Charging a portable power station from a Tesla Model 3

[zacksc]

Portable power stations such as the Jackery E1500, Ecoflow Delta or Goal Zero Yeti typically charge at about 100 watts using a 12 volt source and up to about 500 Watts using a converter powered by 110 volts AC. I am trying to figure out how to charge at the higher rate from a 12 volt DC power. I think this may be pretty straightforward, but I don't really understand how the charging rate is controlled. (The reason this could be important and useful is that, in a power outage or in the boondocks, it would enable transferring energy efficiently from a EV battery to a readily useable form.)

Let me ask about a specific example: charging a Jackery E1500 from a model 3*. The Jackery E1500 comes with 2 AC chargers that can each charge at 300 Watts. These chargers are basically converters, as I understand it, that plug into a standard wall plug, draw about 3 amps at 110 V, and convert that to about 24 amps at 13 volts DC which charges the E1500 via an 8 mm (2 pin) connector. This E1500 also comes with a car charger that charges into the same 8mm ports as the AC chargers. This DC option will charge at about 90 Watts (8 amps). Solar panels can also be used for charging the E1500 through the same 8 mm ports at a variable rate managed by a built-in MPPT controller.

What I would like to be able to do is to charge at 300 Watts using the 13 to 14 volt source at the DC-DC converter of a Tesla model 3. (This would be similar for other EVs.) I understand that one would need to use an appropriate connector on the input side (SB175?) and appropriate wire guage (6 AWG?). I don't understand how the charging speed is controlled? How would one design a charger that utilizes 13.5 volt input and charges the Jackery through its 8mm input port at the same 300 Watt speed one gets with the AC charger? Any help will be greatly appreciated.

Appendix 1. An obvious way to do this is to use an inverter to step up the DC power to 110 volts and then plug the AC chargers that come with the Jackery E1500 to the inverter. Maybe this is the best way, but it seems both inefficient and possibly more costly since it requires purchasing an inverter. I am thinking it should be possible to design a DC-DC charging device that will charge the Jackery at the same 300 Watt speed that one can get with the AC-powered charger.

* A typical model 3 battery can store up to 75 kWh of energy. It includes over 4000 21700 cells incorporated into a BMS. I think the string length is 96 and the group size is 46. I am guessing these cells may be somewhat similar to a 30Q??? They seem to have very long lifetime and also allow high discharge at least for short periods if time...

 

[flippy]

from what i understand you can just jack the 12V from the car directly into the DC jack of the jackery. the "charger" is inside the device. just like your phone.

the internal charger is current limited, so the regular "chargers" are actually really just power supplies for the internal charging circuit.

jackery does not know what is connected. it just draws power until the power starts to sag. all power is run into the MPPT converters behind the DC jacks. that is why it does not care about the voltage. andthing between 9 and 48V will work, its just current limited at 6A.

if the jackery internal charger is limted to 6A wich it appears to be then you need a 12 to 48V converter to jack the voltage up to 40+ volts. (no more then 48V!)

this should do the trick:
https://www.amazon.com/Daygreen-960W-Step-Converter-Non-Isolated/dp/B07KQSSWSR
get the 960W model so you can charge with both DC jacks at 600W total.

just use some 8AWG or better on the input of that converter as it can pull 50A+ AND USE BOTH DC INPUT JACKS. these things are ran pretty "hot" for dicky little barrel jacks so buy proper ones and no fake aliexpress ones and have decent wires.

that should fill the thing from dead to full in 2~3 hours.


and the M3/MY cells are not related to any other cells, they are teslas own 11 herbs and spices. :wink:

we could say exactly how it charges if there were pictures of the inside but i cant find any. not many people are willing to crack open their overpriced powerbank....

 

[zacksc]

Thanks a lot Flippy. Your reply is amazing. You explain everything with crystal clarity. I am in your dept.

So it is all about the 6 amp limit and the input voltage. So if you plug into your car's normal 12 volt port, you will just get 6 amps times 12 or 13 volts, a nominal 80 Watt charging rate. Do I have the right?

And the AC powered converters probably convert down to just 48 volts, not 13 volts like I thought originally, and that is how they get the 6x48 nominal 300 Watt charging rate. So cool. So Simple.

I will buy that Daygreen 12 to 48 Volt converter. That seems way better, cheaper, and more efficient than getting two inverters to use in parallel. They say the Daygreen is 95% efficient, which seems pretty great. Does the Daygreen have to convert to AC to do the step up with induction, or is there another way that is more efficient?

Thanks so much!

 

[zacksc]

this should do the trick:
https://www.amazon.com/Daygreen-960W-St ... B07KQSSWSR
get the 960W model so you can charge with both DC jacks at 600W total.

