RAM battery replacement - which one to choose ?

[Theo]

Hi,
The "current" rated on the batteries is just their capacity, (the amount of
energie stored in them).
A 250mAh batterie can deliver 250mA during one hour before its empty.

1% a year decremention is a little optimistic.
A normal value for backup batteries would be something like 3.6V.
Most 10 year old RAMs need 2.2V mimium in data retention mode.
In praxis they often hold out longer, some times down to 1V.

For the replacement batteries, it depends.
If the old ones where Lithium batteries, then there is no recharge circuit
on your board.
To use NiCad or NiMH you would need to add this.
So in that case the easy way to go is new Lithium batteries.

Some say NiMH will replace NiCad within the next 2 or 3 years.
Most NiMH cells seem to be happy with a continues charge < 1mA
(check on the correct continues load currend when you buy).
If you're not sure about this, better use NiCad.

Hope this helps

Cheers  Theo

----- Original Message -----
From: Synthusiast <synthusiast1 at yahoo.com>
To: Synth DIY List <synth-diy at node12b53.a2000.nl>
Sent: Friday, April 07, 2000 9:44 PM
Subject: RAM battery replacement - which one to choose ?


> Hi all,
>
> I got rid of the leaking batteries from my Tiracon 6V and finished
cleaning
> the green (oops) tracks. Measuring the leaking batteries, I found that
they
> produce 1,1 V at the moment. My guess here is that this originally was 1,2
V
> (1% voltage decremention per year over a 10 year period). The batteries
are
> noted "TS 225": the number probably stands for 225 mAh. Obviously I want
to
> replace these batteries for new ones and after some research I found the
> following types:
> - 1,2 V / 250 mAh NiMH;
> - 1,2 V / 280 mAh NiCd;
> What I want to know is: can the difference in current between the old
> batteries and the new types cause any harm to the RAM circuits? And what
> type is better to use: NiMH or NiCd? (in case of lifetime, leakage, etc.)
I
> hope you can provide me with some answers on this matter.
>
> Thanks in advance,
> Synthusiast
>
>
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