CJE down to last stocks of CMOS memory batteriesBy Chris Williams. Published: 24th May 2005, 23:39:01 | Permalink | Printable
Machines to lose time, memory, maybe catch fire and explodeDealer CJE Micros says it has received its last delivery of the NiCAD rechargeable batteries used in legacy Acorn kit. The part, the Varta V280H is, according to CJE, no longer manufactured and is now a rarity.
The small aforementioned battery is fitted inside RiscPCs, A7000s, A5000s and other machines, and provides a power supply to the CMOS configuration memory and system clock electronics when the computer is switched off from the mains. It is trickle charged whilst the machine is on, although will eventually die out. With a dead battery on the motherboard, the computer will lose its CMOS memory based configuration settings every time it's switched off.
"The first symptom of a battery problem people often see is that their clock is wrong. Unfortunately by this time the cell will often have already corroded to the point of damaging the tracks and components around it," said Chris Evans, of CJE. "If your battery has started to grow a fur coat (usually white, green or brown deposits on the surface), then it needs to be replaced straight away."
CJE's Andrew Conroy later added, "I'm afraid to say that the type of battery required (V280H) is no longer made, and so we've bought up our supplier's stocks and had pins fitted to suit the RiscPC and A3000 type motherboards."
Suitable NiCAD batteries for the Acorn kit can be tricky to find and NiMH batteries tend run out faster when the computer is switched off. Theo Markettos, who has designed several RISC OS related hardware projects, suggested the 120mA 1.2V NiMH Varta V150H, possibly with a resistor in series to bring the trickle charge down a little.
Another alternative is to fit a normal alkaline AA battery with a diode to block the trickle charge, although this will mean breaking out a soldering iron.
For a no-fuss solution, the CJE option would appear to be the best bet, unless you're competent enough to fit an alternative battery supply. Theo added: "If you're going to pay someone to fit it, the CJE battery makes sense from a least-hassle point of view. But when [the remaining V280H supplies] are gone, there should be some not-too-complex alternative possibilities."
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