MASTER THREAD: Powering house or other things with Model 3

[fiveangle]

re: buffer batteries, I have a relatively small 20Ah 4S8P A123 LiFeP04 pre-made pack strapped to the inverter that I used to ensure the wiring to the front mounted AGM battery cannot be grossly overloaded if the DC-DC converter shuts off for any reason (I don’t want to find out the battery wiring can’t handle 90A the hard way). But also, allows me to disconnect the inverter/pack unit from the EC8 connector hanging out under the rear passenger seat if I need to move the extension cord out a different door, trunk, window, etc., without disrupting whatever 110V appliance I’m using. This solves the precharge problem because the lithium pack charges the inverter good enough to never have a problem when connecting to the car.

I slapped it together to run my fridges during one of PG&Es criminal “pre-emptive power outages” during a wind storm, but I now use it while camping for things like my induction hotplate, air fryer, projector, etc. so this isn’t really inconvenient at all. I’ll probably re-do the pack to 4S4P at some point so it’s smaller, but I’m lazy

But another relatively simple solution for non-permanent installs.

 

[n2mb_racing]

re: buffer batteries, I have a relatively small 20Ah 4S8P A123 LiFeP04 pre-made pack strapped to the inverter that I used to ensure the wiring to the front mounted AGM battery cannot be grossly overloaded if the DC-DC converter shuts off for any reason (I don’t want to find out the battery wiring can’t handle 90A the hard way). But also, allows me to disconnect the inverter/pack unit from the EC8 connector hanging out under the rear passenger seat if I need to move the extension cord out a different door, trunk, window, etc., without disrupting whatever 110V appliance I’m using. This solves the precharge problem because the lithium pack charges the inverter good enough to never have a problem when connecting to the car.

I slapped it together to run my fridges during one of PG&Es criminal “pre-emptive power outages” during a wind storm, but I now use it while camping for things like my induction hotplate, air fryer, projector, etc. so this isn’t really inconvenient at all. I’ll probably re-do the pack to 4S4P at some point so it’s smaller, but I’m lazy

But another relatively simple solution for non-permanent installs.

That's a good idea too. I wonder if you connected one of the DC DC charge controllers and another lithium battery if the DC DC converter wouldn't freak out.

But it's more hardware...


Renogy 12V 20A DC to DC On-Board Battery Charger for Flooded, Gel, AGM, and Lithium, Using Multi-Stage Charging in RVs, Commercial Vehicles, Boats, Yachts, 20A https://a.co/d/7qzQzaY

 

[wwu123]

I've read through the entire thread but don't see any examples. Has anyone successfully tapped into the Subwoofer power source for powering an inverter?

My use case is I'd like to charge an Ecoflow Delta battery @ 200 or 300 watts while using that battery to power something like a fridge and/or a water pump, and I feel like this carries a lot less risk than tapping into the main battery.

Thank you.

So the last deep discussions of using the DC-DC converter under the Model 3 seats to recharge a battery power station was about 18 months ago. Has anyone done this more recently?

Fast-forward to the present, power stations are basically available in "whole-home" form factors. My power station IS the primary backup source, 6000W inverter, will handle typical home loads for up to 6-8 hours. Secondary backup is the propane generator, which will directly power the home for 1-2 days, or recharge the power station for 3-4 days.

I would like to tap into the Model 3 as the tertiary backup solution, re-purposing some equipment used in my secondary backup use case. Basically DC-DC re-charge the power station using DC input ports on rare occasion. Since the power station itself handles the home loads, there is no inverter surge concerns, it would be a steady 1000W or so (so at the Model 3 underseat posts, 12V @ 80-90A for several hours). I could do 120W with the cigarette lighter charger for the power station, but it wouldn't quite keep up with home backup loads, plus it seems inefficient in that it's slow and inefficient, probably for every kwh that goes into the power station, 2 kwh is probably lost to vampire drain keeping the Model 3 awake - thus getting more to 1000W at 48-60V input to the power station would be much more efficient.

So my thought is a 12V to 48V boost converter (many with 1000W sizing claim to be about 95%+ effcient, and then to a Riden RD6024 DC-DC "power supply" (but basically a fancy buck converter face panel). The latter seems gratuitous for this thread, but is something that would allow me to fine-tune control how much volts and amps feeds into the power station (note the RD6024 also can come in a kit with an AC-DC power supply, but I'd just be using the face panel that can take any 0-70V DC power source).

