Looks like Milwaukee is dropping the V18 tool line for the new M18. M18 may be lighter and is rated at 2.8AH vs the V18's 3AH. My guess is that they have new electronics incorporated with the same emoli cells and the lower AH rating is either just more realistic or due to different cut-out limitations.
Anyway, you can get two V18 batteries and a V18/V28 charger for $115
shipped at Amazon.com right now.
http://www.amazon.com/Milwaukee-48-11-1 ... d_sim_hi_4
For someone that specifically needs 36V and values the 5 year 2000 cycle warranty (2 yr 1000 cycle free replacement) this is a decent deal.
I know you can put 2 V28 batteries in series without diodes, but I haven't seen anyone comment on the V18.
[EDIT] I just realised that because the V18 and V28 use the same 3AH cells it might be possible to combine the two in series for 46V.
[EDIT] It seems both the V28 and V18 tool line has been discontinued in favor of the M12 and M18. The $80 V28 price we saw this summer may have been Milwaukee purging inventory and the V18 prices we are seeing now may be the same.