowing that I want to run significant 12v loads while parked, I am GUESSING I'll have to leave MME turned on so that main contactors stay closed, dc-dc is powered up, etc.

I'm guessing the opposite as Ford has said in a number of places that the system keeps the LVB topped off from the HVB when it is parked or stored. You'll find out when you test your rig!

 

[dtbaker61]

I'm guessing the opposite as Ford has said in a number of places that the system keeps the LVB topped off from the HVB when it is parked or stored. You'll find out when you test your rig!

I wouldn't want to force the main contactors to cycle open/closed under load more times than needed if I can avoid it by leaving the MME 'on'.

 

[ChasingCoral]

I wouldn't want to force the main contactors to cycle open/closed under load more times than needed if I can avoid it by leaving the MME 'on'.

Good point.

 

[owenfi]

Hi, sorry to resurrect an old thread, but curious if you ever made progress on testing this.

I'm in a similar boat, faced sporadic power outages during recent storms, and would love to be able to save a fridge during an evacuation (we are near a creek that is a possible mudslide risk when it gets really rainy), keep the internet on, or run our furnace overnight occasionally.

Based on this thread, I'm thinking about buying a Victron Phoenix 12V 1200VA (peak 2200, but continuous 1000 or 800@45C). I might step down to the 800VA option to keep the peak below the DCDC max, but I'd really rather be able to do 800-1k continuous if it's supported. They call for 2AWG or 4AWG respectively (Assuming sub 1.5m DC cable runs.)

I was hoping to mount the inverter underneath the frunk, but it seems unlikely as the dimensions are ~5x9x14 and calls for 4 inches of clearance.

 

[Mach-Lee]

Hi, sorry to resurrect an old thread, but curious if you ever made progress on testing this.

I'm in a similar boat, faced sporadic power outages during recent storms, and would love to be able to save a fridge during an evacuation (we are near a creek that is a possible mudslide risk when it gets really rainy), keep the internet on, or run our furnace overnight occasionally.

Based on this thread, I'm thinking about buying a Victron Phoenix 12V 1200VA (peak 2200, but continuous 1000 or 800@45C). I might step down to the 800VA option to keep the peak below the DCDC max, but I'd really rather be able to do 800-1k continuous if it's supported. They call for 2AWG or 4AWG respectively (Assuming sub 1.5m DC cable runs.)

I was hoping to mount the inverter underneath the frunk, but it seems unlikely as the dimensions are ~5x9x14 and calls for 4 inches of clearance.

I have a rig I made for emergencies I need to do a write up on, but the important thing to know is you need to limit the current draw to around 125A or less. Read the inverter spec sheets and find one that has a maximum input current less than that. You need to leave overhead for the Mach-E systems to run, they take about 20A at idle. I would not permanently mount the inverter since it's not outdoor rated. Mine is portable and just uses giant alligator clips like jumper cables. A bonus is I can use it on another vehicle if necessary (gas vehicle if Mach-E battery runs out).

 

[JohnFoxeSheets]

I have a rig I made for emergencies I need to do a write up on, but the important thing to know is you need to limit the current draw to around 130A or less. Read the inverter spec sheets and find one that has a maximum input current less than that. You need to leave overhead for the Mach-E systems to run, they take about 20A at idle. I would not permanently mount the inverter since it's not outdoor rated. Mine is portable and just uses giant alligator clips like jumper cables. A bonus is I can use it on another vehicle if necessary (gas vehicle if Mach-E battery runs out).

Very interested to see your write up (when you get to it), Lee.

 

[owenfi]

I have a rig I made for emergencies I need to do a write up on, but the important thing to know is you need to limit the current draw to around 130A or less. Read the inverter spec sheets and find one that has a maximum input current less than that. You need to leave overhead for the Mach-E systems to run, they take about 20A at idle. I would not permanently mount the inverter since it's not outdoor rated. Mine is portable and just uses giant alligator clips like jumper cables. A bonus is I can use it on another vehicle if necessary (gas vehicle if Mach-E battery runs out).

