to each negative battery contact 302 of stack by corresponding conductive traces 452 so that battery stack 490 can form a relatively high density power source in which channel 441 forms a positive terminal and channel 442 forms a negative terminal with reference back to fig4 a dashed lines represent optional recessed areas which can be left when forming each rdl 45 in order to form a cavity between each adjacent battery 32 of each stack 490 according to some embodiments the optional cavities can provide some stress and strain relief to individual battery stacks 490 if batteries 32 swell during charge and discharge cycles a height of each cavity preferably ranges between approximately one and five micrometers which is sufficient for the aforementioned lipon type cell fig5 a is a perspective view of an exemplary wafer 50 in which an array of planar solid state batteries 52 is formed according to an initial step of some alternate methods of the present invention and fig5 b is a cross section view taken along a plane defined by section lines b b of fig5 a according to the alternative methods after some rcp processing such as that described below a plurality of wafers 50 are adhered together to form a stack 515 fig5 d wherein each wafer 50 is a silicon wafer in which batteries 52 are originally fabricated for example using thin film cell construction techniques known in the art and employing lithium phosphorous oxynitride lipon electrolyte material fig5 a b illustrate each battery 52 including a positive and negative contacts 501 502 and blind vias 54 which are formed through each contact.