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Old 30th Mar 2023, 11:39 pm   #15
ortek_service
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Join Date: May 2018
Location: Northampton, Northamptonshire, UK.
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Default Re: NEC Storage Device FZ0H4732

Quote:
Originally Posted by SiriusHardware View Post
Quote:
Hopefully then Supercapacitors won't leak
Not my experience, unfortunately.
Well I suppose they are just Electrolytics (even if 'Double Layer'), which have apparently been known to leak and cause PCB damage - especially early SMD ones, that virtually all failed in around a year, when they first started using these in camcorders etc.
But I seem to have been luckily with Electrolytics, never finding one that has leaked and damaged a PCB - Although I've seen a few that have exploded their contents inside equipment (mainly due to someone reversing the 12V supply!)
And many in SMPSU's that have bulged a lot around the vent, after they've got rather too warm due to ESR going high over time. So always try and use at least 105degC rated types, with as long a lifetime at that as possible / fit higher-voltage ones with more margin / bend away from heat-sources, within the space available.

Whilst I've not seen the white powder that comes out of some NiCad batteries damage battery contents, it does (or venting gas?) rather attack PCB tracks, turning copper blank and causing solder-resist to flake off (probably occurs first, exposing the copper). And can be difficult to get solder to stick to the remains of the copper, to try and restore the tracks.
I've not seen NiMH PCB-Mount backup batteries used enough, to see if these are any worse. Although I've jet to see AA ones leaks (Only AA NiCads I saw leak white powder, was after they'd been directly-soldered to ends, without using proper spot-welded tagging, so may have damaged their safety-vent.

On Acorn BBC Master computers, it seems they forgot to put a diode on the main board to stop main supply trying to charge the original Lithium battery mounted next to keyboard, causing them to explode! So they replaced this with an external 3xAA alkaline battery pack, plus put a diode and safety resistor fitted in-line. And this was mounted on a bracket far enough away, for any leaking cells (as most Alkalines these days eventually do) to not cause famage / recommended taking it to a dealer every year! to have the battery pack changed (no doubt at rather a lot of expense...). So most just fitted a standard AA battery holder (hopefully retaining the inline diode lead).
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