DYNABANK Sale

I have already participated in the 1000-mile race across Czechia and Slovakia three times, and it has been five years since my last participation. The race is being held this year for the sixteenth time, and I have registered again. Since I use a mobile phone for navigation (I need it anyway), which is much more convenient and ultimately more reliable than dedicated navigation devices, I developed the DYNABANK power bank, which is charged from a bicycle dynamo hub. I feel that it needs to be innovated, so I am planning a new version for this race. Since I still have a lot of assembled PCBs, it is probably best time to sell them. Therefore, it will now be offered at a reduced price, where I am basically ignoring the entire assembled PCB. At a time when everyone is used to buying low-cost Chinese goods, let's take a look at history and the production cost.

In 2004, I purchased a Garmin Forerunner 101 navigation device. Its NMEA serial output on a 4-pin jack connector was important because I needed to connect it to a map navigation device, which was a Fujitsu-Siemens LOOX 720 PocketPC. Touchscreen phones did not exist at that time (the iPhone was launched in 2007). Connecting it with a custom-made cable and using OziExplorer software, which could display scanned maps and your location on them, as well as add navigation routes by adding points on crossroads, was a huge step forward at the time. Simply not having to look at a large paper map was an incredible leap forward.

Many years have passed, smartphones with GPS have arrived, and even the open mobile phone Neo Freerunner. I didn't use it as a mobile phone, but as a navigation device with my own software, mcnavi, which I no longer develop. After the Neo Freerunner was discontinued, it was replaced by an Android phone and OsmAnd. But when I was out hiking, I needed to charge my phone somewhere, which isn't really possible in the wilderness. I decided on a hub dynamo, but I needed a USB converter, which was hard to find, expensive, and often sold by enthusiasts like me. In the end, I decided to make my own. The first was just a simple rectifier with an LDO linear stabilizer. It worked, but quite limitedly. Older mobile phones with analog charging were still able to cope with changing input power, but newer ones with converters were not. In most cases, when the input voltage dropped, which occurred every time the bike slowed down, they limited the charging current and did not switch to a higher one. As a result, charging was very slow. Some available rectifiers solved this problem with their own battery as a buffer and another converter behind it. Finally, I had the idea of making a power bank, which I need anyway, and charging it at the maximum available power according to the speed of ride.

This is how the DYNABANK power bank was born. The first version was an innovative rectifier with MOSFET transistors, which was more efficient, supplemented by a linear charging circuit. It worked well, but only up to a certain power. It was supplemented with a 5V converter for USB output. The next version was a version with a charging converter, which was already able to achieve maximum charging power, and the same converter was also used for the 5V output (i.e., you cannot charge the power bank and charge a mobile phone from it at the same time, but this turned out to be not needed). It was further supplemented with a USB-C input for fast charging from a power outlet.

I didn't want to keep DYNABANK just for myself, so I created the final version, which you can buy. It was supplemented with a processor and display. This is basically the current version of DYNABANK. The PCB assembly took place here in Europe, which is reflected in the high price. Even so, the selling price is comparable to separate charging circuits without batteries that are available on the market.

Just for comparison, what is the production cost of DYNABANK (excluding VAT):

This is only the price of the components without assembly and VAT, which must also be added and paid. I also tried to have the enclosure manufactured by injection molding, but according to offers from manufacturers, the mold alone would cost thousands of EURs. That is why it is printed on a 3D printer. When selling on eBay, it is necessary to add fees, which amount to approximately 20% of the price. The selling price for the 10,000 mAh version was previously 70 Euro, which was already subsidized, but has now been reduced to 48 Euro including VAT and to 32 Euro for the smaller version with half the capacity (only two battery cells). Just to use the PCBs that have already been manufactured.

So I am faced with the challenge of creating a new version that should be better, more compact, and cheaper. It will probably have to be a miracle. After all, an ordinary 10,000 mAh power bank with a display can be bought today for 25 Euro, including VAT and the retailer's margin! That's less than what I can buy just the battery for (I could lower the price a bit by buying non-branded ones, but I try to maintain quality). It's basically the price for mass production. You can support us by purchasing DYNABANK in our e-shop or on eBay.

We would also appreciate any feedback, i.e., whether you are considering DYNABANK, what you don't like about it, and what you would like to see in the new version. And what price is acceptable to you. Thank you very much!