Rework Instructions for 11th Gen Mainboards to enable powering the RTC circuit from the main battery

We’ve developed an RTC Battery Substitute module that can sit in place of the coin cell battery to keep the RTC circuit powered. Note that this does require soldering a single wire on the top side of the Mainboard. We are currently preparing the process for requesting this module, but have published the guide for it in the meantime.

If you have an 11th Gen system or Mainboard, you can now reach out to support to request a free RTC Battery Substitute module. To make the request process go smoothly, enter the email address that you ordered the 11th Gen product on and/or include photos of the system and Mainboard serial numbers.

Note that there are no constraints making this request other than being an 11th Gen system or Mainboard owner (whether or not you are in warranty). We ask that you really make sure you are comfortable with performing soldering on expensive electronics items before performing the installation, as we won’t be able to provide advice or support around soldering or provide fixes for failed soldering attempts. We also ask that you only make the request if you’ve faced needing to perform a Mainboard reset, as we want to avoid waste.

Archived: an earlier, more complicated rework

@Kieran_Levin has prepared the instructions below for folks who are interested in performing the rework mentioned in this earlier post.

Rework Instructions for 11th Gen Mainboards to enable RTC Battery charging from the main battery

Before you consider this rework, please note that it requires advanced soldering skills, requiring cutting traces on the Mainboard and soldering to small pads and traces. Damaging the Mainboard during the rework process would not be covered under warranty, and we’re unable to provide repair services to attempt to repair failed reworks.

This rework modifies the RTC battery circuit on 11th Gen Mainboards to follow a behavior closer to 12th Gen Mainboards. On 11th Gen, the default behavior is for the RTC battery to recharge only when AC is attached, while on 12th Gen, the RTC circuit and RTC battery are charged off of the main battery. With the rework, this means that when the laptop is left disconnected from power over long periods of time, the RTC battery will remain charged. This will not measurably impact main battery life.

This rework also allows the 11th Gen Mainboard to be used without an RTC battery in many cases. However, if the laptop’s main battery is fully discharged and left for extended periods or the laptop is placed in cold temperatures below 0°C, the main battery will disconnect due to protection conditions being triggered, resulting in the RTC circuit also powering down. The impact of that is the system clock resetting, which your operating system will correct after syncing with a network time server. If the main battery is fully discharged, the system will of course also need to be plugged into power to recharge and power up again.

Items needed for rework

  • Precision hobby knife (e.g. Xacto knife)
  • Soldering iron with a fine tip
  • 499k or 500k ohm resistor 0402 size or similar
  • 150k ohm resistor 0402 size or similar
  • Schottky Diode rated for 100mA 30V. This will be jumper wired across the top side of the Mainboard, so size is not too critical.
  • Fine single strand jumper wire. For example, 30AWG or smaller wire wrap wire.
  • Multimeter to check that the cutting and soldering was successful
  • (Recommended) Microscope or magnifying glass

Rework Overview

This rework will enable a 3.3V LDO on the PU301 regulator that we will connect to the RTC charging circuit so that the RTC battery will always be charged/powered even when the system is fully off and shutdown using the main battery. This modifies the RTC charging path, so we will also connect one additional source to the RTC charging path through a diode to allow the system to power up even if the main battery is dead and the RTC battery is also dead.

Step 1 - Remove the Mainboard and RTC battery

Remove the Mainboard from your laptop, and remove the RTC battery. You can follow steps 1 through 6 in the Mainboard Reset Guide for this. You can follow the steps through step 16 in the Mainboard Guide to remove the Mainboard.

Step 2 (the most difficult step) - Cut the trace

Locate PU301 on the bottom side of the Mainboard near the bottom left corner.

Cut the trace to the upper right pin, between the Via and the pin. Be careful not to cut into the via area, as this will prevent the 5V regulator from turning on.

Cut here:

Step 3 - Check that the trace is cut

Check the LDO EN signal is properly cut by checking that the resistance is open between the EN pin on PU301 and PU502 with a multimeter. Use a DMM (digital multimeter) to probe the following two pins and make sure they are not close to 0 ohms.

