Posted on: June 16th, 2013 by Bill
It’s been over four months since the 787 Dreamliner was grounded due to flaws in its DC power system. As many of you have read, the battery system in the plan was subject to thermal runaway and fire. Not to use the old line, ”This isn’t rocket science”, but in this case, it should not be.
We have seen a monumental leap forward in battery technology in the past five years. Some of this is a result of military technology being passed down to the industrial and commercial sectors, and some of this is related to the stored energy needs for hybrid cars and wind and solar distributed generation power systems. While we now enjoy the luxury of batteries that can tolerate higher and lower temperatures than the traditional 77F; offer varying discharge and charging profiles; and can now offer a wide mix of weight to kW ratios. Super!
At the end of the day, we’re still dealing with a chemically-based stored energy system. And the traditions that we have used for years in data centers to prevent the exact types of failures that occurred on the 787 looked to have been missed or inadequately provisioned in the aircraft. This blog is not about the indictment of the 787 design team. I’m certainly not skilled enough to develop a design that can fly 10,000 miles at 590 MPH under the unwavering scrutiny of the FAA. But some of the old battery rules need to be followed for the same reasons they always have – you don’t want a battery fire.
There are two basis approaches for battery management – voltage and impedance. One of the great adages in our industry is we design for redundancy when failure is not acceptable, and the systems that are subject to failure or maintenance are offered with predictive maintenance or failure precursors that allow for any operator to intervene at an appropriate time. One of the great benefits of batteries is that they tend not to failure quickly and catastrophically, if they are properly monitored.
Of paramount importance is the monitoring and controlling of the battery charger and well as the health of the individual cells, both for impedance and voltage. While the failure of many battery types tend to be open-circuit resulting in the loss of the DC buss, the failure should never be so severe that it results in a life-safety hazard or a hazard to craft or building.
Sometimes, the old school is the best school.
Tags: 787 Dreamliner
, batteries; battery monitoring