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CJE down to last stocks of CMOS memory batteries

By Chris Williams. Published: 24th May 2005, 23:39:01 | Permalink | Printable

Machines to lose time, memory, maybe catch fire and explode

Battery and A7000 motherboardDealer 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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Eighter they want to sell A9's or they have not seen this one. CP300H KM.RL it's now sealed because of the famous leakage.

 is a RISC OS User1234 on 25/5/05 6:05AM
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Theorically every 1.2V battery should work, as long as the current is "around there" and the size is compatible with the holes in the motherboard. A battery with less current will run dry faster, but on a regular compter usage, it gets charged quite often.

 is a RISC OS Usernodoubt73 on 25/5/05 8:06AM
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"Alternative... break out the soldering iron"? When I replaced my RiscPC battery a few years ago (with the type now going scarce) I had to solder it - had something odd happened to my RiscPC before I bought it second hand? I've soldered a couple of things on the motherboard now, so I'm amazed it still works.

 is a RISC OS UserSimonC on 25/5/05 9:59AM
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hmm a RISC PC part now unavailible where have I heard this before?

definatly time to upgrade guys, especially when the stock runs out.

 is a RISC OS Userem2ac on 25/5/05 10:29AM
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> 1234 The CP300H is Ni-Mh, Acorn used a Ni-Cad most opinion says they are not 100% interchangable!

 is a RISC OS UserCJE on 25/5/05 11:39AM
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em2ac: Definately time to think, upgrade or change platform.....

 is a RISC OS Userbernie on 25/5/05 12:35PM
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Just because something gets hard to find for your system does not mean you need to upgrade or change platforms..

 is a RISC OS Userhelf on 25/5/05 2:23PM
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I've a StrongArm RiscPC with the battery that has started to "grow a fur coat". This is the machine I installed the RiscOs4 I just bought. I had strange behaviours (like opening APPS and CONFIGURATION and having the machine crashing right away, w/o any way to get out but reset). Clock was still working. I replaced the battery but I still had bad behaviours. I tested the battery and gave me 1.2V. It's possible it ran out of energy but I managed to recharge it before it was too late. I put it back. Still bad behaviours. So I moved all my stuff (strongarm, disks, cd, memory, rom) to another strongarm machine that was on Riscos 3.7. Problem solved. Machine works well (even if I don't get why the clock apparence settings, when se to user defined, won't stay there after a reboot, this really drives me mad, because I don't want seconds, not "AM /PM"). I put everything else to the board I've tried to replace the battery: now there I have all the stuff I had on the 3.7 strongarm: strongarm, 3.7 roms, its harddisk, it's memory (32Mb x2 + 2Mbvram). Well: it turned out that the board, IMO, is faulty! This board that was behaving so weirdly with RiscOs4, is now terrible with RiscOs3.7!! It happens tha I fire it up, and I see 32+2 Mb ram (but sometimes I see 64+2). Then it's impossible to shutdown and then restart: machine reboots and before doing anything it shows a non blinking cursor on the upper left corner, and nothing happens untill a power cycle.

Could it be the battery ran low and spread acid around? Could it be the board is just faulty? Could it be it's one of those boards (..that I've heard of...) that do not well support a strongarm processor?

 is a RISC OS Usernodoubt73 on 25/5/05 2:27PM
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nodoubt73 - try running with just one stick of ram, and also re-seat the vram. I find that most RPCs here are "wierd" with two sticks of ram in, but behave very solidly with a single stick. If this solves the problem, you could invest in a single 64Mb SIMM which should be quite effective. Also, remember that RiscPCs were designed before EDO SIMMs, and Acorn were always very nervous of EDO in RiscPCs. I know that most people find them to be OK, but it is something else to be wary of.

 is a RISC OS Userarawnsley on 25/5/05 2:41PM
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Thanx, arawnsley , I'll give a try. I know they are wird. Mind I've TWO 128MB simms and they don't work togheter on the RISCPC. I put one and I see 64, then put one plus another (probably 64) and I see 128. And it works. This set was on the faulty board, and now is in the working one with RISCOS4, and there it works well.

 is a RISC OS Usernodoubt73 on 25/5/05 2:54PM
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Hey has anyone seen the "Microsoft has brought Acorn and Acrhimedies trademarks" news story on www.bbc.co.uk yet?

they reckon that it mean's hes brought RISC! AGGHH!!!! oh no wait is this possibly a hoax / "london Bridge" incodent where they have brought the wrong thing (thinking RISC was ARM?)

 is a RISC OS Userem2ac on 25/5/05 4:31PM
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nah ignore that its a hoax! :@P

 is a RISC OS Userem2ac on 25/5/05 4:36PM
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but if we all took this path, why build new machines?

