HowTo: make and install heavy duty 12v cables for import/export power

[dtbaker61]

Making holes in the driver's side beauty cover to expose 12v+, 12v, and HV disconnect is a good DIY mod which takes 5 minutes with a 1-7/8 hole saw; and it works fine for emergency access to charge or jump. BUT, alligator clamps do not provide enough surface area to carry much current for extended periods of time for long FDRS session, or exporting to a little inverter.

So, this thread shows the DIY cables I came up with to provide solid connections to the 12v 'connection posts' capable of carrying 150amps for extended periods without overheating.... and the basics of installing them.

I started with a heavy duty jumper cable set (2awg wire), and then:

- cut stock clamps off one end, and crimped on lugs to match the MME connection points. 2awg x 5/16 lug for the 12v- connection stud, and 2awg x 1/4 for the 12v+ terminal stud on the 12v battery post.

- cut stock clamps off the other end, and crimped on a 175a 'Anderson' connector

- cut another 24" segment, and put an Anderson on one end, and a pair of 2awg x 5/16 lugs on the other end to install on Inverter of choice later.

- installed a third Anderson on the remainder of the cable... essentially enabling me to have a 'permanent' 12v connection which could be stowed under the rear beauty cover area, and two 'pigtails' for choice of connection to standard alligator clamps, or lugs to install on an inverter or power supply/charger

Tools & materials needed to make these cables are:
- heavy duty (2AWG) wire or jumper cables
- wire cutter
- (1) 2awg x 1/4 lug, (3) 2awg x 5/16 lugs
- (3) 2awg - 175amp Anderson connectors w lugs
- crimper ... a BIG one for 2awg crimps!
- heat shrink and heat gun

Materials cost is about $75, but the big crimper needed to make cables may not be something many people have in their garage unless you know a solar installer or commercial electrician. I can fabricate and ship cable sets for $225 including shipping in the lower 48; contact me if you like a set.

Install is not too hard, and takes probably around an hour... The steps are:

1. remove beauty covers, and Frunk tub. You MIGHT be able to do the job without removing the Tub, but you will have to loosen and slide the battery back to reach the 12v+ terminal on the battery. It's easier and probably quicker overall to pull the Frunk Tub.
2. pop off the 12v+ terminal cover, and modify as shown below
3. remove the 12v+ conductor from battery
4. remove the 12v- 'connection post', install 12v- jumper lug, re-install connection post
5. install original 12v+ conductor on 12v+ battery stud, add 12v+ jumper lug and tighten nut on stud
6. replace (modified) 12v+ battery cover
7. replace Frunk tub and side beauty covers.... I leave the rear cover off for access to fluids, and easy storage of the new cable set in the space behind battery

here are the pictures to go along with it

I had mine out when replacing the battery anyway..... just (6) 10mm bolts, and two allans, and disconnect light/button to remove. then, pull the 12v-

then pop off the 12v+ cover, modify, and install 12v+ jumper lug

note the trimming on the cover to enable new cable to poke thru.

this is my favorite little inverter for 120v AC output

and this is one that I can put whatever plug/receptacle is needed to provide 240vAC power; RV shore power, or backfeed to a regular NEMA 14-50 outlet just like a Generator. I have used this setup to run 'critical loads' in my house!

House loads like refrigerator, lights, phone/modem, computer, etc take about 200-300 watts, with the occasional spike for microwave or teapot. This means you CAN run your house for days in case of emergency. You can also plug in your camper/RV and your MME becomes 'mobile shore power'.

You CANNOT run big loads (over 2000 watts) like wellpumps, hot tubs, electric water heaters, or air conditioners

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[ericNdfw]

Thanks for the detailed write-up and clear pictures. I had started the same kind of project a while ago but stopped when I didn't realize the negative post was a simple bolt. Sounds like my weekend plans are set to finish this up now!

 

[dtbaker61]

Thanks for the detailed write-up and clear pictures. I had started the same kind of project a while ago but stopped when I didn't realize the negative post was a simple bolt. Sounds like my weekend plans are set to finish this up now!

.... just be careful not to drop it.... you will have to pull the front tire and fish around on the suspension and belly-pan to find it.... don't ask how I know...

 

[ericNdfw]

Duely noted!

 

[dtbaker61]

and a few pix from today to show 12v export in action.... happily putting out 1800 watts to run a house 'backup' loads.

 

[G.O.C.]

So, this thread shows the DIY cables I came up with to provide solid connections to the 12v 'connection posts' capable of carrying 150amps for extended periods without overheating.... and the basics of installing

House loads like refrigerator, lights, phone/modem, computer, etc take about 200-300 watts, with the occasional spike for microwave or teapot. This means you CAN run your house for days in case of emergency. You can also plug in your camper/RV and your MME becomes 'mobile shore power'.

You CANNOT run big loads (over 2000 watts) like wellpumps, hot tubs, electric water heaters, or air conditioners

I understand there is a load limit with the system you’ve created here, and I get it. I’m in an area that gets really cold several months of the year.

Hypothetically - if one upsized the 12v cables and used a 8000 watt inverter with split phase 240 v AC, could the MME drive a 28 A 240 load like a heat pump? So if there were a power outage in freezing weather I could keep my pipes and my peeps from freezing? I’d still disconnect from the grid but I wouldn’t tie L1 and L2 together in my inverter output cord.

