PSA: Fast Charging derating significantly on hot days

[NAVEWO]

I posted related content at the thread below. Dealer finding leaks on Max Tow package in Schroeder valves and replacing freon. See below.

https://www.f150lightningforum.com/...cion-after-dc-fast-charging.15668/post-413635

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[sd25]

Interesting. That's 2 data points (including mine) with a bad schrader valve for the Max Tow AC.

My dealer had trouble finding the leak initially, before finally locating it at the schrader valve. So for folks with low freon in the Max Tow AC system (which leads to the battery overheating during fast charging), might want the dealer to check/replace the schrader valves (my defective valve was on the high side of the AC system).

 

[NAVEWO]

Interesting. That's 2 data points (including mine) with a bad schrader valve for the Max Tow AC.

My dealer had trouble finding the leak initially, before finally locating it at the schrader valve. So for folks with low freon in the Max Tow AC system (which leads to the battery overheating during fast charging), might want the dealer to check/replace the schrader valves (my defective valve was on the high side of the AC system).

For my part my thanks to you and this forum for giving me the information to take to the dealer. The technician reported finding "oil" on the high side caps. They found the system to be "low" and said it was not that bad...of course since it was leaking...it was certainly not going to get better on its own. Thanks for your post!

 

[sd25]

Just wanted to add some updates...

TL;DR;
Another leak found in the HVB cooling system.

I had another instance of charge speed reduction during a road trip a few months ago.
Same symptoms as before. Around 30% SoC - fast initial charge rate 170KW+ then quickly drops below 100KW and keeps dropping. No alerts received. But didn't hear the noisy cooling fans running during charging. Only clear indication of an issue can be seen after unplugging - the battery temperature gauge is almost all the way to the right and available power is reduced.

The dealer at my destination found the refrigerant in the HV Battery cooling loop was completely empty again. They couldn't find the source of the leak so they just refilled the system.

Return trip was fine and fast charging seemed to work ok - 170KW+ initial rate for a few minutes then levelled off to around 105KW until 80% SoC. Luckily the return trip temps were milder so I'm guessing the cooling system didn't have to work as hard.

Once home I took it to my local dealer. They found that the refrigerant levels were normal and no evidence of a leak. I explained that the system seems to develop a leak after repeated fast charges in hot weather. So they decided to take a closer look.

They found evidence of a leak (uv dye) near the compressor seal on the low side. They said the way the seal was pinched, it may have been there since delivery. Dealer had to drop the HV battery to access the compressor and replace the seal.

Happy to report that after a completing a recent road trip with multiple charge stops during really hot weather (100F) the truck charged really well. 187KW peaks and held steady at 130KW until 80% SoC.

The only downside, now that the cooling system is running properly, is from the outside the truck now sounds louder than an ICE truck - but I'll take it.

 

[jetfixr1]

Just wanted to add some updates...

TL;DR;
Another leak found in the HVB cooling system.

I had another instance of charge speed reduction during a road trip a few months ago.
Same symptoms as before. Around 30% SoC - fast initial charge rate 170KW+ then quickly drops below 100KW and keeps dropping. No alerts received. But didn't hear the noisy cooling fans running during charging. Only clear indication of an issue can be seen after unplugging - the battery temperature gauge is almost all the way to the right and available power is reduced.

The dealer at my destination found the refrigerant in the HV Battery cooling loop was completely empty again. They couldn't find the source of the leak so they just refilled the system.

Return trip was fine and fast charging seemed to work ok - 170KW+ initial rate for a few minutes then levelled off to around 105KW until 80% SoC. Luckily the return trip temps were milder so I'm guessing the cooling system didn't have to work as hard.

Once home I took it to my local dealer. They found that the refrigerant levels were normal and no evidence of a leak. I explained that the system seems to develop a leak after repeated fast charges in hot weather. So they decided to take a closer look.

They found evidence of a leak (uv dye) near the compressor seal on the low side. They said the way the seal was pinched, it may have been there since delivery. Dealer had to drop the HV battery to access the compressor and replace the seal.

Happy to report that after a completing a recent road trip with multiple charge stops during really hot weather (100F) the truck charged really well. 187KW peaks and held steady at 130KW until 80% SoC.

The only downside, now that the cooling system is running properly, is from the outside the truck now sounds louder than an ICE truck - but I'll take it.

What charger brand were you using? My last trip to Florida was brutal. Temps hovering 85F+, the V3 Teslas only gave a max of 165 and would immediately throttle down to 100 after about 6 minutes.
Looking at carscanner, the truck was the one requesting the derated amperage the majority of times and the coupler temp was in the 130F range. I wasnt too pleased with the charging performance this trip but its probably the highest OAT ive encountered during a roadtrip. In the past ive had EA push out 185kw.

 

[sd25]

What charger brand were you using? My last trip to Florida was brutal. Temps hovering 85F+, the V3 Teslas only gave a max of 165 and would immediately throttle down to 100 after about 6 minutes.
Looking at carscanner, the truck was the one requesting the derated amperage the majority of times and the coupler temp was in the 130F range. I wasnt too pleased with the charging performance this trip but its probably the highest OAT ive encountered during a roadtrip. In the past ive had EA push out 185kw.

I've been sticking with Tesla chargers (and a 1 month Tesla membership) with pretty good success - also travelling to Florida. There was one bad Tesla supercharger site in Woodbridge, VA that had 4 out of 12 chargers down - but the rest of the stops were all good.

