Enhanced Memory ME-1 for Kawai K5000
Kawai K5000W
Project final
I replaced the Keystone battery holder of my prototype by the Sony battery holder, which is also found on the ME-1 original. However this needs plated through slots instead of holes in the PCB. The Sony battery holder distinguishes by easy use. No tool is needed to replace the battery. Sony battery products are in Germany distributed exclusively by Jauch Batteries.
Sony battery holder
Low-Battery Warning
The original ME-1 has two different alarm outputs that will trip at 2.5 V resp. 2.35 V battery voltage. I only use the 2.5 V alarm line. As long as everything is ok, the K5000 shows a "Enhanced Battery OK" message when powered up. When battery voltage falls below 2.5 V, the message will be "Enhanced Battery LO".
The BSI RAM that I use has a Data Retention Voltage of 1.5 V, that is as long as the battery voltage does not fall below 1.5 V no data will be lost. So there will remain days or even weeks after the first warning to replace the battery. The battery current is below 1 µA when the K5000 is turned off.
The Toshiba RAMs used on the original ME-1 have a Data Retention Voltage of 2 V, so the data will be lost earlier.
Battery Life Time Calculation
The power consumption of my module is
- below 1,5 µA with 5V supply present
- below 0,5 µA without 5V supply
The capacity of a CR2032 is given at 230 mAh.
Supposing the K5000 is switched on 24 hrs a day, the calculated life time is 153000 hrs or 6388 days or 17.5 years. The shelf life of a lithium cell is given at about 10 years. When the K5000 is switched off, the battery current falls to a third. So the battery shelf life time is the most determining factor of my life time estimation of 10 years.
Advice
Do not touch the battery with your bare fingers. This may increase the self discharge rate.
