The battery charging system used in a wide range of DELL laptops has caused quite a bit of frustration among it's customers. Top ranked is the "AC Power adapter not recognized" warning with DELL laptop batteries not being charged. This alone has triggered a quest for information in many Internet forums mainly because DELL has not come forward with a reasonable explanation into the cause(s) of the problem. So here's info about the architecture and a bit of background of the battery charging system used in DELL laptops.
The Smart Battery System
Based on the schematics of the DELL D610 Latitude, DELL has chosen to adopt the Smart Battery System architecture. The system is apparently introduced by Intel and Duracell for accurate power management for applications running on rechargeable batteries. The initiative has it's own forum with a list of implementors on which DELL, among several chip manufacturers, is listed as the sole end-user / consumer system manufacturer. It's seems a bit odd, because most likely there are more laptop manufacturers who have used the Smart Battery System idea.
The Smart Battery System itself seems like a plausible concept and it appears the supporters have invested quite a bit to get the concept implemented. Also Maxim is part if the implementors which also produced the ID chip in the DELL AC Adapter. Page 9 of the Smart Battery System Specification V1.1 - December 1998 shows the block diagram of the battery charging system found in the schematics of the DELL Latitude D610. Most strikingly, the 1-Wire communication line with the AC - DC Adapter is not mentioned. It seems DELL has decided to walk alone on this. It doesn't sound like a smart thing to do, as the consequences already have shown.
Most components in the Smart Battery System are System Management Bus - SMBUS connected, the communication system invented by Intel® Corporation in 1995.
The DELL C1295 laptop battery with Smart Battery System implementation
The Smart Battery System implemented by DELL
The implementation of the SBS in the DELL Latitude D610 showcases the following components:
1) Smart Battery Host - SMSC LPC47N354 - MacAllen III - Ultra IO controller
2) Smart Battery Charger - Maxim MAX1535B - Level 2 SMBus Battery Charger
3) Smart Battery Selector - Circuitry handling double battery charging
4) Smart Battery - A battery containing a Mitsubishi M37516M6 micro-controller
Quite a sophisticated bunch to charge 6 Li-Ion battery pack. Now the SMSC LPC47N354 - MacAllen III - Ultra IO controller is quite a chip. Unfortunately there's little public information available but it seems this chip executes POST and BIOS functions using a 8051 based micro controller. The latter is a highly popular multi-purpose embedded CPU capable of doing quite a bit of work in the lower dungeons of the D610 laptop.
The Smart Battery Host, the SMSC LPC47N354 - MacAllen III, can talk "1-wire" with the DELL AC Adapter. The Smart Battery Host initiates battery charging over the SMBUS after finding a valid AC adapter.
The Smart Battery Charger, the Maxim MAX1535B , is in control of the method of charging while the micro controller inside the battery merely executes the SMBUS charging commands.
|DELL Media bay laptop battery - replaces the DVD or CDROM player
||Standalone laptop battery charger for DELL laptop batteries.
The Smart Battery Selector circuitry handles the presence of a double battery in the DELL D610 Latitude. The media bay where normally the CD/DVD sits can also hold a battery, doubling battery capacity.
Charging DELL Batteries the software way
Based on the above what are the possibilities of getting a DELL Laptop battery charged using an DELL Adapter with a dead ID chip inside using only a software solution?
A few options;
- Change the DELL BIOS / Controller firmware to disable the ID chip check
- Getting access to the SMBUS and initiate battery charging through 8051 based routines
At this point in time both are not simple exercises and require quite a bit if knowledge and skills to accomplish the task. Nonetheless it's an interesting task - who knows what comes to surface after a little bit of thought?
Now - starting with an interesting observation:
How can a powered down DELL D610 detect the AC Adapter?
It must be through embedded 80x51 software executed by the SMSC LPC47N354 - MacAllen III - Ultra IO controller once the AC adapter is connected.
So here are a few questions:
- Where is the SMSC LPC47N354 controller software located?
- Is the detection software in flash memory? On-chip or off-chip?
- Is it the same embedded software executing POST in the pre-BIOS stage?
Who knows the answer!
More about the DELL Battery charging system: