How to DIY - add access holes for LVB 12v battery connection points & HV Disconnect Relay for Safety

[CHeil402]

would have been nicer if the + and - were actually directly over the terminals, and even nicer if they were molded access covers like the mystery removable covers in the front. First thing I did was pop those off to see what they were covering... nothing interesting or needing common access as far as I see ?!

Maybe they just misaligned the access panels in design (one team was working in metric and the other is US units?). Get out your tin hats!

Ford Engineering: "Done designing the perfect access panel"
Ford Drafting: "I don't know why you'd want these panels here, but whatever you say"
Ford Engineering: [...breathes heavily]
Ford Management: "We need to ship it now so we can deliver those three cars to Texas to meet our 2020 deadline! Nobody is going to need access to that anyway this is an EV after all"

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[dtbaker61]

Maybe they just misaligned the access panels in design (one team was working in metric and the other is US units?). Get out your tin hats!

Ford Engineering: "Done designing the perfect access panel"
Ford Drafting: "I don't know why you'd want these panels here, but whatever you say"
Ford Engineering: [...breathes heavily]
Ford Management: "We need to ship it now so we can deliver those three cars to Texas to meet our 2020 deadline! Nobody is going to need access to that anyway this is an EV after all"

mmmm.... yes, could have been a 'Dilbert'

 

[dtbaker61]

The start current (power) might be less than what people are thinking. Does anyone know what the start current for a MME is? The wire gauge needed to start a MME might be relatively small.

I guess there might be two numbers, one for a more discharged 12 V LVB (more initial current to bring the LVB back towards 12V), and the actual load current for the car systems alone to boot up.

I can probably get some numbers, at least for a good 12V battery, by putting a high frequency DC current clamp over one of the LVB cables (HF to see any fast changes, it is still DC current) and watching a couple of normal start ups with a digitizer.

the starting 'inrush current' for the EV isn't that bad... but there are a couple considerations and very different needs for access to the LVB.

1. if and when the MME LVB dies, it is nice to have 'reasonable' access so that once you get into the Frunk via the bumper port leads from a friendly passerby or towtruck with jumper cables.... you can apply jumper cables to charge the LVB enough to start your MME and be on your way.

2. Having easy access to your LVB connection points actually enables YOU to be a friendly passerby, and give a jump to anybody with a dead 12v battery. since you'll be pulling juice from your LVB while the MME is running, the traction pack will quickly replace the energy you use to 'jump' an external vehicle.

3. extended export of 12v energy via connection points MUST be limited to the maximum amps that the MME dc-dc converter can support... All specs I can find indicate that limit is 160amps, which at 12v nominal (12.6-12.8 under load) that is about 2000 watts continuous. This is something to keep in mind if you have any interest in running any AC loads with your MME. For instance, you can get a decent pure-sine Inverter (12vDC to 120vAC) for under $500, and use it to power tool chargers, a refrigerator, (in the Frunk maybe ?!), or even your house... as long as you keep the average continuous energy draw below 2000 watts, the dc-dc from traction pack can keep up, and you *should* have access to all the energy in your traction battery as is keeps the LVB charged up while you export energy to external loads.

This is why I'm so excited to have access..... I can literally run my house for a week in case of emergency from the 68kWhr in my MME.

 

[ChasingCoral]

Maybe the special select group Ford has chosen can pass this recommendation on to Ford?

I've already suggested it.

 

[louibluey]

the starting 'inrush current' for the EV isn't that bad... but there are a couple considerations and very different needs for access to the LVB.

1. if and when the MME LVB dies, it is nice to have 'reasonable' access so that once you get into the Frunk via the bumper port leads from a friendly passerby or towtruck with jumper cables.... you can apply jumper cables to charge the LVB enough to start your MME and be on your way.

2. Having easy access to your LVB connection points actually enables YOU to be a friendly passerby, and give a jump to anybody with a dead 12v battery. since you'll be pulling juice from your LVB while the MME is running, the traction pack will quickly replace the energy you use to 'jump' an external vehicle.

3. extended export of 12v energy via connection points MUST be limited to the maximum amps that the MME dc-dc converter can support... All specs I can find indicate that limit is 160amps, which at 12v nominal (12.6-12.8 under load) that is about 2000 watts continuous. This is something to keep in mind if you have any interest in running any AC loads with your MME. For instance, you can get a decent pure-sine Inverter (12vDC to 120vAC) for under $500, and use it to power tool chargers, a refrigerator, (in the Frunk maybe ?!), or even your house... as long as you keep the average continuous energy draw below 2000 watts, the dc-dc from traction pack can keep up, and you *should* have access to all the energy in your traction battery as is keeps the LVB charged up while you export energy to external loads.

This is why I'm so excited to have access..... I can literally run my house for a week in case of emergency from the 68kWhr in my MME.

First, it is incredibly good to put those holes in for easy access, congrats for pushing us towards drilling those holes! Nothing is simpler than that access with a small jump pack. Every EV or PHEV I had before this had easy access to either the the 12V LVB posts or more recently, those jump posts.