So reading first and last portions of this long thread, it seems the main concern would be the inrush for capacitors in the DC-DC circuitry on the 12V-48V, or the RD6024 backside. These feel relatively small compared to what a 1200-1500W DC-AC inverter would need to directly handle surge loads, but then again I've never seen the inside of an inverter underneath the heatsink. Are these sized capacitors of concern that I should work on doing a pre-charge circuit? I saw the last page or two discussed the capacitor current ramp based on the capacitor specs, but I don't recall this thread ever stating exactly what watt or amp level of sudden inrush would cause the Model 3 to shut down the DC-DC circuitry and require the painful reset....

 

[cali8484]

1500W should be okay for inrush. What's the DC charging current limit in the power station? Does it have adjustable control for DC charging current?

 

[n2mb_racing]

So the last deep discussions of using the DC-DC converter under the Model 3 seats to recharge a battery power station was about 18 months ago. Has anyone done this more recently?

Fast-forward to the present, power stations are basically available in "whole-home" form factors. My power station IS the primary backup source, 6000W inverter, will handle typical home loads for up to 6-8 hours. Secondary backup is the propane generator, which will directly power the home for 1-2 days, or recharge the power station for 3-4 days.

I would like to tap into the Model 3 as the tertiary backup solution, re-purposing some equipment used in my secondary backup use case. Basically DC-DC re-charge the power station using DC input ports on rare occasion. Since the power station itself handles the home loads, there is no inverter surge concerns, it would be a steady 1000W or so (so at the Model 3 underseat posts, 12V @ 80-90A for several hours). I could do 120W with the cigarette lighter charger for the power station, but it wouldn't quite keep up with home backup loads, plus it seems inefficient in that it's slow and inefficient, probably for every kwh that goes into the power station, 2 kwh is probably lost to vampire drain keeping the Model 3 awake - thus getting more to 1000W at 48-60V input to the power station would be much more efficient.

So my thought is a 12V to 48V boost converter (many with 1000W sizing claim to be about 95%+ effcient, and then to a Riden RD6024 DC-DC "power supply" (but basically a fancy buck converter face panel). The latter seems gratuitous for this thread, but is something that would allow me to fine-tune control how much volts and amps feeds into the power station (note the RD6024 also can come in a kit with an AC-DC power supply, but I'd just be using the face panel that can take any 0-70V DC power source).

So reading first and last portions of this long thread, it seems the main concern would be the inrush for capacitors in the DC-DC circuitry on the 12V-48V, or the RD6024 backside. These feel relatively small compared to what a 1200-1500W DC-AC inverter would need to directly handle surge loads, but then again I've never seen the inside of an inverter underneath the heatsink. Are these sized capacitors of concern that I should work on doing a pre-charge circuit? I saw the last page or two discussed the capacitor current ramp based on the capacitor specs, but I don't recall this thread ever stating exactly what watt or amp level of sudden inrush would cause the Model 3 to shut down the DC-DC circuitry and require the painful reset....

View attachment 1021134

FYI, I think that Riden 6024 will only step down voltage, not up. There are similar step up options available. However, you won't get anywhere near 1500W at 12V in. To achieve those inflated ratings you need higher voltage near the max of the input range. I have this one, but it kind of sucks. You'll only get ~180W or less out with a 12V input.

Amazon.com

 

[stopcrazypp]

FYI, I think that Riden 6024 will only step down voltage, not up. There are similar step up options available. However, you won't get anywhere near 1500W at 12V in. To achieve those inflated ratings you need higher voltage near the max of the input range. I have this one, but it kind of sucks. You'll only get ~180W or less out with a 12V input.

Amazon.com

Yep, looking at only the watts is misleading. Look at the current rating instead. Like you say, even though that one your linked is rated "900W", it is only rated for 15A max, which means 180W max @12V as you pointed out. OP probably was fooled by the same thing.

 

[Max Spaghetti]

Some time ago I looked into setting up a 48V (nominal - actually 56V LFP) house battery for my camper - to be charged from the 12V vehicle alternator. I could not find a suitable 12-48V DC-DC charger anywhere. The only option available really was to invert directly to 230VAC with a 12V inverter and then use an AC 48V battery charger, with all the associated weight, bulk and efficiency losses.

