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SXD Driver Advice

Andrew124C41

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I was in remission from my laser addiction but recently relapsed.

I have 2 maglite mods that were done by Jayrob including his battery monitoring module.
They are both two cell for a 32650 battery. (I have several of them.)

Recently I noticed when I had an sxd on my dummy load, that with only 2 of these fully charged cells, I am only able to get a little under 4 amps out of the SXD. I think the 32650s are garden variety lithium ion chemistry.

However, if I run three of them, I can easily get the 4.5 amps that I want for my NUBM44 built.

The driver gets pretty hot and I am not sure I can heatsink it well enough to handle the heat.

Lifetime777 built some 20 mm bore heat sinks for me as well as a 20 mm circular driver holder with a shelf.

I use Deen's ultra-miniature connectors (which can handle the amperage) to allow me to keep the diode module and driver separate from the battery. This allows me to troubleshoot each individual component if necessary and having longer leads allows me to use an inductive current measurement

Can I use the 3 cells or will I burn up both the driver and or the diode?

I am assuming Jarob's battery monitoring system won't burn out....it just will not be able to give the right info since it was designed for two cells.
 



Lifetime17

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Hi,
The SXD driver can handle up to 12v no problem with 3 - 32650 batteries in series.
Rich:)
 

Andrew124C41

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The driver gets very, very hot. I am going to test it in the sink....speahin of which, check your email.
 

RedCowboy

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You need 2 good quality cells of INR or IMR formulation such as EFest 18650 or 26650 that can supply the current without sagging below the drivers cutoff voltage or just use 3 cells and you need to thermally bond the 8-pin chip to your heat sink or housing.




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Andrew124C41

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Using INR or IMR does not seem to make a difference.

Why do you think the same 32650 batteries have no trouble with the ACS4500 getting to 4.5 amp.
 

RedCowboy

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Minimum Vin for the SXD is 6.8v and 6.0v for the ACS4500 but input needs to exceed output by at least 1.0v which in the case of a nubm44 @ 4.5a would be around 4.5v so I expect your no-name 32650's are sagging below 6.8v or your SXD could be damaged, I have used 2 x 26650's to drive a nubm44 with an SXD with no problems but I use EFest IMR cells.

Batteries sag under load, your 32650's are bigger and likely have a higher mAh rating but if not a quality cell they may sag more under load than a smaller cell, say a 26650 of a quality brand and high discharge rate formulation, IMR/INR cells don't sag as badly under load as do normal li cells, you can remedy by using better formulated cells or adding a 3rd cell to stay above the drivers dropout voltage, also your battery current draw will be less at a higher voltage so your runtime will be greatly extended with a 3rd cell.

The driver will draw 2a @ 12v to output 4.5a or it will draw 3a @ 8v to output the same 4.5a which in the case of a nubm44 will take about 4.5v @ 4.5a so I would expect your two 32650's would be up to the task, you can test your batteries by driving a big 1 ohm resistor and watching your voltage sag under load.

Are your 32650's rated at 3.7v or 3.0v ??? If 3.0v then there's your problem, if not you can check your input voltage under load and see if it's above 6.8

These 32650 cells will do the job unless your driver is damaged although you do need the heat sink @ 4.5a output.
 
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Andrew124C41

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Minimum Vin for the SXD is 6.8v and 6.0v for the ACS4500 but input needs to exceed output by at least 1.0v which in the case of a nubm44 @ 4.5a would be around 4.5v so I expect your no-name 32650's are sagging below 6.8v or your SXD could be damaged, I have used 2 x 26650's to drive a nubm44 with an SXD with no problems but I use EFest IMR cells.

Batteries sag under load, your 32650's are bigger and likely have a higher mAh rating but if not a quality cell they may sag more under load than a smaller cell, say a 26650 of a quality brand and high discharge rate formulation, IMR/INR cells don't sag as badly under load as do normal li cells, you can remedy by using better formulated cells or adding a 3rd cell to stay above the drivers dropout voltage, also your battery current draw will be less at a higher voltage so your runtime will be greatly extended with a 3rd cell.

The driver will draw 2a @ 12v to output 4.5a or it will draw 3a @ 8v to output the same 4.5a which in the case of a nubm44 will take about 4.5v @ 4.5a so I would expect your two 32650's would be up to the task, you can test your batteries by driving a big 1 ohm resistor and watching your voltage sag under load.

Are your 32650's rated at 3.7v or 3.0v ??? If 3.0v then there's your problem, if not you can check your input voltage under load and see if it's above 6.8

These 32650 cells will do the job unless your driver is damaged although you do need the heat sink @ 4.5a output.
You are absolutely right. The 32650s drop to a little over 7 volts. Strangely, the Keepsake INRs also drop. 3 32650s drop to 11 V. I just ordered some 32650 LFP which operate at a little lower v. 3.6 is their nominal voltage. So, they should generate less heat for the driver when using 3. We shall see!

Do you prefer us in nf 3 cells,? They really sag!
 

Andrew124C41

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Minimum Vin for the SXD is 6.8v and 6.0v for the ACS4500 but input needs to exceed output by at least 1.0v which in the case of a nubm44 @ 4.5a would be around 4.5v so I expect your no-name 32650's are sagging below 6.8v or your SXD could be damaged, I have used 2 x 26650's to drive a nubm44 with an SXD with no problems but I use EFest IMR cells.

