| From:    Lauw Lim Un Tung <tung@PETER.PETRA.AC.ID>
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| I want to backup SRAM6264 and RTC, but I fail to keep my data for a long
| time. After I checked, the battery voltage was drop below 2 volt in 2 days.
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Hi Lauw,

Check the current consumption of the RAM: although the standby current may be
low *typically*, the maximum standby current can be quite high (several mA on
older parts).

Make sure your PIC is actually asleep, and not in any way active

Make sure your PIC does not wake up every WTD timeout only to go to sleep
again

Make sure there are no 'current leaks'. Sometimes a chip is sourcing power
through its input or output pins.

Make sure your RAM is deselected. Active RAM is power hungry.

Make sure your battery is properly charged (!)

60mAh is not a lot of juice to run a circuit on, even for backup purposes.
Although NiCad batteries may seem to be a good idea, we have had terrible
problems with them in rechargable memory modules (pre PCMCIA cards of a
proprietary format for car computers). In the end, I used a very high capacity
Lithium cell for backup. Much cheaper than having to recall dodgy units from
the field.

Hope this gives you some pointers,

Wouter

Wouter.Suverkropp@jet.uk