How to replace the RTC (CMOS) battery in a Toshiba Satellite A45-S151


Nov 6, 2009
This isn't a question, but a solution that I thought I'd share:

On a Toshiba Satellite A45-S151, the CMOS battery (also called the “real time clock” or RTC battery) is located under the wrist rest to the right of the trackpad. This means that you’ve got some major surgery ahead of you in order to replace this battery.

Disclaimer: I’m a hobbyist, not a Toshiba-certified service tech, so the procedure I’m about to detail is based on the Toshiba maintenance manual for A40 Series laptops—there may be a shortcut method to accomplishing all this (though I’ve not found one).

Before you start, download a copy of the Toshiba maintenance manual for A40 Series laptops (

You might as well also order your replacement battery (Real Time Clock (RTC) Battery, Nickel Metal Hydride, DC3.0V 17mAh, Toshiba #P71035017110). The best deal I could find online in Oct 09 was at for $25 (including shipping; FYI, they automatically ship 2-day air). I called every computer repair store (and Radio Shack) in our area, but couldn’t find anyone who carried this battery in stock.

Tools & supplies you’ll need:

* Precision screwdriver set—at a minimum, you’ll need a #0 Phillips head driver. Don’t try to use a #1 or larger screwdriver—you’ll only end up stripping a screw head (or two or three or ten) or at some point. If you don’t already have a set (they’re really useful for working on laptops), Sears has them for less than $15 (<$10 on sale). If you have a Harbor Freight Tools store in your area, you can also find a cheap set there.
* Pair of small needle-nose pliers (the precision screwdriver set at Sears includes one); I really don’t think that you’ll be happy with standard-size needle-nose pliers.
* A “micro” screw extractor (needed if you find that any screws are stripped; this could happen during original assembly or prior service work). I have the Craftsman screw extractor set (model 52157), available from Sears; the “M3” size extractor is just right for removing small case screws. This set’s not cheap (unless you get it on sale), so you may want to look for a less expense set that has the M3 size in it.
* Power drill w/ adjustable chuck (for using the screw extractor). I used a full-sized cordless VSR drill, but if you have a VSR rotary tool with a chuck, that would be a lot easier to handle.
* Flashlight or good work light.
* Roll of Scotch “magic” tape (you’ll see why in a moment).

A word on “screw management”:
You’re going to be removing a whole boatload of screws to separate the top half of the laptop shell from the bottom half—keeping track of the many screws (in different sizes) is a real pain. My way of handling this is to take a small piece of Scotch tape, fold over one end about 1/8” to make a tab (for later easy removal), and to use it to secure each screw in place as I remove it (with some exceptions, which I’ll mention as we go). For case screws that are inset in wells, a piece of tape over the top of the screw well will keep it in place. For exposed screws, you can usually loosely tape a screw in place after it’s been screwed out—just don’t push it back into the hole’s threads, as that will defeat the purpose of removing the screw. As you go through the procedure, if you find that the parts you’re trying to separate seem stuck together, you may have a screw that dropped back into place—just look for the likely screw, pull up the tape, screw it back out again, then put the tape back in place.

About stripped screw heads: You can hope that you won’t encounter any of these, but with over two dozen screws to remove, your chances are at least fair of having at least one stripped screw head—I recommend being prepared.

About cleaning out your laptop: While you've got it opened up, this is a good time to give it a blow-out with a can of compressed air--you may be surprised where you'll find clumps of dust hiding!

Here’s the procedure (citing the relevant pages of the Toshiba maintenance manual):

1. Remove the main battery pack (p. 4-8).

2. Remove the hard drive (p. 4-13). The covers is secured with both screws and plastic "snaps," so you'll need to use something with a thin blade to gently (!) pry it loose with after you remove the screws; I used one of the flathead screwdrivers from my precision screwdriver set.

3. Remove the heat sink and CPU covers (p. 4-16)—just the covers, not the heat sink or CPU themselves. These covers are also secured with both screws and plastic "snaps."
Note: While you’re here, this would be a good time to take some compressed air and blow the dust out of the heat sink fins and CPU fan (remember to not overspeed the fan).

