Hi all,
Back in July (See below and
Battery issues...MP5 player...Solved) I had figured out my battery problem and knew I needed another battery. While I didn't do an exhaustive search, I discovered finding an exact replacement at a reasonable price was not going to be impossible, but certainly close. As I mention below, I considered using the battery out of an old cell phone, but it was nearing the end of its life and I tried to take it apart to see if I could get it to fit. Unfortunately, that made this battery unusable. As a result, I decided I would look for another commercially-made battery I could use as a replacement.
Here is my journey, now complete......
In my continued search, I also decided to find a larger capacity (settled on 1,100 ma-Hrs, 2x the original battery) to increase expected playtime. This resulted in 3 concerns/challenges:
* Fit: While there was some flexibility in the length and width, even the thinnest commercial batteries were thicker than the original and would not fit into the player without making modifications.
* Connections: The original battery was manufactured with wires as connections. Any commercial battery I considered had contact points and I would have to figure out how to make the connection.
* Charging: From what I've read, Li-based batteries require chargers with some level of intelligence. Without details about the charging hardware and control s/w, I didn't know whether the MP5/MP3 player charger had enough smarts to handle a battery with a different capacity. I would have to do a test.
So, I finally got motivated and started to look at what mods I could do to use a different size battery.
* Fit: I knew I'd have to modify the existing metal back cover to make room for the battery and then create a new back cover to hold the battery in place. My first thought was to cut (using a rotary hobby tool like a Dremel (tm)) the metal back cover and create a "battery box" by bending "tabs" in towards the circuit board. I initially abandoned this idea becaue I would have to use hand tools (pliers, cutters, etc.) to bend the tabs and was concerned about accuracy of bending 1-1/2" long tabs and how this process might distort the back cover (It was already a really tight and small-toleranced fit).
My next idea was to build a battery box using double-sided PC material and then figure out how to mount and secure this box inside the MP5 player. Two advantages to this was that it meant no bending, just cutting the back cover and using a "tab and slot" method to secure the battery box and I also figured that using PC material might allow me to create some sort of contact arrangement (possibly using stuff from an old cell phone) for connecting to the battery. My concern here was that the battery box, while easy to make and fairly easy to mount, would take up a bit too much room inside the player.
So, before I actually did anything, I set it aside and thought some more. A couple of weeks later I had a D'oh!! moment
I realized I didn't have to cut 1-1/2" long tabs to make a battery box. I only needed enough "sides" to keep the battery in place. I designed the tabs to be a manageable 1/2" wide and was able to bend and adjust until the battery fit very nicely. I ended up with 2 tabs on each side of the battery and one tab at the top and bottom (with the top offset for access to the battery connections). Once I had the battery fitting well, even tho I filed down any rough edges I could find, I added heat-shrink tubing to the side tabs to prevent any rubbing of the battery paper wrap (the battery top and bottom had thick plastic support pieces, so I didn't worry about them as much).
I also had to make a new back cover. The folks at Tap Plastics here in Silicon Valley were very nice. I went over and picked out an 1/8" (actually was 5/32") thick piece of scrap plastic. I went to pay for it (~$1.00) and since they were a bit busy, they just waived me off and said don't worry about it. It was about 1' x 1' square of plastic so I had enough to cover a few mistakes (and experiments).
It was a fairly straightforward process. Cut to size, add screw holes (and countersink), and drill out for the speaker and mic (I had no plan to use these functions, but I expect they helped heat escape during charging time). I ran into a couple of snags, tho. The battery was thicker than I thought and it stuck out beyond the original back cover. I essentially had to sand/mill the new plastic cover over the battery area to allow the new cover to sit flat. Also, because of where the battery was located in the player, there wasn't enough room on one side for a screw. To solve this, I found a piece of thick right-angled plastic, cut a slot in the new plastic cover and glued in the RA plastic piece as a "catch" to serve as the 3rd screw. Then I formed a slot in the original cover (between 2 tabs of the "battery box") where the "catch" piece would be inserted and hold down that side of the new cover. It took a bit of effort and a couple of scrap pieces to make this work right.
To make it look nice, I did some molding and forming using the rotary tool and made the new cover lines follow those of the old cover. Actually turned out pretty nice.
* Connection: I chose to do what the manufacturers warn you not to do, and what I wouldn't normally recommend anyone to do. I soldered wires directly to the battery terminals and then soldered those to the MP5 board (as was the original battery). To do this runs the risk of reducing the battery life, destroying the battery completely or, in the worse case, having the battery blow up. I used a fine tip and set my soldering iron to the lowest temp that would melt solder. I also kept contact between the iron and the battery to the bare minimum so as not to overheat the battery. I'm happy to say the battery seems to be fine.
I had considered some kind of spring-loaded connection arrangement but decided it would be hard to implement and I had no need for a consumer-style of battery removal/replacement access like in cell phones (possibly for SIM card access) or PDAs. If the battery needed to be removed/replaced (and hopefully wouldn't for at least a couple of years), I would be the one to do it.
* Charging: So, now I have the battery installed with a new back cover and I now needed to test it. I had taken new measurements since my previous posting and found I had an error in the original results. Using the new values and factoring in my estimation of the low-battery shut-off point, as well as having the display enabled occasionally during use, I calculated about 16-17 hours of actual play time. I charged the battery up (using what the MP5 battery indicator showed) and then set it to play music until it shut off. I did occasionally enable the display as part of the test and to check battery level. I ended up with over 16 hours of play time. Not bad at all (I went back and calculated what the original battery should have provided and that was about half the play time I now have). I guess the MP5 player charger does have the smarts.....
Needless to say, I'm very happy. Everything works fine and I increased the thickness of the MP5 player a mere 1/8" (still thin enough to fit most anywhere). I bought a new pair of in-ear earbuds and am amazed at how much better the sound is than with the original earphones (well, duh!!!
Re: Photos...
1st photo shows the modified back cover with the "battery box" and battery out. The white line on the left side of the new back (black) cover is the "catch" piece (See photo 3 for better detail). The scrape marks on the new back cover was my "sanding/milling" to make room for the battery height.
2nd photo shows the battery in place. Nice cozy fit.
3rd photo is a close up of the catch and slot arrangement. Note how there was no room to make a screw hole.
4th photo (sorry for blurriness) was meant to show how the battery sticks up beyond the existing metal back cover. You can see the 1/32"-1/16" added height of the battery coming out just above the metal back cover.
Last/5th photo shows the unit completely assembled. You can see how I tried to make the new back cover follow the pattern of the original cover (note the inverted corner pattern).
Cheers...Steph
Quote:
Originally Posted by stepher
Well, I found a cell phone that isn't in use and "borrowed" the battery out of it. It's rated 3.7V @ 1020mAh, double the current capacity of the MP5 battery I believe has failed (and similar in size...yay! I'm in the process of testing it and all seems to be going OK. Did a full (hopefully) charge and have been playing uninterrupted for 2+ hours so far. Battery level shows still mostly charged. Prob'ly "borrow" it permanently (cell phone has a broken micro-USB connector so I can't charge the battery in it 
Cheers...Steph |
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Battery issues...MP5 player...Solved
