Charging a portable power station from a Tesla Model 3

[zacksc]

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

Looking at those voltages you just posted, I am guessing now that the E1000 is 6 groups in series, 6 x 3.6 = 21.6 volts. And the the E1500 is 10 groups in series (36 volts). I get that now.

I guess I am not sure at all how the MPPT charging actually is implemented in the Jackery. I don't understand how you can charge a 21.6 volt battery with a 12 volt input, or how you can charge it twice as fast with a 24 volt input. How does that work? What limits or controls the current? What limits the range of voltages one can supply at the 8 mm charging port input?

At full charge the E1000 must reach about 25.2 volts (6x4.2) and yet you can charge it to full with a 12 or 13 volt input at the 8mm? I would love to understand that.

 

[fatty]

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.

You may be confusing devices. The solar panel has Short Circuit Current: 6A. This is unrelated to DC or AC charging current.
It also has Open Circuit Voltage: 21.6V, which falls within the safe 12V-30V E1000 input voltage.
The 12VDC and AC devices are not chargers -- just supplies. The actual charging circuit (and thus limitations) is housed within the power station.
For the 12VDC car charger, I do not see a 6A limit. Where do you see this? 12VDC should charge at 163W/12V = 13.6A.
For the AC supply, it supplies 24V at 7.5-8.3A, not 6A.

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?

No, >30V will burn up the integrated charging circuit. The MPPT input only has to track between 12-21.6V of the solar panel.
Again, you may be conflating the 6A solar output limit. The onboard charger has a clear limit of 163W, not 6A.
You are still limited by the 12-30V, 163W hard limits limits. Yes, I'm sure.

 

[fatty]

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?

This is already answered above, and also directly available under Tech Specs.

 

[fatty]

Looking at those voltages you just posted, I am guessing now that the E1000 is 6 groups in series, 6 x 3.6 = 21.6 volts. And the the E1500 is 10 groups in series (36 volts). I get that now.

Correct

I guess I am not sure at all how the MPPT charging actually is implemented in the Jackery. I don't understand how you can charge a 21.6 volt battery with a 12 volt input, or how you can charge it twice as fast with a 24 volt input. How does that work? What limits or controls the current? What limits the range of voltages one can supply at the 8 mm charging port input?
At full charge the E1000 must reach about 25.2 volts (6x4.2) and yet you can charge it to full with a 12 or 13 volt input at the 8mm? I would love to understand that.

As above, you are confusing devices. The charging circuit is housed within the power station, not the solar panel or AC adapter. The onboard charging circuit accepts any DC input from 12-30V from these devices and converts it to the correct battery voltage. This charging circuit only draws so much current -- in fact, it is limited by power (163W), not directly by current. The input voltage is limited by the components used in the charging circuit, which have a maximum voltage rating. The charging circuit should also be protected by input overvoltage protection to prevent damage/danger in the case of a mixed-up (wrong/unsafe) DC input over 30V.

 

[zacksc]

Looking at those voltages you just posted, I am guessing now that the E1000 is 6 groups in series, 6 x 3.6 = 21.6 volts. And the the E1500 is 10 groups in series (36 volts). I get that now.

Correct

I guess I am not sure at all how the MPPT charging actually is implemented in the Jackery. I don't understand how you can charge a 21.6 volt battery with a 12 volt input, or how you can charge it twice as fast with a 24 volt input. How does that work? What limits or controls the current? What limits the range of voltages one can supply at the 8 mm charging port input?
At full charge the E1000 must reach about 25.2 volts (6x4.2) and yet you can charge it to full with a 12 or 13 volt input at the 8mm? I would love to understand that.

As above, you are confusing devices. The charging circuit is housed within the power station, not the solar panel or AC adapter. The onboard charging circuit accepts any DC input from 12-30V from these devices and converts it to the correct battery voltage. This charging circuit only draws so much current -- in fact, it is limited by power (163W), not directly by current. The input voltage is limited by the components used in the charging circuit, which have a maximum voltage rating. The charging circuit should also be protected by input overvoltage protection to prevent damage/danger in the case of a mixed-up (wrong/unsafe) DC input over 30V.

Thanks a lot. I think I understand a little more now. Here is what I am understanding so far. Does this seem correct?:
The charger is in the Jackery and it is basically a converter which can handle a range of input voltages and then outputs an appropriate voltage and current to charge the battery inside the Jackery. It also has some MPPT intelligence that it uses with solar panel input, but for a fixed voltage input it basically just does some conversion of voltage and regulates current to enable charging. The current at which it charges can depend on the input voltage to the converter/charging system.

So for the E1000, the range of input voltage it will accept (at the 8 mm power input) is around 9 to 28 or 30 volts. In my experience (I have an E1000) it charges at about 72 Watts with a 12 or 13 volt input and at around 144 Watts when the input voltage is 24 volts.

