Multi-cell battery monitoring
23 September 2008
Linear Technology moves into multi-cell battery monitoring with the LTC6802 IC.
The LTC6802 can measure up to 12 individual battery cells, using its proprietary, stackable architecture, which allows multiple ICs to be stacked without optocouplers or isolators. It enables 1,000V plus systems. The IC monitors the voltage of every cell in strings of connected batteries.
Application areas are electric and hybrid vehicles, scooters, motorcycles, golf carts, wheelchairs, boats, forkligts, robotics, portable medical equipment and UPS (uninterruptible power supply) systems. Higher power applications demand bigger battery stacks of four or more cell counts. These can be tens or hundreds of cells. Hybrid electric applications can require between 48 to 192 cells. This multiplication of cells, their funnelling and synchronisation present voltage and current issue. The LTC6802 makes the management of each cell accurate, from avoiding over-charging or over-discharging, even in the presence of over 1,000V, claims Linear.
Higher voltages require extreme precision of measurements and, in applications such as automotive, reliability and cost-effectiveness are also important.
The maximum total error for the LTC6802 is guaranteed at less that 0.25 per cent from -40°C to 85°C and all cell voltages in a battery stack can be measured within 13msec. Each cell is monitored for under-voltage and over-voltage conditions. An on-board FET for cell discharge switches over-charged cells.
Each IC communicates using a 1MHz serial interface, with packet error checking and each has temperature sensor inputs, GPIO lines and a precision voltage reference.
The IC is in a small surface mount 44pin SSOP, measuring just 8mm x 12mm. Initially, the IC is described as a general-purpose device, although Linear’s Erik Soule confirmed that there will be a follow-up product in the spring.
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