Voltage regulation circuity can be removed from embedded systems, commonly saving 30% of the printed circuit board area. Most unregulated systems suffer from performance degradation or premature failure as battery voltage decreases. Researchers have described a technique called power deregulation, in which performance is preserved by activating processor cores as battery voltage decreases. Unfortunately, the operating lifespans of such systems may be limited due to mismatches between the battery discharge profiles and the voltage-performance characteristics of processors. This paper provides a technique for codesign of power deregulated systems in which battery, processor, and workload characteristics are jointly considered. This technique extends lifespans of deregulated embedded systems. We also describe new battery and system performance and power models, some of which are based on a recently commercialized silver-zinc battery technology that is well suited to power deregulated systems. These models support lifetime simulation of regulated and deregulated embedded systems. If it is possible to find an appropriate match between embedded system and battery characteristics, the proposed design technique results in lifetimes similar to those of regulated systems and eliminates the need for bulky power regulation components.