The E1500 is a different animal in terms of battery voltage, and also has a converter/charger system that can take a wider range of input voltages than the E1000 and handle about twice as much total power. Specifically, I think the E1500 can handle inputs from 9 to 48 volts. I believe that its charging speed with 12 volt input at the 8 mm is just 72 Watts. I am pretty sure that its charging speed with 48 volt input is around 290 Watts. (I don't think that 8 mm plug (where the power is inputed to the charger circuitry) can handle much more than 6 amps.).

Does that all sound correct? Thanks very much!

 

[fatty]

Thanks a lot. I think I understand a little more now. Here is what I am understanding so far. Does this seem correct?:
The charger is in the Jackery and it is basically a converter which can handle a range of input voltages and then outputs an appropriate voltage and current to charge the battery inside the Jackery. It also has some MPPT intelligence that it uses with solar panel input, but for a fixed voltage input it basically just does some conversion of voltage and regulates current to enable charging. The current at which it charges can depend on the input voltage to the converter/charging system.

Correct

So for the E1000, the range of input voltage it will accept (at the 8 mm power input) is around 9 to 28 or 30 volts. In my experience (I have an E1000) it charges at about 72 Watts with a 12 or 13 volt input and at around 144 Watts when the input voltage is 24 volts.

Well, this doesn't match the (minimal) specs given, so your observations may be of charging at different states of charge -- that is, if the battery was in the CV ("trickle") charge stage, power would have been much lower than during the CC (bulk) charge stage. But as with all things Chinese, who knows.

The E1500 is a different animal in terms of battery voltage, and also has a converter/charger system that can take a wider range of input voltages than the E1000 and handle about twice as much total power. Specifically, I think the E1500 can handle inputs from 9 to 48 volts. I believe that its charging speed with 12 volt input at the 8 mm is just 72 Watts. I am pretty sure that its charging speed with 48 volt input is around 290 Watts. (I don't think that 8 mm plug (where the power is inputed to the charger circuitry) can handle much more than 6 amps.).

Does that all sound correct? Thanks very much!

Maybe a cheap Chinese 8mm, but even 5.5mm can be rated up to 8A.
Otherwise, sounds correct.

 

[zacksc]

Thanks a lot. So then the chance that you could charge the E1000 more rapidly by just supplying it with 36 volts at the 8 mm input is really really low?

 

[fatty]

So then the chance that you could charge the E1000 more rapidly by just supplying it with 36 volts at the 8 mm input is really really low?

For the 4th or 5th time, 30V is the max DC input voltage. 36V will either not charge or will fry the charging circuit.

As discussed in this thread, there are about a million better ways to improve on what you're trying to do. Overvolting a power station isn't one of them.

 

[zacksc]

So then the chance that you could charge the E1000 more rapidly by just supplying it with 36 volts at the 8 mm input is really really low?

For the 4th or 5th time, 30V is the max DC input voltage. 36V will either not charge or will fry the charging circuit.

As discussed in this thread, there are about a million better ways to improve on what you're trying to do. Overvolting a power station isn't one of them.

Fair enough. I appreciate your patience and sticking with me here. So what I did is order a 12 to 24 volt 240 Watt converter that I can plug into the 14 volt stud under the rear seat. So at least that way I will be charging at 144 Watts, instead of the 72 Watt charging rate I would get from the cigarette-lighter-style power port in the cabin. That is probably good enough for an occasional power outage and can hopefully save me from needing to set up a generator for 3 or 4 days at least.

I also made a switch box with a 2 Ohm precharge resistor, out of fear of a current surge occurring when I switch on the power to the Daygreen converter. I don't know if that is necessary, but I am pretty paranoid about tripping something associated with the DC-DC converter in the car. Actually, out of even more paranoia, I am thinking of adding an additional 1 Ohm resistor with its own switch in parallel, so that I can get the resistance down to 2/3 Ohm before I switch the direct power on to the converter. (I am assuming a converter has capacitors and may look a bit like a short for a brief moment when it is switched on. Is that true?) All the switching is manual. Some pictures are attached. (The ground/return from the car goes via a separate wire (not shown) directly from a 2nd 8 mm stud under the seat to the appropriate Daygreen converter input.)

 

[zacksc]

Does that (above) seem like it will work? Does current surge tend to be an issue with converters?

(I could have gotten a 12 to 28 volt converter with a higher power rating, but it was a bit more expensive.)

 

[tungsten2k]

Those DC-DC converters usually get only about 60% of rating before turning into a hot mess, at least the several I tried that looked very similar which I use for converting my 14S bike pack down to 12V for running automotive accessories as well as charging my FPV drone setup with when out on a back country mountainside. In the end I had to limit running them at 50% rated power to keep them from burning out.

