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How to Build OKL T20 Box Mod Tutorial

OKL T20 Box ModI know many of you have built your OKR T/10 box mods that I showed you several months ago. But with everything in the vape market, we want bigger and stronger.

That is exactly what describes this OKL T20 box mod. This build has the ability to handle 20 amps, which means roughly 110 watts with a variable voltage of 3.5 to 5.5 volts. It’s best to stick to a coil resistance of 0.3 ohms and above to ensure you are not over working the OKL T20 chip.

If you would like to build this same OKL T20 Box Mod that I show in this video, I do have complete DIY box mod kits available to you at www.shop.findmyvapes.com

IMPORTANT: Purchasing a kit from my store will help support this channel and allow me to bring you more tutorials in the near future. I appreciate everyone’s support

Probably the most recognized box mod using the OKL T20 chip is the infamous Hex Ohm V2 box mods by Craving Vapor.

The box mod that we will build today is very similar to the Hex Ohms but with a few additional features that I always like to add in all my box mod.

Overall this build is pretty basic in features, which was the intent. I want to make sure that all you modders will have the ability to complete this build with as little headaches as possible.

Although this build is basic, it doesn’t mean we can’t add in some really cool features.

In addition to the OKL T20 chip, we will have reverse polarity protection as well as a master on/off switch. The reverse polarity protection will prevent the user from damaging the OKL T20 chip if the batteries are place incorrectly. The master on/off switch is also useful for those times you carry your box mod in a pocket or bag.

Alright, enough of that. Let’s get started!

Items Needed:

OKL T20 Chip (Negative Logic)
Custom CNC 1590 G+ Enclosure
Spring Loaded 510 Connector
Dual 18650 Battery Sled
12mm Fire Switch
Master ON/OFF Switch
1k Ohm Potentiometer
20k Ohm Resistor
1.43k Ohm Resistor
1/4 x 1/8 Round Magnets
6/32 x 1/4 Grub Screws
18g and 24g Stranded Wire

Tools Needed:

Soldering Iron
Solder Flux
Heat Shrink
3/4” Clear Heat Shrink (For the OKL Chip)

Wiring the OKL T20 Chip

The wiring of this chip is, in my opinion, pretty simple when compared to other chips out on the market. If you practice neat wire management, you should be able to complete the wiring of this chip fairly easily. Take a look at the wiring diagram below.

OKL T20 Wiring Diagram

I’m not going to explain every detail of the chip in this article since that would require a lot of writing. Instead, watch the build tutorial video for a more detailed explanation of what everything does.

Once your wiring is complete, we can move onto the enclosure of our box mod.

Choosing the Right Enclosure

CNC 1590g EnclosureFor this box mod build I am specifically choosing to go with the custom CNC machined 1590 G+ enclosure that I reviewed a few months back.

The reason I am using this enclosure is because it is just a hair larger than your standard Hammond 1590G boxes that I have used in the past. It’s a very small size difference but it make a huge difference when you are trying to squeeze in all your wiring.

The other advantages with the CNC 1590 G+ enclosure is that it has hidden magnets and no “Hammond Lean” issues. These two advantages gives your box mod an ultra-professional look. It literally appears that your box mod was manufactured instead of built at home.

The first thing you need to do with your enclosure is figure out the layout of your components.

Do you want your 510 connector centered or off to one side? How high do you want your switch placement and on which side? Where do you want to place your potentiometer to adjust voltage?

These are all personal preferences that I will leave up to you. However, I will show you in the video my preferred layout of all the components. If you are nervous about the layout options, just follow what I did and you should be good.

Once you have your layout figured out, you can now drill the holes needed for your 510 connector, fire switch, and potentiometer.

I do have a video showing you how to drill out your holes for box mods if you need more detailed instructions. However, the holes sizes are listed below.

510 Connector = 7/16” hole
Fire Switch = 1/2” hole
Potentiometer = 3/8” hole

When your enclosure is prepared and ready to go, move onto the battery sled because we need to do some small modifications

Wiring the Battery Sled

Battery Sled WiringA lot of readers asked if it was possible to wiring the OKR box mod in parallel instead of series. Well, the answer is no. This also applies to the OKL T20 build as well.

The OKL T20 chip requires an input voltage of 4.5v to 14v in order to operate.

A freshly charged single 18650 battery delivers only 4.2v at its max charge. This means that you cannot wire your sled as parallel because the voltage output is lower than what is required by the chip.

However when you wire your sled in series, the voltage of the two 18650 batteries are now doubled giving you 8.4 volts at a max charge. This falls perfectly within operating range of the OKL T20 Chip.

Just simply follow the wire diagram I drew out for you. Just remember that series is NEGATIVE->POSITIVE->NEGATIVE->POSITIVE.

You will want to pop off all the contacts before soldering because you do not want to melt the plastic frame of the sled. You also want to cut off all the tabs on your contacts.

Cutting off the contact tabs will prevent you from shorting out your batteries on your enclosure.

Another modification that needs to be done to the battery sled is to cut out a notch in the bottom right corner of the sled. This is done so that the sled can fit nicely in the bottom right corner of your enclosure and will clear the screw posts of the enclosure.

Reverse Battery Protection

Having reverse battery protection is an important added feature to this OKL T20 box mod.

There’s no shame! We all do it!

