The　aging　of　power　batteries　is　likely　to　cause　problems　such　as　inaccurate　state　of　charge,　difficult　screening　of　retired　batteries,　and　thermal　safety,　which　limit　the　development　of　electric　vehicles　and　the　use　of　old　batteries.　Furthermore,　it　may　offer　theoretical　foundation　to　solve　the　above　problems　by　studying　on　the　aging　characteristics　and　analyze　the　variation　of　electro-thermal　performance　between　fresh　and　aged　batteries　in　a　variety　of　environments　or　conditions　by　comparison.　Therefore,　it　is　researched　and　discussed　based　on　the　power　battery　test　system　through　experiments.　It　is　found　that　effective　capacity,　energy　and　energy　efficiency　reduces　gradually　as　well　as　the　increase　of　cycle　numbers.　Meanwhile,　there　is　a　slight　swelling　phenomenon　accompanied　by　aging　at　the　bottom　section.　The　rate　characteristics　and　the　adaptability　of　ambient　temperature　become　worse　with　the　increase　of　aging　degree.　Moreover,　the　resistances　and　temperature　sensitivity　of　resistances　increase　obviously.　The　variation　of　electrical　performance　affects　its　thermal　performance　directly　so　that　working　temperature　and　temperature　gradient　of　battery　increase　obviously　with　comparison　of　fresh　battery.　The　difference　of　working　temperature　between　fresh　and　aged　batteries　is　more　serious　especially　for　discharging　under　low　ambient　temperature　or　by　high　rate.　©　All　Right　Reserved.