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Discussion Starter #1
I'm going to be staying at a campground with a TT-30 RV-style outlet (125V/30A). I read on a forum post that the Bolt when charging at 120V is limited to 12A. Is this true, or did the post actually mean just with the GM OEM EVSE?

In particular, I have a Tesla UMC EVSE + JDapter Stub, and EVSEadapters does make a compatible TT-30 plug that at least works with the Tesla, so I'm wondering if it will work with the Bolt and if it will deliver the promised 24A continuous current. Thanks!
 

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Correct on the 8 or 12A limit for 120V charging. Those are your only 2 options. To use this receptacle, you will need a TT-30 to 5-15 adapter.

On 240V, it's the minimum of the EVSE or 32A. I wish I could adjust the rate, like on a Model S.
 

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I wish it would charge faster than 12A on 120V, but it just won't. As others mentioned, the car will limit you. Heck, 5-20 outlets are pretty common (120V / 20A, look almost like a standard 3-prong, but with the left hand port looking like a sideways T). It may not seem like a lot, but 16A is still 33% faster than 12A (more once you factor in overhead).
 

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I wish it would charge faster than 12A on 120V, but it just won't. As others mentioned, the car will limit you. Heck, 5-20 outlets are pretty common (120V / 20A, look almost like a standard 3-prong, but with the left hand port looking like a sideways T). It may not seem like a lot, but 16A is still 33% faster than 12A (more once you factor in overhead).
GM being GM really decided to play it safe with the Bolt, as I am sure they do with lots of their other vehicles in other ways. This is the same reason we have such an aggressive taper and low overall DCFC speeds. I wouldn't expect Tesla-speed charging in any GM EV ever.
 

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GM being GM really decided to play it safe with the Bolt, as I am sure they do with lots of their other vehicles in other ways. This is the same reason we have such an aggressive taper and low overall DCFC speeds. I wouldn't expect Tesla-speed charging in any GM EV ever.
True. Doesn't stop me from wishing for it.

On the flip side, Tesla is perhaps a little too aggressive with their charging rates. The original EVSEs they sold were notorious for overheating. I'm sure they are getting better, but I still have concerns. I also wonder if this is why "20kW" 80A (technically 19.2kW) on-board chargers are no longer an option on Teslas.

I will take slower charge rates for higher reliability and safety any day.
 

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True. Doesn't stop me from wishing for it.

On the flip side, Tesla is perhaps a little too aggressive with their charging rates. The original EVSEs they sold were notorious for overheating. I'm sure they are getting better, but I still have concerns. I also wonder if this is why "20kW" 80A (technically 19.2kW) on-board chargers are no longer an option on Teslas.

I will take slower charge rates for higher reliability and safety any day.
Agreed. I'm sure Tesla has mountains of data regarding safe charging & operating windows for their cars (which is prob why they reduced charging speed on some older Model S's), but my personality makes me lean toward a more conservative approach, even if it limits performance somewhat.
 

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Discussion Starter #10
Thanks everybody for the confirmation. A pity. I've gotten a simple adapter from TT-30 to NEMA 5-15 and added it to my travel kit.
 

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I wish it would charge faster than 12A on 120V, but it just won't. As others mentioned, the car will limit you. Heck, 5-20 outlets are pretty common (120V / 20A, look almost like a standard 3-prong, but with the left hand port looking like a sideways T). It may not seem like a lot, but 16A is still 33% faster than 12A (more once you factor in overhead).
I keep on seeing this cited all over - but I can't find any evidence of the original test where this was determined (using an EVSE that reported 16A or more, but the vehicle dropping to 12) - any idea where to find the original test data for this?

Has anyone retested with a newer Bolt to see if this was stealth-changed?
 

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I have an EVSE that has a programmable current. It is 240V nominally but I have tested at 120V via adapter. My 2017 Bolt only ever pulls up to 12A at 120V.
OK, that's the first time I have seen an actual confirmation of that. OpenEVSE by any chance?

Slight chance it might be worth trying in a 2020, but sounds unlikely. Once lockdown ends I may try a TT-30 to 6-20R adapter and an EVSE with a 6-20 plug that reports 16A.
 

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The OEM EVSE has a 5-15 plug. So they assume you are going to plug in a 5-15 receptacle, which is 15A max. It is quite reasonable to limit the current to 12A for prolonged period of operation. I don't think you can get anything more than that, try as you can.

The only way one can get more juice out of the charger is to double the voltage. TT-30 won't do it as it is still 120V. It is no different from 5-15 in this regard.

Low-power as it may sound, a 5-15 or a TT-30 is still way better than nothing. Plugging in over night can give you up to 30kwh, or over 100 miles. Probably enough to get you to the next stop.

-TL

Sent from my SM-N960U using Tapatalk
 

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The OEM EVSE has a 5-15 plug. So they assume you are going to plug in a 5-15 receptacle, which is 15A max. It is quite reasonable to limit the current to 12A for prolonged period of operation. I don't think you can get anything more than that, try as you can.
The OEM EVSE is in no way relevant, and its limitations are not relevant to this discussion.

