Princeton Tec 40 (bulbs) and NiMH (batteries)

[lemlux]

Reliability Report:

I've been using the KPR 139 3.85 V 1.20 A bulbs off and on for a while now in the PT40 with no visible damage to the reflector. It runs fairly hot, but apparently cooler than an XPR or HPR of the same amperage would.

I'm very happy with the combination. The color temperature is similar to that of my 8X and it's only slightly dimmer. This PT40 combo is considerably brighter than my E2.

 

[lemlux]

Grummond:

KPR 3.6V but what amperage? Many C and D cell 3 cell OEM lamps are .75 amps.

It seems that many CPF'ers are using Nimhs and KPR 3.6V or 3.7V .75 amp bulbs. With Lithium AA's you are overdriving the bulb more. With lithium AA's, I'd be inclined to use a 4 cell xenon bulb rated at between 4.8V and 5.2V and amperage of between 0.7 and 0.85.

Those of us who use higher amperage bulbs are testing the temperature tolerance of the PT40 reflector and lens.

The 3.85 1.2 amp KPR and a 4.0V HPR 1.0 Amp bulb is available through topbulb.com. The first bulb is $1.41. The second is $2.57. Shipping is $5.95 per order.

Krypton Bulbs seem to be much more tolerant of overdriving than Xenon or Halogen. Remember to figure in your voltage drop. Brocks incandescent sheet gives you a good feel for what voltage drops you'll see with various combinations of batteries and current draws.

Krypton bulbs, available at < $2 most places are painlesss for most of us to drive to a short life expectancy because they're so cheap. We save far more than the bulb cost with Nimhs.

With the 1.2 A KPR 3.85V and 1800 mAh GP Nimh's I'm getting over an hour before I recharge. Relatively new batteries should run for > 75 minutes. It's so easy to rotate my stock of recharged Nimh batteries that I rarely run them down much beyond a half hour in practice.

 

[Grummond]

Lemlux:
Of course I should have mentioned the Amps, you are correct however it is .75
It's a Philips, if I remember correctly it cost about 29 kroner (about $3) so as long as I don't damage the reflector I don't mind playing around with these.

 

[lemlux]

Grummond:

No problem with that .75 amp bulb. You can run with considerably more safely.

 

[Grummond]

Lemlux
Wow, you weren't kidding, I could not find a KPR 3.85v bulb, but I did find a KPR 3.6v and stuck it in the Tec40 and it is brighter than my 6P with fresh Duracells.

I know I am seriously overdriving the bulb and am going to have to take it out again and put it back where I found it, which in this case was my girlfriends 3D Philips! (not only do I have to worry about melting the Tec40 reflector, I could be in for a severe talking to if it blows!)

What kind of run time are you getting from a KPR 3.85?

 

[Grummond]

Sorry I should have mentioned, I am running it with a fresh set of Energizer e2 Lithiums which also helps the brightness.

 

[FNG]

I found that Radio Shack Canada, http://www.radioshack.ca , has the #23-410 for $70 Canadian which is about $45 US. I dont know if itll be a lot extra to ship to the US. The C Crane unit is $50 shipped.

 

[lemlux]

BrightNorm:

Energizer shows a graph on semi log paper for alkaline batteries that doesn't mention size, but shows the relative reduction of capacity to 1.0 V at various amperage drains. I think the 14 Ah low drain capacity suggests that Energizer is using D cells as their reference.

AA cells would experience much greater internal resistance. For example, I imagine that the AA curve probably parallels the D curve at about half the drain rates.

Points from Energizer Graph
10 mA = 14 Ah
100 mA = 12 Ah
200 mA = 10 Ah
300 mA = 8 Ah
400 mA = 7 Ah
550 mA = 6 Ah
700 mA = 5 Ah
1000 mA = 4 Ah
1050 mA = 2 Ah
1100 mA = 1 Ah

This steep curve is why you never see alkaline cells marketed with capacity data the way you do with Nimh and NiCad.

This curve is also why I use rechargeable Alkalines in some of my infrequently used flashlights that have high amperage draws.

Commonly, the brightest available D cell bulbs for alkalines have a drain of .85 Amps placing them on a run time of about 4.5 Ah hours = 5.3 hours run time. I'll run 1.0 A bulbs that have a 4 hour forecast run rate with D's. My PR base bulbs drawing between 1.2A and 1.7 A are run only with Rechargeable Nicads or Nimh's.

The rechargeable alkaline batteries don't appreciably self discharge, and the battery recharges more fully from a fast discharge to a given charge level than it would if it were more efficiently discharged to the same capacity level.

For frequent use and long run use I use Nimh's

Energizer shows a graph of run time vs. amperage drain on log / log paper that shows a series of almost straight lines. This is because the capacity changes little with drain.

I've seen posts that suggest that AA Alkalines will only last about 30% as long as AA Nimh's at 400 mA. At 750 mA the ratio should be considerably worse.

PT estimates that the Surge which draws 550 ma per cell will run for three to five hours. Probably three hours with Alkalines and five hours with Alkalines. Effective Alkaline capacity for the Surge at 550 mA is therefore probably around 1650 mAh compared to 6000 mAh at 550 mA with a D cell.

I would guess that the .75 A bulbs would probably cause a severe voltage drop and rapid dimming with alkaline AA's. Capacity would probably be in the neighborhood of an hour.

 

[brightnorm]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by lemlux:
Grummond:

No problem with that .75 amp bulb. You can run with considerably more safely.<HR></BLOCKQUOTE>

Lemlux,

Do you have any idea how long this will run with alkalines?

Brightnorm