Batteries sag under load, your 32650's are bigger and likely have a higher mAh rating but if not a quality cell they may sag more under load than a smaller cell, say a 26650 of a quality brand and high discharge rate formulation, IMR/INR cells don't sag as badly under load as do normal li cells, you can remedy by using better formulated cells or adding a 3rd cell to stay above the drivers dropout voltage, also your battery current draw will be less at a higher voltage so your runtime will be greatly extended with a 3rd cell.

The driver will draw 2a @ 12v to output 4.5a or it will draw 3a @ 8v to output the same 4.5a which in the case of a nubm44 will take about 4.5v @ 4.5a so I would expect your two 32650's would be up to the task, you can test your batteries by driving a big 1 ohm resistor and watching your voltage sag under load.

Are your 32650's rated at 3.7v or 3.0v ??? If 3.0v then there's your problem, if not you can check your input voltage under load and see if it's above 6.8

These 32650 cells will do the job unless your driver is damaged although you do need the heat sink @ 4.5a output.
Have you ever purchased a new sxd and found it detective?
 

RedCowboy

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SXD drivers are my favorite and they have always been functional upon arrival, they have reverse polarity protection and open circuit protection, also if you connect your laser diode backwards or short the output the driver has a protection to shut it down, they work well, just remember to heat sink at the 8 pin chip and don't be rough with the pot.
 

Andrew124C41

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SXD drivers are my favorite and they have always been functional upon arrival, they have reverse polarity protection and open circuit protection, also if you connect your laser diode backwards or short the output the driver has a protection to shut it down, they work well, just remember to heat sink at the 8 pin chip and don't be rough with the pot.
My batteries are only sagging to 7 v. Don't you think that should be enough for 2 cells. For your 44 builds, do you use 2 or 3. I have a battery monitor that Jarob put in my maglite. BTW, he just told me where he buys them from since he does not use them. Last year I built a 50 amo hour LFP battery from headway cells. I live it for a portable amatuer radio station setup. The difference though is the lower nominal voltage. I will let you know how they work when they arrive. For amatuer radio, it is 5P,4S. Charge to 14.2 V. But for the 44, I think 3S will do it...just can't run them down or you kill them.
 

RedCowboy

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I have used both 2 and 3 cells in mine and a pair of fully charged EFest 26650's will each float @ 4.2v fully charged and will only dip down to 4.0v each ( 8.0v for the pair ) in the first 10 seconds of driving a nubm44 via an SXD @ 4.5a output.
If your cells are dropping to 7.0v right away then you need new cells or you need to charge them.

Even driving a 1 ohm load a fully charged IMR cell will only sag to 4.0v and output 4.0a in the first 10 seconds and the SXD only draws 3.0a from a pair of cells to supply a nubm44 with 4.5a as the nubm44 will flow about 4.5-4.6v @ 4.5a so that's 24 watts into your SXD and 20.5 watts out to your nubm44 which makes 7.5 watts of light and 13 watts of waste heat.

Switching to 3 cells your SXD will only draw 2.0a @ 12v from 3 cells ( 24w ) to drive a nubm44 @ 4.5a and as your cells discharge they will still easily meet the demand until discharged, I typically recharge when cells reach 3.5v sometimes sooner.
 
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Andrew124C41

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I have used both 2 and 3 cells in mine and a pair of fully charged EFest 26650's will each float @ 4.2v fully charged and will only dip down to 4.0v each ( 8.0v for the pair ) in the first 10 seconds of driving a nubm44 via an SXD @ 4.5a output.
If your cells are dropping to 7.0v right away then you need new cells or you need to charge them.

Even driving a 1 ohm load a fully charged IMR cell will only sag to 4.0v and output 4.0a in the first 10 seconds and the SXD only draws 3.0a from a pair of cells to supply a nubm44 with 4.5a as the nubm44 will flow about 4.5-4.6v @ 4.5a so that's 24 watts into your SXD and 20.5 watts out to your nubm44 which makes 7.5 watts of light and 13 watts of waste heat.

Switching to 3 cells your SXD will only draw 2.0a @ 12v from 3 cells ( 24w ) to drive a nubm44 @ 4.5a and as your cells discharge they will still easily meet the demand until discharged, I typically recharge when cells reach 3.5v sometimes sooner.
I should be getting the LFP cells today. Nominal V on these is 3.6 V. For a 12 V pack normally 4S I charge to 14.2 V. They can handle a 10 amp draw. I will only use 3 of them and see how it goes.

Right now I am trying an ASC4500. It seems to work quite well. I am going to post the modular way I built it in the 445 section of the forum.

I purchased a combo soldering station on Amazon... Chinese type. Use Hako think that is the name, tips. It is digital. It is beginning to fade on me. Heat gun us fine, but soldering us just not working right. Smaller tips are difficult to work with.

I saw you are using something I never heard of before. What is it and how did you find it?

Thanks
 

icecruncher

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Maybe its just me, but in my experience with 32650 batteries. Even the Feilong ones don't seem to measure up in my opinion. I use them in my Jayrob build, but never really impressed with them as I am with some of the smaller sizes.

See this
 

RedCowboy

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I use kester "44" rosin core solder, it's 63% Tin and 37% Lead which is what you want, it goes from molten to solid pretty much instantly once you remove heat, I have several soldering stations but on my bench here I am using a basic cheap temp controlled soldering station with a small point tip.

Try to set things up so that you can brace your hands against your workbench and use magnification and plenty of light to see well, when I was younger I could see the smallest detail unaided but now I have to wear reading glasses, it happens to most of us.
 
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