What I’m asking is - is there an upper limit on the rate of draw from the 12 V MME battery and would this set up exceed it? Or Where could I find the answer to that question?

 

[VaporTrails]

I understand there is a load limit with the system you’ve created here, and I get it. I’m in an area that gets really cold several months of the year.

Hypothetically - if one upsized the 12v cables and used a 8000 watt inverter with split phase 240 v AC, could the MME drive a 28 A 240 load like a heat pump? So if there were a power outage in freezing weather I could keep my pipes and my peeps from freezing? I’d still disconnect from the grid but I wouldn’t tie L1 and L2 together in my inverter output cord.

What I’m asking is - is there an upper limit on the rate of draw from the 12 V MME battery and would this set up exceed it? Or Where could I find the answer to that question?

That’s a “no”. The MME is recharging the 12V system using a DC to DC converter from pack voltage to 12V. The long-term limit of this is the limit of that DC converter. There is a 160A breaker and the system usually sees about 30-40A to recharge the battery.

There are more extreme versions of this setup that use Direct HV to a SolarInverter. Caveat Emptor applies.

https://www.macheforum.com/site/threads/export-power-via-solar-inverter-diy.31014/

 

[dtbaker61]

I understand there is a load limit with the system you’ve created here, and I get it. I’m in an area that gets really cold several months of the year.

Hypothetically - if one upsized the 12v cables and used a 8000 watt inverter with split phase 240 v AC, could the MME drive a 28 A 240 load like a heat pump? So if there were a power outage in freezing weather I could keep my pipes and my peeps from freezing? I’d still disconnect from the grid but I wouldn’t tie L1 and L2 together in my inverter output cord.

What I’m asking is - is there an upper limit on the rate of draw from the 12 V MME battery and would this set up exceed it? Or Where could I find the answer to that question?

no

max export from mme 12v is About 1500 watts.

enough for refrigerator and lights, but not heat or hot water.

your house will stay above freezing for several days without heat in winter... but you.ll need some other way to heat

 

[Mach-Lee]

I understand there is a load limit with the system you’ve created here, and I get it. I’m in an area that gets really cold several months of the year.

Hypothetically - if one upsized the 12v cables and used a 8000 watt inverter with split phase 240 v AC, could the MME drive a 28 A 240 load like a heat pump? So if there were a power outage in freezing weather I could keep my pipes and my peeps from freezing? I’d still disconnect from the grid but I wouldn’t tie L1 and L2 together in my inverter output cord.

What I’m asking is - is there an upper limit on the rate of draw from the 12 V MME battery and would this set up exceed it? Or Where could I find the answer to that question?

No way it’s running 8000W. The upper limit of power export is about 1300W continuous. If you draw more than that, the output wire on the DC/DC converter gets extremely hot and could melt. It was not designed for continuous maximum duty. The typical load is less than 500W.

 

[CTZ]

Thanks to Dan for posting this. I put a 1200W inverter today in my Mach-E to run computers, TVs, etc during power outages. I pulled about 400W easily from my computer. The space heater tripped it but I think on start-up it pulled about 1400W. I tried to get it to run on low at about 800W but couldn't get that far. As long as I can run my electronics, wifi, charge phones, I'm happy.

 

[YeOldeTraveller]

Leasing, so limits on what I can actually change. However, if I were going to do something like this, I would use the 12 VDC source to power a power station. This allows me to protect the DC-DC converter from the surges.

 

[dtbaker61]

Thanks to Dan for posting this. I put a 1200W inverter today in my Mach-E to run computers, TVs, etc during power outages. I pulled about 400W easily from my computer. The space heater tripped it but I think on start-up it pulled about 1400W. I tried to get it to run on low at about 800W but couldn't get that far. As long as I can run my electronics, wifi, charge phones, I'm happy.

the total load MUST be less than 1800watts, and this includes about 250watts just to run the car computer, so 1500 watts external load is a pretty hard limit.

be sure to:
- turn MME "on"
- disable auto-off
- turn off headlights, heat/AC
- close doors, hatch can be up

 

[CTZ]

the total load MUST be less than 1800watts, and this includes about 250watts just to run the car computer, so 1500 watts external load is a pretty hard limit.

be sure to:
- turn MME "on"
- disable auto-off
- turn off headlights, heat/AC
- close doors, hatch can be up

Yeah, the heater was more of a test. I don't see pulling more than 300W continuous which shouldn't cause it too much stress.

 

[dtbaker61]

Yeah, the heater was more of a test. I don't see pulling more than 300W continuous which shouldn't cause it too much stress.

yup, 200-400 watts is a pretty realistic background load for an average house by the way... excluding heat and ac of course.

which means that our MME is perfect for an 'emergency generator' with minimal cost for cables and an inverter that can run a house for 5 -10 days !

 

[cablecarcruisader]

Do you know of any way of connecting to the 12v battery without pulling the entire frunk out?
I have these cables already made both the alligator clamps and the Anderson connectors with lugs. I have a 1k renogy inverter with anderson connectors and a 150 amp fuse as well that I use on my maverick currently. Wanting to add the quick connectors on my MME as well. TIA for any advise. Crazy to see this and the other set up with the solar inverter somewhere else

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