Originally Posted by
Richard Cranium 
I believe the old batteries were 2100mA cells and the new ones are 2250mA. This equals 3Ah increase in capacity, 42 to 45, in theory about 30 minutes more run time on high, but using two lights perhaps 20 or less.
Yeah I totally botched that post, I meant to say it was a three "watt hour" increase.
It's actually an 0.3 Ah increase in capacity, not 3 Ah (as the pack is 2s2p.)
I don't get that math either, amp hours and watt hours are apples and oranges.
Put in more useful terms, if the capacity is 7% higher, you should get 7% longer runtimes -- so if you got 3 hours before, you should get around 3 hours and 12 minutes now. 4h before? Then 4h 17m now.
Amp hours rating only accounts for current during discharge. Watt hours, at least -
unless you want educate me in another way - actually reflects "power" coming out of a light. (current x voltage)
So I compute the rating of a battery in amp hours - only in conjunction with known current flowing during light operation, and arrive at the theoretical discharge capacity in
watt-hours. if my previous testing is repeated with a newer battery, I will expect to see 10-11 watts delivered to the light head for about .3 of an hours - like my previous botched post says - 3 "watt hours." (10-11 watts x .3) - ~3-3.1
However, i do continue to be full of crap - so i could have all this wrong, but basically my assumptions still should bear out accurately in reality.
As I've said, the only "real way" is to measure is recording the current and voltage over the life of a battery cycle (time).
The bottom line, for the batteries I've been using, I'll expect about 15 minutes on high, or maybe an hour longer runt time on low. (1 hour at 3watt consumption) in other words - 3 watt hours.
But i digress.