I will defer to others and you as to running a 2 kW sine inverter from MME. I went down that route with the APM in my Gen 1 Volt (I still have a nice 2 kW sine inverter and very heavy cables from that time, and a gigantic Greenlee crimper too!). (I was really into the project, even bought a spare APM to experiment with.) But, along the way, for me, I decided that I do not want to risk an accident that might damage my EV with that sort of project. I bought a Honda 2000 generator which does the same much easier (no humongous 12V cables needed). There are many less expensive inverter generators as alternatives to Honda now too.

Go that way if it interests you. From my view point now, the only way EV to home (V2H, V2G) is going to be practical is when the transfer happens at the traction battery voltage. And then, only when it is common enough that the HV transfer hardware comes down in price. No more 12V 150A DC cables for me. This is the most expensive vehicle I have ever owned, I am not taking any unnecessary risk (although I might do some measurements, especially the non contact kind which are less risky to the EV). For those making measurements, remember when plugged in, there is a ground through the EVSE to the house ground, and the same ground on any non-isolated input of a plug in instrument on your bench (I remembered that the hard way with a past EV when one of my non-isolated signal cables started to get warm.)

 

[Fat Mach]

If you want to go big, get a matching pair of "forklift" connectors. They're the power cable quick disconnects and you could hard mount one to the car and keep the other with some leads on it to connect to a jumper cable.

 

[Jimrpa]

There is a rumor over at Jalopnik that we hold cockfights rather than shrimp cocktail in the Mach-E's frunk.

That’s a waste of a perfectly good koi pond!

 

[Accord07]

That’s a waste of a perfectly good koi pond!

Don't forget to plug the drain hole first though, or you will end up with dead fish in the Mach-E frunk.

 

[dtbaker61]

If you want to go big, get a matching pair of "forklift" connectors. They're the power cable quick disconnects and you could hard mount one to the car and keep the other with some leads on it to connect to a jumper cable.

yes, some big fat anderson connectors and 'permanent' leads to connection points would be good, BUT will require a big fat crimper and the ability to make some custom cables that is a bit beyond the average DIY toolset.

to take full advantage of available 12v current for heavy loads and continuous use beyond the occasional 'jump', it would need to be sized to carry 150amps.... probably 1/0 or 2/0 welding cable, which is pretty big

 

[louibluey]

yes, some big fat anderson connectors and 'permanent' leads to connection points would be good, BUT will require a big fat crimper and the ability to make some custom cables that is a bit beyond the average DIY toolset.

to take full advantage of available 12v current for heavy loads and continuous use beyond the occasional 'jump', it would need to be sized to carry 150amps.... probably 1/0 or 2/0 welding cable, which is pretty big

How do you protect the little 35Ah battery at 150A if the DC-DC converter switches off, even for minutes, and the 12V inverter load stays on?

 

[dtbaker61]

How do you protect the little 35Ah battery at 150A if the DC-DC converter switches off, even for minutes, and the 12V inverter load stays on?

if the dc-dc fails to wake up and charge the LVB when it's getting low, the Inverters have low-voltage sense, and shut down.

 

[Fat Mach]

yes, some big fat anderson connectors and 'permanent' leads to connection points would be good, BUT will require a big fat crimper and the ability to make some custom cables that is a bit beyond the average DIY toolset.

to take full advantage of available 12v current for heavy loads and continuous use beyond the occasional 'jump', it would need to be sized to carry 150amps.... probably 1/0 or 2/0 welding cable, which is pretty big

Nah, you can solder them with a propane torch. I have a set inline in my roll around battery charger. Maybe I'll do the mod this fall and do make a write up.

 

[louibluey]

if the dc-dc fails to wake up and charge the LVB when it's getting low, the Inverters have low-voltage sense, and shut down.

Think of the LVB more like a parallel capacitor in this case. The DC-DC converter would need to be on 100% duty cycle (the LVB is tiny) at 100A + loads (if the DC-DC can handle that sort of load).

 

[dtbaker61]

Think of the LVB more like a parallel capacitor in this case. The DC-DC converter would need to be on 100% duty cycle (the LVB is tiny) at 100A + loads (if the DC-DC can handle that sort of load).

yes, sorta.
everything I can find indicates dc-dc is capable of sending about 150-160 amps from traction pack to 'run stuff' and charge LBV at the same time basically as a parallel, until LVB tells HV it is full. HV->dc-dc stops sending juice, and runs off LVB until LVB asks for recharge.... or something like that.

so..... for extended external loads, if HV, dc-dc, LVB are all working correctly we *should* be able to run external loads averaging up to 150 amps (2000 watts) and the whole system should be able to keep up.

 

[dtbaker61]

Nah, you can solder them with a propane torch. I have a set inline in my roll around battery charger. Maybe I'll do the mod this fall and do make a write up.

mmmmm, crimper results better than solder. Just my opinion, but in the EV world under heavy (1000 amp loads), proper crimps hold up better and more dependable over time.

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