4. Remove the optical drive (p. 4-20). I’m not sure that this step is really necessary, as I can’t see how the optical drive would affect the shell disassembly, but it’s easy to do—if nothing else it removes a lot of weight, and will make the laptop easier to handle later. Since the case holes have no threads, I just threaded these screws into the holes in the optical drive itself in order to keep track of them.
Note: Before reassembly, I gave the full system a thorough blow-out with compressed air; a lot of dust came out through the open optical drive bay, so that may be reason enough to remove it now.

5. Remove the keyboard (p. 4-23). Do also remove the “keyboard hold plate” and “keyboard support plate” and set them aside; note how they are oriented, so that you can put them back in place correctly later. Be gentle when pulling out the keyboard cable from the mainboard connector—I used a side-to-side shimmy motion to ease it out.

6. Remove the wireless LAN board cover and carefully disconnect the wireless LAN antenna leads (p. 4-28). I used the needle-nose pliers to disconnect the antenna leads from their mounting posts on the wireless LAN board—just pull straight up (gently!). Note that the black antenna lead connects to the post nearest the screen hinge, while the white lead connects to the post nearest the wrist rest. You do not need to remove the wireless LAN board itself, so just skip those steps.

7. Remove the CD/DVD (audio) play button circuit board (p. 4-33). Disconnecting the thin ribbon cable connector looks scary, but it slips right out with a gentle tug.

8. Remove the display assembly (p. 4-34). This is where you’ll go bugnuts keeping track of the screws if you’re not using my Scotch tape method! Note that by “display assembly,” we’re talking about the LCD screen assembly and the upper half of the laptop shell.
Note 1: In addition to the two screws show in figure 4-20 on p. 4-35, there are two other screws that need to be removed that I can't find mentioned anywhere in the manual. These screws are located next to the memory module bay (one "above" and one in the "top right" corner; "up" means toward the screen hinge); both have "B4" marked in plastic next to their holes.
Note 2: Disconnecting all the (tiny!) cable connectors in step #7 goes easiest with the small needle-nose pliers, grasping the plastic head of each connector and pulling straight back (I suspect that standard size needle-nose pliers will prove to have tips too thick for this delicate work). Whatever you do, resist the temptation to just tug on the wires to disconnect the cables!
Note 3: The display assembly has plastic "snaps" in addition to screws, so you may need to do a little gentle levering to remove it.

9. Remove and replace the RTC battery (p. 4-43). You’ll need to be careful to maneuver the “insulator” tab around the ribbon cable for the LED board, but it’s manageable without removing the LED board.

10. Reassemble the laptop in the reverse order of disassembly (hope you know where all the screws are!).
Note on reversing step #7 (CD/DVD play button circuit board): The connector socket for the ribbon cable is on the bottom of the board, inset from the edge. Consequently, I found that it was easier to reinsert the ribbon cable into the connector socket before putting the circuit board back into place. Also, because this ribbon cable doesn't have a hard plastic plug on the end, I had to gently (!) grip the ribbon cable with needle-nose pliers in order to reinsert it into the connector socket (which is just a thin slot, and somewhat hard to see while positioning the circuit board). Be careful to not put too much pressure on the ribbon cable--it's relatively fragile due to its thinness.
Note on reversing step #6 (wireless LAN antenna): The antenna leads are on the small side; while easy to position over their sockets on the LAN board, pushing them onto the sockets would be difficult to do with a finger tip. My solution was to take my needle-nose pliers, close them, then use the closed tip of the pliers to apply moderate pressure to the cable connectors until I felt them snap into place. Note that I did not grip the cable connectors with the pliers--I only used the closed tip of the pliers to apply the necessary pressure.

You should now be able to boot up the laptop (after setting the clock, of course)—unless, like the one I’m working on, there are other problems to fix…


Nov 6, 2009
I'm waiting for delivery of a replacement keyboard ($20), but that was a "pre-existing condition." The laptop works fine with an external keyboard. I've reimaged the hard drive, updated Windows and apps, and created a new baseline disk image. The system is snappy once again.