Thanks! Would love to see a writeup, but good advice in the meantime. The Victron 1200 calls for ~2AWG which is in the ballpark. It has a 200A fuse internally, while the 800 has a 125A.

Maybe I would get the 1200 but use something like this 125A DC breaker (meant for solar, but looks okay) as a fuse to protect and keep it safely under the limit.

Do you have to keep the Mach-E "running" in order to use they system? If so, can it be left on "indefinitely" (or does it auto-shut off after some minutes/hours in park)? The tiny little 12V battery is giving me second thoughts, but glad to hear it has been done.

I guess an alternate approach in my case is to use a lower voltage DC-DC charger from the Mach-E to our Van's 24V-house batteries which has a 5kW inverter behind it (just that's not home when we evacuate) to keep the van powered up which can run the necessary appliances at home.

 

[Mach-Lee]

Thanks! Would love to see a writeup, but good advice in the meantime. The Victron 1200 calls for ~2AWG which is in the ballpark. It has a 200A fuse internally, while the 800 has a 125A.

Maybe I would get the 1200 but use something like this 125A DC breaker (meant for solar, but looks okay) as a fuse to protect and keep it safely under the limit.

Do you have to keep the Mach-E "running" in order to use they system? If so, can it be left on "indefinitely" (or does it auto-shut off after some minutes/hours in park)? The tiny little 12V battery is giving me second thoughts, but glad to hear it has been done.

I guess an alternate approach in my case is to use a lower voltage DC-DC charger from the Mach-E to our Van's 24V-house batteries which has a 5kW inverter behind it (just that's not home when we evacuate) to keep the van powered up which can run the necessary appliances at home.

I would not use a circuit breaker on an inverter because it does need to draw a lot of power for a short time while starting motors. It would likely nuisance trip. Exceeding 150A for a couple seconds is okay since it will draw the surplus from the 12V battery, you just don't want an inverter that can possibly run at more than 125A continuously so you don't overload the DC/DC.

I've pulled 125A continuously with no issues. That's about as high as I would go though, as the DC/DC positive cable was starting to get hot (35 mm^2 or #2 size, good to about 140A). Be sure to consider the 20A base load of the Mach-E. Subtracting that, the maximum safe external load for the Mach-E is 120A continuous so as not to overheat the DC/DC positive cable.

System voltage can drop down to as low as 12.7V while on (voltage drops when the BMS thinks the 12V battery is full), use that for your amperage calculations.

Yes you need to leave the Mach-E fully ON while using the inverter so the DC/DC runs. There is a 30-minute auto shutdown you need to disable in the vehicle settings (it does not stick, must be disabled each time the vehicle is turned on). Take all keys out of it while on, it can't be taken out of park without a key nearby.

 

[dtbaker61]

I have a rig I made for emergencies I need to do a write up on, but the important thing to know is you need to limit the current draw to around 125A or less. Read the inverter spec sheets and find one that has a maximum input current less than that. You need to leave overhead for the Mach-E systems to run, they take about 20A at idle. I would not permanently mount the inverter since it's not outdoor rated. Mine is portable and just uses giant alligator clips like jumper cables. A bonus is I can use it on another vehicle if necessary (gas vehicle if Mach-E battery runs out).

I totally concur with 125a or so being the max 'continuous' load (125a x 13v = 1625 watts) you want to extract from the MME 12v connection points. The background 12v load on the MME looks to be 20-30 amps when it is 'on', and the dc-dc converter in non-GT is specced at 160a max. so 125a is a pretty safe ceiling.

No matter which way you go, I'd suggest using a 'pure-sine' inverter rather than 'modified' square-wave power which is really hard on equipment.

so, you could run AC loads several different ways:

1. (under $200) direct drive with jumper cables to a 1500 watt inverter... enough to run a teapot, or a few lights, computer, cordless tool chargers and stuff like that.