Because of the lack of products available, I ended up doing a 24V house battery for which there were good 12-24V DC-DC chargers available.

Bring on the next generation of vehicles with 48V alternators, I say...

 

[n2mb_racing]

Some time ago I looked into setting up a 48V (nominal - actually 56V LFP) house battery for my camper - to be charged from the 12V vehicle alternator. I could not find a suitable 12-48V DC-DC charger anywhere. The only option available really was to invert directly to 230VAC with a 12V inverter and then use an AC 48V battery charger, with all the associated weight, bulk and efficiency losses.

Because of the lack of products available, I ended up doing a 24V house battery for which there were good 12-24V DC-DC chargers available.

Bring on the next generation of vehicles with 48V alternators, I say...

I also got a 48v inverter because I have a number of high power ebikes batteries around.

I wonder if any of these cheap, non adjustable ones will work. https://www.amazon.com/Converter-EA...0&psc=1&mcid=f13dce75228333529ed26879646d979d

 

[wwu123]

FYI, I think that Riden 6024 will only step down voltage, not up. There are similar step up options available. However, you won't get anywhere near 1500W at 12V in. To achieve those inflated ratings you need higher voltage near the max of the input range. I have this one, but it kind of sucks. You'll only get ~180W or less out with a 12V input.

Amazon.com

Thanks to all the folks for the multiple comments and replies. Yes, I think I was also fooled by the wattage rating, I was looking at something like this 1500W one: Amazon . Well, I didn't completely ignore the current limits, this one had a 30A rating, but I was only thinking of the output side. as 48V x 30A was greater than the 1200W my power station could max out. But you're pointing out the current limit on the input side, which it says is 35-40A a@ 12V, so yeah tops I could get would be maybe 480W or so.

1500W should be okay for inrush. What's the DC charging current limit in the power station? Does it have adjustable control for DC charging current?

So the power station itself has a 25A limit at 32-60V (and 1200W total), at those levels it has a solar MPPT tracker that could theoretically get confused by a DC power supply, but multiple folks have had success with a 48-60V SMPS AC-DC power supplies at the max limit. The power station itself I understand will try to pull as many amps to max out the 1200W, so has no adjustable control. But that was going to be the function of having the Riden RD6024 in the chain - because otherwise I would have just fed the 12V-48V step-up converter (which I not have no high-wattage solution) directly to the power station.

The Riden you can set both the desired output voltage and the desired max output current, the power station would only be able to draw the max amps that you set. So just to understand whether the inrush issue still exists or not - for regular 12V inverters, it's stated in the thread the inrush is due to the large capacitors - inrush proportional to the initial load on the inverter, or is it an issue with the capacitors even if there's no initial load hooked up to the inverter? Do capacitors not charge up as soon a power source is supplied?

I guess I'm asking, if I have a 12-48V step-up converter feeding the Riden, and set the Riden initially to 48V output and 1A when initially hooking up to the Tesla penthouse, will that cause less inrush than setting the Riden initially to 48V and 20A? Or is it strictly about the size of the capacitors on the Riden, irrespective of the Riden output settings or the actual initial load?

 

[wwu123]

I also got a 48v inverter because I have a number of high power ebikes batteries around.

I wonder if any of these cheap, non adjustable ones will work. https://www.amazon.com/Converter-EA...0&psc=1&mcid=f13dce75228333529ed26879646d979d

I think again the issue, at least for my use case, is the limited input or output current, the largest in that listing only does 6A out at 48V, or 288W.

It's interesting that there are multiple solutions previously discussed in the thread to do > 1200W using a DC-AC 12V inverter to output AC, and then I could feed that back into a $100 SMPS or $250 AC-DC power supply (including the Riden RD6024 full kit), so I could solve this if I was willing to do the DC-AC-DC conversion for 1200W with the associated conversion losses. But not any cheap or easy way to directly convert 12V DC - 48V DC at 1200W. ...

With both 48V e-bike batteries and 48V server rack batteries (esp as people extend off-grid battery/solar to not just RV's but entire homes) become more common, hopefully there will be more solutions forthcoming to step up 12 to 48V at higher power.

 

[n2mb_racing]

I think again the issue, at least for my use case, is the limited input or output current, the largest in that listing only does 6A out at 48V, or 288W.

