Extremely short runtime with Surefire P90 and 2x 17500 cells.

JCD · Mar 4, 2013

I've been experimenting with upgrading my bike lights from LED to incandescent. I have a 9P and a C3, each with a P90 lamp assembly and 2x 17500 cells. One pair of cells is AW, and the other pair is UltraFire. They were purchased new about three years ago, and have fewer than 10 cycles per pair.

On the first trial run, the light with the UltraFire cells lasted about 40-45 minutes (with a 2-3 hour break after 25 minutes), and the AW cells slightly longer. That was about what I expected, given the age of the cells. The outside temperature that night was around 45º F (about 7º C). Every subsequent run, the light with the UF cells goes out after about 10 minutes, and the light with the AW cells lasts only slightly longer. Until tonight, I thought the problem might be the sub-freezing temperatures, but tonight the temperature was about 55º F (about 13º C) and the lights again shut off quickly.

As soon as the light goes out, I switch the hosts off, without exception. I've tried switching which light gets which pair of cells, with no discernible difference. I keep the tailcaps locked out when the lights are not in use, so I can rule out accidental activation while they are in my backpack.

Checking the voltage before I put the lights on the charger, the UF cells read just over 4.0 V, and the AW cells read just under 4.0 V. When they come off the charger (XTAR WP6II), they read around 4.21-4.22 V, which is well within recommended range.

What is causing the P90s to shut down so soon?

ampdude · Mar 5, 2013

JCD said:
I've been experimenting with upgrading my bike lights from LED to incandescent. I have a 9P and a C3, each with a P90 lamp assembly and 2x 17500 cells. One pair of cells is AW, and the other pair is UltraFire. They were purchased new about three years ago, and have fewer than 10 cycles per pair.

On the first trial run, the light with the UltraFire cells lasted about 40-45 minutes (with a 2-3 hour break after 25 minutes), and the AW cells slightly longer. That was about what I expected, given the age of the cells. The outside temperature that night was around 45º F (about 7º C). Every subsequent run, the light with the UF cells goes out after about 10 minutes, and the light with the AW cells lasts only slightly longer. Until tonight, I thought the problem might be the sub-freezing temperatures, but tonight the temperature was about 55º F (about 13º C) and the lights again shut off quickly.

As soon as the light goes out, I switch the hosts off, without exception. I've tried switching which light gets which pair of cells, with no discernible difference. I keep the tailcaps locked out when the lights are not in use, so I can rule out accidental activation while they are in my backpack.

Checking the voltage before I put the lights on the charger, the UF cells read just over 4.0 V, and the AW cells read just under 4.0 V. When they come off the charger (XTAR WP6II), they read around 4.21-4.22 V, which is well within recommended range.

What is causing the P90s to shut down so soon?

Maybe the cells were on their last legs. Sometimes if you run old li-ion cells down they will not come back. But then it's strange both did the same thing. I'd try ordering a new pair of cells first and see if it's the cells and then I'd look closer at the charger if you still have the same problem. But if the cells are dead at just under 4 volts it really seems like there's something strange with them. Is the charger set correctly?

JCD · Mar 5, 2013

ampdude said:
Maybe the cells were on their last legs. Sometimes if you run old li-ion cells down they will not come back. But then it's strange both did the same thing. I'd try ordering a new pair of cells first and see if it's the cells and then I'd look closer at the charger if you still have the same problem. But if the cells are dead at just under 4 volts it really seems like there's something strange with them. Is the charger set correctly?

Thanks for the reply. The 17670 cells I use in my 6Ps are charged in the same charger and work as expected. (It might be worth noting that the Xtar charger recently replaced my Trustfire charger (model 001, I think, but I'm not at home to verify the exact model number). I don't see any way to change the settings on the Xtar charger. The 17670 cells I use are as old and older than the 17500 cells I'm using with the P90s, but they have been used regularly, while the 17500 cells have been kept charged in lights that have been rarely used. I'm not sure how non-use affects cell life.