When this is initially plugged in to the 14 volts at the DC-DC converter, will their be a brief current surge?

 

[flippy]

When this is initially plugged in to the 14 volts at the DC-DC converter, will their be a brief current surge?

yes. you will probably see some sparks when connecting. i recommend you keep it connected as the connection needs to be beefy in order to take 50A for several hours and the sparks might kill the capacitors if you are really unlucky.

if you want it removable: take 8awg or better directly from the car battery, put in a AMG fuse holder, get a 80A AMG fuse from bussman (get a expensive real one, not the cheap fake AMG fuses!) and connect the ends to a SB50 Anderson that exits at your frunk where you can connect the daygreen.

but personally i would find a space in the area behind the frunk tub to mount the daygreen permanently and only have a 4 pin SD20 chassis mount on the inside of the tub.
https://www.amazon.com/MCCAMSTORE-Waterproof-Connector-Aviation-Electric/dp/B08B83WRHF
(double up, so 2 negatives and 2 positives)
its certainly the cleanest setup and the safest if you plan to use the jackery often of just have it with you. and if you sell the car you sell it with the jackery as a bonus. :wink:

(the AMG fuse is still needed in a fixed setup)

Does the Daygreen have to convert to AC to do the step up with induction, or is there another way that is more efficient?

https://www.youtube.com/watch?v=vmNpsofY4-U

Do I have the right?

yes.

ps: if you mount it permanently with the SD20 plug you can just have the chargery on a lead (14awg would be good for a 30ft lead) and charge it permanetly from the car while having the jackery 25ft from the car and the car still locked with the wire coming out of the frunk. just find the biggest panel gap.
you can use cable like this so its more robust outside: https://www.amazon.com/GearIT-2-Conductor-Speaker-Meters-Outdoor/dp/B08R566RRS
(try to find something better or preferably with neoprene outside sheath to make it very flexible and durable.)
thanks to the 48V you can have pretty long leads without problems. 100ft should even work if but you really want 14awg or better if you go that long...

and i might be overstating this but this is important: only use good quality -real- copper wires. none of that aluminium or CCA crap. and use wire lugs and crimp connections. DO NOT SOLDER lugs to wires, only crimp. and use heat shrink with adhesive liner (aka: glue) on the inside so mostiure can never get into the wire.

 

[zacksc]

Thanks again Flippy. There a a couple of issues specific to the Tesla Model 3, and, I wonder if I should incorporate some precharge circuitry or an NTC inrush current limiter. (Not that I really know exactly what those things are, but I think they might be important.)

The specific issues are:
1) You can't hook it up in the frunk by the 12 v battery because there is something between the Model 3 DC-DC converter and the M3 battery that limits current flow to about 10 amps up there. So you have to connect to some terminals closer to the M3 DC-DC converter (under the passenger seat) where you can draw 100 amps at 13 or 14 volts with "no problem".
2) When the car goes to sleep, the contactors to the main battery open and the voltage drops to zero. So I think whenever the car wakes up, it is like connecting the Daygreen for the first time and there could be inrush current (which could trip a "fuse" if it is too much).

So I was wondering a couple of things. Would it make the transient inrush current less of a problem to use two smaller Daygreen step up converters? (Like two 480 Watt converters instead of one 960 Watt converter?) And, maybe I should put in switches, so I can turn them on one at a time when needed, and also some sort of precharge resistor, with its own separate switch or an NTC inrush current limiter? What is an NTC inrush current limiter?

 

[flippy]

pro tip: if you enable sentry mode the 12V stays on and you can tap off the PCM main 12V bus under the seat or in the frunk. :wink:

an inrush limiter is a resistor that has high resitance when its cold and low resistance when its hot. when you plug the device in the resistor needs to heat up in order to let power pass properly. i do not know if that daygreen has one. i would not recommend fitting one (its a real science getting a properly rated one) and just make it a permanent install on the correct PCM power rail. and add a precharge resistor over a time delay relay. pretty simple setup and would avoid upsetting the model 3's delicate feelings...
you might need 2 relays, one low power time delayed one that switches a big 200A relay. i dont think there are 200A relays with a time delay built in.

that way the 48V only works if the car is on or in sentry mode and it auto-enables when you turn the car on. the PCM can push 200A or so so there is enough on tap. just look for the proper tap point.

 

[nicobie]

It's much easier on a Chevy Volt. All I do is connect the 2kW sine wave inverter to the 12V battery with short 6 gauge wires then run the car with the shift button clamped on and in park. I have the wires and a big Anderson connecter permanently installed on the battery.