It's interesting that there are multiple solutions previously discussed in the thread to do > 1200W using a DC-AC 12V inverter to output AC, and then I could feed that back into a $100 SMPS or $250 AC-DC power supply (including the Riden RD6024 full kit), so I could solve this if I was willing to do the DC-AC-DC conversion for 1200W with the associated conversion losses. But not any cheap or easy way to directly convert 12V DC - 48V DC at 1200W. ...

With both 48V e-bike batteries and 48V server rack batteries (esp as people extend off-grid battery/solar to not just RV's but entire homes) become more common, hopefully there will be more solutions forthcoming to step up 12 to 48V at higher power.

There are some bigger 12V to 48V converters that should work if they are going into your solar input on your power bank.

https://www.amazon.com/Cllena-Converter-Voltage-Regulator-Transformer/dp/B0CKRXSMNR

I don't know if they will work to directly charge 48V batteries, though. I don't know if they switch into constant current mode for battery charging directly. This one definitely works for charging lithium ion batteries directly. It has adjustable voltage and current limits.

Amazon.com

 

[stopcrazypp]

I guess I'm asking, if I have a 12-48V step-up converter feeding the Riden, and set the Riden initially to 48V output and 1A when initially hooking up to the Tesla penthouse, will that cause less inrush than setting the Riden initially to 48V and 20A? Or is it strictly about the size of the capacitors on the Riden, irrespective of the Riden output settings or the actual initial load?

Thanks to all the folks for the multiple comments and replies. Yes, I think I was also fooled by the wattage rating, I was looking at something like this 1500W one: Amazon . Well, I didn't completely ignore the current limits, this one had a 30A rating, but I was only thinking of the output side. as 48V x 30A was greater than the 1200W my power station could max out. But you're pointing out the current limit on the input side, which it says is 35-40A a@ 12V, so yeah tops I could get would be maybe 480W or so.



So the power station itself has a 25A limit at 32-60V (and 1200W total), at those levels it has a solar MPPT tracker that could theoretically get confused by a DC power supply, but multiple folks have had success with a 48-60V SMPS AC-DC power supplies at the max limit. The power station itself I understand will try to pull as many amps to max out the 1200W, so has no adjustable control. But that was going to be the function of having the Riden RD6024 in the chain - because otherwise I would have just fed the 12V-48V step-up converter (which I not have no high-wattage solution) directly to the power station.

The Riden you can set both the desired output voltage and the desired max output current, the power station would only be able to draw the max amps that you set. So just to understand whether the inrush issue still exists or not - for regular 12V inverters, it's stated in the thread the inrush is due to the large capacitors - inrush proportional to the initial load on the inverter, or is it an issue with the capacitors even if there's no initial load hooked up to the inverter? Do capacitors not charge up as soon a power source is supplied?

I guess I'm asking, if I have a 12-48V step-up converter feeding the Riden, and set the Riden initially to 48V output and 1A when initially hooking up to the Tesla penthouse, will that cause less inrush than setting the Riden initially to 48V and 20A? Or is it strictly about the size of the capacitors on the Riden, irrespective of the Riden output settings or the actual initial load?

It has nothing to do with initial load, the load side can be completely disconnected. The inverter doesn't even need to be powered on. The issue is there are supply side capacitors on the inverter to smooth out the input. For high power inverters, they can be quite large. I have read one way to tell is if you connect the battery cable to the supply side, there may be sparks. That is why people add pre-charge circuits to high power inverters. The circuits use a resistor (with appropriate power rating) to limit the current while the capacitor is charging, then the resistor is disconnected after the capacitor is done charging.

This was mentioned up thread, but if you are using it with the inverter permanently attached (or you allow the car to go to sleep while still attached for other reasons), that may negate the pre-charge circuit. This is because the input capacitors may discharge, and when car wakes up, there is a surge of current as it recharges it. More complex circuits have been suggested up thread to automatically handle this case.

The load side is actually less of a worry, given usually there are fuses or breakers on the inverter itself that would cut off power, well before it hits limits. You just pick one that doesn't exceed the max current the car can supply. There is no such limiter however for the input capacitors (at least for most on the market; there may be some niche ones that have a build in circuit), nor is the inrush current specified (if it were, you can just pick one that doesn't exceed the car's specs).