Step 4 - Build a resistor divider

Using the 150k and 499k resistors and the thin wire, build a resistor divider between the system rail (VSYS) and GND and connect it to the EN pin of PU301. This will power on the internal LDO of PU301 whenever the main battery is connected or a charger is attached.

Step 4 - Cut the trace

On the top side of the Mainboard, just below the SSD fastener, there is an unpopulated resistor footprint with a short trace. Cut the trace in this pad. Measure the resistance between the two sides of the pads with your multimeter to confirm the cut has broken continuity.

Step 5 - Connect the LDO output

Flip the Mainboard back over to look at the bottom side. Using a thin wire, connect the LDO output to the RTC charging net input. You may want to apply some kapton tape or other thin, non-conductive tape over the cable to prevent it from touching any part of the housing.

Step 6 - Connecting to the RTC Battery circuit

Flip the Mainboard back over to look at the top side. Connect a diode to the RTC battery diode package from the 3V_EC regulator. This ensures that the Mainboard will turn on when the battery is disconnected and the RTC battery is dead. The reason for this is the EC (Embedded Controller) power will come up before the power output from the PU301 regulator, so the RTC voltage also needs to come up at the same time, otherwise the EC will not power on.

Step 7 - Initial Validation

Without installing the Mainboard into the system and with the RTC battery still removed, plug a USB-C power adapter in and check that the side LEDs flash. This means the EC has successfully initialized, and the RTC circuit can power on with the system.

If the side LEDs do not turn on, check for voltage in the RTC battery holder.

Step 8 - Install the Mainboard

Follow steps 17 through 28 to assemble the Mainboard into the system and plug in the battery. Ensure the system powers on without the RTC battery installed and with the main battery attached. Optionally, reinstall the RTC battery.

Step 9 - Complete assembly of the Laptop

Follow the rest of the Mainboard Guide to complete assembly of your laptop. Great work!

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  1. With the rework, it will charge on either of main battery or power adapter attached.
  2. Part of the added complexity is “This ensures that the Mainboard will turn on when the battery is disconnected and the RTC battery is dead. The reason for this is the EC (Embedded Controller) power will come up before the power output from the PU301 regulator, so the RTC voltage also needs to come up at the same time, otherwise the EC will not power on.”
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We’ve moved this thread out to a dedicated topic so that any questions surrounding the rework process can continue to be discussed as the original thread has since been closed.

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The dedication framework gives to help consumers makes me very happy that I’ve bought their laptop. Keep on keeping on!

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This seems awesome. I might have to try this as I just recently had to replace my cmos battery. I have everything I need to do this already and it would give me a reason to break out my soldering station again.

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Hello everyone. An important note is that our repair centers will not be able to perform this rework and you will either need to perform the work on your own, if technically able, or source a local repair shop that is willing to do the necessary work.

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hello, I have a addition which might be usefull for bios update
I oberved that my rtc has only 2.2v (measured with DMM) and searched here for the issue, found that I have to charge it with laptop turned on or plugged in, got a bit better after some hours but still was at 2.5v, so I decided to charge it with bench powersupply manualy.
I set it to 3v and like 10mA and nothing happend, so I was confused if I reversed polarity or contact was bad, but in fact when I measured the short circut current of the RTC Battery and my DMM said 140uA so 0.14mA, I checked my DMMs resistance at that range, its 1kOhms

so my guess is, that the RTC Battery got discarged pretty far for multiple times and is just pretty dead with a high amount of internal resistance, cant check how it should be normally, since I dont have new one here.
maybe there should be an addititon to the firmware so it just turns off the RTC when the battery is very low, since its not working for much more anyways and just destroyes it (when my guess is correct)

if someone is interested I can try to measure/calculate the real internal resistance, forgot to do that

edit: I am stupid, I have everything I need to calculate internal resistance, it should be 16.86kOhms, but I can still remasure everything, when its charged up a bit more, it should be lower then
and someone like has to write an exam in circuit theory in 5 days …

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By the way the instructions have two Step 4s

Step 4 - Build a resistor divider

Step 4 - Cut the trace



EDIT 1

  • between the Via and the pin. Be careful not to cut into the via area

What is the ‘Via’ and ‘via area’, and could you clarify the images. Is there a cut on both sides of the board?

