2,8V 0,85A pr-base halogen bulb

on brocks website i saw several volt/ampere/watt relations.
the surefire e1 uses a 2.8 volt 0,7 ampere bulb.
Now when i put a 2,8v 0,85A bulb in the pt tec20 would the light output be the same ?

artar,

from a pure Watt / lumen output thingie probably yes - similar to the Tec40 with high output bulb which was discussed at length in a different thread just days ago - but you almost can´t beat SF´s beam purity - maybe PK was part of the X-files "Purity Control"

Klaus

Atar, beam quality asides, I wonder if 2 alkaline AAs could handle 0.85A at 2.8v for long without getting dim real fast.

Alan

ok...it was only i an idea

klaus, did you see the new lights at globetrotter.de ? they now have pt impact and attitude.

Alan, i dont care much about beam quality. a surefire beam is not always the right thing.

what do you think how long will the 2aa last with this bulb ?

There are many different types of incandescent bulbs, each one with different efficiency rating.

Also even same types of bulbs with the same voltage/current rating may put out different amounts of light depending on the design.

Xenon-halogen bulbs are the most efficient but burns very hot. I'm pretty sure that is what Surefure uses.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>what do you think how long will the 2aa last with this bulb ?<HR></BLOCKQUOTE>
The 0.85A current draw will probably kill it in less than 1 hour. High-capacity NiMH batteries would probably last a bit longer.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by artar:
.
Now when i put a 2,8v 0,85A bulb in the pt tec20 would the light output be the same ?<HR></BLOCKQUOTE>I hate to tell you, but that combination is going to start dim & get worse quickly. 3 NiMH's would probably give you a good beam. TX

From the data I've got it looks like AA 1700mAh NiMH and alkalines would last around 1:40 and 0:30 respectively before significant dimming.

That's the problem with numbers. It may work with pen & paper, but the 2.8V lamp pulling .85 amps is going to knock the alkalines in the dirt right out of the gate. Even the NIMH's @ 2.4V won't be bright, & when you hit them with that load, it'll be worse. For that bulb, you need 3 NIMH's & the 3.6V they supply. TX

Like I said at 0.85A the alkalines will only last about half an hour. It will actually be bright for that time, then it'll dim as the internal resistance increases.

Alkalines most of the time don't actually run at 1.5V, it drops to around 1.3 or 1.2v, then continiously decreases. Thus most battery operated devices are designed to run at these voltages.

NiMH on the other hand start off around 1.4V and then quickly drop to around 1.25V and stays that way until the battery capacity is almost depleted.

I've actually tried running a XH bulb rated at 5.5V/0.7A with both NiMH and alkalines. While I didn't run any runtime tests, the light output wasn't noticeably different.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>It may work with pen & paper, but the 2.8V lamp pulling .85 amps is going to knock the alkalines in the dirt right out of the gate<HR></BLOCKQUOTE>BTW check out the various battery datasheets. They actually give you performance characteristics with different variables (current draw, usage, resistive load, cut-off voltage).