Direct drive p7 maglite draw

I have a no load voltage of 4.6 volts using alkalines. I am seeing 1.25 amp draw at the tailcap. Is this correct? I thought the draw would be more. Is the alkalines sagging too much under load?

I am using Duracell's and I see 1.65A at tailcap measurment after 5 minutes. Using CSWOJ. When using 3x NiMh setup I see 4A at the start and goes down to 3.2A after 5 minutes.

Dorkwheeler said:

I have a no load voltage of 4.6 volts using alkalines. I am seeing 1.25 amp draw at the tailcap. Is this correct? I thought the draw would be more. Is the alkalines sagging too much under load?

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Don't be too surprised. Alkalines aren't able to supply power like NiMH, NiCad, or Li-ion batteries can.

Well it looks like i'm going to have to get some D size NiMH

What's the burden voltage imposed by your ammeter?

burden voltage means?

How big a voltage drop does your ammeter impose on the circuit?

Ok, Alkaline batteries may not work brightly on a direct drive 3D set up, but what about using a circuit running at 3amps. Would the alkaline cell handle that kind of draw?

I would like to have a P7 that could run on anything that that I can find at a grocery store.

If the P7 is only drawing a little over a amp on alkalines, I might as well use a SSC U bin and save the cost of the P7. Comments?

Nell said:

If the P7 is only drawing a little over a amp on alkalines, I might as well use a SSC U bin and save the cost of the P7. Comments?

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Comment: "That makes sense." If those are fresh alkalines the current draw will only go downhill from there as they flatten. These are D cells, right?

Alkaline batteries have higher internal resistance than do rechargeables. More internal resistance means more of a voltage drop across the load. Meaning the voltage from the battery will sag. As the battery discharges the voltage sag gets worse. Rechargeable batteries maintain a lower internal resistance while they discharge.
Alkaline batteries are actually great for a softer start to an incandescent light bulb because of the sag for the inital surge current. They are terrible for a high constant current load requirement. Use rechargeables or cut the load current requirement to under 1 amp. Nickel Cadmium batteries are actually very good for delivering high continuous load currents as a rechargeable. It was one of their features. The maintenance requirements to get rid of or prevent internal gas bubbles that caused "memory effect" (limited charge holding capacity) is what ruined their popularity.

The voltage drop across most new digital multimeters in ammeter mode is somewhere in the 10mV no more than 100mV worst case range, it should be insignificant for most readings. The real problem is the voltage sag of alkaline batteries. Lower temperature will make it worse also.

TorchBoy said:

Comment: "That makes sense." If those are fresh alkalines the current draw will only go downhill from there as they flatten. These are D cells, right?

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Yes, they would be D cells.

eprom said:

I am using Duracell's and I see 1.65A at tailcap measurment after 5 minutes. Using CSWOH. When using 3x NiMh setup I see 4A at the start and goes down to 3.2A after 5 minutes.

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Where did you get the H bin?

Pardon, Bin Code Corrected as CSWOJ from KD...

I'm running a p7 in a 3d maglite too. I tried it direct, then switched to stefan's how to thread setup. I haven't tried it with NIMH yet, though. It's pretty bright with alkaline.

Is there any advantage to using the CSXOI bin vs the J vF bin? How does vF affect the light output using 3 d cells?

I have the same led from Kd, but I'm afraid to put it in the 3d maglite because maybe the batteries won't have enough volts during discharge. Is that stupid? of does it make sense?

Sorry if this is a newb question.