 

[flippy]

It's much easier on a Chevy Volt. All I do is connect the 2kW sine wave inverter to the 12V battery with short 6 gauge wires then run the car with the shift button clamped on and in park. I have the wires and a big Anderson connecter permanently installed on the battery.

how is that "much easier" exactly? the car needs to be "on" all the time. the teslas do not. and you have several places to steal 12V from.

 

[nicobie]

Granted, it's not much easier but you don't have to take the rear seat out every time in order to get to a good (high Amp) 12V source for the inverter. As I'm sure you know, The Tesla 3's don't provide much in the way of charging Amperage at their aux battery.

Also the Volt will automatically keep the HV/12V batteries charged up as long as there is gas in the tank (or hooked up to my solar).

If you wish I'll gladly provide some links.

I'm not knocking Tesla, just pointing out emergency use of the big EV battery on another car. For what it's worth, I'd own a Tesla if the Volt didn't serve my personal needs better. :wink:

 

[flippy]

you dont have to take out the rear seats every time, nothing is stopping you from just hooking up a SB50 that comes out at the trunk or frunk if you really want to connect stuff up constantly. but its still a very out-there thing to want/have in general.

if you really want the best you can get you can just tap off the 400v battery pack and run that into the solar mppt input of a solar inverter. then you can just run your house or whatever like normal at very stupid power levels.

 

[nicobie]

if you really want the best you can get you can just tap off the 400v battery pack and run that into the solar mppt input of a solar inverter. then you can just run your house or whatever like normal at very stupid power levels.

:lol:

I don't have either the balls or qualifications for that. 1.5kW will keep me going fine.

 

[fatty]

It's much easier on a Chevy Volt. All I do is connect the 2kW sine wave inverter to the 12V battery with short 6 gauge wires then run the car with the shift button clamped on and in park. I have the wires and a big Anderson connecter permanently installed on the battery.

if you really want the best you can get you can just tap off the 400v battery pack and run that into the solar mppt input of a solar inverter. then you can just run your house or whatever like normal at very stupid power levels.

This was actually my first thought as well.

Why not use the Tesla itself as the portable power station? It's already a sunk cost, and much higher quality and more robust than a Chinese power station. That way you're not doing 300VDC to 12VDC to 48VDC to 110VAC.

But since most use cases for a 1500Wh power bank are probably DC inside anyway, why do DC>DC>DC>AC>DC at all? Why not use a proper isolated & regulated DC-DC converter instead of derating a Chinese inverter or non-isolated DC-DC converter?
You could permanently mount a common voltage high-current always-on converter in the car -- maybe 12V 33A? (just speaking generally -- not needed on a Tesla if you have 14V@100A available)
Then a 200W DC>USB-C PD module, which gives 5V, 9V, 12V, and 15V @ 3A, and 20V @ 5A.
Then USB-C to DC barrel in any of those voltages.
Or for a device that isn't native USB-C or DC barrel, just splice in a trigger cable above, or modernize the device with a female USB-C PD trigger module.

 

[zacksc]

you dont have to take out the rear seats every time, nothing is stopping you from just hooking up a SB50 that comes out at the trunk or frunk if you really want to connect stuff up constantly. but its still a very out-there thing to want/have in general.

if you really want the best you can get you can just tap off the 400v battery pack and run that into the solar mppt input of a solar inverter. then you can just run your house or whatever like normal at very stupid power levels.

Do you think it would be okay to charge a Jackery E1000 at 48 volts (6 amps)? (using a Daygreen Boost converter.)

I think the normal charger for the E1000 is a 24 volt converter, which charges at 24 volts x 6 amps, so the 48 volt would presumably be twice as fast, but still about C/3 range. Will the E1000 likely accept that 48 v x 6A charge rate?

 

[flippy]

Where would you connect the daygreen on?

 

[fatty]

Do you think it would be okay to charge a Jackery E1000 at 48 volts (6 amps)? (using a Daygreen Boost converter.)

No
DC Input: 12V-30V (163W Max)

 

[zacksc]

Where would you connect the daygreen on?

I would connect the Daygreen to the Model 3 14 volts under the rear seat. And then have an 8mm plug on the Daygreen 48 volt output which would plug in to the E1000 charging port.

 

[zacksc]

Do you think it would be okay to charge a Jackery E1000 at 48 volts (6 amps)? (using a Daygreen Boost converter.)

No
DC Input: 12V-30V (163W Max)

Well, I see what you mean. That is in the technical specs. But I wonder what would happen if you connected that 8mm charging port, which usually takes 24 volts, to a 48 volt source? Would the BMS trip or something? Would something bad happen? Or would the MPPT just limit the current to 6 amps and charge at 290 Watts? (As Flippy explained before, the current is limited to 6 amps.)

