P7 Battery Advice

[Dan Harris]

Gentlemen:

I need your advice in selecting the right battery configuration to power a direct drive P7 in a Mag 2C or 2D

I can build things, but I'm a noob when discussing batteries more complex than a CR123 or Eneloop! I just built a 2D ROP using a 6AA>2D adapter and while it's a hoot playing with at the dock, I need much better run time.

This will be a serious duty light, used in a marine environment, so reliability, simplicity and rechargability are the goals. Staying with the 2 cell length gives a good compromise with portability and "impactfullness."

I would like to stay away from unregulated cells or ones with a propensity to go poof, boom or bang! Ease of reloading in the field is important, as I dropped a partially loaded 6AA>2d adapter while putting in new cells. Eneloops do not float in salt water! :shakehead

I will need 2 sets and a charger. Estimated run times would be very helpful. Also, if alkalines can be used in an emergency, that would be a big plus.

CPF is an incredible source of knowledge and I thank you all for sharing!

Dan

 

[Gunnerboy]

I believe you can only direct drive a P7 with one li-ion cell, unless the multiple li-ion cells are in parallel configuration. For multiple li-ions in series, you'll need a buck-converter.

How about a Mag2D running two of AW's protected C-cells using one of member Der Wichtel's P7 buck converters? The extra length of those cells plus the buck circuit may not fit in the shorter Mag2C.

You can direct drive a P7 with three NiMH cells in series.

I know you want to build it yourself, but member ElektroLumens sells a ready to use direct drive P7 in a Mag3D designed for three NiMH, but will run on alkalines if needed.

Cheers,
Gary

 

[gswitter]

3x NiMH cells in series will direct drive a P7 just fine. You can fit three C's in a 2D Mag (or a 3C, obviously), though I think the extra run time of three D's in 3D Mag might be worth the increase in size.

A direct driven P7 will draw ~2.8A, so figure a little under 2 hours run time on 5000mAh C cells or double that on 10,000mAh D cells.

Alkaline cells can be used as well, but the output will be lower.

 

[jcvjcvjcvjcv]

For a 2D P7: three Ni-Mh C cells. Two AW C cells parallel would also be possible, but requires a more complicated adapter and would cost more, but would also give the option to save weight and only put one cell in it, but that's not good for the "impactfullness" offcourse

A 3D with 3x Ni-Mh D cells has indeed double the runtime at the cost of 60mm more length and a lot more weight. My MagLite 3D P7 (CxxxI) Direct-Drive on three AccuPower LSD 10,000 mAh D cells has a weight of 880 gram, just 10% more then my Mag85.

 

[divinginn]

I have mine set up using 3 nmh c cells in a 2 d light,had to cut the spring shorter and cut a piece of pvc for a sleeve for the narrower c cell batts.I have been happy with the set up,very reliable with good burn times.

 

[eFxA2C]

you can't direct drive a p7 with just 2 NiMh D batteries ?

 

[Cydonia]

you can't direct drive a p7 with just 2 NiMh D batteries ?

2.4v is too low a voltage for it to light I think.

 

[spc]

I have mine set up using 3 nmh c cells in a 2 d light,had to cut the spring shorter and cut a piece of pvc for a sleeve for the narrower c cell batts.I have been happy with the set up,very reliable with good burn times.

x2! I think its the best way to go..
reliable indeed.

 

[Dan Harris]

Thanks for all of your input! I think a Mag 2D with 3 NIMH C cells would work very well for my needs.

Having used Eneloops for a while, I like the concept of low self discharge cells. I found these: http://thomasdistributing.com/shop/...html?SP_id=&osCsid=825pmu1rld5gjn0hdpkucl5nm3

Upon further reading, I found that the P7 comes in several flavors: DSXPJ, DSWOI, etc. Given the 3 C cells, which led is best?

Is there much difference between heat sinks?

gswitter & spc - You guys build some really nice lights!!!

Am I missing anything?

Thanks for the help!

Dan

 

[gswitter]

Having used Eneloops for a while, I like the concept of low self discharge cells. I found these: http://thomasdistributing.com/shop/...html?SP_id=&osCsid=825pmu1rld5gjn0hdpkucl5nm3

Upon further reading, I found that the P7 comes in several flavors: DSXPJ, DSWOI, etc. Given the 3 C cells, which led is best?

I use those Accupower LSD C cells in a couple lights. Neither light is a daily user, so I haven't beat on the cells too much, but I haven't had any problems with them.

As for the different P7 emitters, the first letter in the bin code specifies the luminous flux, the next three letters specify the color, and the last letter specifies the forward voltage. (See the "P7 series binning & labeling" doc available here for more info.)