If you have the Max Tow package, and you don't hear the truck's cooling system get really loud when charging then the throttling behavior you're getting is similar to what mine was doing before getting the refrigerant leak fixed.

Did your battery temp gauge read high right after charging? That's another clue.

 

[jetfixr1]

I've been sticking with Tesla chargers (and a 1 month Tesla membership) with pretty good success - also travelling to Florida. There was one bad Tesla supercharger site in Woodbridge, VA that had 4 out of 12 chargers down - but the rest of the stops were all good.

If you have the Max Tow package, and you don't hear the truck's cooling system get really loud when charging then the throttling behavior you're getting is similar to what mine was doing before getting the refrigerant leak fixed.

Did your battery temp gauge read high right after charging? That's another clue.

It read within range, about halfway between 1/2 and 3/4. Carscanner was showing the pack around 115F after charging. Im probably going to test on an EA 350 charger to see if I get the full 500A on a "normal" temp day

 

[bizz]

Ran into this exact issue over the weekend while on a roadtrip. Calling dealer today to schedule a service appointment.

 

[astrand1]

I had this issue on my 23 lariat ER when new. Picked up in Napa ca. drove down to LA and then was going home (Michigan) on the way to La noticed slower charging and the battery indicator staying on the high end of the normal bracket. Got to LA and took to a dealer who was amazing btw. They took truck in immediately and had me in a loner out the door within an hour of my call. Was fixed in about 4 days. Was the same issue. A rolled gasket or something close to that plus another part I can’t remember now. This was Aug of 24 and I’m having a case of Sometimers. but 42k later no issues. (Knock on wood)

 

[TaxmanHog]

I had this issue on my 23 lariat ER when new. Picked up in Napa ca. drove down to LA and then was going home (Michigan) on the way to La noticed slower charging and the battery indicator staying on the high end of the normal bracket. Got to LA and took to a dealer who was amazing btw. They took truck in immediately and had me in a loner out the door within an hour of my call. Was fixed in about 4 days. Was the same issue. A rolled gasket or something close to that plus another part I can’t remember now. This was Aug of 24 and I’m having a case of Sometimers. but 42k later no issues. (Knock on wood)

Can you share a sanitized version of the work order showing parts used?

 

[astrand1]

Can you share a sanitized version of the work order showing parts used?

I’ll have to see if I can find the invoice. If not I’ll give them a call and see if they can email it to me.

 

[bizz]

Ran into this exact issue over the weekend while on a roadtrip. Calling dealer today to schedule a service appointment.

Truck went into the dealer last week for an issue I’ve been having while DC fast charging. They pulled code P0F47 – “A/C System B Charge Loss” and told me they were going to run some tests.


The next day, they said everything tested fine and that they had hooked the truck up to their “fast charger” to try to replicate the problem, but couldn’t. They said they were going to contact Ford Engineering for assistance.


I thought the “fast charger” comment was odd because I’ve never seen a DC fast charger at this dealership. I checked my charging history in the FordPass app, and sure enough, they had plugged it into their Level 2 charger.


I texted them explaining the difference between Level 1, Level 2, and Level 3/DC fast charging and reiterated that the fault only occurs during DC fast charging. They told me they’d pass that information along to Engineering when they heard back.


Fast-forward a day, and the service manager calls to tell me they spoke with Ford Engineering. According to him, Engineering said my truck had an active air dam fault and that the active air dam was “part of the battery cooling system.” I questioned that explanation, but he insisted that’s what Ford Engineering told them. They said the air dam needed to be repaired before they could proceed any further with diagnosing the original issue.


The repair was going to be around $1,800, although the service manager was able to get Ford to assist with some of the cost. I authorized the repair, and after five days at the dealership, I picked the truck up.


Once I got the SOC low enough, I finally had a chance to DC fast charge again and see if the original problem was actually fixed.


Sure enough, it wasn’t.


This time I monitored live data with FORScan. During DCFC, the battery warms up until it reaches the point where the truck commands the battery chiller to start cooling it. However, I never hear the A/C compressor or cooling fans kick on, and the battery temperature just keeps climbing.


Once the battery reaches about 45°C, the truck derates the charging speed to protect the battery.


If I unplug the truck and turn it back on, I get the “Service Vehicle Soon” message on the dash, with P0F47 – A/C System B Charge Loss stored again.


This is really the first significant issue I’ve had with the truck in 3 years and 48,000 miles where the service department hasn’t been able to figure it out relatively quickly. I’m less than thrilled with Ford at the moment, especially after the Level 2/“fast charger” confusion and the active air dam diagnosis.


At this point, though, my main concern is getting the truck properly diagnosed and repaired so I can reliably DC fast charge on road trips.


Can anyone recommend a Ford dealership in the Central New York area that you’ve had a good experience with specifically for F-150 Lightning/EV service? Ideally, I’d like to find one with knowledgeable EV technicians and, preferably, a DC fast charger on-site so they can actually reproduce the problem under the conditions where it occurs.


The lack of EV knowledge at my current dealership has been incredibly frustrating. It’s honestly making me reconsider going with a legacy OEM for my next EV because it feels like the dealership service network just isn’t prepared to support these vehicles when an EV-specific problem comes up.

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