What's the board it goes on?

wiretap wrote on 2021-08-29, 01:54:

What's the board it goes on?

HP Vectra XM2 (Late 486 Era Motherboard)

I don't see it listed in the HP service handbook for that model -- they just list Part# 1420-0513 which appears to be a HP 4.5V battery pack with a two wire lead that plugs into the external battery connector.

wiretap wrote on 2021-08-29, 02:18:

I don't see it listed in the HP service handbook for that model -- they just list Part# 1420-0513 which appears to be a HP 4.5V battery pack with a two wire lead that plugs into the external battery connector.

Yeah this is the original soldered in battery. I prefer to remove them and replace them with a battery holder for a modern battery rather than use the alkaline external battery.

But I don't know if this is rechargeable and so I don't know if it needs a diode or not. I'll just put one in to be safe.

I'd still like to know for next time though. It's currently charged to 3.1V so I'm thinking it must have been a rechargeable lithium battery of some kind. Should have been dead by now if it weren't rechargeable.

Thanks all!

The package looks a lot like a supercapacitor to me. It isn't common but they were used to store CMOS data afaik.

Doornkaat wrote on 2021-08-29, 05:15:

The package looks a lot like a supercapacitor to me. It isn't common but they were used to store CMOS data afaik.

Ahhh that looks like the guy! I measured the output from the mobo and while the computer is on it’s being charged with 3.6V. A diode would seem to be indicated.

I could probably just replace the super capacitor but the old one didn’t have any markings so I’m not sure of the needed Farad capacity. Easier to go with the battery I think.

If it actually is a supercap I wouldn't replace it with a battery. Batteries have different charging characteristics and tend to react violently when charged wrong.
Used as an RTC buffer on a mainboard the capacitance shouldn't be critical. A supercap with the correct voltage is just stops charging when it's full. Higher capacitance will keep your RTC running longer, lower capacitance will be depleted earlier. I'd just get a 5V supercap of similar physical dimensions and see if I'm satisfied with how long the time/settings are retained.