Is it safe to connect a large inverter to the 12V battery?

[Evoforce]

The service cars don’t run lithium 12v battery’s, at least the Tech I spoke with said they don’t. Im not debating anything, just passing along what the Tesla service tech said in regards to this. I don’t have an inverter in any of our Teslas so this is only what he told me. I honestly have no interest in running anything off my car.

Inverter will also work with lead acid. I do not want this to get confused. Tech gave you misinformation... Tesla really only wants you to cycle your HV battery by driving the car and not powering up something else.

 

[FlatSix911]

The thinner yellow wire with clamp is attached by ring terminal at one of the four bolts that bolt the inverter in place inside the microwave box that have black sealer applied to the outside. The other clamp end goes to chassis ground.

The red (hot 0 gauge) attaches to the battery at the location shown (red shrink) without the need to unbolt the car hot lead from the circuit breaker block located at the top of the 12 volt battery and is in the picture at lower left. The bolt is long enough to place the hot ring terminal on the bolt and add a top nut without having to unbolt the existing hot cable underneath.

The black 0 gauge attaches as shown in the far right of the picture to the 12 volt negative attachment. Again no need to remove the negative clamp on the terminal but you can combine it as shown.

I put a heavy gauge Andersen connector between the battery and the tub for ease of assembly and disassembly. I have provided pictures of the measurements of the two harness wires to be made. One side of the harness attaches to the 12 volt battery and attaches to the other half that feeds through the tub. the inner tub side connects to a resettable circuit breaker on the positive side and then continues to the converter.

The negative gets another detachable Andersen before continuing to the inverter.

Take note of the modification of the tub liner at the pass through holes for the harness and the wiring protection and grommets.

I'm having trouble with the internet and pictures so sorry if it is disorganized. It is not taking all of my pictures etc... I had a picture of the supplies to do this project but can't find it. I know one of the pictures shows a 250 amp re-settable breaker but you should use something smaller like a 200 amp to make sure that it trips before the high amp (I believe is 235 amp) fuse between the HV and the 12 volt battery.

This installation uses a 2000 watt inverter that has internal fuses as well.

Well done! Where did you source the components and wiring? Thanks

 

[Evoforce]

@FlatSix911 Thanks! The 0 gauge wire is welding cable and can be sourced at local welding supplies or purchased online. 6 foot of each color should be plenty but extra length for some great jumper cables is something to think about.

The (8) tinned ring terminals for the 0 gauge (online), the crimper for big ring terminals (online) the 200 amp reset breaker (online), wire heat shrink (Harbor freight, Home depot, electronic stores, online). 2 grommets for tub holes, 6 foot wire loom, cable ties (auto parts stores, Harbor freight etc).

Andersen connectors online or ham radio shop or heavy equipment supplier. Keep in mind with the Andersens that you need the internal contacts (6) for 0 gauge as well as the outer housings. I get mine online through Andersen Powerpole. There are some cheaper Chinese knockoffs.

Inside the microwave tub I hot glued a few things into position to secure them... so glue gun, cable straps, or Velcro. The correct threaded nut for the positive battery connection (hardware store).

I'm hoping still to find the picture of the supplies and post it in this thread.

I got this 2000 watt surge to 4000 inverter at Harbor freight years ago and it powered some solar circuits at my home for a few years until I installed a larger one. It is not pure sine wave but it still worked well with everything that I have used it with including computers and sensitive equipment without any adversity.

I have an identical one installed in one of my Nissan Leafs. I have actually charged another Leaf with it to get range to make it home. Although only about 4 miles per hour is what you get at 120 volts.

 

[Evoforce]

I forgot to include the yellow 14 or 12 gauge ground wire with 3/8" hole to 14/12 gauge ring terminal and pinch clamp for chassis ground in the supplies list and the bolts/nuts/washers for the inverter mounting. There were 4 of each type for my application and i believe they were 3/8" x 1" bolts. I also used liquid tape for the sealer of these mounting bolts to waterproof the outer "microwave box" that the inverter mounts inside.

