Dear All,
I am more commonly found helping in the Thermal Imaging sub forum but I have come out into ‘General Population’ to ask for some help for a change.
This post relates to replacing cells in laptop and tablet battery packs that are using the various Texas Instruments BQ series battery management chips. For those unaware, the TI BQ chips come in many types and with varying features. What is common to all is the ‘battery lockout’ feature that basically disconnects the battery supply terminal if an imbalance or failure of a cell in the pack is detected. This is a safety feature and not a bad idea as it prevents overheating cells ! Sadly the BQ chips have evolved over the years. Whilst early versions were quite ‘dumb’ and could be persuaded to reconnect the battery to the outside world if the fault condition was corrected, later versions are more sophisticated and can permanently lock-out the battery terminals unless the BQ chip is ‘unsealed’ and ten the fault flag reset after new cells are fitted. Even accidentally disconnecting good cells in such a battery can cause a lock-out and effective loss of the battery from use. I am all for safety where Lithium cells are concerned but sadly the battery ‘lock-out’ feature has expanded to cover not only faults, but also charge/discharge cycles ! So in theory, perfectly healthy cells are placed beyond use by an arbitrary charge count. Now the killer..... to unseal a modern BQ chip to change its settings is lock-out status you need a password ! And, you guessed it, many manufacturers set their own password and even use custom firmware in the TI BQ chips. If you get lucky, the default TI password is used but such is not to be expected these days.
So the situation that faces me is having several different modern Lithium Ion battery packs that are in Lock-out, likely due to long term storage as they are almost new. I can buy new Lithium Ion cells for them without difficulty but I suspect the TI BQ chip will hamper or even prevent my plan to fit new cells in the packs. These tablet and laptop batteries are uncommon Military types so I cannot just buy new ones.
So, to the topic of this post. Has anyone else had experiences, good, or bad, when trying to fit new cells into a battery that is in ‘Lock-out’ and contains a BQ series battery management chip. Any and all experiences are welcomed. Does anyone know any BQ chip passwords ? Sharing those might help others who read this post. I am dealing with Samwell, Itronix (General Instruments) and Getac batteries but Dell, HP and other makes are also of interest to me.
I just bought the official Texas Instruments EV2400 USB interface unit to communicate with the batteries via their normal SMBus I/O path so that side of things is covered.
Regards to all
Fraser