• DSXPJ: "D" - 800-900 lumens, "SXP" - 6700K, "J" - 3.50v-3.75v
• DSWOI: "D" - 800-900 lumens, "SWO" - 6050K, "I" - 3.25v-3.50v

I'll leave it to someone else to recommend a specific emitter. I don't know if it's better to have the higher vF to account for the initial voltage of the cells (which will be closer to 4.5v total), or the lower vF to account for the voltage sag under the 2.8A load, or whatever other consideration I haven't thought of.

For what it's worth, I actually bought my P7 Mag mod. Wish I would have done it myself and added a TaskLED PWM driver.

 

[spc]

Thanks!

As for the emitter, out of the 2 colors you have listed, I would choose the *SWO* because it is warmer than *SXP*.

I never tried a I bin p7(3.25-3.50v) with 3nimh cells(3.6v), but I don't think it would hurt anything because there is a tiny voltage drop. I would make sure to rest them after charging so you don't spike it.. I wouldn't use a li-ion with a I bin, that could be too much power.

I would use a J bin to be safe, it can handle a little more voltage.

My fav emitter so far is the DSWOJ- good volt/color combo handles a li-ion great and also 3nimh cells.

 

[jimmyswan]

Dont mean to hijack this thread but I have a question that relates. I have a 3 d mag with a P7 running direct drive. At first i ran on 3 d alkalines and everything looked good. Swithed to 3D Tenergy NiMh's and it looks good for about 20 seconds then LED starts turning blue. I'm new to all this so bear with me here, I checked resistance from negative side of batteries to inside tube and read around 2.8a at first, then it rose to around 4a when LED turns blue.What's going on?

Now it gets worse, just put alkys back in and it still turns blue. Did I just ruin my P7?

 

[gswitter]

Assuming the P7 behaves like the P4 when it gets hot, it sounds like the LED has insufficient heat sinking.

 

[PCC]

2.4v is too low a voltage for it to light I think.

It'll light but it won't be very bright. Somewhere around 40 lumens, I think.

 

[Mike Painter]

At first i ran on 3 d alkalines and everything looked good. Swithed to 3D Tenergy NiMh's and it looks good for about 20 seconds then LED starts turning blue. I'm new to all this so bear with me here, I checked resistance from negative side of batteries to inside tube and read around 2.8a at first, then it rose to around 4a when LED turns blue.What's going on?

This is a lesson that most seem to have forgotten in the last few years.
In an Incan the bulb has a much higher resistance that the battery, wires, switches so there is no need to be concerned with anything but the right bulb for the voltage.
A LED has a very low resistance in one direction. Without some regulation it is *only* the internal resistance of the battery that limits the amperage to the LED. Alkalines have a high resistance so you got a safe current draw.
Rechargeables have a low resistance so the LED saw a lot more current.

The rules haven't changed from "the old days" and a lot of people experienced what you have, only with three dollar LEDs.
There has been a lot of comment here about thin wires being used on some commercial P7's and I think it is done becasue it is cheaper than putting a resistor in the line.

 

[jimmyswan]

So is the LED shot Or can I use a buck convertor and have no issues from here on out?

 

[nailbender]

Hey Jimmy it depends on if the led stay blue all the time if it lights full strength and then turns blue there is chance as has been said it is getting hot but if it stays blue all the time then it is probably in pretty bad shape.
Alot of the buck converters are going to want at least five or 5.5 to be able to regulate which you are only 4.5 or so.
I build 3d using tenergy 10,000 mah batteries and use dsxpj and have no problem running at extended periods of time. Unless it is real low C bin you should be able to run on that.

Dave

 

[jimmyswan]

Thanks for the reply Dave and everyone else, I'll try one of DX's convertors and hope for the best. Hopefully this helps the OP before he runs into any problems like I have.

Dave, is it possible for you to post a link to what your using. Thanks.

 

[nailbender]

The 3 d nimh tenergy is a direct drive using britelumens heat sinks and the switch wired hot to the led no dimmer to keep cost down. There is no driver electrolumens has been going this route for months.

If you are going to use a driver the one at KD need at least 5.5 volts to regulate http://www.kaidomain.com/ProductDetails.aspx?ProductId=1866
some don't like this driver but it does not need a momentary switch just hot and ground and has worked fine for me the few times I have used it.

If you all are just talking about 3 ds at 1.2 apiece or 3.6 direct drive is the way to go. If your VF is low let the batteries sit for awhile. Alkalines will sag fast enough you will probably be ok.
Most all the drivers either need more going out than going in for a boost or more coming in than going out for a buck as I am sure you all know. You can go to http://www.taskled.com/order.html and look around but I did not see any help.
I use 18650 right out of the charger for P7's and have yet to burn one if heat sinked right. I toasted an MC-E but that is a different beast.

Just remember that all drivers use some battery power. DD is all yours.

Thanks
Dave

 

[jimmyswan]

I just found this and it looks like to me what I need http://kaidomain.com/ProductDetails.aspx?ProductId=1770

Thanks for being patient and helping, it seems like the more I read the more confused I get. But its fun learning this suff and experimenting