Did someone try to flash a BSF 8 using a serial adapter connected on the PCB? I saw 4 contacts on the board and I guess that are there for a reason like this.
I had a station for which the battery had low voltage and when I connect the new battery the station does not turn on and the buzzer it's continously beep. Is it any way to reset it to default if cannot be flashed using a serial adapter?
I'm not sure where you see 4 contacts on the board and don't know why you would need four contacts anyway, a classical serial connection would only need three wires (GND, RXD, TXD). There is an 8-pin header (or holes for population of such header), which is used for the SRR-modules in the specific BS8-SRR stations, however the signals on that header are enabled only with specific firmware, same as for the BSM8-USB model. So even if you did contact the serial lines you probably wouldn't get a response. Also please check what serial voltage levels you're talking about, you certainly don't want to apply +/- 12 Volt RS232 signals to the TTL logic on the board.
All that said, a continuous beep sounds to me like you may have inadvertently created a short circuit while replacing the battery, possibly a blob of solder splattered somewhere or the battery wire was not cut to the correct length and is now protruding on to an adjacent pad.
However you do say the station had a "low battery", if this means it was deep-discharged before exchange there is a possibility that an electronic brownout caused memory corruption and the station therefore needs reflashing from scratch using the pogo-pin pads on the perimeter of the board (general rule is don't let the station run below 2.8 Volts otherwise memory corruption risk increases rapidly). This reflash can be done by the SPORTident company, obviously at a price for service and postage there and back.
On the red BSF8 model I have a 4-pin header like the one from the image (https://www.orienteering.cz/_data/obrazky/obr_3560...
). I will recheck for any shortcircuit but it's for the first time when I see this after dozens of batteries replaced on SportIdent stations. Also I've replaced batteries for stations which were completly dead and now are working properly. That's why I'm suspecting something with the memory and I would like to reflash it by myself but it seems that it's not possible.
Oh sorry, my bad, nearly all my SI-stations are BS8-SRR for radio controls and they use board-version v4_0, your picture shows an older board v3_0.
The four contacts you mention are for connecting the Silicon Labs CP2102 USB-to-UART-bridge, which on BSF boards is not populated (see the empty QFN 28 pads in the picture you linked to), and therefore the two signal pads in the middle aren't even connected to anything.
Don't get me wrong, I don't doubt your soldering skills, however having seen enough botched hardware in my days, starting with bathroom silicone, plumbing solder splatters, and battery wires protruding outside the pads, I was politely mentioning those possibilities.
Also the brownout memory corruption happens rarely, but just sometimes does. Normally the boot-loader would survive and allow a reflash over the air-interface (station coupling), so the continuous beep points me more towards a hardware issue than firmware. Even with memory-corruption in the firmware you would normally get a "BOOTER"-message on the display. Is your display showing anything at all?
In fact looking back a few threads here at somebody mentioning new-but-already-dead batteries, possibly you can test with a known-good battery (taken from or checked with another station, or measure battery voltage during the continuous beep to be over 3 Volts) to exclude that option also.
Good luck with your troubleshooting! :)
Battery is ok as I've tested on another station and is working. On the display nothing is shown. I'll recheck the soldering part. As you suggested, it may happen that during soldering a short circuit can appear.
I've rechecked the soldering part also with a help of the microscope and using a multimeter but I could not find any shortcircuit. Also I've tested with 2 different batteries (3.65 and 3.66 volts) but the same behavior: continuous beep sounds and red led on. What I've observed, on the other side of PCB are 2 contacts marked with reset. Is someone knowing for what are these used?
I'm sorry to hear there's no progress with that station.
The reset pads are a simple way to do just that, reset the station. The two pads can be briefly connected to pull the reset-line of the microprocessor, which reboots the station. However having exchanged the battery your station has reset anyway, so I doubt those pads will improve anything.
Depending on how long your station had a discharged battery, there is a (small) possibility that something happened similar to this Swedish guy many years ago: https://axotron.se/blog/sportident-station-with-pu...
Otherwise, from your description, I am sadly out of troubleshooting tips and would recommend looking at sending the station (without battery, but with error description) to SPORTident, possibly via your usual regional distributor.