Brigadier · Mar 5, 2013

The world needs AW 17500 IMR's in the worst way

Illum · Mar 5, 2013

Colder it is, the less chemical reactions occur and therefore sharper voltage sag. Colder it is, the higher filament resistance you'll see. It would seem that once the P90 gets hot enough this wouldn't be an issue, but the batteries themselves don't like the cold.

I use the P90+2x17500 setup in my work light, it was 40F yesterday night... a set of 1 year old AW17500s only lasted me 15 minutes, whereas on 80F nights it'll run 30- minutes with no issues.

JCD · Mar 5, 2013

Illum said:
Colder it is, the less chemical reactions occur and therefore sharper voltage sag. Colder it is, the higher filament resistance you'll see. It would seem that once the P90 gets hot enough this wouldn't be an issue, but the batteries themselves don't like the cold.

I use the P90+2x17500 setup in my work light, it was 40F yesterday night... a set of 1 year old AW17500s only lasted me 15 minutes, whereas on 80F nights it'll run 30- minutes with no issues.

Thanks for sharing your own experience with a very similar setup.

Temperature was my first thought regarding the short runtime. I had tentatively ruled it out after I experienced the much shorter runtime in 55º F temperatures than in the 45º temps of my first trial run. Also, I don't notice large runtime differences with my LED equipped 6Ps in different temps. From your experience, it appears I may have ruled it out prematurely.

It is plausible that wind speed plays a larger role in the cooling than I thought. If my first trial run occurred with a tailwind (I didn't note the wind speed or direction, so I can't be sure what the wind was doing), the flashlights would have been moving through the air at a much lower speed than if I rode into a headwind, or even through still air or crosswind. The 6Ps have less exposed surface area than the 9P & C3, so they would cool less effectively, all else equal. That might explain the inconsistencies observed.

Regardless, it appears I need to reconsider temperature as a possible factor. I might have to come up with some sort of flashlight koozie to see how it affects runtime.

JCD · Mar 5, 2013

I warmed my lights up to body temperature before riding one way of my commute, which is a 16-20 minute ride each direction. The temperature was 30º F, with a small headwind (plus the speed of my bike). I only used the light with the AW cells, but it was still going when I arrived at my destination. It seemed like it might have been dimming near the end, but the ambient light was also increasing significantly at about the same time, so it may have been my imagination. I'll repeat the experiment on the return leg with the Ultrafire cells.

HotWire · Mar 6, 2013

I bored one of my 9Ps and use IMR 18650 cells. It seems brighter and has good run time, but I've never checked it. I switch out the batteries at the first sign of dimming. Most batteries don't like being drained completely. I'd avoid that, even if you need to carry spare batteries.

JCD · Mar 6, 2013

HotWire said:
Most batteries don't like being drained completely. I'd avoid that, even if you need to carry spare batteries.

This probably sounds like a silly question, but what exactly do you mean by "drained completely"? When the runtime is very short before the P90 goes out, the cells read right around 4.0 volts, with the Ultrafire cells reading slightly higher and the AW cells reading slightly lower. So, does drained completely mean drained down to 3.6 volts or lower, or does it mean used until they no longer power the lamp? I've always assumed it means drained down to 3.6 volts or lower, but we all know what happens when we assume things.

HotWire · Mar 6, 2013

I would say that running the P90 until the light goes out is "drained completely." There might be some measurable voltage left, but it will not be good for the battery to be so stressed. There is information here: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

JCD · Mar 6, 2013

JCD said:
I warmed my lights up to body temperature before riding one way of my commute, which is a 16-20 minute ride each direction. The temperature was 30º F, with a small headwind (plus the speed of my bike). I only used the light with the AW cells, but it was still going when I arrived at my destination. It seemed like it might have been dimming near the end, but the ambient light was also increasing significantly at about the same time, so it may have been my imagination. I'll repeat the experiment on the return leg with the Ultrafire cells.

On the way back home (27º F, slight tailwind), both lights started at body temperature. I started out using the light with the Ultrafire cells. They lasted between 5-10 minutes only. At that point, I turned on the light with AW cells, which had not yet been charged. It lasted the rest of the way.

