Is it more cost effective to charge at 48 amps or 32amps?

[Irodger199]

Hi , so my question is what is more cost effective Charging at 48 amps or 32 amps. I know 48 will be faster then 32 . What would the cost difference be between higher but faster versus lower but longer . Any help greatly appreciated. Thanks

 

[DrChaos]

My primary concern isn’t cost but preservation of battery life. I usually limit charging to 24A instead of 32A to produce less heat, the slower the better and most folks have enough time to charge overnight.

That won't make much of a difference for battery longevity. Both are considered very slow and benign charging with the size of a Tesla battery with no material effect on longevity.

More important (see long threads here) is keeping average state of charge low, ideally below 50%. Most of the battery life degradation people observe (unless you drive 50K+ miles a year every year) is "calendar aging", from chemical reactions occurring over time, not from battery cycles discharging or charging. Below 55% lowers calendar aging rate.

 

[Mark Z]

Even with an 80 amp Wall Connector, I decided years ago that 32 amps would add longevity to the EVSE. Cybertruck incompatibility forced replacing the Gen 1 with a newer Wall Connector. The thinner cable warmth is more noticeable so I took temperature readings. About 10 degrees warmer at 48 amps. Voltage is 135 at 48 amps and 137 at 32 amps. To decrease higher temperatures, the cord was raised to avoid looping. My question would be any cost savings if an EVSE had an 6 AWG cord instead of the 8 AWG Tesla provides? The additional cost for the cable most likely would wipe out those electric cost savings.

 

[dafish]

I tested this roughly a year ago. It’s here in the forum somewhere. As was suggested, 48 losses some to heat, 32 to time. 36 and 40 are better. 40, as I recall, was optimum. The differences are, however, trivial.

 

[DuncanM]

I tested this roughly a year ago. It’s here in the forum somewhere. As was suggested, 48 losses some to heat, 32 to time. 36 and 40 are better. 40, as I recall, was optimum. The differences are, however, trivial.

The other factor is the cost of the installation vs cost recovery time due to higher potential efficiency and cost/kwh of the electricity.

 

[tga]

I tested this roughly a year ago. It’s here in the forum somewhere. As was suggested, 48 losses some to heat, 32 to time. 36 and 40 are better. 40, as I recall, was optimum. The differences are, however, trivial.

Also, losses due to time a linear (the awake car uses the X Watts continuously while charging), but losses due to resistive heating are exponential (square of current, P=I^2*R), so the curves are guaranteed to cross somewhere.

My old S had dual chargers (80A capable) and my parents have an 80A Wall Connector. I rarely charged there over 56A (80/sqrt(2)) because it was fast enough and cut heating in half.

 

[SageBrush]

Voltage is 135 at 48 amps and 137 at 32 amps

Did you mean 235 and 237 ?

 

[SageBrush]

The efficiency differences from 32A to 48A are trivial. Other considerations however may apply

E.g., I drop down to 32A in the winter over concerns about Li plating. My cars and branch circuit support 48A, but I don't go above 40A, mostly so that most of my charging is from our PV and the utility load stays under 5 kW. This is not forced on me, nor do I receive any consideration. I just think it prudent and civil to be a decent grid customer.

 

[Watts_Up]

The other factor is the cost of the installation vs cost recovery time due to higher potential efficiency and cost/kwh of the electricity.

For a long distance installations, wires can be very costly.

I was limited to 30A from my main panel, but from my calculations,
by installing a NEMA 15-30 insted of 15-50, I was able to use AWG #8 instead of #6.

I could also had saved on the Neutral by installing a NEMA 10-30 or 10-50,
but I thought that having a receptacle with a Neutral might be useful in the future.

The Mobile Connector was included with the car, otherwise I would had bought and installed a wall connector.

 

[ucmndd]

by installing a NEMA 15-30 insted of 15-50,

You mean 14-30 and 14-50.

I could also had saved on the Neutral by installing a NEMA 10-30 or 10-50

NEMA 10-series receptacles (ungrounded hot-hot-neutral) have been banned since the 1990s. New ones cannot be installed or retrofitted into existing homes.

You probably mean NEMA 6-series (6-30 or 6-50), which are the current 240v-only standard (hot-hot-ground).

 

[Watts_Up]

You mean 14-30 and 14-50.


NEMA 10-series receptacles (ungrounded hot-hot-neutral) have been banned since the 1990s. New ones cannot be installed or retrofitted into existing homes.

You probably mean NEMA 6-series (6-30 or 6-50), which are the current 240v-only standard (hot-hot-ground).

Good catch!! Yes 14-30 and 14-50 and also 6-30 and 6-50.
I have all those Tesla adapters, including a NEMA TT-30P for camp sites.

But honestly, there are now Superchargers and Public L2 chargers almost everywhere,
so I never use my Mobile Connector anymore.