Ok - this is weird:
I flashed the chip using sixty545's files - now the light just gives out 2 bright flashes when i turn it on, and then is constant on, at what seems like full level.
Here are the results from verifying the chip after flashing it with sixty545's files - perhaps you guys can see something from the fuse settings:
avrdude -P /dev/tty.usbserial-A600aSmp -p t13 -b 19200 -c arduino -v
avrdude: Version 5.8cvs, compiled on Jan 15 2010 at 17:27:01
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
Copyright (c) 2007-2009 Joerg Wunsch
System wide configuration file is "/usr/local/CrossPack-AVR-20100115/etc/avrdude.conf"
User configuration file is "/Users/nicolai/.avrduderc"
User configuration file does not exist or is not a regular file, skipping
Using Port : /dev/tty.usbserial-A600aSmp
Using Programmer : arduino
Overriding Baud Rate : 19200
AVR Part : ATtiny13
Chip Erase delay : 4000 us
PAGEL : P00
BS2 : P00
RESET disposition : dedicated
RETRY pulse : SCK
serial program mode : yes
parallel program mode : yes
Timeout : 200
StabDelay : 100
CmdexeDelay : 25
SyncLoops : 32
ByteDelay : 0
PollIndex : 3
PollValue : 0x53
Memory Detail :
Block Poll Page Polled
Memory Type Mode Delay Size Indx Paged Size Size #Pages MinW MaxW ReadBack
----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
eeprom 65 5 4 0 no 64 4 0 4000 4000 0xff 0xff
flash 65 6 32 0 yes 1024 32 32 4500 4500 0xff 0xff
signature 0 0 0 0 no 3 0 0 0 0 0x00 0x00
lock 0 0 0 0 no 1 0 0 4500 4500 0x00 0x00
calibration 0 0 0 0 no 2 0 0 0 0 0x00 0x00
lfuse 0 0 0 0 no 1 0 0 4500 4500 0x00 0x00
hfuse 0 0 0 0 no 1 0 0 4500 4500 0x00 0x00
Programmer Type : Arduino
Description : Arduino
Hardware Version: 2
Firmware Version: 1.18
Topcard : Unknown
Vtarget : 0.0 V
Varef : 0.0 V
Oscillator : Off
SCK period : 0.1 us
avrdude: please define PAGEL and BS2 signals in the configuration file for part ATtiny13
avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.04s
avrdude: Device signature = 0x1e9007
avrdude: safemode: lfuse reads as 79
avrdude: safemode: hfuse reads as EF
avrdude: current erase-rewrite cycle count is 808531511 (if being tracked)
avrdude: safemode: lfuse reads as 79
avrdude: safemode: hfuse reads as EF
avrdude: safemode: Fuses OK
avrdude done. Thank you.
However - no real harm has been done - as I tried flashing back to the BLF-VLD without problems :-)
Edit: I forgot to write, that the light actually turns on with both NiMH and Li-ion with sixty545's files now - even if it first blinks twice and then is constant on...