The　fixed　threshold　equalization　strategy　and　the　traditional　fuzzy　equalization　strategy　usually　result　in　overvoltage　or　undervoltage　protection　to　malfunction　at　the　end　of　the　battery　pack　charge　and　discharge,　and　it　is　difficult　to　be　fully　balanced,　because　a　large　difference　between　the　batteries　makes　the　balance　insufficient.　A　variable　universe　double　fuzzy　controller　(VDF)　equalization　strategy　is　thus　proposed.　The　lithium　battery　simulation　model　is　established　according　to　the　experimental　data　of　charged　and　discharged　NCR18650B　ternary　lithium　battery.　The　state　of　charge　(SOC)　of　the　single　lithium　battery　is　used　as　the　input　of　the　first-level　fuzzy　controller,　and　its　output　multiplied　by　the　lithium　battery　working　current　value　is　used　to　adjust　the　output　domain　of　the　second-level　fuzzy　controller;　the　difference　between　the　SOC　of　a　single　lithium　battery　and　the　average　SOC　of　the　battery　pack　and　its　rate　of　change　are　used　as　the　input　of　the　second-level　fuzzy　controller,　and　its　output　is　used　as　the　equalizing　current;　the　extreme　difference　of　SOC　between　the　single　cells　in　the　battery　pack　represents　the　inconsistency,　and　the　equilibrium　time　is　determined　by　the　first　convergence　of　the　extreme　difference　to　0.05.　The　simulation　results　from　Simulink　show　that　the　VDF　equalization　strategy　effectively　reduces　the　voltage　protection　malfunction.　With　constant　charge　and　discharge　current　and　in　custom　dynamic　stress　test　(DST),　VDF　equalization　strategy　is　compared　with　the　traditional　fuzzy　equalization　strategy,　and　the　results　show　that　the　equalization　rate　increases　by　above　30%,　and　as　a　large　difference　exists　between　the　batteries,　the　consistency　increases　by　above　20%　after　the　end　of　the　equalization.　©　2020,　China　Food　Publishing　Company.　All　right　reserved.