The battery in the keys are used for the central locking functions not the EWS chip inside the key, that is simply read with the key in the ignition switch by a loop aeriel inside and around the ignition switch. If the key batteries are both flat you might get them recharged by placing them on a toothbrush charger overnight., worth a try. Otherwise you have to cut the keys open to get at the battery. There are places that refurb keys, might be worth taking that route one key at a time. As others have said the keys should unlock / lock the doors manually, same for the boot, if they don't then maybe a link inside the door has become disconnected as its purley a manual operation.