I'm second guessing myself on the length of the 1/0 welding cable. probably should get 8 feet of each color to be sure...

 

[Cape Coddess]

I forgot to include the yellow 14 or 12 gauge ground wire with 3/8" hole to 14/12 gauge ring terminal and pinch clamp for chassis ground in the supplies list and the bolts/nuts/washers for the inverter mounting. There were 4 of each type for my application and i believe they were 3/8" x 1" bolts. I also used liquid tape for the sealer of these mounting bolts to waterproof the outer "microwave box" that the inverter mounts inside.

I'm second guessing myself on the length of the 1/0 welding cable. probably should get 8 feet of each color to be sure...

That setup is amazing! As much as I love the convenience of it it is way beyond anything my li'l pea brain can take in. I'm just not there yet. I was thinking more of just simply hooking the inverter up to the battery like in the video below. I know it's a pain and has to be unhooked every time you're finished with it but until I can understand how to do it differently this is what I would need to do for now during a power outage.

He's got the inverter hooked up to his Tesla's 12 volt, but the
cables go in two different directions. It looks like the positive is hooked up to the
battery, right? But where is the negative going?

Plus my pure sine wave 1200 w has bolt holes on the ends and not clamps. How would I hook those up?

 

[Evoforce]

@Cape Coddess You have "holes" (ring terminals) at both ends of your black cable and red cable? If so, to make your inverter more portable, one end of each cable must be cut off and stripped and then install (crimp on) new pinch clamp cable ends (one per cable). Clamp ends can be found at auto supply stores. Or, you can buy heavy duty jumper cables (6 gauge or lower) and cut to length strip and install/crimp on "holes" (ring terminals) on one end of each cable. Or you can order pre-made cables online.

The above mentioned fix is a simple fix and not really the best circuit protection option.

If you are modifying cables, (and even if not) it would be good to incorporate an inline fuse somewhere sized below the circuit rating of your attachment to your positive connection so it blows the fuse to the inverter instead of blowing the car circuit if overloaded. You can find heavy duty cable re-settable fuses online to suit your need.

In the video you provided, it appears his connection is hooked to a 250 amp post to which any inverter would not want a breaker higher than 200 amp for a 2000 watt inverter. If in the video, he is in fact hooked to a lower rated circuit, than you would need to size your inverter circuit breaker under that size.

You would get less inverter sparking if you first hook your inverter to a re-settable fuse permanently mounted (connected) to the battery that you can switch the breaker off when attaching the inverter to the hot battery circuit having no load and inverter off and then switching breaker on after attaching. Different breakers have different types of cable attachments that you will need your inverter cable to match up with. I mentioned Andersen Powerpole connectors earlier which would be ideal for quick connect.

Your other question of where his negative cable is attached can't be seen but if it isn't attached directly to the battery, it is attached to the vehicle grounded chassis.

 

[Rusty1]

Here is what I recently did with my Model 3 when the power was out for three days after a tornado went through town. Worked well.

 

[FlatSix911]

Nice work!

 

[Watts_Up]

Here is what I recently did with my Model 3 when the power was out for three days after a tornado went through town. Worked well.

What did you connect to?
- Where you able to run a refrigerator or a microwave?
- Did you measure how much power you used (Max kW load, and total kWh consumption each day)?

Note: I have ToU and paid about $0.10 per kWh off peak, and about $0.50 during peak hour in the summer.
And I use about 15 kWh every day.

If I am not using my car during the day, it could be very simple, using a relay and a timer,
to connect my refrigerator to the car using this $190 Power Inverter during peak hours.
I just wonder if this might have any bad effect on the 12 V battery and the Traction battery?

 

[n2mb_racing]

View attachment 533444 Here is what I recently did with my Model 3 when the power was out for three days after a tornado went through town. Worked well.

That's interesting that that worked. Another member said the 12V battery charging was limited to 6A on the Model 3, so you can't draw more than about 70W continuous without draining the 12V battery. How much power did you use?

