Explain the Math of AC vs DC Charging

[Noctivigan]

According to my window sticker, we're maxxed at 10.5kW:

bummer, appreciate the update

Sponsored

 

[ChasingCoral]

Chasing Coral, I caught this too on the Lightning launch, the Ford Charge Station Pro is an 80-amp compared to the Ford Connected Station of 48-amp (which I ordered in Feb and never received because of the stop ship). BUT Mirak educated me that if the max is 11.3kW, the 48-amp is the max that the MME can take in from a L2. The Lightning's cap must be at 19.2kW.

I was hoping to get the Ford Charge Station Pro, but apparently won't buy me any faster charge time as we're maxed at 11.3kW.

Thank you Mirak for the math formula (attached pict, couldn't upload XLS)

Actually, Ford has been a bit vague about some of these things. I would love to know the actual cap of the Mach E 240v charge rate. We know it is more than 7.68. We think it is around 11.5. Is it really 11.3? Where did you find that specified by Ford?

As for the Lightning, there is no reason it couldn't take 22.6 if the Mach E takes 11.3. However, the limit for the 80A Ford Pro Charger will be 19.2. Ford may have capped the charger to avoid requiring 120A circuit. As it is, the 80A Ford Pro Charger requires a 100A circuit.

While Darren Palmer hints it might be possible to do vehicle-to-home with the Mach E in the future, the Mach E only has a single 240v charger onboard, so the 80A charger will be no faster than a 48A.

 

[ChasingCoral]

According to my window sticker, we're maxxed at 10.5kW:

I believe this is correct. That is one of the only places I've seen Ford state the Mach E charge rate directly. If the Lightning has two of these, that would be a 21kW max -- just over the 19.2 the 80A charger provides.

 

[EVmodeler]

The onboard charger is rated at 10.5 kW Output (DC) just like motors and engines are rated by output power. The onboard charger can draw up to 11.5 kW AC input (240 V * 48 A) for about 91% AC to DC conversion. plus there are parasitic loads like modules powered by the DC-DC converter for 12V, and thermal management (fans, etc) during charging.
The onboard charger is likely limited to about 30 or 32 A DC at the battery voltage ~343 V. As SOC and battery voltage increase, the current and power decrease.

I believe this is correct. That is one of the only places I've seen Ford state the Mach E charge rate directly. If the Lightning has two of these, that would be a 21kW max -- just over the 19.2 the 80A charger provides.

 

[ChasingCoral]

The onboard charger is rated at 10.5 kW Output (DC) just like motors and engines are rated by output power. The onboard charger can draw up to 11.5 kW input (240 V * 48 A) for about 91% AC to DC conversion. plus there are parasitic loads like modules powered by the DC-DC converter for 12V, and thermal management (fans, etc).

Now that makes sense! Thanks.

 

[benk016]

My charge point reports that my MME pulls 11kw while charging on my 60amp line at 48amp.

 

[Mirak]

Sorry all for spreading any misinformation. I read the 11.3kW on a few websites. Sounds like the official cap is 10.5kW but maybe the output can actually be a bit higher? Anyway, the AC cap seems to be somewhere in range of 10.5 to 11. Bottom line is there is absolutely no point in buying a home charger greater than 48amps.

Very interesting discussion about the DCFC. I’m not going to pretend to understand all the technicalities, but it sounds like a larger pack with more cells can accept more current, thus enabling the larger F150 battery pack to recharge in roughly the same amount of time as the smaller MME pack.

One of the best aspects of this forum (besides the memes) is the good technical input from very smart people.

 

[EV Lab]

It's not too hard to understand... and I don't think 150kW max is necessarily bad. The amount of time in the charge curve that close to 150kW is enabled is key to maximizing the charge rate and reducing the overall charge time. Judging by the numbers shared so far, the overall time to charge from 10% to 80% is almost the same for the MME and Lightning, so due to the fact the Lightning has a much higher capacity pack, it must be able to maintain a higher charge rate for longer than the MME.

FWIW, there are still relatively few 350kW stations out there and most BEVs that can support that high of a rate are ~710V nominal (~806V max). While the max charge rate of the CCS spec is 350kW, the max current is 350A (max voltage is 1000V), so the actual max charge rate possible is ~270kW.

4V x 192 x 350A = 268.8kW

where:
4V ≈80% state of charge on a single Lithium-Ion cell
192 = number of series cells in a typical "800V" pack
350A = max allowed charge current in the CCS spec

 

[ChasingCoral]

It's not too hard to understand... and I don't think 150kW max is necessarily bad. The amount of time in the charge curve that close to 150kW is enabled is key to maximizing the charge rate and reducing the overall charge time. Judging by the numbers shared so far, the overall time to charge from 10% to 80% is almost the same for the MME and Lightning, so due to the fact the Lightning has a much higher capacity pack, it must be able to maintain a higher charge rate for longer than the MME.

FWIW, there are still relatively few 350kW stations out there and most BEVs that can support that high of a rate are ~710V nominal (~806V max). While the max charge rate of the CCS spec is 350kW, the max current is 350A (max voltage is 1000V), so the actual max charge rate possible is ~270kW.

4V x 192 x 350A = 268.8kW

where:
4V ≈80% state of charge on a single Lithium-Ion cell
192 = number of series cells in a typical "800V" pack
350A = max allowed charge current in the CCS spec

I did find the Mach E charges at a bit higher rate on 350kW chargers than 150kW chargers. One part of that is the initial zap at 165kW when on a 350kW charger. Even after it drops down to the two lower plateaus, I recall these were a little higher on the 350s.

 

[EV Lab]

From looking at various studies of infrastructure cost, and just seeing the ratio of installed 350kW stations vs all other DCFC rates, the bulk of installed stations are 150kW. The study here (https://theicct.org/sites/default/files/publications/ICCT_EV_Charging_Cost_20190813.pdf) also shows the cost of 150kW vs 50kW to be roughly the same, and almost half of a 350kW installation. I think the vast majority for the foreseeable future will be 150kW.

Not sure what configuration you are specifically referring to (MME, Lightning or typical "800V") but I would assume most charge curves start out approximately the same and then scale based on ambient and pack temperature. With my MME I've noticed whether I start at 10% or 50%, it initially starts at ~123 - 150kW then slowly ramps down to ~80 - 90kW before dropping to 11kW at 80%.

 

[theo1000]

FWIW, there are still relatively few 350kW stations out there and most BEVs that can support that high of a rate are ~710V nominal (~806V max). While the max charge rate of the CCS spec is 350kW, the max current is 350A (max voltage is 1000V), so the actual max charge rate possible is ~270kW.

CCS spec max amps is actually 500 amps. There are not too many out in the field for the public though. 500 kw max.

 

[EV Lab]

CCS spec max amps is actually 500 amps. There are not too many out in the field for the public though. 500 kw max.

Sorry, I need to correct you (and myself!)... the max rated current is 375A and the max PEAK current is 500A. The rated and max power are both 350kW. You can see the numbers in table 5 of the document linked below.

https://www.charin.global/media/pag...83-1619689951/charin_dc_ccs_power_classes.pdf

Sponsored