Capacitors instead of RTC/CMOS batteries

[STKR123]

Hi, would there be somekind of knowledgebase for laptops, that are using capacitors (+laptop battery) instead of RTC/CMOS batteries for keeping BIOS/UEFI values "alive/stored"?

I learned hp and lenovo are doing this on their newer models a lot. I myself have a 2016 ASUS X540L here, that has not RTC/BIOS battery.

Id like to know what to look for on the mainboards.
Thank you in advance.

[stj]

bios settings are in flash,
the rtc is built into the bridge chip and probably powered by a lithium rechargeable battery soldered to the board.
super-capacitors as they are called are shit - companies tried them and mostly dropped the idea.

[stj]

bios settings are in flash,
the rtc is built into the bridge chip and probably powered by a lithium rechargeable battery soldered to the board.
super-capacitors as they are called are shit - companies tried them and mostly dropped the idea.

[STKR123]

Ah, "super capacitor".
Now I found some more things to consider and to read.

https://www.badcaps.net/forum/genera...uper-capacitor

Thank you!

[CapLeaker]

Stj just said it. While I do have some success with large super capacitors, the small one are a pain in the rear. If you want you can read my Fluke 289:super capacitor thread. That is one device for example where the manufacturer went from super caps to battery.

[aurgathor]

Super caps are good when they need to provide power for a short time [seconds, maybe minutes], such as in a dash cam after the ignition is turned off.

They need to power it long enough to close files and do an orderly shutdown -- which shouldn't take more than a couple of seconds. Unlike batteries, their capacity won't change much, so they're a better option in that particular use.

[stj]

they leak - they have no safe use

[370forlife]

The original Xbox used a supercap. It was a 2.5v 1F cap and they are prone to failure. As long as the xbox was connected to mains, it would keep the cap charged and maintain the date/time. They expected that this would be the case as most people just leave their consoles plugged in all the time. In the event it was unplugged or there was a power failure, the cap would last a few hours or so before completely discharging.

[aurgathor]

they leak - they have no safe use

Evidence please showing that this is a widespread issue.

[CapLeaker]

Evidence please showing that this is a widespread issue.

That’s true for the small supercaps. The big ones do not have that leaking problem. I am running an experiment using large supercaps (two 25F in series) and with a solar panel and some device for 8 years now and all is good. The small supercaps just keep looking at the fluke 289 thread.

[sam_sam_sam]

I have used the lager super cap before with out any issues but I was not aware of issues with the smaller version of them because I used one in a project for a company that had a storage tank for sanding blasting material and wanted to how much material was in the storage tank I used it for a memory retention time chip and I tested it several times for several hours and retained it memory

I no longer work for this company anymore but the last time I talked to a person who used to work there a couple years later said that they were still using so who knows now if it is still working or not this was over 15 years ago

[aurgathor]

That’s true for the small supercaps. The big ones do not have that leaking problem. I am running an experiment using large supercaps (two 25F in series) and with a solar panel and some device for 8 years now and all is good. The small supercaps just keep looking at the fluke 289 thread.

To me that looks like *one* bad cap in one particular product. Or in the XBOX, but I have not seen any indication that this is a widespread issue. I do know that with regular caps, certain years from certain manufacturers can leak, but that doesn't apply to all caps. I have at least a couple of devices (i.e. dash cam) with a supercap, and had zero issue with them. I know that's a very small sample size, but on the other hand I've had bad cap issues with probably over 2 dozen pieces of equipment over the years.

[CapLeaker]

To me that looks like *one* bad cap in one particular product. Or in the XBOX, but I have not seen any indication that this is a widespread issue. I do know that with regular caps, certain years from certain manufacturers can leak, but that doesn't apply to all caps. I have at least a couple of devices (i.e. dash cam) with a supercap, and had zero issue with them. I know that's a very small sample size, but on the other hand I've had bad cap issues with probably over 2 dozen pieces of equipment over the years.

It’s similar to regular capacitors. Little ones are usually they go bad and the big ones are better and last. How long, I have no idea.
For example: My first CFL bulb I bought 22 years ago, is still working, while most CFL bulbs is the house went dead and got replaced for LED. I still got one 19 year old incandescent bulb running. Some things run longer than others, even so it is the same product.

[stj]

they leak in sega arcade equipment leading to trace repairs
they used to leak in vrc's but it was a minor issue because they used single-sided boards.
the only ones that didnt leak were the old ELNA ones that were in thick steel cans - they probably knew something!