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When to use 8 vs. 12amp option

67K views 47 replies 23 participants last post by  Msats 
#1 · (Edited by Moderator)
New EV owner here...

My understanding is that if you are charging on a 120-volt outlet, you set it to 8amps.

If I'm charging at a Level 2 Charge Point Station, can I set it to 12amps for a faster charge?

I have the DC Fast Charger on my Bolt; however, we don't have a DC Charging station in the area. We do plan to get a home charging unit installed soon.

Can someone steer me in the right direction on when to use the 8 vs. 12amp setting? Many thanks!
 
#2 · (Edited)
JSheehan: Both these settings are for Level 1 (supplied EVSE/cable) charging. In older houses, some circuit's wires cannot handle 12 amps. In any house, someone may have added a new outlet in the garage (or elsewhere) for a specific "low watt" need, not from its own circuit breaker, and using small (18 gauge) wire. In these cases, you may need to charge at only 8 amps to keep the wire from overheating. (The Bolt even gives you this warning.) 8 amps gives you only ~ 4 rmpch (range miles per charging hour).

MOST of the time, any home circuit can handle 12 amps. This past weekend, I charged (to full) at my sister's house at 12 amps (7-8 rmpch), using a 120 volt plug in the garage. When she plugged in the steam iron (in the family room) not knowing it was on the same circuit, the extra 14 amps tripped the breaker. I unplugged my Bolt, reset the breaker, and she finished ironing. Then, I finished charging (@ 12 amps).

When you charge at 240 volts [Level 2] (at home or at an outside EVSE station) you do NOT set the 8/12 option as all these EVSEs are at 16 amps or above (usually 30, 32, or 40 amps). I installed my Siemens VersiCharge, 240 volt, 30 amp EVSE only 3 feet from the service box [40 amp breaker] and safely used 10 gauge wire.

Hope this helps.
 
#4 ·
When you charge at 240 volts [Level 2] (at home or at an outside EVSE station) you do NOT set the 8/12 option
You can set it if you want, but the setting is ignored as it only applies to 120 V charging.
 
#5 ·
I still think Chevy need to provide control over the amp's used by the car's charger for both 120 & 240 volt charge sessions. I find this feature very useful in my other EV's…

charging at 28 amps right now (even thought he EVSE advertises 30 amps) because I know this charger at work is more reliable at 28 amps than 30 amps - if you charge at 30 amps it pop's on/off all day - where as at 28 amps it charges all day with no problems - this particular charger is a known problem child at my employeer and to date they haven't had the ability to fix it - something to do with tearing up the parking lot to "fix" the wire…

just easier to lower the charge rate slightly and it then works flawlessly.
 
#7 ·
So helpful...thank you! When I took ownership of the car a Chevy rep pointed out the settings. From what I can see the Bolt has to be set to one of the other so if I'm reading correctly it doesn't matter which since at a charging station since it will override any setting. Or is there a way to opt for neither?

Yesterday I was at a Charge Point level 2 charing station and the Bolt was set at 12 amps. It charged for about 30-45 minutes and when I returned to the car it had stopped charging despite not being at a full charge. I only received 4.5 kWh for the charge. Is this common, a user error or a Charge Point issue?
 
#8 ·
There are a few settings in the car that *might* cause this. If you have "hilltop" mode set without specifying the location, this would stop the charge at around 87%. There are Time of Use (TOU) setting that might cause the car to stop charging as well. Have you looked these items over? Charge mode can be set as "Immediate", "Departure" , or "Departure and Rate". How is yours set?

I have experienced public chargers that are poorly maintained, and the handle loses contact over time (especially with big temperature swings), causing the charger to stop charging.
 
#17 ·
120V * 8A = .96kw
2017-earlier 2019 60kwh / .96 * 1.1 (10% loss) = ~68.75 hours

120 * 12 = 1.44kw
60 / 1.44 * 1.1 = 45.8 hours

I'd say just about a whole other day is a substantial difference.
If you're over-heating an outlet/wiring while running something equivalent to an electric heater at full blast the entire time...you've got electrical problems.
It would be best to not plug in said heater or vacuum or hair dryer in the same circuit as that L1 EVSE otherwise you might trip the breaker.
 
#18 · (Edited)
8A actually exists because it is the lowest common denominator in US wiring. There are a few obscure codes out there that allow for sockets on 10A circuits.

It is also useful when you are charging the car on circuits which may have other loads on them.

(Apparently, in the UK you are limited to 8A continuous off their 13A socket and it has to have its own fuse... Crazy.)
 
#29 ·
Be sure to check with your Utility for the Super Off Peak hours, as they may be different (e.g.: In AZ, the Off Peak hours with APS are (if I remember correctly), 2-8:00PM, Jun - Oct. Here in GA, with Georgia Power, it's 2-7:00PM, Jun - Sept)

"I don't want to risk someone stealing my Charger"
You could put a small padlock through the hole in the J1772 handle to prevent someone from stealing your EVSE or you could loop the cord through your wheel and lock it.
Good Idea. Thanks.
 
#28 ·
"I don't want to risk someone stealing my Charger"
You could put a small padlock through the hole in the J1772 handle to prevent someone from stealing your EVSE or you could loop the cord through your wheel and lock it.

35993
 
#35 ·
Just too slow at 8 or 12 amps. And i only drive 50 miles a week so it would be fine but would much have faster charging. With my cheap L2 charger and two way cord for my drier it is only around 5 hours to charge and don't have to step on a cord all day when i am in my garage.
 
#39 ·
There have been a number of ways to calculate how many outlets can be on a circuit. At one time you had to calculate and then they went to a points deal. You have to remember that circuits could be used on quite a number of other things unless you have a dedicated outlet. Using 8 Amp is always the safe bet on any home made before 1990. Hopefully the worst that can happen on 12 Amp on newer home is breaker will trip.
 
#40 ·
Seems like the vast majority of folks drive home from the dealer after buying an EV (or before) and immediately install the fastest charging they can get, without really thinking about what they need. There's been some (IMHO) good advice on this forum to wait a month or two after getting your EV, so you understand what your charging needs really are, based on your personal use patterns.

I've had my Bolt for 2 years now, and never bothered to put in a 240V outlet for charging it. I would install a 240V outlet myself for the cost of the wire & breaker, but I just haven't seen the need yet. Most times, it's also not worth the effort to go through the menus to change from 8A to 12A. I work from home, so my car spends many days just sitting in the driveway. During the summer, I drive 90 miles each way to a lake 2-3 weekends each month. When I return from the lake Sunday afternoon, my car will be at 30% charge. It takes a couple long days to get back to full battery, but that's never caused me any grief. It has plenty of range left for any chores I need to do around town, and a couple days later it's full again. If some emergency came up, I would plug in my car to a public L2 charger a few blocks from home and walk home. But that hasn't happened in 2 years. Maybe the pandemic has been a factor, It's hard to say. I DO have a L2 charger which I carry in the back of the Bolt as a "travel charger", but at home I always use the L1 charger that came with the Bolt.

My house was built in 1920. It was upgraded to 200A service at some point, presumably when central air was added. When I got the Bolt, I tapped off an existing branch circuit in my cellar and added a 120V outlet close to the driveway to plug in the OEM charger. I've charged at both 8A and 12A without problems, but am usually just too lazy to change the Bolt's menu to 12A. My living room wasn't built with overhead lighting, so we use lamps plugged into the outlets in the room. That's the same branch circuit I added my charger outlet onto. I believe modern electrical construction guidelines call for the room outlets to be a separate branch circuit than the lights. And I believe this is primarily so the lights don't dim when you start your vacuum cleaner or other appliances - cuz that gives residents the heebee-geebees. But my house was also wired for incandescent lighting, and now it's all LEDs, so by my thinking, that leaves extra capacity on the circuit for charging my Bolt. I've never noticed the lights dim when I plug in my car, but then again I'm out in the driveway when I plug it in!
 
#41 · (Edited)
Seems like the vast majority of folks drive home from the dealer after buying an EV (or before) and immediately install the fastest charging they can get, without really thinking about what they need. There's been some (IMHO) good advice on this forum to wait a month or two after getting your EV, so you understand what your charging needs really are, based on your personal use patterns.
That's a bit silly; I know exactly what my driving habits and patterns were before I got the car. I know what the charging profile is. That's not going to really change after buying it. Not figuring out your charging needs before you get your car is... well... something.

Not having your electrical infrastructure taken care of before buying a $25K+ car is opening yourself up to a surprise service upgrade and rewire which might cost more than the car or worse, burning down your house. (I did get my garage wired for an addition 40A of capacity a few years before I got my Bolt in anticipation of EVs which in retrospect, was probably too little.)
 
#42 ·
I had the L2 charger almost two years before I bought an EV. Kind of worried since it was out of warranty by then.

There is a menu setting to sound alarm if charger is removed. For some reason that is default from dealer. Scared me when that happened.
 
#43 ·
New EV owner here...

My understanding is that if you are charging on a 120 volt outlet you set it to 8amps. If I'm charging at a Level 2 Charge Point Station can I set it to 12amps for a faster charge? I do have the DC Fast Charger on my Bolt however we don't have a DC Charging station in the area. We do plan to get a home charging unit installed soon.

Can someone steer me in the right direction on when to use the 8 vs. 12amp setting? Many thanks!
So helpful...thank you! When I took ownership of the car a Chevy rep pointed out the settings. From what I can see the Bolt has to be set to one of the other so if I'm reading correctly it doesn't matter which since at a charging station since it will override any setting. Or is there a way to opt for neither?

Yesterday I was at a Charge Point level 2 charing station and the Bolt was set at 12 amps. It charged for about 30-45 minutes and when I returned to the car it had stopped charging despite not being at a full charge. I only received 4.5 kWh for the charge. Is this common, a user error or a Charge Point issue?
 
#44 ·
Can someone steer me in the right direction on when to use the 8 vs. 12amp setting? Many thanks!

Yesterday I was at a Charge Point level 2 charing station and the Bolt was set at 12 amps. It charged for about 30-45 minutes and when I returned to the car it had stopped charging despite not being at a full charge. I only received 4.5 kWh for the charge. Is this common, a user error or a Charge Point issue?
Before addressing your questions, a quick lesson on how to use quotes. Anything between [QUOTE and /QUOTE] will be lost in the original quote like your post. I have recently seen this from a few new members, so maybe worth bringing up.

8-12A settings are in the Energy screens, and may vary depending on model year. There is a temporary setting for each session, and a semi-permanent one for location based settings that resets every 90 days. If is all covered in detail in user manuals.

The 8-12A settings are for L1 (120V) charging only. Whenever you use L2, be it at home or in public, the BMS will attempt to use up to the onboard inverter's capacity if the EVSE is capable of matching it. So, up to 32A (7.68kW) for pre-2022 models and up to 48A (~11kW) for 2022 models.
 
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#46 ·
L2 is set at/inside L2 charger.
EVSE. This is one of those times when being precise is important.

Technically both the EVSE, plugged into the wall, and the on board charger, under the hood, can determine the rate of charge. The EVSE makes an offer of the maximum charge available, and the on board charger can draw up to that maximum. That's what happens in the 8/12A selector for L1. The L1 offers 12A. But if set to 8A in the Bolt, its on board charger will draw only 8A.

ga2500ev
 
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