 

[Snowstorm]

That's interesting that that worked. Another member said the 12V battery charging was limited to 6A on the Model 3, so you can't draw more than about 70W continuous without draining the 12V battery. How much power did you use?

That doesn’t seem right. Model S has a 200A DCDC unit to charge the 12V from the HV battery. The 12V is used for everything from seat heaters to lights etc and needs to pull over 1kw. I would make sense for Model 3 to have a similar DCDC charger for the 12V battery. Check the fuse diagram and see the fuse size for that DCDC unit, it is 250A in the model S.

 

[Watts_Up]

That's interesting that that worked. Another member said the 12V battery charging was limited to 6A on the Model 3, so you can't draw more than about 70W continuous without draining the 12V battery. How much power did you use?

That doesn’t seem right. Model S has a 200A DCDC unit to charge the 12V from the HV battery. The 12V is used for everything from seat heaters to lights etc and needs to pull over 1kw. I would make sense for Model 3 to have a similar DCDC charger for the 12V battery. Check the fuse diagram and see the fuse size for that DCDC unit, it is 250A in the model S.

@Snowstorm You are right about the 200 Amp DC/DC unit but let me clarify a little bit your comment.

From what I observed using a Battery Monitor, when the car is asleep, the DC/DC converter recharges the 12 V battery when the voltage drops around 12.5 V.
The DC/DC then recharge the battery under 14.5 V for about 2 hours, and typically this is done under 3 to 6 Amp. And this process occurs about every 2 days.

Now when you are driving, or use Sentry, Camp Mode, Dog Mode... then the DC/DC is activated producing about 13.5 V and works in a simillar way as an alternator in an ICE car.
So the battery doesn't get discharged and the energy used to heat the seats and the lights is generated from the propulsion battery.

Connecting a 1500-Watt Power Inverter directly to the 12 V battery will quickly trigger the DC/DC converter,
but I assume that the Tesla DC/DC converter will trigger a 12 V Battery alert if too much current is need when trying to recharge the battery.
Now I imagine that the Cybertruck providing some AC voltage for power tools usage must have a special DC/DC mode to do so.

 

[miimura]

That doesn’t seem right. Model S has a 200A DCDC unit to charge the 12V from the HV battery. The 12V is used for everything from seat heaters to lights etc and needs to pull over 1kw. I would make sense for Model 3 to have a similar DCDC charger for the 12V battery. Check the fuse diagram and see the fuse size for that DCDC unit, it is 250A in the model S.

The Model 3 has a smart electrical system that does not have individual traditional fuses. Sure, there are big fuses in the PCS for the HV battery and probably the 12V system too, but the primary protection is in the Body Controllers that distribute the power and can cut individual circuits electronically.

The most obvious problem with pulling energy from the 12V battery instead of the PCS 12V terminals is that the car is monitoring the battery charging current. If it sees excessive draw from that circuit, it will throw a fault because it thinks the battery is bad, like an internal short or something.

 

[Evoforce]

I have been using a 2000-5000 surge for years on model S with the inverter connected to the 12 volt and it is always kept topped up with the dc/dc automatically whether the car is on or off. I also run the largest Massimo cooler they make (think CX50) from a wired in 12 volt power socket tied into the liftgate circuit. No camp modes etc is necessary if tied into an always hot circuit. I just got back from a trip where I was using both... First time using the electric cooler/freezer was really a plus. The cooler plus a c-pap machine used about 4 miles for every five hours of use. Fully powering up a house uses much more of course and depending what you power up. Usually we are powering lights and TV and movie player at the cabin but all of that stuff uses much more than the above described pieces of equipment.

 

[n2mb_racing]

I have been using a 2000-5000 surge for years on model S with the inverter connected to the 12 volt and it is always kept topped up with the dc/dc automatically whether the car is on or off. I also run the largest Massimo cooler they make (think CX50) from a wired in 12 volt power socket tied into the liftgate circuit. No camp modes etc is necessary if tied into an always hot circuit. I just got back from a trip where I was using both... First time using the electric cooler/freezer was really a plus. The cooler plus a c-pap machine used about 4 miles for every five hours of use. Fully powering up a house uses much more of course and depending what you power up. Usually we are powering lights and TV and movie player at the cabin but all of that stuff uses much more than the above described pieces of equipment.

