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FLIR E series 12V Charger

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Hi all,

I need a way to charge my E4+ while in the field and NOT using that way-to-fragile micro USB connector.  So, I decided to design and make my own charger and offer it as open source.  Attached is the initial schematic.  The plan is that this PCB will be mounted in a small 3D printed enclosure that fits on the end of the (removed from camera) cell. 

Bullet points:
- Powered by 7.5 to 20VDC
- Charges at 2A
- LEDs indicates GRN when charging, RED if there is a fault such as a bad cell or over temp
- When charging is complete, it's current draw from the source drops to typically 85uA

Once the PCB is designed I'll release the native files.  If there is enough interest I may offer the PCB stuffed with the SMT parts.

Feel free to comment or ridicule.    :-)

BTW:  Selecting a part in the pdf displays the part data and the links to the datasheet and supplier will open in your browser.


Bill W:
I'd have something else for D2, small shottky say as the datasheet says rate over 100mA.
Is the NTC in the FLIR battery what is expected by the IC ?

Why two inductors, just for layout ?  I'd take a look at Wurth.
Could put a divider onto SHDN in case the input goes low, if that is likely.


The 4148 should be ok, it's rated at 200mA.  I originally had the same diode as D4 in there but changed it to make it smaller.

Yeah, the two inductors look weird, I want to keep all the parts (except J1) under the height of the battery connector of about 1.8mm.  I had to use two to make them small enough.  :)


I attached a preliminary placement 3D pdf and updated schematic.  I don't know of any pdf viewers that will work with 3D other than Adobe, unfortunately.   

Some mods, I changed D2 to a schottky as Bill suggested.  I was able to find one in a smaller package although after the placement it really doesn't look like I need to be that small. 

Added a minimal EMI filter just because I'd feel guilty if I didn't.  It's not a commercial product and I'm not designing to a spec but it would be better if it didn't radiate too much.

Added a heat sink that will be taped to the bottom of the PCB.  I was going to slide this assembly into the plastic enclosure but now I'll have to think of something else.

OH, yes, the thermistor on the FLIR cell does look like a 10K B=3380 NTC that the LT part is assuming. 


This is how the board will mate with the FLIR cell assembly.


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