DC Jack Mod for KSGER T12 Soldering Station

As described in my earlier review of the KSGER Soldering Station, I had planned to add a DC jack for powering it via a battery pack, instead of the 24V supply that comes from the AC input. This would allow me to use the soldering station when I do not have access to a mains socket.



Looking at the back panel, I noticed that there is quite an ample space for a switch and a DC 2.1mm jack to be mounted next to the IEC connector.


Back Panel with Masking Tape

As with all paneling, it is a good idea to use masking tape to plan the layout of the components to ensure proper spacing. Thus, I traced the outer diameter of the 2.1mm jack and the centre of it. However, I realised that the top and bottom of the case had extrusions slots that allows PCBs to be slotted in, thus I moved the centre of the hole for the DC jack leftwards by a few mm.



Since I will be using a step drill bit to drill the 12mm hole required, I had to drill a pilot hole. Although the step drill will do the job just fine without a pilot hole, I just wanted to make sure that it won’t run around.

3mm pilot hole drilled


A big mistake that I made while drilling with the step drill, I held the soldering station in my hand. The step drill had a slight difficulty and with the drill spinning pretty fast, the drill bit got stuck in the hole, I lost my grip and it threw the whole station down on the floor. The impact produced was so great that it bent the back panel. Lesson learnt – always properly clamp the object that you are drilling.

Bent Back Panel


Once done, the hole for the switch was also done similarly to the DC jack, only thing that its hole was only ~6mm.

DC Jack and DPDT switch installed



The connection for the switchover is quite simple. It basically consists of a Double Pole – Double Throw (DPDT) switch to switch the positive and negative input to the controller.

I unsoldered the 24V output from the power supply and extended its wires so it could reach the switch at the back. It is then soldered to the centre poles of the switch. As for the DC jack and 24V PSU Output, I then soldered to the 2 outer poles, following the wiring diagram below. Soldering the wires to the switch is especially a daunting task as the space between it and the PCB of the PSU is quite close.

One thing that is very important is that all of the exposed wire connections should be insulated properly as the wires are quite near to a ‘Live’ mains power supply. For this, I used heatshrink tubing for all of the terminals.



With that done, the mod is finally complete! Its finally time to test it out!

Before testing it, I first made sure that I activated the input voltage display on the soldering station. For the battery test, I used a 12V LiPo battery which can provide high currents. I firstly flipped the switch to the 24V supply to make sure that everything still works properly. Did a proper heatup to 275°C from standby mode (180°C), and it stills works as expected.

Subsequently, I turned off the AC power supply, made sure that the station turned off completely, and then switched the switch to the DC jack, just to be on the safe side in case any remaining power from the controller board feeds back into the DC jack. I then connected the battery and the station powers up correctly!




I then did a proper heatup from standby temp (180°C) to 275°C, and the first thing I noticed was that the slower heat up times. It is to be expected as lesser voltage = lesser current flowing for the same amount of resistance, according to Ohm’s Law.

I = V/R

I measured the times and here are my finding

26.1V (Onboard PSU) – 3 secs

12.1V (3 cell LiPo Battery) – 24 secs

The 12V seemed to quite struggle to heat up to the required temperature. I highly think that the PID needs to be re-tuned if using with a different power supply voltage. The power percentage seems to drop off from 100% to 50%-60% when it reaches within 30°C of the setpoint. This amount of damping is ok with 24V, but with 12V, the damping is too much.

In conclusion, this modification is quite easy to make, and it allows the user to use the soldering iron in the field without a mains power supply.

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