 

[cali8484]

So the power station itself has a 25A limit at 32-60V (and 1200W total), at those levels it has a solar MPPT tracker that could theoretically get confused by a DC power supply, but multiple folks have had success with a 48-60V SMPS AC-DC power supplies at the max limit. The power station itself I understand will try to pull as many amps to max out the 1200W, so has no adjustable control. But that was going to be the function of having the Riden RD6024 in the chain - because otherwise I would have just fed the 12V-48V step-up converter (which I not have no high-wattage solution) directly to the power station.

It's risky to assume the external DC-DC current control will work as expected. Unless you know the specific impedances of the power station input and DC-DC output are compatible the MPPT can easily end up pulling the voltage way down. Fixed voltage and current supplies typically work much better than DC-DC converters with MPPT.

 

[Max Spaghetti]

I don't know if they will work to directly charge 48V batteries, though. I don't know if they switch into constant current mode for battery charging directly. This one definitely works for charging lithium ion batteries directly. It has adjustable voltage and current limits.
Amazon.com

From specs: "Input current: 0-15A"

It falls into the same boat as the rest: i.e. limited input current at 12V.

12V x 15A = 180W maximum. Don't let the "900W" in the advertising fool you.

 

[n2mb_racing]

From specs: "Input current: 0-15A"

It falls into the same boat as the rest: i.e. limited input current at 12V.

12V x 15A = 180W maximum. Don't let the "900W" in the advertising fool you.

yeah, I mean, it works, but not very powerful for 12V inputs. I have it. It reaches closer to 900W with high voltage inputs, ie. powered from 60V batteries.

 

[wwu123]

It has nothing to do with initial load, the load side can be completely disconnected. The inverter doesn't even need to be powered on. The issue is there are supply side capacitors on the inverter to smooth out the input. For high power inverters, they can be quite large. I have read one way to tell is if you connect the battery cable to the supply side, there may be sparks. That is why people add pre-charge circuits to high power inverters. The circuits use a resistor (with appropriate power rating) to limit the current while the capacitor is charging, then the resistor is disconnected after the capacitor is done charging.

This was mentioned up thread, but if you are using it with the inverter permanently attached (or you allow the car to go to sleep while still attached for other reasons), that may negate the pre-charge circuit. This is because the input capacitors may discharge, and when car wakes up, there is a surge of current as it recharges it. More complex circuits have been suggested up thread to automatically handle this case.

The load side is actually less of a worry, given usually there are fuses or breakers on the inverter itself that would cut off power, well before it hits limits. You just pick one that doesn't exceed the max current the car can supply. There is no such limiter however for the input capacitors (at least for most on the market; there may be some niche ones that have a build in circuit), nor is the inrush current specified (if it were, you can just pick one that doesn't exceed the car's specs).

Thanks, appreciate the explanation and when the pre-charge circuit is useful!

It's risky to assume the external DC-DC current control will work as expected. Unless you know the specific impedances of the power station input and DC-DC output are compatible the MPPT can easily end up pulling the voltage way down. Fixed voltage and current supplies typically work much better than DC-DC converters with MPPT.

Yes, in various solar/battery forums, there's definitely some experimental hit-and-miss across different DC power sources and across different power station brands. Some cases the MPPT controller hunts endlessly, sometimes it can refuse to accept any power in despite sensing a voltage input, sometimes it drops into the lower current "cigarette lighter" 10A limit, etc.

 

[wwu123]

There are some bigger 12V to 48V converters that should work if they are going into your solar input on your power bank.

https://www.amazon.com/Cllena-Converter-Voltage-Regulator-Transformer/dp/B0CKRXSMNR

I don't know if they will work to directly charge 48V batteries, though. I don't know if they switch into constant current mode for battery charging directly. This one definitely works for charging lithium ion batteries directly. It has adjustable voltage and current limits.

Amazon.com

Thanks for finding those - the first one is probably what I've been looking around for, I think, with the suggestion of adding a pre-charge circuit. I would get me to 960W, there's no 20A input limit, just output limit, is that correct?

The second one again is too small for my use case, 15A input limit means at 12V x 15A = 180W max power, barely different from using the 120W cigarette lighter charger that comes with the power station., heh heh (EDIT: saw Max Spaghetti beat me to it on this one)