Problems with Romisen RC-F4 and Ultrafire RCR123s - SOLUTION

I have been having a lot of trouble with this combination. The RC-F4 works fine with primary cells, and when I can get it to work with the 3.6v Ultrafire RCRs, it is fine. But it often will not light at all with these cells. Is it the protection circuits in the cells or what? The same cells work fine in an RC-N3 I have when used as a single cell 123 light. Once I get 2 cells that will light, they seem to work okay until I have to charge them again. Generally, they work with one protected cell and one primary, but I don't want to run them that way.

I just ordered some of AWs cells to try these. So, any ideas or advice, other than just not to use the grey Ultrafires? BTW, the Ultrafires are the DX SKU 03273. I have 2 of the RC-F4s with the Q5 from shiningbeam and one SKU 07999 from DX. It seems to be the same with all of them.

Re: Problems with Romisen RC-F4 and Ultrafire RCR123s

I guess your batteries are not doing good contact inside RC-F4.

Re: Problems with Romisen RC-F4 and Ultrafire RCR123s

No, I don't think it is a contact problem, as I can replace the rear RCR with a primary and the light will work. I thought that at first, as the Ultrafires + end does not stick out very far at all. The RC-F4 does not have a spring at the front end of the light, so I was thinking that might be the cause, but like I said, with an Ultrafire RCR in front and a primary in back, it works fine, so I don't think that is the problem. It almost has to have something to do with the protection circuit somehow. As another data point, I also have an Ultrafire C1 Q5 (DX SKU 14027), and it works with these batteries more consistently. Also, I am using the Trustfire all in one charger (DX SKU 04151), which seems to work very well so far for both RCR123s and 18600s.

Re: Problems with Romisen RC-F4 and Ultrafire RCR123s

Can you isolate the discrepancy to one particular cell?... swap cells in and out in an effort to see of the discrepancy follows one cell.

I'm guessing the spring pressure of the RC-F4 causes some kind of dis-connect in the DC protection circuit of the bum cell when the circuit board is under compression. Does the lights spring bottom out completely, and "crush" the cells? If it does, this could be the added pressure that causes the failure with the protected cells. The protection circuit adds ~2mm to the overall cell length, with a total of 4 extra mm from the two, it might be too much for the single spring of the RC-F4.

I have 4 of those gray ultrafires and two only worked for a month, while the other two are going strong. I prefer the white trustfires, as my pair have not had any problems although I think its just hit or miss luck with all of them.

FWIW... I disected one of the DX03273 cells and was a little surprised to see that the physical spring-load bearing components of the circuit are the wave soldered components!!

I went back and looked at BessieBenny's reviews of this light, and found a thread discussing a similar problem. It turns out that the problem is that protected cells are sometimes a touch too long. So, I took the head off and loosened the emitter by about one turn, then put the head back on. The light now works perfectly. The original thread mentioned having to sand the ring around the tailcap switch a bit, but seemed to conclude by noting that this might have been overkill. If you do a search for RC-F4 problem, you will find the thread, like I should have originally! Oh well....