DGX600 Burn time 18650 vs cr123a

[loosenit2]

Did an experiment today. Tested burn time on a DGX600 with the DGX sold 18650 rechargeable battery and compared it to the burn time on 2x Amazon Basic CR123a batteries. Was a little surprised by the results.

With the 18650 battery I got a 1 hour 15 min minute burn time (which was consistent with what I expected from past usage). I don't have a way to measure lumens but it was at full brightness the whole time.

I then did the burn time with 2xCR123a batteries (Amazon Basic brand). The burn time was 2 hr 43 minutes. The output on the light was obviously not the full 600 but was more than adequate. As the time went on the light dimmed slightly, which I would expect with an alkaline battery but it was still plenty bright until about 2 hours. At 2:43 it started to cycle on and off about every 5 mins.

Was pleasantly surprised that the circuit board on the DGX600 was fine producing light at the reduced voltage of the CR123a. Was truly surprised that the 2xCR123A lasted so long. Nice to know I can keep a couple of CR123A batteries in the back-up kit for an emergency.

 

[davehicks]

There are a range of capacities for 18650's. I've seen 1800-3400 mAh. What did you use?

 

[loosenit2]

There are a range of capacities for 18650's. I've seen 1800-3400 mAh. What did you use?

3000mAh.

 

[tursiops]

Did an experiment today. Tested burn time on a DGX600 with the DGX sold 18650 rechargeable battery and compared it to the burn time on 2x Amazon Basic CR123a batteries. Was a little surprised by the results.

With the 18650 battery I got a 1 hour 15 min minute burn time (which was consistent with what I expected from past usage). I don't have a way to measure lumens but it was at full brightness the whole time.

I then did the burn time with 2xCR123a batteries (Amazon Basic brand). The burn time was 2 hr 43 minutes. The output on the light was obviously not the full 600 but was more than adequate. As the time went on the light dimmed slightly, which I would expect with an alkaline battery but it was still plenty bright until about 2 hours. At 2:43 it started to cycle on and off about every 5 mins.

Was pleasantly surprised that the circuit board on the DGX600 was fine producing light at the reduced voltage of the CR123a. Was truly surprised that the 2xCR123A lasted so long. Nice to know I can keep a couple of CR123A batteries in the back-up kit for an emergency.

I don't understand this.

• the CR123A is a Lithium-Manganese Dioxide, not alkaline battery, output 3V, so two in series is 6V; typical capacity is 1500mAh. Size is 34.5x17mmm, so two in series is 17x69....an artificial 17690 cell in size. The DGX600 battery compartment must have some length to spare. Two in series still only supplies 1500 mAh.
• the 18650 is a Lithium-Ion, output, 3.7V; typical capacity is 2800 mAh.

i don't even understand how the DGX600 worked with the two CR123As. The driver board must be capable of taking 6V and knocking it down to 3.7V (or less) and thus makes better use of the available capacity?

 

[kelemvor]

I suspect the chip actually wants 5v. That means a boost converter for the lithium-ion to get the voltage up. Buck converter to take the 6v down to 5v. Boost converters are a lot less efficient than buck converters hence the discrepancy. I haven't actually looked at the circuit, but that's a simple explanation for the behavior.

Edit: I looked it up. They're using a cree xm-l2 that wants 2.77v so it's a buck converter either way. Perhaps since the cr123a can be drained far lower than the 18650 they're just doing that. With a disposable battery you don't have to worry about damaging it, so long as it doesn't burst into flames.

 

[loosenit2]

I don't understand this.

• the CR123A is a Lithium-Manganese Dioxide, not alkaline battery, output 3V, so two in series is 6V; typical capacity is 1500mAh. Size is 34.5x17mmm, so two in series is 17x69....an artificial 17690 cell in size. The DGX600 battery compartment must have some length to spare. Two in series still only supplies 1500 mAh.
• the 18650 is a Lithium-Ion, output, 3.7V; typical capacity is 2800 mAh.

i don't even understand how the DGX600 worked with the two CR123As. The driver board must be capable of taking 6V and knocking it down to 3.7V (or less) and thus makes better use of the available capacity?

I was really surprised by the result too. All of the research I had done said using cr123a batteries would not work, that it did was a pleasant surprise. That it had such alongburn time was a shocker.

 

[tursiops]

I suspect the chip actually wants 5v. That means a boost converter for the lithium-ion to get the voltage up. Buck converter to take the 6v down to 5v. Boost converters are a lot less efficient than buck converters hence the discrepancy. I haven't actually looked at the circuit, but that's a simple explanation for the behavior.

Edit: I looked it up. They're using a cree xm-l2 that wants 2.77v so it's a buck converter either way. Perhaps since the cr123a can be drained far lower than the 18650 they're just doing that. With a disposable battery you don't have to worry about damaging it, so long as it doesn't burst into flames.

Interesting info. Thanks.

 

[Grogus]

I've been running the Klarus 3400 mAh. Had 3 dives at lake Travis a week ago and my DGX600 worked as my primary through the entire time 1hr 57min. When I got home I put the batter on the charger and it was at 10%. The DGX batteries wouldn't give me much more than 1hr.

Thanks for the information!
I will be adding CR123a's to my battery kit!

 

[fmerkel]

I will be adding CR123a's to my battery kit!

The DGX seems to be one of the better/more consistent re-branded Chinese lights. But.....as @tursiops pointed out using 2xCR123 bumps up your voltage to 6.0v (vs 4.2v max with Li-on), at least for a little while. We have no idea what driver is in there, or if the same driver is spec'ed and used consistently. It's not unusual for brands like this to change components during production runs.
There is a possibility that one light might be fine with 6v, and another would not.

 

[Grogus]

It's not unusual for brands like this to change components during production runs.
There is a possibility that one light might be fine with 6v, and another would not.

I will definitely do a burn test on the bench before I make the CR123's part of my kit!
I do like the idea of traveling without a thousand different batter chargers and plug gender benders!!