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I have a somewhat weird problem where my Latitude 7300 won't charge over USB-C port when powered on with a specific non-Dell charger; I can charge the Latitude, but only when I power it off. The laptop originally came with a 65W AC charger.

I recently bought this LinkOn car charger that delivers up to 140W (28V/5A) of power over USB-C port. I bought it to charge a few different laptops while on the go. The charger works because, for example, I can charge my work MacBook Pro without any issues (it draws 100W). However, when I plugin my Latitude, nothing happens at all, it does not even recognize that it's plugged in.

The weird thing is, if I power off the Latitude, it starts to charge immediately. As soon as I power it on, and it gets past POST (from what I can tell), it immediately stops charging. Why??

Here's what I've done to troubleshoot:

  1. Tried two different USB-C PD 3.1 cables. Same result.
  2. Tried charging over USB-C with the MacBook Pro 96W wall charger. It charges fine, no issues.
  3. Updated BIOS to 1.27.0. Same result.
  4. Tried enabling/disabling ExpressCharge in BIOS, no luck.

For comparison, here are the details on the two chargers I've been testing with:

LinkOn car charger 140W (not working)

  • Output: 28V/5A or 20V/5A or 15V/3A or 12V/3A or 9V/3A or 5V/3A
  • Latitude: Does not charge.
  • MacBook: Charges, drawing 100W.

Apple charger 96W (working)

  • Output: 20.5V/4.7A or 15V/3A or 12V/3A or 9V/3A or 5.2V/3A
  • Latitude: Charges, drawing 65W.
  • MacBook: Charges, drawing 96W.

Based on the tests, obviously the LinkOn car charger is functioning properly because I can charge other laptops with it and I can charge the Latitude, but only when I power it off.

So, there must be something in the BIOS that's preventing the charge when the Latitude is powered on, but what and why?

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  • The third-party charger (LinkOn) supplies the voltages I posted above. Based on my limited knowledge about the USB PD 3.1 protocol, the source and sink are supposed to negotiate the amount of power that's needed (among other things). Highly doubt there's any damage because I can charge it with other chargers just fine. I can even charge it with LinkOn, but only when it's powered off (weird).
    – ikrnjajic
    Commented Dec 10, 2023 at 4:41

3 Answers 3

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Many devices check USB-C chargers for "compatibility" with that device. Some use simple resistors to indicate a compatible charger, and some use an "e-marker", i.e., an ID chip, to make that handshake.

It's not at all surprising that some manufacturers want you to use an original equipment manufacturer (OEM) charger - both for safety for the device and for profitability for the OEM.

So, simply put, the Dell Latitude PC is not compatible with the LinkOn charger. Since LinkOn advertises it is Dell-compatible (though it does not state which models), then consider returning the charger.

You might try to find out the specifications for a Dell charger, perhaps by checking the working Apple charger resistances on each pin to ground and to V+, and comparing that with the resistances on the nonfunctional one. If that is the only difference, you could make a USB-C extension cable with the appropriate resistors added. However, if there is an ID chip, it's doubtful you'd be able to obtain one. There are cables to "spoof" the power supply ratings, such as this, but that may cost more than a charger, and invites destruction of both charger and device.

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  • Thanks for the explanation, it provides context to the research I've been doing. But what I still don't understand is that, if I understood correctly, the ID chip and the "e-markers" you mentioned are all embedded in the cable, not the chargers, so how does the laptop decide whether to negotiate with the charger? Do the cables somehow facilitate the negotiation process and the identification of the charger? If that's the case, then I'm even more confused as to why the laptop charges when it's powered off? Is this process somehow bypassed when the laptop is powered off?
    – ikrnjajic
    Commented Dec 10, 2023 at 4:52
  • By the way, I did contact LinkOn and I'm about to contact Dell as well to see if any of them might have an answer. The reason I'm so adamant about finding the root cause here is because it's fairly important to me, so I need to know what to look for if I need to get another charger.
    – ikrnjajic
    Commented Dec 10, 2023 at 4:55
  • No, some chargers have the resistors and/or e-marker. That is fundamental to the charger "identifying" its power capabilities.
    – DrMoishe Pippik
    Commented Dec 10, 2023 at 5:29
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You'r laptop (Latitude 7300, quick Googling reveals those ship with Intel Core 8Gen CPU - launched Q2 2019) may not work at all with EPR (Extended Power Range) chargers (when those expose EPR mode).

EPR (released in May 2021) is an extension to a USB-PD protocol that adds voltages higher than 20V at up to 5A for power rating above 100W.

Using a third party 100W cable may help. USB PD compliant charger shouldn't expose EPR if cable not rated for it.

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It seems like the Dell Latitude 7300 charges at 65W only or 90W only over USB C (according to the specs) and that the Apple charger might be 96W but can negotiate 65W on the Dell Latitude 7300.

I know it seems odd, but it is the only explanation that makes sense.

According to the LinkOn specs, this is what wattage it can deliver:

  • 5V/3A: 15W
  • 9V/3A: 18W
  • 12V/3A: 36W
  • 15V/3A: 45W
  • 20V/5A: 100W
  • 28V/5A: 140W

And the Apple 96W charger can deliver this wattage:

  • 5.2V/3A: 15.6W
  • 9V/3A: 18W
  • 12V/3A: 36W
  • 15V/3A: 45W
  • 20.5V/4.7A: 96.35W

It seems like for the Dell Latitude 7300 to charge the Apple AC adapter has to deliver 65W as follows:

  • 20V/3.25A: 65W

Who knows. Apple is mysterious about there specs on AC adapters. Where did you get the specs on the Apple 96W charger from?

Anyway, I think the fact the LinkOn can’t do a solid 65W or 90W is the cause of the failing to charge the Dell Latitude 7300.

I would contact LinkOn for a full refund since they clearly say in their Amazon listing they will accommodate such a request:

WORRY FREE PURCHASE – Let us worry about anything which may not work as planned. Our 24/7 support helps each and every customer who has a question or a problem and most issues are completely resolved within 24 hours. We have one goal to - make all our customers happy.

Your Dell Latitude 7300 won’t work with their adaptor so get a full refund. They might let you keep the thing anyway since it’s a hassle to process returns.

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  • I got the specs from the printout on the Apple charger. It doesn't matter if I use the original Dell AC charger (65W) or the Apple charger (96W), the laptop draws 65W in both cases. I think that's because once the voltage is negotiated, the laptop calculates how much amperage it needs. As for LinkOn, the odd ball here is, why does it charge the laptop when it's off? :D
    – ikrnjajic
    Commented Dec 10, 2023 at 5:01
  • Haha I plan to, but what do I get after I return this one? I'm trying to figure out the root cause so I know what to look for next. Don't want to keep buying and returning indefinitely.
    – ikrnjajic
    Commented Dec 10, 2023 at 5:26
  • Oh!! Looks like Dell has some options, double the price though... dell.com/en-us/shop/…
    – ikrnjajic
    Commented Dec 10, 2023 at 5:29

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