I'll replicate the experiment before reaching any conclusions, but it does appear that low temperature is indeed the culprit. Next time I make the round trip after dark, I'll try the AW cells for the entirety of both legs.

Illum · Mar 6, 2013

The P90 will look orange-ish in the shotpot when the batteries approach 3.8v. They were designed to be operated at essentially 8V. tried running a P90 on a bench supply set at 9V... blew rather quickly. Same goes for P60s on 6V, they love 5V

JCD said:
Temperature was my first thought regarding the short runtime. I had tentatively ruled it out after I experienced the much shorter runtime in 55º F temperatures than in the 45º temps of my first trial run. Also, I don't notice large runtime differences with my LED equipped 6Ps in different temps. From your experience, it appears I may have ruled it out prematurely.

It is plausible that wind speed plays a larger role in the cooling than I thought.

Well, just to put it out there, wind didn't play a factor in my test, my light was stored in a bucketboss pouch and sat in the bed of a pickup until I needed it. After every use, regardless of duration, usually by the time I close shop it's back on the charger. Gotta love AW's protected cells, don't have to keep an eye on them every other minute.

SemiMan · Mar 6, 2013

JCD said:
They were purchased new about three years ago, and have fewer than 10 cycles per pair.

JCD said:
The 17670 cells I use are as old and older than the 17500 cells I'm using with the P90s, but they have been used regularly, while the 17500 cells have been kept charged in lights that have been rarely used. I'm not sure how non-use affects cell life.

Lithium-Ion fully charged at room temperature can lose 20% of their capacity per year. If they are stored warmer (car in a warm climate), then they will lose even more.

Those batteries could be at 50% of their original capacity (or worse). Depending on the cutoff voltage, you may have started out only using 80-90% of the pack, so now you are down to say 40% of the original installed capacity.

This is lost capacity, it does not come back. In addition, I would expect internal resistance to rise and that has temperature dependence so this would make the cold issues even worse.

Semiman

fivemega · Mar 6, 2013

Illum said:
The P90 will look orange-ish in the shotpot when the batteries approach 3.8v. They were designed to be operated at essentially 8V. tried running a P90 on a bench supply set at 9V... blew rather quickly. Same goes for P60s on 6V, they love 5V

As you mentioned, P60 works fine (infact designed for) 5 volts or 2.5 volts per cell. Therefore P90 (which has same current draw) is designed for 7.5 volts or 3.75 per Li-ion.

JCD · Mar 16, 2013

I resumed my experimentation last night. The temperature was almost 60º F. My trip was about twice as long as usual.

The Ultrafire cells lasted about 15-18 minutes. The AW cells lasted approximately 45-50 minutes. I can live with that AW runtime, considering the cells are about three years old and haven't been stored with optimal charge.

It appears that the cold weather was the culprit for the short runtime, and that the UF cells are shot. Well, when I bought them, I bought one pair of each to see if there was a real difference. It looks like there is. (To be fair, the sample size is too small to justifiably and confidently draw such a conclusion, but I still won't be buying any more UF cells.)

JCD · Mar 16, 2013

Almost forgot: Thanks, everyone, for your input.

taylorst · Jul 21, 2014

JCD said:
Almost forgot: Thanks, everyone, for your input.

Here's what I'm thinking:
1. Your batteries are just too old after resting for so many years. For lithium ion batteries, you have to charge them for every 3 months to protect them from being totally drained. My concern is thoese batteries could being totally drained during the past three years which caused a non-recovery capacity lose.

2. Temperature factor. Low temperature will not allow all the energy inside being discharged out because the chemical reaction inside is limited as the temperature get those reactions activities decreased.

If you want to know some more about the battery, here's some useful information. http://www.transret.com/faq.html

fivemega · Jul 29, 2014

With high capacity 26650 cells, P90 will run LLOONNGG time in 2x26650 host.

ampdude · Aug 14, 2014

Brigadier said:
The world needs AW 17500 IMR's in the worst way

Tell me about it! I've been trying to convince AW since he first introduced IMR's. No one else seems to make them either.

Extremely short runtime with Surefire P90 and 2x 17500 cells.

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