--- a/FC-handset-spec	Sat Jul 03 07:01:39 2021 +0000
+++ b/FC-handset-spec	Sat Jul 03 18:10:56 2021 +0000
@@ -730,6 +730,24 @@
 even worse, as their discharge curve is said to be even flatter.  For these
 reasons, we are going to play it safe and stick with Li-ion.
 
+1.10.1. Battery ID resistors or thermistors
+
+In all classic dumbphones from the era which we seek to revive (the ones with
+user-removable batteries), the battery pack (flat pouch) has 3 or 4 contacts
+rather than just 2: in addition to battery +ve and -ve terminals, there are some
+ID resistors or thermistors included.  Both Motorola C1xx and Pirelli DP-L10
+batteries have 3 contacts, and so does Nokia BL-6C battery form factor that was
+copied by FIC/Openmoko.  In contrast, cylindrical Li-ion battery cells like
+18650 have no such third terminal.
+
+Because we are deferring our handset battery design to a later project phase
+(not included on the Venus board), we don't know at this time whether or not
+our final handset battery pack will have any ID resistor and/or thermistor
+connected to Iota ADIN1 or ADIN2.  Our current FCHG battery charging driver
+does not touch ADIN1 or ADIN2 at all; if we do end up having an ID resistor or
+thermistor and needing to support it, that custom support will have to be added
+at the time of the actual handset design.
+
 1.11. Charging circuit
 
 Our FC Libre Dumbphone will feature a USB port (mini-B, device role only, no