The limiting factor is the MCU (Micro Controller Unit) which is specified running from 2V to 5.5V. Add to this about 0.3V for the schottky diode that feeds the MCU (polarity protection). Then you have the range 2.3V to 5.8V for guarantied running. The absolute maximum voltage is specified to 6.5V, that becomes 6.8V battery voltage. Above that you could destroy the MCU. The low voltage is given by Vf of the LED (plus a small voltage drop, say 0.15V in the 7135's) or about 3V.
So it is possible to run the Nanjg 105A with 2 x CR123A but not very safe/not recommended to do so over any longer period of time, if I understood correctly?
I will be happy to measure the current draw, but am not able to do it yet. Thanks to our dear government I could not buy a drop-in with XM-L which costs way over our import limit, so I had to make two orders of one XM-L star each at DX. That happened dec.23 and I have heard nothing from them since. I have a Skyray P60 host and reflector with pill ready to assemble my first XM-L light.
The percentage numbers in my review are from oscilloscope measurements of pulse width's.
I think it will be safe (but expensive) to use 2 x CR123A 3V primaries if you only look at voltages. But there will be generated lots of heat. The two extra Volts dropped in the regulator at 2.8 Amp will generate 2 x 2.8 = 5.6 Watt on top of the 10-11 Watt with a single Li-Ion cell. That must be a no-go.
I think the free of duty limit is set by the EU. The UK version is £18 which is roughly the same amount. But our Post Office doesn't seem to care much about stuff from China. Up until now, I have never had any order queried or opened. And I doubt Customs here are all that bothered.
Since the values on the packages are all incorrect, what our customs know, they check them from time to time. Sure they are unable to estimate the real value either way. But when they open one and they feel like asking for a proof, they usually charge 11 euros for the procedure, regardless if the receipt shows, it was less than 22 euros or not. When I order goods from a store, where I have to pay the shippment I don't split the orders. Usually, three out of four of them go through anyway without to get checked. So finally, when I count all together I still win.
The limit where you have to pay 25% VAT is 80 Danish Crowns and has NOT been changed in 15 years!. That limit is equal to about $13.80 but the PO add another $28 fee to do you the favour. That way an order of $14 becomes $45 . In the Christmas razzia I got confiscated 3 lights costing around $16 each. I will not throw good money after bad ones so I just cry a little and wait for another opportunity to re-order. The PO returns the goods to HK I think.
We only have to pay toll on orders bigger than about $198 and normally this is only 6%.