Arwnsley: Have been running for a few years with 128 Megs in mine + 2Meg VRAM :@P 2X64 had no trouble, but i have seen that trouble in other machines..mine must be the pick of the litter.

Although the Network Card refuses to talk to some switches / Linux cannot see it (ANT Combi)

 is a RISC OS Userem2ac on 25/5/05 4:43PM
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My battery gave out a good few years ago, I just got a generic replacement nicad of similar capacity with solder tags; ran two flying leads where the old battery was soldered to the motherboard, wrapped it in PVC tape and doublesided sticky taped it to the PCB/case side. Works brilliantly.

You can even do it without removing the PCB from the case if you cut the old battery out with a pair of side cutters leaving yourself enough to solder onto. (You still need to strip the case down etc, but it should make it a lot harder to damage the motherboard as long as you're careful with the cutters ;-) )

 is a RISC OS Userjogu on 25/5/05 4:57PM
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I should add some of the bits of my email that Chris didn't quote:

The V150H was the first likely battery I picked out of the CPC catalogue - it wasn't an exhaustive search and I imagine there are others suitable.

As nodoubt says any 1.2V NiCd would do - but watch self-discharge. It's better to get one designed as a memory backup battery rather than a consumer NiCd for cameras etc, since consumer NiCds can go flat (self-discharge) in the order of 3 months even when not used. You can still use a consumer NiCd, but you won't be able to leave your machine off for months and keep the settings. NiMH self-discharge is worse than NiCd.

For anyone who wants the gory details, the NiCd is charged off 5V through two 180 ohm resistors in series (one R130 at the positive terminal, the other R212 at the negative). That sets a trickle charge current of 13mA. For a battery of capacity C=280mAh that's C/20 charging. If I were to put in a smaller capacity like the V150H I'd want to keep this at C/20, so would want to restrict the current to 120/20=6mA. That means increasing the total series resistance to 5V/6mA = 833 ohms, or adding another 470 ohm resistor in series with the battery positive terminal.

Personally I'd go for an alkaline 1.5V button cell in a vertical mounting holder with a Schottky diode in the positive leg (diode anode towards the battery) which would roughly fit the mounting position of the NiCd in a RiscPC.

 is a RISC OS Usercaliston2 on 25/5/05 5:04PM
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I Upgraded my A310 with an A5000 motherboard. Unfortunately, the CMOS battery shorted as it touched the disk bridge. At first, I didn't notice this and thought the battery was bad, so I cut off the battery and soldered leads to the A310 CMOS batteries at the left side of the case. This worked perfectly.

Later, I discovered the real reason for the failure of the original battery and reinserted it (wrapped in tape to avoid shorting). So, in conclusion, you don't have to use original batteries.

 is a RISC OS Usertorbenm on 26/5/05 7:35AM
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Do we really actually need batteries any more? Can't we just have a small app in the !Boot?

Then we could just cut the batteries off and throw them away before they grow green fur.

 is a RISC OS UserLoris on 26/5/05 10:39AM
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Loris, no. While you can store some configuration settings in !Boot that were previously in CMOS (many have been moved under Select), you still need fundemental settings such as which interface and drive to boot from, and not forgetting the real time clock which has to remain running if the time is going to be correct when you start it back up.

 is a RISC OS Userdruck on 26/5/05 11:51AM
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Oh yeah. I feel silly now.

 is a RISC OS UserLoris on 27/5/05 10:37AM
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Well, the time can be synchronised with a time-server during boot.

 is a RISC OS UserJGZimmerle on 27/5/05 12:15PM
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Setting the filesystem and drive to boot from within !boot still has certain obvious problems, however. For a future version of the OS you might be able to put that kind of thing into flash instead of CMOS, but that wouldn't work for the clock....

 is a RISC OS Userchrisj on 27/5/05 2:09PM
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