Seraph + SF M4 = ?

[Chrisdm]

I just picked up an FM 2x26500 body, how will this compare to running this head with 3x18650s? Brighter, more runtime? Both? Neither? I don't have any IMR 26500s, but I have a bunch or regular rechargeable NiMH 26500s... Thanks!

 

[Stephen Wallace]

It's not going to work on two NiMH C cells. The nominal output on a NiMH cell is 1.2 volts. Even fresh off the charger, you're looking at maybe 1.44 volts max. So between 2.4 and 2.88 volts for the two batteries - considerably lower than the 3.6/3.7 volt nominal voltage of a Li-ion cell (4.2 volts fresh off the charger), let alone the 7.2-8.4 volts for two of them.

NiMH C cells and Li-ion 26500 cells may have the same dimensions, but the different chemistries that each use lead to very different performance.

At the least, you need two LiCo Li-ion batteries. That'll give you the voltage that you need. However, the protection circuit (and I would strongly recommend protected cells when using LiCo) could limit the current draw required to get maximum brightness from this configuration. In that respect, you would no doubt do better with IMR (LiMn) 26500 Li-ion batteries instead. Funnily enough, having contacted Lumensfactory, I myself ordered the SST-90 head and a FM 2x26500 Megalennium this morning, and the latter is exactly the configuration I intend to use - IMRs.

 

[Chrisdm]

It's not going to work on two NiMH C cells. The nominal output on a NiMH cell is 1.2 volts. Even fresh off the charger, you're looking at maybe 1.44 volts max. So between 2.4 and 2.88 volts for the two batteries - considerably lower than the 3.6/3.7 volt nominal voltage of a Li-ion cell (4.2 volts fresh off the charger), let alone the 7.2-8.4 volts for two of them.

NiMH C cells and Li-ion 26500 cells may have the same dimensions, but the different chemistries that each use lead to very different performance.

At the least, you need two LiCo Li-ion batteries. That'll give you the voltage that you need. However, the protection circuit (and I would strongly recommend protected cells when using LiCo) could limit the current draw required to get maximum brightness from this configuration. In that respect, you would no doubt do better with IMR (LiMn) 26500 Li-ion batteries instead. Funnily enough, having contacted Lumensfactory, I myself ordered the SST-90 head and a FM 2x26500 Megalennium this morning, and the latter is exactly the configuration I intend to use - IMRs.

Thanks so much for the info, I am trying to grasp all this... I guess its the diff between voltage & amperage thats confusing me.. I thought voltage was what drives.. But the IMR 18650 cells I bought have the same listed voltage as my normal protected 18650s... But the IMR's push my LF SST-90 a lot brighter... So which would give me better performance with this head, 2x26650IMRs or 3x18650IMRs? I also ordered that P7 drop-in that FM recommended for that 2x26650 host, so at least my research/experimenting will net me with another cool light that I don't need

 

[Stephen Wallace]

At this point, I will bow out to someone with more experience - I don't currently have any suitable 3 cell hosts to test this - but I would suspect that the 3 cell configuration would be brighter, as per Superdave's sphere tests.

Thing is though, the eye does not perceive brightness on a linear scale, and it is often stated that you need to quadruple the lumen count in order to perceive that a light is twice as bright. In this instance, the difference in lumen count is considerably smaller, so while the 3 cell light is brighter, you wouldn't perceive much difference - as a couple of people have stated already, they perceived that the 2 cell configuration was just as bright. With that being said, the 2 cell configuration would be handier, which is why I'm happy with it.

Funnily enough, my other Megalennium 2x26500 already has the Seraph P7 turbohead on it. It was liking that head so much that made me interested in getting the SST-90 version in the first place.

 

[pageyjim]

Is the stock M6 switch appropriate for the Seraph SST-90 head?

 

[Fusion_m8]

In my M6 I am running 6xIMR123s or 3x17670s, in that configuration the tailcap sees about 2.5-2.8A which is fine with the stock twisty. If you are using a 2x18650 holder with 2xIMR18650s, the tailcap sees about 4.1A which is about the limit I'd dare to put the stock twisty tailcap through.

Is the stock M6 switch appropriate for the Seraph SST-90 head?