Hi I would like to enquire if i want to monitor 54 cells in series that provides 194.5V to the load, can 6x BQ77PL900 be stacked up to provide the necessary protection, monitoring and management as indicated in the datasheet?
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It may be possible to construct a system using the bq77PL900, however it does not support this in its design. You will need level shifters for the outputs as well as the communication path. Such a system may not be practical. A better approach for such a system may be to use the bq76PL536 in your battery monitoring system design. It is designed to stack.
Well, not necessarily this is that impractical :-)
My design based on bq77pl900 supports much higher voltages. Every module is optoisolated and connected via CAN with the bus.
Eeach bq has its own Atmega floating with it on high potential. The MCP2515 is on high potential side, the MCP2551 is on optoisolated side.
Eeach module has its own sequencing/galvanic isolation subsystem based on small signal relays driven by dedicated Atmega.
This approach works beautifully and allows to chain (through CAN) as many modules as you want. Each bank is responsible for its
own 5 to 10 cells.
I can provide schematic for review.
brgds!
Hi Adrian,
I've realised a 20S Stack with the BQ77PL900 as a prototype so far. Programming can be done with an optoisolated bus, two CHG- & DCH-Fetsin series (relating to the max. VDS and a min. RDSon) each, the both CHG-FET's are switched simultaneously, same with the DCH-FET's. Controlled via two BQ77PL900 ships with a self designed driver circuit. It would be interesting for me - just for information of course - how you did solve this problem with that needed level shifting circuit. Kind regards from Germany, Mike
uuuppps, sorry, forgot to let you know my email for sending your schematic. Here it is: m.hentschel@cellcon-gmbh.de. Kind regards again, Mike
Adrian,
Would you mind sending the schematic to my email as well? Thanks.
allen652 at comcast d0t net