Explain the "Reduced AC Current" Charging Option

If you aren’t plugging direct into a modern outlet you can get heat in an extension or the outlet. Another use is if you don’t want to exceed your solar power to prevent pulling off the grid or if you are charging on a system during heavy use and want to prevent overload. Most of us will never be in these situations but when traveling you never know.

I watched a video of someone explaining they were planning on using that setting when they visited old relatives that have very questionable electrical wiring for their old home, so wanted to make sure not to draw too many amps while charging there, just to be safe.

... or even if you find yourself in dire straits forced to use a long, underrated extension cord, or where a circuit breaker keeps tripping.

Any idea exactly how much it gets 'reduced'? Is it variable based on conditions it senses or is it just some fixed percentage of what the EVSE tells it?

From the manual it says 8 amp which isn’t much of a drop from the 10 amp normal.

I'm expecting the 16A I use also gets reduced to 8A, based on what I've read.

On my other car, the reduced current is relative to the starting ampereage, and there are two reduction steps to select from. If I was carrying a 16A for use wth the ID.4, this might annoy me if I was in a situation where 12A would be acceptable.

I ought to check this and know what to expect, just in case. VW's method actually makes sense — it's simple — and yet 8A is a big compromise if 16A can't be used.

From my testing using my 32A charger connected to a NEMA 14-50, when I selected Reduced A/C Current it dropped it from 31.1A (7.2kW) to 8.0A (1.9kW), dropping the charge speed from 27mph to 6mph.

i would assume this is for level 1 charging. the bolt had a setting to toggle btwn 8/12 amps

“Reduced AC current” can also be used to slow charge up to 100% before a long trip, so that your battery is not sitting at that state of charge too long before you are ready to leave. It’s been shown that when you do need to charge to 100%, it’s best not to leave your battery at that state of charge for longer than necessary (hours are better than days at that level).

And... if you are not in any hurry, and plugged in at home for awhile, slower rates of charge (less amps) have been shown to be the least stressful way to charge your battery, theoretically promoting greater longevity. But, I wouldn’t overthink this strategy and penalize yourself in your daily travel range. The effects of AC charging slow vs fast are minor differences...

Consider also 240v charging is roughly 10% more energy efficient than 120v, depending on whose data you're reading. It's pretty normal to see mid 70s for 120 to mid 80s for 240, due to transmission and conversion losses.

I realize that's apples to oranges when discussing 8A vs 10/12/16, but is a factor if deciding between any L1 vs. any L2. Slower is less stressful, but not necessarily more efficient.

I guess, if VW's intent was only to pair this with the included 10A EVSE.

If I was buying a 120V EVSE for regular use (such as plugging in at work or a motel) I see a 16A model that appear to allow the user to step down to a custom amperage. So in other words, let the EVSE handle it rather that the car.

Too bad, I'm sure it's software selectable if VW wanted to give us the option.

Is there a cheat code for Expert Mode on this thing?

Nai3t said:

I guess, if VW's intent was only to pair this with the included 10A EVSE.

If I was buying a 120V EVSE for regular use (such as plugging in at work or a motel) I see a 16A model that appear to allow the user to step down to a custom amperage. So in other words, let the EVSE handle it rather that the car.

Click to expand...

I realize I forgot to explicitly say something. My assumption is that the EVSE shipped in the EU and other countries isn't necessarily 10 amps- I think that was a US-market specific decision for whatever reason, since we have . It makes almost no sense to differentiate between 10 amps and 8 amps, but it makes a lot more sense to allow for "reduced" current if the included charger was a 16 amp version (or maybe even 12 amps), and turning that option on actually does reduce the current more than 2 amps.

Maybe @ID.Furkan or some other EU owner can take a picture of the label on the back of their included EVSE so we see what other countries are getting.

My guess would be to compensate for a 10 amp extension cable. 80% continuous load on a 10 amp cable.

bluedanube said:

Any idea exactly how much it gets 'reduced'? Is it variable based on conditions it senses or is it just some fixed percentage of what the EVSE tells it?

Click to expand...

I encountered this yday. My charging was set to "max" previously and i was getting around 30-35Amp on my 40Amp charger. Not sure what I did but somehow my setting were changed to "reduce" and when I charged yday - i was only getting 7-9amps.

Skirmish said:

If you aren’t plugging direct into a modern outlet you can get heat in an extension or the outlet. Another use is if you don’t want to exceed your solar power to prevent pulling off the grid or if you are charging on a system during heavy use and want to prevent overload. Most of us will never be in these situations but when traveling you never know.

Click to expand...

I use it for exactly that (solar charging) so as not to pull from the grid. Certainly wouln't do that if I need the car charged right now. Many times, however, it still takes only 30 seconds to charge the car; 15 secs to plug it in and 15 to unplug. Usually don't care if it's a couple of hours or 15 hours between those two things.

It would just be nice it it was user selectable. 8 vs. 40 is a pretty wide chasm.

Nai3t said:

It would just be nice it it was user selectable. 8 vs. 40 is a pretty wide chasm.

Click to expand...

It’s 8 amps per Phase (fase? How is it written)
I think you guys charge with a 2-phase AC circuit to get to 40 amps? So that would reduce it to 16 amps.

I have a 3-phase charger and flicking that option will lower charge speed from 11KW (3x16amp) to 5.5KW (3x8amp).

Doesn't work that way, just like we don't install double 20 amp breakers to feed a 240 volt 40 amp circuit.

240 x 8 = 1.9 kW and that matches the Reduced charging speed, same as other owners have reported. It's really truly 8 measly amps, not 16.