Li-X charger circuitry

The RF noise and the extreme heat noticed during the very first use of this B3AC charger convinced me to have a look inside. Four screws hold the plastic case together, so it's really easy to open it up.
The PCB is a mix of through hole components and SMD parts. Near the AC socket is what looks like a switching mode power supply (SMPS). The RFI filter is not missing: it was left out on purpose since no provision is made for its components! The SMPS continues after the transformer. So far no smart charging circuit was met.

Moving to the bottom layer of the PCB, SMD parts appear and three SOIC8 chips are amongst them. The marking is easy to read: 5056. A bit of googling brings up the XA5056 datasheet from Xinna Semi. This chip is rated for 1A max current and "Mystery B3AC" exploits it for all three chips.

I tried a recharge with the box open (don't try this at home!) and measured temperature on the three 5056 and the PCB. In a minute or so IC surface was measuring 70°C (158F), which is about +40°C above room temperature. No wonder the whole thing gets hot!

XA5056 chips are configured to push 1 Amp into cells, meaning 12W (4V * 1A * 3 cells) must be dissipated somewhere. That value is configured with R2 (ref. datasheet) of 1500 ohm. I am considering of increasing it to 2000 ohm, so that charge current decreases and overall temperature doesn't go too high.

By the way, this chip looks similar to big brands product(s), even the datasheet gives clues... but I haven't found yet the equivalent.

XT60 connectors

After assembling my own Li-X battery packs I realised I needed a safe way to use their energy, and finally solve my fear of inverting DC polarity of my 12V power cables.

Discussions on some mailing lists I read mentioned Anderson Power Poles and XT60 pairs. I went for the latter and ordered 20 pairs, which should be enough to wire all my polarity sensitive devices.

Windows 8.1 and Bluetooth SPP

According to recorded videos from //build/ 2013 conference, Win8.1 will support (again) I/O devices. Fortunately MS offers a Win8.1 Pro preview installation ISO (lasts until January 2014), which does work on VirtualBox VM, so I could quickly test it out.

Even though I didn't spend more than 5 minutes fiddling with it, (virtualised) Win8.1 could pair with the CAT-to-BT adapter (HC-05 derivative), correctly assign two COM ports and Ham Radio Deluxe connect to the radio.

The whole process still seems a bit buggy as OS level, but at least this kind of I/O will be possible with newer computers too.

Windows 8 and Bluetooth SPP

Bluetooth-to-CAT dongles for FT-817/857/897 use the Bluetooth SPP protocol ("Serial Port Profile") which does not seem to be available on MS Windows 8. At least in the preview version I have been able to try (Win8 Enterprise build 9200).

Device is found. Pairing with PIN works, a "serial-in" and "serial-out on Dev. B" device are created but no COM port is allocated on the system, therefore the serial-over-Bluetooth device is not reachable from the PC application.

Serial-over-Bluetooth HC-05 device is found and paired. But then...

Is this a Win8 limitation. Has it been solved with newer releases? Comments (moderated) are open, please write your experience if you land on this page looking for Win8/SPP information.

Li-X charger, first impressions

The Li-ion/poly charger finally arrived from China. At less than 10USD shipped I expected it to get the job done and nothing more.

In 10 minutes I threw together a 3S 2200 mAh pack and started charging. Cells were highly unbalanced and had been restored from the deep sleep state with a constant voltage about one month ago. They measured something like 3.2 and 3.6V unloaded.

The "Mystery B3AC" charger reports a worrying "do not leave charging unattended". It should charge a 3S pack at 1A and 2S pack at 1.5A.

I was listening to 2m SSB when I first plugged the battery pack and a strong QRM appeared. Uh! Oh! The charger is absolutely NOT RF-friendly! (No, I haven't checked if the noise was coming through the antenna or the PSU) I looked every now and then what was happening in the shack, without monitoring the actual DC current flow. The charger temperature was high, it was smelling too. I couldn't almost keep my hand on it.

Nevertheless, about two hours after charging, first LED turned green, shortly followed by other two. Temperature returned normal.

Next step will be to power the FT817 with this 11.1V (nominal) pack while studying the charger circuit.

So far .. no fire.

2m ES opening - antenna

Yesterday I didn't use a high-end antenna for my sporadic-E QSOs, not even an antenna in a good position!

When propagation helps, a big antenna is not needed. Of course I could not hear everything that was on the band, but I worked what I could hear.

Given the typical figure-8 dipole radiation pattern, I wonder if I should have installed it vertical. Original polarization is lost when the ionoshpere reflects our signals, so for ES DX-ing you don't need to match with the correspondant. "Same polarization" is true for (almost) line-of-sight contacts and, probably, tropo.

2m ES opening

I was home this time! A strong sporadic E opening reached 144 MHZ today. I could hear DX traffic on the rubber duckie antenna, indoor.

How to participate, since I have no antenna?! Laying in the shack was the dipole of my homebrew VHF yagi. I quickly hanged it outside on the HF antenna fishing rod support, fired up the IC706 at 20W RF and worked two stations at 1600 and 1200 km distance (SSB).

In DX terms that counts for two squares and two DXCC entities. Probably only one of them is a new-one for me (but do I really care?).

Da b0mb :)

This battery pack worries me, and I created it!

You are looking at a 4S(1P) Li-ion battery and charging electronics assembled out of parts from an hp/Compaq battery pack.

Five wires run from cells to the charger, which are used for charge balance. Since cells were already partially charged I had to be very careful not to short wires together. Next time I will solder first on the PCB side and then to the cells!

Charging at 1C (> 2 Amps) heats up cells. At one point the charging electronics was drawing 250mA into a couple of SMD transistors, which got pretty warm. I have no idea why that happened, because re-applying the power restored the charging process.

Once again charge was stopped at 4.0x V per cell, with a light unbalance. The bq2060 chip reports 80% charge, but that's probably computed from its past "experience" with other cells.

Next step will be to evaluate residual capacity, both of this 4S1P pack and the refurbished 4S2P. I don't have a costant current load so I will stick to a 12V car lamp and stop discharge at 3.2V/cell.