🚀 go-pugleaf

John <john@mabuhay.demon.co.Zuk> wrote:

> When fitting SIMMS last year I remember thinking the Pram Battery looks
> quite accessable and wondering why it costs so much to have changed at an
> Apple Centre.

'cos it's a bleedin' rip-off, that's why.

> Well, my battery is now dead. It is a Sonnenschein inorganic lithium,
> number SL-150
> 
> I've seen a 3.6 volt in the Farnell catalogue which looks similar. Would
> this one do?  It's a 1/2 AA size with a 1.1 Ah capacity,  number SL235L/S

I don't know for sure - if the voltage and fitting is correct, it's
fine.

> As long as the voltage is correct and the connecters fit properly are
> there any other specifications that I need to worry about (amps per hour
> rating etc. etc.)

It's amp-hours (amps times hours); a measure of how many electrons you
can get out of the beastie.  That is, a 4 Amp-hour battery can
(supposedly, and roughly) supply 4 A for 1 hr, or 0.4 A for 10 hrs, etc.

But just so long as the voltage and connectors are correct, there's
nothing else to consider.  A greater capacity than spec will mean it
lasts longer; less capacity than spec means it'll last less time.
Neither case will cause any damage.  These lithium batteries are
non-rechargable (with a vengeance - they can't take more than a handful
of microamps charging current), so you don't have to worry about
anything to do with charging.

> Are there any precautions I should bear in mind when replacing the
> battery?  If it is as easy to do as it looks why do Apple say only Apple
> Centres should change it?  

It's conceiveable that you might run the risk of damaging some circuitry
with static, so you might like to take precautions to discharge any
static electricity you might be carrying around with you.  What I do is
ensure that my Mac is switched off (at the back of the Mac *and* at the
mains socket) but plugged in.  Then I touch the metal case of the PSU
firmly to discharge any static I'm carrying to ground, and do the job in
hand (fitting a SIMM, or whatever).

I recall hearing about some of these batteries being a bit fiddly to
replace on account of a strange fitment locking them in place.  I seem
to recall coming across a Mac PRAM battery site somewhere - you might
try a Web search to see if you can track it down.

Rowland.

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