2. (under $1000) package your 1500watt inverter in a 'carry -on', with an internal battery, and use the MME as a charger when the portable battery gets low. Basically 'give it a jump' when if gets down to 12.4 to bring it back up to 13.8v+. This is super handy if you want to use the portable pack some distance from the MME.... like at a campsite or job site.

3. (under $2000) upsize the 'portable' case to hold more battery and a bigger inverter, but still use the MME as a charger rather than 'direct drive'. This is a good solution if you want to run loads that occasionally peak over 1500 watts.... like multiple small tools, or critical loads in a house.

4. (under $3000) upsize with MORE batteries and put everything on shelves in the garage. Again using the MME as a 'generator' to charge the external buffer batteries. You can run all your garage goodies, or even go a few steps further to use the system as a emergency generator for important loads in case of grid outage.... as long as you take steps to isolate from the Grid safely and don't run huge loads like ovens and air conditioners the MME has enough Energy to run critical loads for days.

 

[owenfi]

I totally concur with 125a or so being the max 'continuous' load (125a x 13v = 1625 watts) you want to extract from the MME 12v connection points. The background 12v load on the MME looks to be 20-30 amps when it is 'on', and the dc-dc converter in non-GT is specced at 160a max. so 125a is a pretty safe ceiling.

No matter which way you go, I'd suggest using a 'pure-sine' inverter rather than 'modified' square-wave power which is really hard on equipment.

so, you could run AC loads several different ways:

1. (under $200) direct drive with jumper cables to a 1500 watt inverter... enough to run a teapot, or a few lights, computer, cordless tool chargers and stuff like that.

2. (under $1000) package your 1500watt inverter in a 'carry -on', with an internal battery, and use the MME as a charger when the portable battery gets low. Basically 'give it a jump' when if gets down to 12.4 to bring it back up to 13.8v+. This is super handy if you want to use the portable pack some distance from the MME.... like at a campsite or job site.

3. (under $2000) upsize the 'portable' case to hold more battery and a bigger inverter, but still use the MME as a charger rather than 'direct drive'. This is a good solution if you want to run loads that occasionally peak over 1500 watts.... like multiple small tools, or critical loads in a house.

4. (under $3000) upsize with MORE batteries and put everything on shelves in the garage. Again using the MME as a 'generator' to charge the external buffer batteries. You can run all your garage goodies, or even go a few steps further to use the system as a emergency generator for important loads in case of grid outage.... as long as you take steps to isolate from the Grid safely and don't run huge loads like ovens and air conditioners the MME has enough Energy to run critical loads for days.

For options 2-4 do you use a DC-DC converter? (I notice in 2 you use lithium, can’t quite tell in the others.) if not, isn’t that a risk to draw too much current? Recommendations on one in the 100A range?

Based on the numbers the Victron 1200 is actually looking like it sits pretty well, perhaps instead of a breaker I would look into a 120A slow-blow fuse. I’d love to get a disconnect so I don’t have to use jumper cables. Worst case I think I have a bluesea DC switch leftover from the van electrical:

…that one is my complicated-do-everything system. So I’m leaning to keep this simpler, just for emergency use, and could keep an eye on it and keep it under the load limit.

if I could find a 1kW 12v -> 24v converter then I could use the MachE to keep the 10kWh in the van topped up.

 

[dtbaker61]

For options 2-4 do you use a DC-DC converter? (I notice in 2 you use lithium, can’t quite tell in the others.) if not, isn’t that a risk to draw too much current?

yes, overcurrent is a risk if you are using direct jumpers from MME at 14.4v to a partially discharged portable that could be anywhere between 12.0 and 12.5 before you hook it up. Especially with Li batteries that have low internal resistance.

Probably best to add a dcdc charger designed to 'throttle' the current. This one does 40a (500watts)
https://www.renogy.com/12v-40a-dc-to-dc-on-board-battery-charger/?

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