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1 Rookie
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6 Posts
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5 Points
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66
October 4th, 2025 19:36
M6600 CMOS battery. Rechargeable or not? How to confirm?
I want to first mention some symptoms. Some are likely battery related, some maybe not.
1. Time randomly jumps around. Sometimes tracks right for an hour, then changes by hours.
2. Machine will not boot correctly with AC adapter present. If I remove, it will boot fine, then plug AC back in, all is good. AC power meter shows max 40W if trying to boot with adapter plugged in. Boot fails. If allow to boot with battery, then AC adapter pulls up to 160W.
3. Wifi loses connection constantly. 3-4x/hr. Reconnect and all is good.
4. Loss of display (black screen) randomly but rare. Can still hear Windows running. Reboot and it works again.
5. Full charge battery will randomly just show 0% and shut machine down. With AC present, it still does that. 100%, then pops to 0% for about 10sec, then back to 100%
BIOS
A12, Optimus turned off, Events are low batt from years ago, nothing recent, fan malf recent. Thermal events 3x fan1 stopped recent. Date is correct but clock seems stopped from when power was removed. Seconds do not change. AC adapter IDs as a 240W, which is correct.
On the battery, per "AI", the battery is rechargeable, others are saying it isn't! I cannot confirm the PN on the battery, already looked.
Would this erratic behavior be caused by the battery?
ejn63
12 Elder
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31K Posts
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153.7K Points
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October 5th, 2025 20:15
The CMOS battery (reserve battery) is not rechargeable -- it's one time use.
peemints
2 Intern
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33 Posts
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October 9th, 2025 01:08
Hello,
To add extra confirmation, CMOS batteries are not rechargeable. Luckily, they are pretty cheap and easy to replace. Steps to do so can be found in the M6600 Owner's Manual. Look at Section 18 (page 49).
That being said, your other issues seems to be related to either out of date drivers or failing hardware. Given the age of the laptop, I'd say it's probably the latter. These laptops were released in 2011, so it's very possible that the hardware is starting to fail.
However, you mentioned that your BIOS is A12; the most recent version (2018) is A18, which you can find here. Normally I would say to install Dell Command Update and let it update all of your drivers, but the last version that is compatible with your laptop is from 2014, so I'm not even sure it will be able to find an update catalog for your computer. If you want to try it anyway, use this link to find it under drivers: https://www.dell.com/support/product-details/en-us/product/precision-m6600/drivers
GaryWright
2 Intern
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29 Posts
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November 22nd, 2025 21:03
@ejn63 You say that but some CMOS batteries do indeed seem to possess rechargeable qualities. I have a Studio XPS 1640 from 2009 and its CMOS battery still functions and has never been replaced. It was even powered off for years. Yet 16 years later and it still holds the date/time and all other altered BIOS settings.