I love Behringer’s approach to tech and synths. The TD-3 is super affordable and performs like a charm. The community has quickly started modding the TB303 clone and I also decided to give it a simple mod: if there is something I don’t like, its cables! Also why use a 9V power wart, when there’s USB power.
I wanted to experiment with 18650 lithium ion battery cells that I will use in other contexts. The Sony 18650 VTC6 batteries that I am using deliver 3.7V on average and around 3000mAh. I would need charging electronics and then somehow try to make them deliver the 9V that the TD-3 expects.
My requirements were:
- all components are located in the TD-3
- battery is charged using USB or 9V while powering the device (USB preferred)
- when unplugged, deliver 9V for the device
- seamless plugging and unplugging (like a mobile phone)
- enough power for a day
After some research I found the TP4056 USB charging module and MT3608 step-up converter that seem to work almost perfectly. I am picking up USB Bus (5V) and deliver the 9V at the wart connector.
Here are some pics:
![](https://ekartco.com/wp-content/uploads/2020/03/Bildschirmfoto-2020-03-21-um-10.35.43.png)
![](https://ekartco.com/wp-content/uploads/2020/03/4DCBEC1E-B7A9-4ECF-A639-C1DFBE815FA6_1_201_a-1024x671.jpeg)
![](https://ekartco.com/wp-content/uploads/2020/03/A5B3DCD3-92E1-48AE-B3F3-D7213B5EEA23_1_201_a-1024x648.jpeg)
![](https://ekartco.com/wp-content/uploads/2020/03/518DDAAC-37C9-4FAE-BBBF-CA1DD0192E71_1_201_a-1024x768.jpeg)
![](https://ekartco.com/wp-content/uploads/2020/03/672CBED6-EAEB-4CC7-B31A-EF34F23E33CF_1_201_a-1-1024x768.jpeg)
![](https://ekartco.com/wp-content/uploads/2020/03/44C3E787-878A-44BB-B794-888BCF8255F5_1_201_a-1-1024x677.jpeg)
![](https://ekartco.com/wp-content/uploads/2020/03/A96C27E3-3E69-4C37-B5FC-5E4AF4ACFB99_1_201_a-1-768x1024.jpeg)
![](https://ekartco.com/wp-content/uploads/2020/03/0AE59C27-90F8-4CFE-9363-A8574C6C7D3C_1_201_a-1-1024x768.jpeg)
Issues:
- It seems that the protection circuit of the TP4056 fires when switching on the TD-3. My tests with the KORG monologue do not show that power surge. The quick fix was to short-circuit BAT- and OUT- on the TP module, since the MT3608 includes a protection module anyway. But I would like to solve this before calling it a day.
- I am using the TP4056 OUT+/- as power delivery to the MT3608 even during charging. It works, but I suppose a better way would be to take the USB Vbus and OR it with the battery out using two Schottky diodes, or even better ideal diodes (like SM74611 with a super low loss).
- The 9V in connector needs to be desoldered (I am not using it anymore, but it would lead to problems if anyone connects the wart…).
- MT3608 draws power constantly (300µA) from the battery, even when the device is off. However, it should take a year to drain the battery before the undervolt protection circuit kicks in.
- I need to test USB power draw. It worked with all chargers that I tested and my iMac.
A nice coincidence: The charging LED is bleeding softly through the function LED of the TD-3 (exaggerated in the pic), so that I can see when charging is finished (red charging/ blue fully charge):
![](https://ekartco.com/wp-content/uploads/2020/03/D6DEAF74-4760-43BF-9668-F00C1AC7CDA1_1_201_a-1-1024x768.jpeg)
Parts cost is less than 10$ / 10€. I found on the following offerings on amazon.de:
WARNING: This is a prototype that I built for my own testing purposes and is not finished yet. Whatever you do to your device: It is your own responsibility. Batteries are dangerous, if not handled properly!
It would be nice if Behringer offered a battery add-on (granted, not everybody needs lithium in their devices). @gekart