Once in a while we are all guilty of placing our batteries in backwards. Unfortunately the OKL T20 chip, in its standard form, does not provide protection from this.

If batteries are placed incorrectly, there is a chance that you can ruin the OKL unit

So taking matters into our own hands, we will wire in a PFET to prevent any damages to ever occurring.

We will be using PFET SUP75P03-07-E3 to provide this protection for us in this project. Follow the above wiring diagram to see the proper way to make your connections.

This PFET wiring may look similar to the MOSFET wiring on my previous Unregulated Box Mod tutorial. It looks similar because it essentially is the same. You will want to use 18 gauge wiring for these connections.

Epoxy the Potentiometer

Potentiometer WiringOur 1k ohm potentiometer is needed in our box mod to regulate our voltage output. With this potentiometer in place, we can adjust the voltage between 3.5 and 5.5 volts.

This is a great voltage range that allows you to utilize many different coil resistances. Remember, it is recommended to build your coil resistance at 0.3 ohms or above.

You will want to wire your potentiometer according to the wiring diagram above. Watch the video for a visual step by step guide.

Special care is needed when you are ready to epoxy the potentiometer to your enclosure.

The key to this step is making sure that you cover the entire potentiometer with electrical tape. I used some high quality electrical tape because it provides really good adhesion and is very flexible.

Once you carefully and neatly cover your potentiometer with electrical tape, you can now spread your epoxy over the tape.

Mix your 2 part epoxy according to the manufacturer’s directions. You may need to wait over night for the epoxy to fully cure before moving on.

I also took this time to epoxy the battery sled to my enclosure as well setting to magnets in the lid.

 Correct Wire Gauge

The wire size I used in this build are 18g and 24g stranded copper wires.

The larger 18g wires were used for any wire that will be carrying a heavy electrical load. In the diagram I have differentiated where 18g wire was used as oppose to the 24g wire.

The smaller 24g wire was used to connect components that do not carry a high amp load. These were mainly “switching” components such as the fire switch, master on/off switch, and potentiometer.

Like with all builds, you can substitute these wires for a LARGER gauge wire but do not use SMALLER gauge wire. What I mean by this is that you can use 18g wire throughout the whole build but you should not use 24g wire for the entire build.

However, the issue with using large wire throughout the entire build is that it can be difficult to squeeze all your wiring into your enclosure.

Final Thoughts

If you have finished watching the tutorial video and have reached this point in this article, hopefully that means that you are ready to build your own OKL T20 box mod.

I have been using the OKL T20 chip for several months now and have had absolutely no issues with it. This box mod really does provide an enjoyable vape and is relatively easy to build.

I have no doubt that when you finish building your OKL box mod, you will love it as much as I do.

So head over to www.shop.findmyvapes.com if you would like to build this same OKL T20 box mod. I will have complete DIY box mod kits available to you.

But this is all I have for you today, I will see you on the next build!



Check Also

How to Build Unregulated Dual 18650 Box Mod

How to Build Unregulated Dual 18650 Box Mod with MOSFET

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  1. Hello Ferd, Quick question I know you mention that base on the wire ring is the voltage you are going to get, 3.5 to 5.5. What voltage do you get with the one on this video?? I just finish building one and I’m only getting 4.7 to 5.2. Why is that? I will like to get the full potential on this, the 3.5 to 5.5? Any help you can give me?

  2. Hello, I was wondering if there is another safe alternative for wire guage other than 24 guage?

  3. can i make it without PFET?

  4. Hi Ferd. I’d like to ask if 1.)Instead of 18650 batteries use lipo batteries because they take less space in project box and 2.) can we add a charging circuit to charge either 18650 batteries or lipo batteries? Thanks in advance.(Sorry for my English,i’m from Greece)

  5. just wonder if you have diagram for positive logic board?

  6. Hi thanks for this great How to ! one questinon? can we change for 2 * 26650 ? does it improve the autonomy as we keep in series?

  7. Hi Fred, to make it cheaper for myself I purchased the v3 clone of the hex, then I’ve purchased the chip and resistors etc that way no drilling etc.. The only question I’d like to ask you is the v3 comes with voltage screen, can this be wired in to your wiring and if so is there any chance you could email me a diagram of how I could change it…
    Thanks Gregg

  8. hi fred ..
    can i have wiring diagram for unregulate mod with volt meter and pulse wattage module (pwm) chip

  9. The enclosure you have listed for this build is way too small! It needs to be a bit more room for the chip and Mosfet. I aIso have replaced the potentiometer to a Linear Taper Rotary one. I also have found that the “1590B” will work fine WITHOUT any modifications to the sled or anything. (*NOTE* CHECK SIZES!) (112mm x 60.5mm x 32mm) Just sharing the info to pass this info to other and help prevent any confusions or future problems. So currently I’ve wasted $15 on getting the wrong enclosure and turned it into scrap. Other than that this is a great build and batteries last about 3/4 of the day so have spares on you! Currently this is my main MOD until the 300W is released.

    Thanks for the Tutorial!

  10. Hi Fred,
    Thanks for the tutorials. They’ve been very educational, especially for me that have no idea how circuits work but thanks to you I can build cool boxes.
    I have a request: can you make a tutorial for a box mod with ohm, volt/watt, battery level display? Or at least point the right direction for parts?