The true test is can you charge them in a standard desktop charger. If you can’t, they are proprietary and should be avoided.
It would be very dangerous to charge these in a normal charger, since chargers often are made for multiple sizes of cells and the positive terminal is not just a button but rather a rectangle, and if it has raised points it could contact both the positive and negative terminals of the batteries at the same time since they are on the same side, shoring the cell.
You can’t without risking shorting due to the negative on the positive side. Once I modified the modified battery with insulators I could.
Once again, that too is not exactly correct. The high current drain is not the issue requiring protected cells. The fact that these 4 batteries are in parallel with common positive and negative termination points is the issue with unprotected cells. In such a setup, an internal short in any 1 battery would cause the other 3 to overheat badly, perhaps even catch on fire, even with the light off. 4x21700 high drain batteries provide way more current that this led requires. That is not the case with an internal short of 1 battery which effectively completes the circuit with a 0 resistence load. I would not recommend even a 2 cell light having unprotected batteries, but 4 cells might burn someones house down as they sleep. With 1 cell, the protection can be in the lights PCB. I had no issue with protected batteries. The idiotic negative termination point on the positive side serving no purpose, was my issue with the design. As designed that negative only touches an insulator, so there is no reason for it to be there. I was an electrician/mechanical troubleshooter so I know electronics. The only really safe means of protecting 4 cells in the light itself would require 4 seperate termination points to the lights circuits.
Or just use a mechanical lockout, by unscrewing the tube or tail half a turn.
I feel that just had those protected cells already designed and wanted to use them rather than getting new ones made.
Mechanical lockout might avert disaster if using unprotected cells, because in truth, during use an internal short of the battery would make the light too hot to hold before venting. In that case, you could then unscrew the head or toss the light a safe distance away. I know in my case, I would at some point forget. Now I should stress that only an internal short of a battery would cause such an issue, and that is admittedly a fairly rare event, so chances are better than not, it would not happen. The potential is there however. It is sort of like failing to change batteries in a smoke alarm, most would get away with that, but such oversite can, and has cost lives. In both cases, it is not worth the risk to life or losing your house, IMO.
Probably the case, there may very well be other Thrunite lights that actuallly use the negative post on the positive side. Using them in this light made them very proprietary, whether that was their intent or not. The removal of the insulator, and adding 20 cents worth of insulator to the batteries fixed the issue, so not a big deal for someone who is aware of the issue, and knows about the fix. I don’t really like how close those negative screws are to the positive ring, but my fluke meter indicates that it is not touching, showing high mega-ohms resistence, so it is safe, in spite of how close it looks. It was close enough for me to check that prior to putting the batteries in.
Excuse me my ignorance, but i see you ranting about unprotected cells.
You do know you’re on BLF here?
You do know about the BLF Q8?
And many other lights that use the same principle?
The original TN42 has always been one of the lights that I always wanted to have but couldn’t justify the expense. From what others said it was a good host with a good reflector and it was very lightweight considering its capabilities.
4x21700….thanks but no thanks. 4x18650 is as thick as I’m willing to handle and even that is too large for comfort.
Which is why my BLFQ8 and Sofirn Q8 both have protected cells in them. I do not care what they ship with, if it has 4 cells with common termination points it gets protected batteries period. My Nitecore TM16GT has 4 unprotected cells, but also has 4 seperate termination points and the protection is built into the light. What was hard to understand about my statement that any such designed light needs protected cells.
^
To each his own.I have been using UNPROTECTED CELLS in ALL my lights for 8 years Never One issue.
I have heard many debate on these forums that Unprotected cells are actually safer…can not recall the exact detail as to why.
I think the protection part of the protection circuit diminishes the more cells a light has. You really need a BMS with four cells to be “protected.” On the other hand, if you don’t do foolish things and try to use four used batteries from four different broken laptops, you should be fine with unprotected. Matter of fact , unprotected is always recommended for performance lights.
You may never have an issue, but the fact remains, with four cells that connect all the positive contacts together, and all the negative contacts together, it is a safety issue. Even with the switch off, and internal short in any one cell becomes a 0 ohm load and starts drawing maximum power from the other 3 cells until the batteries vent, of burns through the shorted cell until it opens. In either case the condition can and has burned peoples house down. I will give you the fact that such a short is a somewhat rare occourance, and if it happened while using the light it would be apparent, and the light would be too hot to hold. Having had a major house fire due to teenagers breaking in and catching my house on fire, I will err on the side of caution. The protection circuits on batteries does not engage until 10-12 amps, so the batteries can supply between 40-48 amps to the light.
Well the 21700 Thrunite modified batteries are now showing on their website, and they are now 5000 mah. They are a very high price of 25.95 each. I will stick with the Orbtronics 5000mah protected 21700 that sale for 13.95. Using those requires removal of the plastic insulator head in the light. It also requires use of insulators that cover the unnecessary negative post on the positive side to use the thrunite batteries that came with the light also. So thrunite is selling their batteries of the same capacity for 12 dollars more, but includes a negative post that is not needed for any function in this light. The negative post on the positive side only contacts the insulator ring that also prevents the orbtronic cells from working. The insulator ring is held in the head by three screws that also hold in the PCB, so they must be re-installed after removing the insulator ring. A simple fix to save 48 bucks for 4 extra batteries. I have bought many batteries from orbtronics, and they use high quality cells.
Strange as it may seem, the actual feel of the added thickness of the base over the feel of a 4x18650 base is not a problem for me. I know the added diamater must be there, unless the carriage also adds that much in a 4x18650 carrier. I doubt that, but have not measured. I just know when in my hand, I am not thinking of the extra tube diamater. With the mods completed on the head and the batteries, I actually like the light much better. My next target is the Acebeam K75, if only I can someday find a sale or discount code to get that one in my light budget. That is just a very expensive light. Does it ever go on sale? I have been lusting over that one a while. If I can ever secure one in the 200-225 dollar range I will likely pull the trigger. Go figure, as an avid gun collector, 300 bucks is a low starting point for a decent sidearm. A few years back, I would never have even imagined spending 200 bucks for a flashlight though. I need cheaper hobbies.
I have been seriously looking into lights of this size for the first time since I started this hobby in the last month. I just bought a MF02s v2 sbt90.2, and I have been plotting my acquisition of the k75, which when all said and done seems to be the best in class after ouch research (which seems can be attributed to its reflector & driver 4 batteries in series I believe!?)
Anyway, I also am having a hard time with the $275 price tag.
But also - the WildTrails WT90 group buy which is only weeks away from fruition, which is also led by TexasAce! Tom E has been testing the Prototype, and looks like a clear winner in the same size as this Tn42, but with more throw.
I’m buying one, definitely. Oh and it comes in clear aluminum anodized. Check it out
Thanks for the discussion here. I learned a lot.
A simple question: I want to get a second set of batteries for backup. What should I get? I prefer not to modify the light.
The proprietary batteries from thrunit are the only option that I know of that will work without modifying the light. If others will work I have not found them.
I measured my TN42 V2 as well 1.2Mcd. Measured 3020 lux at 20 meter distance. This was at switch on.