CMOS Battery Replacement
If your computer forgets the time whenever it's unplugged, throws a "CMOS checksum error" at startup, or keeps losing its BIOS settings, the little coin battery on the motherboard is flat. It's a quick, inexpensive fix at our Marlboro shop.
Yuriy — owner, JY Computer Services · repairing computers and electronics since 2007 · Updated September 2026
What the CMOS battery does
That coin cell keeps the motherboard’s clock running and its BIOS settings saved while the computer is off or unplugged. They last years, but when one dies the machine loses track of the date and its configuration every time it loses power.
The fix
We confirm the battery is the cause, fit a fresh one, reset the BIOS to the correct settings and date, and make sure it boots to the right drive. On desktops it’s usually done while you wait. If the machine also has deeper board issues, we’ll flag them — see motherboard repair.
Frequently asked questions
How much does a CMOS battery replacement cost in Marlboro, NJ?
CMOS battery replacement runs $25 to $115, about $69 typical. Desktops are at the low end because the battery is easy to reach; many laptops are higher because the machine has to be partly disassembled to get to it.
What are the symptoms of a dead CMOS battery?
The clock resets when the computer is unplugged, you see "CMOS checksum error" or "date/time not set" at boot, BIOS settings won't stick, or the machine skips your usual boot drive. Websites may also complain your certificates are invalid because the date is wrong.
Can a dead CMOS battery stop my computer from booting?
It can make boot slow or send it to the BIOS screen every time, and on some machines it stops boot until you press a key. It won't damage anything, but it's annoying enough to be worth the small fix.
Can I replace the CMOS battery myself?
On a desktop, often yes — it's a standard CR2032 coin cell. On a laptop it's frequently soldered or buried under the board, which is where people get stuck. Bring it to our Marlboro shop and we'll handle it.