By your logic of applying the OEM EVSE's limitations, the vehicle should never be able to charge at more than 12A from any source regardless of the capability reported by that source over PWM on the J1772 CP line.

Sadly, Chevy made the choice of ignoring the reported capability of the attached EVSE if it sees 120 volts, for no legitimate reason.

The only way one can get more juice out of the charger is to double the voltage. TT-30 won't do it as it is still 120V. It is no different from 5-15 in this regard.
Wrong. Watts = Volts * Amps

J1772 supports amperages significantly greater than 12 amps. This is obvious given that 12 amps corresponds to only 20% duty cycle on the CP line, and the fact that the car will charge up to 32 amps when it's not making boneheaded decisions to ignore the EVSE's reported capability via the duty cycle on the CP line.

Every component in the Bolt, and every component in the J1772 connector, is capable of 32 amps sustained operation.

Not crippling the entire system because someone made an EVSE with a 5-15 plug is the whole point of why a J1772 EVSE is required to report its continuous current delivery capability to the vehicle.
 

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The OEM EVSE is in no way relevant, and its limitations are not relevant to this discussion.

By your logic of applying the OEM EVSE's limitations, the vehicle should never be able to charge at more than 12A from any source regardless of the capability reported by that source over PWM on the J1772 CP line.

Sadly, Chevy made the choice of ignoring the reported capability of the attached EVSE if it sees 120 volts, for no legitimate reason.


Wrong. Watts = Volts * Amps

J1772 supports amperages significantly greater than 12 amps. This is obvious given that 12 amps corresponds to only 20% duty cycle on the CP line, and the fact that the car will charge up to 32 amps when it's not making boneheaded decisions to ignore the EVSE's reported capability via the duty cycle on the CP line.

Every component in the Bolt, and every component in the J1772 connector, is capable of 32 amps sustained operation.

Not crippling the entire system because someone made an EVSE with a 5-15 plug is the whole point of why a J1772 EVSE is required to report its continuous current delivery capability to the vehicle.
I suspect that decision was made to err on the side of safety. While the EVSE can report its capability to the car, it has no means of knowing the safe capacity of the circuit it is plugged into.
 

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I suspect that decision was made to err on the side of safety. While the EVSE can report its capability to the car, it has no means of knowing the safe capacity of the circuit is is plugged into.
The assumption should that the EVSE was designed properly and reports a capacity consistent with the connector it has.

The car doesn't forcefully assume that you used an adapter you should not have (such as a 6-20P to 14-50R adapter) when charging at 240, so why do it for 120?

Even to handle those conditions, unfortunately the Bolt has no way for you to force it to charge at a lower rate on 240 - other EVs do allow you to limit the AC charging rate in the event that you've got an EVSE which is reporting a current level too high for its circuit. :( The only option in the Bolt is the 8A derate on 120.

@GetOffYourGas - out of curiosity, which current settings on the EVSE did you try, and was it on a TT-30 or just a 5-20? I'm curious if there's a possibility that only current levels close to the home charger level of 12A get detected as an "OEM home charger" due to rounding errors or an intentional hysteresis/tolerance window. Did you try an EVSE reporting 24A on a TT-30?
 

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This is the EVSE I have (although I didn't get it for this cheap!):

It is programmable to advertise 10, 13, 16, or 32A. It comes with a 14-50 plug. The car obeys the advertised current limit when plugged into a 14-50 outlet.

I built a very simple 14-50 receptacle - to - 5-15 plug adapter. I simply left the "common" open, and connected one of the hot pins to common on the 5-15 side. So what would normally be 240V was only 120V.

So with the adapter, I tried setting the current limit to 10, 13, and 16A. The car obeyed 10A, but self-limited to 12 when given 13 or 16A.

I have never tried this on a TT-30, or a 5-20 for that matter. I haven't (yet) had reason to build the appropriate adapter.

NOTE TO THE CASUAL READER: I know what I am doing, and keep tight control of this adapter. It is dangerous in the wrong hands, since normally something plugging into a 14-50 expects to safely draw up to 50A, but it's really on a 15A circuit!
 

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OK, so there's a slight possibility an EVSE reporting 24A from a TT-30 might see different results, but very unlikely.

There's also a slight possibility the 2020 might behave differently, but very unlikely.

It's enough that once I can get to a TT-30 (harder right now, I'm not sure if the CVSP ranger would be OK with someone requesting temporary 20 minute access to a campsite for an electrical test when the campgrounds are completely closed) it might be worth building a TT-30 to 10-30R adapter, but probably not worth bothering with an interim TT-30 to 6-20R adapter.

:(

This is the first time I've seen concrete test methodology regarding this issue though, thanks!

Edit: For reference, I currently have a Mustart Travelmaster. It switches its reported current based on the plug attached (the only EVSE other than Tesla UMCs to do this to my knowledge?). For a 10-30, it does unfortunately choose 25A when it should be choosing 24... I am considering upgrading to a Tesla UMC as evseadapters can provide plug modules for the more esoteric plugs out there. I'm going to attempt to see what happens if a 25A current capability is reported to a 2020 whenever I can get to a TT-30 again.
 
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