Browse Category: Mixed

Mixed language, mixed target :)

Tronsmart Mega Pro 60 – battery design fail

What are the symptoms?

After a year or two (but not heavy usage – mostly lying around) speaker was unable to charge to 100% (also charging never finished) and Bluetooth showed at best 90%. Immediately after charging disconnect, it dropped to 60% or even less. While playing, it could barely withstand 30min of playback.

Wild guess would be the battery issue – I’ve assumed that manufacturer used some crappy lithium cells and that how it ended. I can’t confirm or deny this now – since definitely, by how they where charged, it damaged them a bit聽 – but they seems to be around 2500mAh, so decent.

So what is/was wrong?

Speaker have four 18650 lion cells, grouped by two. This gives around 7,4-8V total. Contrary, to what I’ve supposed before dissembling it, it had 2S lion protection board installed (on the first battery pack, under the shrinking tape) but it’s missing balancing feature. So one pair was charged to 4,4V and another was 3,3V. BMS (let’s call it this way for now) was cutting charging off (overcharge protection of one pair), but never reached top voltage (so charger IC was still trying to charge it – it’s a separate component on the main board – not on BMS). The other pair was all the time undercharge and quickly dropped to undervoltage protection, that’s why speaker could only play 30min or less.

In theory, if the cells are equal quality and used proportionally – this unbalancing could not have happened or took much longer time. But usually designers do some shortcuts (this is often in power cells for hand held devices – drills etc) and sometime power the low current BMS electronics with only one pair of batteries – because it’s easier – pushing cells to imbalance (I’ve seen this behavior in few Parkside and Makita devices). This is just an example – but it shows the idea.


Tronsmart Mega Pro - new BMS
Tronsmart Mega Pro – new BMS

So what it takes to fix the issue, is to use BMS with cell balancing and replace broken cells. In my case one of four cells where totally broken (unable to fully charge and was loosing charge).

I’ve used HX-2S-JH20 BMS board – plenty of those on Aliexpress for few bucks – because I had it at hand.

Oh and I forgot to mention – I have two of those speakers, and both face the same issue – so it’s not a fluke 馃檪

PIDKiln v1.2 update

I’ve just created v1.1 release of PIDKiln, and bumped development version to v1.2.

Most significant change in release 1.1 are:

  • replaced MAX31855 library with another one – it’s much cleaner and easier to modify
  • much better MAX31855 error handling, both with thermocouple and MAX31855 itself
  • introduced network logging with syslog protocol – so you can watch all debug information on remote host
  • all logging settings are now in Preferences
  • compressed local JS, and created separate Preference setting to allow remote downloading of JS scripts (Internet connection required – recommended to use)

And I have also (after some 1.2 changes) first, real Kiln test run.

With two termocouples and power meters.

Source like always on GitHub.

Engraving, cutting 5.5W laser – description and proper connection

During upgrading my engraving machine (Chinese so called CNC 3018) I had to do some reverse engineering to do proper connection.聽 Perhaps someone else may find this information useful – so here you go 馃檪

Laser itself is distributed as two part set. Laser in aluminium cooling block with fan (and four wires), and PWM/TTL controller board.

Controller board uses this main components:

  • XL4003E1 – voltage regulator with input voltage 5V-32V, 4A CC max with 300kHz switching frequency
  • IC chip MCP60021 OPAMP – operational amplifier
  • Voltage regulator 78L05 – 5V output, 100mA
  • NPN transistor D476 61C

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Sim Wiocha

Sim Wiocha - przykladowa karta
Sim Wiocha - przykladowa karta

I kolejna zapomniana rzecz – karcianka stworzona przez Telefaxa, swego czasu za darmo do 艣ci膮gni臋cia ze strony magazynu Portal – obecnie zagin臋艂a w sieci, zapewne komu艣 si臋 jeszcze przyda do grania 馃檪 Sim Wiocha (pdf)