Sounds great! Just a reminder to everyone, this doesn't seem to work on the Model 3 and Y, since they limit the 12V battery charge current to 6 amps. On the 3/Y, you can tap into the DC/DC terminal directly.

And we don't know yet about the newest Model S / X vehicles, since they have a totally different 12V. But, they also likely will limit the charge current to the 12V li-ion battery, so it's likely we'll have to tap into the DC/DC converter directly on those cars as well.

 

[Snowstorm]

limit the 12V battery charge current to 6 amps

That doesn't seem right. The model 3, like the model S/X and all other cars today, uses 12V accessories such as seat heater, lights, seat motors etc... and they can pull serious amps when running. I believe the seat heaters alone will use more than 6A. As such, the 12V battery must be topped off by something that can provide a lot more current.

 

[miimura]

That doesn't seem right. The model 3, like the model S/X and all other cars today, uses 12V accessories such as seat heater, lights, seat motors etc... and they can pull serious amps when running. I believe the seat heaters alone will use more than 6A. As such, the 12V battery must be topped off by something that can provide a lot more current.

When the car is ON, the power comes from the DC-DC converter, called PCS (Power Conversion System) in Model 3 / Y. The 12V battery is only supplying current when the car is OFF and the HV battery is disconnected from the car.

 

[n2mb_racing]

When the car is ON, the power comes from the DC-DC converter, called PCS (Power Conversion System) in Model 3 / Y. The 12V battery is only supplying current when the car is OFF and the HV battery is disconnected from the car.

Yup. Seems like they separated out the high current 12V stuff and run those things direct from the DC/DC. The 12V battery is only used to keep essential things running when the car is off, such as computers for sentry mode. The 12V battery seems to be isolated from the rest of the 12V system or at least has the capability of being isolated.

 

[Watts_Up]

Yup. Seems like they separated out the high current 12V stuff and run those things direct from the DC/DC. The 12V battery is only used to keep essential things running when the car is off, such as computers for sentry mode. The 12V battery seems to be isolated from the rest of the 12V system or at least has the capability of being isolated.

In fact its is very simple and it is similar to an ICE car with an alternator:

- Typically, when the car is 'sleeping', the battery voltage is around 12.5 V.

- When the car 'weak up', I would say when you open a door or unlock the car remotely....,
but also when you have Sentry on, or Camp mode, watch a movie...
the inboard DC/DC converter is activated and generates a voltage around 13.5 V.
So all the current used is coming from the inboard converter, and the battery don't get discharged.

- When the 12 V battery needs to get recharged, typically the car is 'sleeping' and the voltage gets below the 12.5 V
the inboard converter is activated and generated a voltage around 14.5 V, for about two hours to recharge the battery.
When the car is parked for a long time, because of the little consuption from various sensors,
the battery starts to get discharged and after about two days the inboard charger is again activated to 14.5 V.

 

[n2mb_racing]

In fact its is very simple and it is similar to an ICE car with an alternator:

- Typically, when the car is 'sleeping', the battery voltage is around 12.5 V.

- When the car 'weak up', I would say when you open a door or unlock the car remotely....,
but also when you have Sentry on, or Camp mode, watch a movie...
the inboard DC/DC converter is activated and generates a voltage around 13.5 V.
So all the current used is coming from the inboard converter, and the battery don't get discharged.

- When the 12 V battery needs to get recharged, typically the car is 'sleeping' and the voltage gets below the 12.5 V
the inboard converter is activated and generated a voltage around 14.5 V, for about two hours to recharge the battery.
When the car is parked for a long time, because of the little consuption from various sensors,
the battery starts to get discharged and after about two days the inboard charger is again activated to 14.5 V.

And they also monitor the current going to the battery? I'm guessing there's a solid state switch in there between the 12V DC/DC bus and the battery to allow them to measure charge current.