 

[fatty]

Well, I see what you mean. That is in the technical specs. But I wonder what would happen if you connected that 8mm charging port, which usually takes 24 volts, to a 48 volt source? Would the BMS trip or something? Would something bad happen? Or would the MPPT just limit the current to 6 amps and charge at 290 Watts? (As Flippy explained before, the current is limited to 6 amps.)

If it has charge OVP, it would not charge.
If not, it would blow something in the charging circuit.

 

[zacksc]

Well, I see what you mean. That is in the technical specs. But I wonder what would happen if you connected that 8mm charging port, which usually takes 24 volts, to a 48 volt source? Would the BMS trip or something? Would something bad happen? Or would the MPPT just limit the current to 6 amps and charge at 290 Watts? (As Flippy explained before, the current is limited to 6 amps.)

If it has charge OVP, it would not charge.
If not, it would blow something in the charging circuit.

I see. Well that could happen pretty easily, because the 110 AC charger for the Jackery E1500 has a 48 volt dc output and uses the same 8mm plug as the E1000 charger. They look very similar and I think someone could very easily plug that 48 volt charger into the E1000 by mistake (or trying to get a faster charge).
(165 Watts seems like an awfully low max charging rate for a 1000 kWh battery.)

 

[fatty]

I see. Well that could happen pretty easily, because the 110 AC charger for the Jackery E1500 has a 48 volt dc output and uses the same 8mm plug as the E1000 charger. They look very similar and I think someone could very easily plug that 48 volt charger into the E1000 by mistake (or trying to get a faster charge).
(165 Watts seems like an awfully low max charging rate for a 1000 kWh battery.)

I donno -- how many Jackery customers own both an E1000 and E1500 simultaneously (0.1%?), let alone co-locate them? 0.01%?

Seems more likely to mix up the ubiquitous 5.5mm DC barrel -- I have at least 5 in a variety of voltages.

 

[zacksc]

I see. Well that could happen pretty easily, because the 110 AC charger for the Jackery E1500 has a 48 volt dc output and uses the same 8mm plug as the E1000 charger. They look very similar and I think someone could very easily plug that 48 volt charger into the E1000 by mistake (or trying to get a faster charge).
(165 Watts seems like an awfully low max charging rate for a 1000 kWh battery.)

I donno -- how many Jackery customers own both an E1000 and E1500 simultaneously (0.1%?), let alone co-locate them? 0.01%?

Seems more likely to mix up the ubiquitous 5.5mm DC barrel -- I have at least 5 in a variety of voltages.

True. I don't really know much, but I just kind of thought that with bike batteries you can charge at 2 amps or 4 amps or 6 amps or ..., and I was hoping to be able to charge my E1000 a little faster. I would be fine with 36 volts (216 Watts), but I haven't seen a lot of options for 12 volt to 36 volt boost converters. C/6 is awfully slow.

I didn't know if they really meant it when they put those limits in the specs or if they had just chosen to use a small 24 volt converter charger to keep the price low.

 

[fatty]

True. I don't really know much, but I just kind of thought that with bike batteries you can charge at 2 amps or 4 amps or 6 amps or ..., and I was hoping to be able to charge my E1000 a little faster. I would be fine with 36 volts (216 Watts), but I haven't seen a lot of options for 12 volt to 36 volt boost converters. C/6 is awfully slow.

But you're not asking about amps, you're asking about volts.

I didn't know if they really meant it when they put those limits in the specs or if they had just chosen to use a small 24 volt converter charger to keep the price low.

It's not a limit, it's just designed for the voltage of the battery inside. It's in Tech Specs:
E1000: 21.6V
E1500: 36V

 

[zacksc]

"
But you're not asking about amps, you're asking about volts."

For the E1000, my understanding is that the charging is MPPT, but with a current limit of 6 amps. So when you charge with a solar panel, you are on the MPPT curve, and, On the other hand, the 12 volt charger charges at 12 volts x 6 amps (72 Watts), and the AC powered charger is a 110 AC to 24 volt converter, which just supplies a simple 24 volts to the MPPT 8mm input and charges at 24 volts x 6 amps = 144 Watts. To get a higher charging speed then, I am thinking, you could try a 36 volt or 48 volt input, which would charge at 216 Watts or 288 Watts, respectively due to the 6 amp limit. I was thinking (hoping) that they provided a 24 volt charger just to save money, cause a 48 volt 288 Watt inverter would cost them more to make.
So basically, I am asking about charging speed, and in this case, with this that is connected to volts in the input. Are you sure that that MPPT input won't accept a higher voltage and charge faster?

 

[zacksc]

Is the E1500 a higher voltage battery? Does it have longer strings? I imagine that both are made from 18650 cells. I was assuming that the difference in capacity was due to larger groups and that the overall battery voltage is the same for the E1000 and the E1500. But maybe my assumption about that is wrong?