To make sure your question is clear, you also have a Chevy Volt and you have recently added Clarity to your fleet, and you are charging Clarity using the same EVSE that you use on your Volt. And if I understand correctly you feel that you are getting a slower charge rate in your Clarity than you do when using the same EVSE on your Volt. And although you didn't state it your message implies that using that same charger you are able to fully charge your Volt battery in the same time period (midnight to 8:00 am). Is that a correct summary? Can you tell us something about the EVSE that you are using, is it the original Chevy OEM or something you purchased? Do you know what amps the EVSE is rated for? Also what year is your Volt, the battery sizes in the Volt ranged from 16 to 18 kWh, Clarity has 17 kWh. Although to extend battery life none of them use the full battery capacity, I'm not sure about the Volt but the Clarity uses about 14 kWh of its battery.
I get the same rate in the Clarity as with my Volt when using any of my three EVSEs plugged into a 120v 20 amp circuit, assuming I tell the Volt to charge at 12 amps. The Clarity appears to not have the 8 amp option.
Clarity doesn't have an amperage setting, does your Volt? The Clarity will take whatever the EVSE provides up to 32 amp. Although for Level 1 the highest EVSE available is 16 amp. The Clarity OEM EVSE is 12 amp. Note that 16 amp charging can only be safely done on a 20 amp circuit, per the electrical code continuous power on a circuit should not exceed 80% of the circuit capacity, thus 16 amp EVSE for a 20 amp circuit, 12 amp EVSE for a 15 amp circuit.
The Gen 2 (2016-2019) Volt defaults to 8 amps when using L1 charging. This is to protect older house wiring that is barely up to code for 15 amp circuits. There is an override that you can set to use 12 amps at your "home". The Home setting has to be redone every 90 days. The EVSE that ships with the Gen 2 Volt is also capable of charging at 220V 12 amps with an appropriate adapter. I use a Duosida charger that gives me 16 amps on my 20 amp 240V circuit.
Also any particular charging session does not always run at the same amps the entire time. If the system detects that the battery is getting warm it will turn on a fan and it may slow down the charging rate for a period of time. Also once you get to about 85% the charge rate slows down quite a bit until you get to 100%. Although I would expect the Volt works the same.
All that being said I don't know of any obvious reasons why you seem to experience slower charging with your Clarity than you do using the same charger with your Volt. There might be differences between the two cars that causes it, but also two charge sessions may not be representative it might become more clear after you charge a few more times.
Sorry if I was confusing. Here's my EVSE setup:
- GM/Volt EVSE: 120V 8/12 amp or 240V 12 amp charging. This is currently the EVSE I use on the Clarity when at home as it plugs into a 120V 20 amp circuit.
- Clarity EVSE: 120V 12 amps.
- Duosida EVSE: 120/240V 16 amps charging. This is the EVSE I use daily for my Volt and is plugged into a 240V 20 amp outlet.
I use the GM and Duosida EVSEs because the outlets are inside the garage and the cars are on the driveway. These two EVSEs have 25 ft cables so they reach. I mounted cable management on the outside of both sides of the garage door. My wife doesn't want the birds pooping on her Clarity so it's on the 120V side of the driveway and my Volt is on the 240V side (under the tree). Both circuits were installed to be 20 amp circuits to drive Christmas lights. As such, they're 10 gauge 4 strand wire direct from the breaker box to the outlet. The 120V has my sprinkler system hard wired into it at the outlet so I couldn't convert it to 240V. Max current draw from my sprinkler controller is less than 5 amps, and then for only about 30 seconds at a time. The other circuit has been converted to a 240V circuit specifically to support the Duosida EVSE.
The Clarity's EVSE, which has a 12 ft. cable, plus a 40 ft. bright yellow 10 gauge 3 strand all weather extension cord are on the floorboard behind the driver's seat in my Volt, but I move it to the Clarity when we road trip in the Clarity. The Duosida came with a hard sided case - that's where I put the Clarity's EVSE to keep it clean.
As far as I can tell, all three EVSEs charge the two cars at the same speed as long as I remember to tell the Volt to use 12 amps on L1 charging. The Clarity fully charges a little faster because the battery is about 800 Wh smaller, but the charge rates appear to be the same. The Duosida maxes out my Volt's charging speed so I had no reason to install a larger circuit. I set my Volt's departure time to 5 AM so it won't start charging until after midnight, well after high usage. The Clarity is set to charge as soon as I plug it in as it normally sits on an L1 charger.