EDIT 2

  • Check the LDO EN signal

What is the LDO EN signal ?

LDO EN is the signal that you would have cut.

1 Like

The via is the copper hole that goes through the board to some other board layer. The via area is the circular copper area around that hole.

From looking at the photo the via is the small hole, and the via area is the circular raised bump around that.

You only should cut the indicated trace on the indicated side.

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Ok so on the first image in [Step 2] the cut is green line to the left, and the other green line, isn’t the underside of the board but a circuit diagram representation. Slowly becoming clearer :slight_smile:

So is there another ‘object’ soldered to the underside of the Via else it would make sense to cut on the other side as there is more room etc.

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The guide wouldn’t direct you to cut at the shown location if you were able to do it in an easier spot. The connection through the via would need to stay intact. That via would connect that circuit trace to something, or else the via would not be there.

This step indicates that the trace travels through the via, across on the bottom, and connects to the PU502 (5V ALW chip). Cutting the trace in any other spot will likely disable the PU502 as well, which is not what you want.

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That’s what I was imagining, I was hoping to get a clear indication of what is actually connect to the via etc.

OK So what is the LDO EN signal, any idea? :slight_smile:

No fuss, I am not about to try it whilst I still have warranty. Just getting a more informed idea of what I am doing

Thanks

Without checking the part datasheet I would guess “LDO EN signal” stands for Low Drop Out (regulator) ENable. Connected to the enable pin of the chips.

2 Likes

A few tips.

Resistors:
500k is a bit unusual, and the ubiquitous 470k and 560k may be too far off. With two common resistors one should get close enough (no warranty, though!): 470k + 27k = 497k, that’s only 2k off.

(Open question: Are other resistors in the same ratio OK, or are exactly the given absolute resistances necessary?)

Form types and placement:
Diode and resistors in THT type are much easier to solder to the tiny contacts on the board than SMDs. Their long thin wires are easier to handle, and also can be bent to make a larger contact area and to get less in the way of the solder iron tip.

Diode and voltage divider can be “free floating”, i.e. connected at all points through pieces of insulated wire. Fix them with a piece of tape against rattling loose and straining their soldering during transport.

Insulation
For insulation of unprotected wires and part contacts, use heat shrink tube, as an alternative take Kapton tape. Do not use electrician’s tape, its glue will become gooey and less sticky with time. Other tapes may or may and be heat resistant enough, but better safe than sorry.

I think Framework or someone else should offer kits with all the materials for a few bucks. If Framework did so, this would be an enormous boost of their ‘repairability’ reputation, and a great PR coup when contrasted with Apple’s shenanigans in that department. The longer they wait the lesser the impact.

Good luck to all the daring!

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It’s really just the ratio that is important, as these resistors are just used to build a voltage divider.

However, if the resistances are too small, that could lead to a lot of wasted power between Vsys and GND. So it would be good not to use tiny values.

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Then any tiny trim potentiometer >650k (e.g. no particular recommendation) can serve; the higher the resistance the better.

EDIT: If we can set the resistances ratio arbitrarily – what would be the ideal ratio?

Using a trimpot is likely very difficult if not done as “free floating”, where you can do the setting and fixating on the workbench.

  1. Measure the resistances with an ohmmeter to find the point of correct R1/R2 ratio.

  2. Set and fixate it with a drop of nail polish or hard and heat resistant glue.

  3. Insulate and stick to the mainboard with Kapton tape.

  4. Take pictures of this perfect dose of hacky-ugly in a Framework. :slight_smile:

BTW and slightly off-topic: My kudos and thanks to the person who figured out this fix!

Nope nope nope, exactly how you get many boards with ripped pads in for repair.

3 Likes

Fair point.


Moderators: if this attracts more non-technical debate, it might be good to split the thread early, and limit this one for the technical points.

A post was merged into an existing topic: Louis Rossmann commented on the RTC battery handling situation