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taking apart a Sony NP-FM500H Lithium Ion Battery

taking apart a Sony NP-FM500H Lithium Ion Battery

Posted on Sep 26, 2016 by Paul White

NP-FM500H Lithium Battery
If you own a Sony DSLR or DSLT camera the chances are its powered by the NP-FM500H battery.  And like many other accessories sony sells they charge a premium for them.  This drives many of us to Ebay and Amazon to buy generic versions for our gear.  But the thought occured to me is it possible to rebuild these little battery packs? I had a bad battery on hand that would no longer hold a charge so I decided to crack it open to find out. 

What is the Sony NP-FM500H?

The battery is a Lithium Ion Battery back rated at 7.2V and 11.9 Watt hours.  Its commonly used in Sony Cameras from the original Sony a100 all the way up to the flagship a99.  Chances are you have several of these in your camera bag, especially those of you who do a lot of video work.  However on the downside the OEM Sony ones cost about $30 each, and the generics cost about $10 each via ebay.  
NP-FM500H Lithium Battery Cracked Open

Not Designed to be serviceable

Of course Sony doesn't want consumers rebuilding their batteries, as that would cuts into their profits, so on the label it says DO NOT DISASSEMBLE.  However I am just going to ignore that and assume Sony has that for legal reasons so the average person without a tech background doesn't try to be a MacGyver.  We are all very familar with the dangers of Lithium Ion batteries.  When they get too hot they tend to catch on fire and explode, as a few poor Telsa Drivers found out the hard way.  So I don't recommend anyone try this.  I did it just out of my own curiousity.


NP-FM500H Lithium Battery Cracked Open with exposed SANYO cells
Opening the battery

Using a small precision flat blade screw driver I was able to crack open the two halves of the casing.  There is a very small lip between the two halves that keeps the thing together.  Unfortunately the plastic is very thin and soft, so attempting to pry them apart will ultimately deform them, meaning if you are able to put them back together it won't be very pretty.  As you can see I somewhat destroyed them trying to get them part.

On the inside I found 2 Lithium Ion Cells that were slightly larger than a AA battery.  On the side of each cell is printed SANYO UR18500FK.  They are setup in series, with a bridge soldered to them bottoms and a small circuit soldered to the top.

I used a volt meter to test them and one battery still read 2.6V, while the other was dead. Obviously this unit no longer works due to a bad cell.  There is a piece of double sided sticky tape holding the two battery togethre and to the inside of the shell casing.  This makes getting them out of the cell a little difficult, but it is doable.  
SANYO UR18500FK Lithium Ion cells

About the SANYO UR18500FK

When I googled for inforation about these cells turns out they can be bought online for about $7.50 each , and in higher quantities for as little as $5 each.  The cells are rated for 1700mAh and 3.7V.  
SANYO UR18500FK Lithium Ion cells compared to AA battery

Future Project

In the future I plan on buying up some cells to see if I can rebuild the battery pack.  Still considering you can buy the generics on ebay for about $10 each, there isn't much financial gain from doing it yourself.  Unless of course the generics are using some really cheap Lithium Ion cells.  Unfortunately I don't see how its will be possible to not destroy the casings to get to the cells.  It might be possible to 3D print some custom cases, and then move over the protection circuitry from older cells to a new set.  Maybe even design the cases so the cells could be removed similar to AA batteries in most electronics.  


Just wanted to see what was inside. I hope this was as amusing to everyone else as it was me.

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