Gen 2 Mobile Charger Charge Rate Update

Andy Jones reports:

The recent update 2021.12.25.7 has an update which allows the Universal Mobile Charger (UMC) Gen 2 charger to now charge at full rated power.

Previously the 10amp and 15amp tails only actually allowed / limited to 8amp and 12amp speeds respectively. It’s now gone up to 10amps and 15amps respectively.

Great news especially for those who only use the UMC at home. The pictures show before and after the update using the same socket and charger setup. Current was 12A and is now 15A.

Note the power says 3kw in both pics because it’s rounded.

Also note that I didn’t get the higher rate straight after the update. apparently you needed to plug in the UMC for the car to communicate with the UMC to update its firmware. We got it this morning after plugging in overnight.

25 Replies to “Gen 2 Mobile Charger Charge Rate Update”

  1. From further investigation this faster speed only seems to appear for tails with MIC vehicles where the included tails are marked (in small print)
    10 10A 250V and 15 15A 250V.

    For those with older Model 3s where the tails are marked
    10 8A 250V and 15 12A 250V
    No such speed bump.

    1. Mark, I’m puzzled as to how the tail actually controls the amps (10 vs 8 … I get 10 vs 15). Surely, the current is controlled electronically inside the box, not in the tail, where I imagine it is just wires?

      1. There is a MAX31826 1-Wire temperature sensor with a 1Kb password protected EEPROM which is encapsulated in the head of the plug. This is used to ensure the plug does not overheat and also tells the UMC the maximum current rating of the tail – and hence the maximum current to offer to the car.

  2. Couldn’t persuade my new Model 3 to go above 12A then found if I turned off Scheduled Departure and set Scheduled Start it could be changed! Bad news is that next day it was back to limiting setting to 12A again. Annoying. Various other setting revert overnight also, getting to be a pain.

  3. Saw somewhere you have to set the charge limit to 1% above SoC. Is this is a furphy, and why does my MY charge at 12amp on the 15amp tail? Surely this has been fixed by now?

    1. You just need to set it to something above your current SoC, so that it runs a charging session.

      Some tails are specifically marked as 8A and 12A on the tail, and those ones won’t update – you can exchange them at Tesla (although they may want a fee to do so)

  4. Tesla Southport traded in my 2021 lfp and I purchesed a 2023 model y performance. It would only charge 8 amps max on the portable charger they advised me that’s all they do and that is that. I need to purchase a Tesla wall charger. I asked them for my old one back. That was not going to happen. Service said yes old ones work but they overheat. I said but mine have 10 amps written on them. This is misleading. It’s frustrating to pick up a brand new car and have so many issues

  5. I’ve been trying to update.reset my 10A and 15A marked 240V UMC pigtails (supplied with a Perf Y June 2023) for the last couple of days using a variety of methods but none have worked. Is there somewhere where a simple clear unambiguous reset method is provided?

    1. Yep – exactly as per the above comments – let the car finish charging with the mobile connector connected and it will push the software update to the mobile connector.

      1. Thanks Ken but which comments above? Sorry to be a PITA but what exactly do I do – ie a step by step.

        Is is as simple as plugging the UMC into mains and the vehicle and setting the max charge just above the SOC and waiting for a charging session to finish? And then waiting ?

        1. Yes – it’s that simple. Charge and let it end by itself and leave it plugged in for a while – the car will push the update.

          1. Thanks. I thought I maybe wasn’t holding my tongue the right way 🙂 Strange thing is I have doing exactly what you said every night this week so so I wonder why it hasn’t happened yet?

  6. I had the same issue that the UMC is not able to charge at 10A, and after calling Tesla, they investigated and confirmed the firmware push from the car have failed during the update process. They have suspected this is an know issue of the car software and suggest I need to wait for the new software to be available that has the fix to be installed on the car so that the UMC update will be pushed again.

    I will still try to leave the UMC plugged into for longer time which I may not do last time when I charged the car to the set limit and see how it goes

    1. Thanks Jeff, That makes sense because I really have repeatedly tried a half dozen different ways. After a system reset and an ON charge/wait I actually saw 16A (yes not a typo 16A!) on the screen as the max charge possible. But as soon as I brought the Max charge level up above the SOC it dropped to 12A.

      1. I’m seeing exactly the same BobL – shows 16A then as soon as plugged in, reverts to 12A.

        Showing 17km/hr charging rate at 12A.

  7. Has anyone managed to update the UMC in recent past? Tried it once, by leaving it plugged in overnight (fully charged) and has not worked for me.

  8. I have the same issue here not getting the full 10a charing from UMC, tried the above-mentioned method for the last few charging sessions

  9. It would appear there’s a bug in a recent software update on the cars that is causing the UMC update to fail – Tesla is aware, and hopefully this will be resolved soon.

  10. Confirmed this morning that the issue with the 2023.20 versions of the car software look to be fixed in 2023.26.7. Successfully updated a spare UMC this morning with my MY.

  11. Hello. Has anyone managed to get this issue sorted?

    New MY owner here, and bought the mobile charger. Salesman before I bought the car said that can use a 15A socket to charge at around 24km/hr. However the 15A tail is still only charging at 12A, 17km/hr

    I left it plugged in overnight after it charged but still the same for me.

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