For my $$$ i would have just grabbed a sinewave inverter to connect to the same lugs under the rear passenger seat so you could just use the Jackery adapter, as well as any other 110v accessories you might want. If your DC-DC grenades when ran at-rated-power like mine did, you might want to consider the 110v inverter route.

 

[fatty]

Does that (above) seem like it will work? Does current surge tend to be an issue with converters?

I've used that family of boost converters (12V to 15V in my case), and it will work if you don't mind risking burning your Tesla to the ground. I only used them in a high-temp resistant engine compartment.

As above, there's no empirical evidence boosted voltage will even charge faster. Certainly not worth the dirty output, inefficiency, and risk.

There are much better ideas discussed earlier in this thread. Why bother posting the same question over and over, then ignoring the detailed technical advice you receive?

 

[zacksc]

I do really appreciate your advice. I thought I was following it, by getting the 24 volt output converter rather than a 48 volt, but maybe I did not see the big picture. I have never really done anything that involved much power before, so I have a lot to learn. I really appreciate the warnings about heat and the danger of using inexpensive converters and so I am not going to use that. Thank you both for alerting me to the risk there.

So maybe just using an inverter is better? The AC charger for the Jackery E1000 is literally just a Hunt-key converter (Model HKA18024075-6C) with output rated as 24 volts and 7.5 amps. I was thinking it might be "clever" to bypass that and just go directly from the 14 volts of the car to the 24 volts to the E1000, but I understand now that that is not prudent, at least with the converter I picked out. Are there better converters that would be as safe as an inverter? Maybe not?

Anyway, I can try to get a good inverter, go from 14 volts to 110 AC and then using the converter that comes with the Jackery (The Hunt-key 24 volt output converter) to supply power to the Jackery E1000 charging system. So then 14 volts --> 110 VAC --> 24 volts (7 amps) sounds like the safest path? Does that sound right?

 

[zacksc]

The Jackery E1000 comes with two charging options. One is a cable with a car outlet on one end and an 8 mm plug on the output end, which charges at a constant 75 Watts from 10% to 90%. The other is a 110 AC powered 24 volt output converter, which charges at a constant 145 Watts.

 

[zacksc]

Those DC-DC converters usually get only about 60% of rating before turning into a hot mess, at least the several I tried that looked very similar which I use for converting my 14S bike pack down to 12V for running automotive accessories as well as charging my FPV drone setup with when out on a back country mountainside. In the end I had to limit running them at 50% rated power to keep them from burning out.

For my $$$ i would have just grabbed a sinewave inverter to connect to the same lugs under the rear passenger seat so you could just use the Jackery adapter, as well as any other 110v accessories you might want. If your DC-DC grenades when ran at-rated-power like mine did, you might want to consider the 110v inverter route.

Thank you for looking out for me. Maybe an inverter is the best idea. I can still return that converter. It was like $25 which maybe should have been a warning. By the way, does anyone make good converters that are safe and don't get hot?

Anyway, with my experience level, it is probably best just to get a really good 300 Watt inverter, surge protect it with a 1 or 2 Ohm parallel resistor, and go through the "conventional" 14 volt to 110 VAC to 24 volt route rather that try to take a short-cut (14 to 24 volt) in a risky manner.

 

[zacksc]

What do you think of this inverter? I am thinking that even though it is tempting to get one with higher VA rating, that one with a lower VA rating may have smaller capacitors and less tendency to create surge current each time it is connected to the car and powered up.) In fact, maybe the 250 VA version is preferable for that reason???

 

[zacksc]

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.

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?

I read through the whole thread again to trying to see what you were referring to. Is this what you mean by fully isolated converter? Would this Samlex inverter be a safer option?

 

[zacksc]

Does that (above) seem like it will work? Does current surge tend to be an issue with converters?

I've used that family of boost converters (12V to 15V in my case), and it will work if you don't mind risking burning your Tesla to the ground. I only used them in a high-temp resistant engine compartment.

As above, there's no empirical evidence boosted voltage will even charge faster. Certainly not worth the dirty output, inefficiency, and risk.

There are much better ideas discussed earlier in this thread. Why bother posting the same question over and over, then ignoring the detailed technical advice you receive?

I will return that inexpensive DayGreen boost converter. Thank you for the warning. Much appreciated.

I am not sure exactly which technical advice you are referring to. Is it the idea of using a better converter? One that is fully isolated? I found a Samplex that has roughly the right power rating.

As far as charging speed goes, I think is empirically observed and correct that the Jackery charging speeds are directly correlated with the input voltage at the 8 mm MPPT input, at least within a certain range. Again, thanks, and I will heed your advice and not use that inexpensive Daygreen converter.