I hadn’t done any battery life tests on the slate, somewhat amiss, so I added a couple lines of code that turned on the display at full brightness for 1 second every minute in Jam mode. I think this maybe a reasonable test, and it’s easily repeatable.

The batteries are Panasonic NiMh 2100mAh, almost new, with less than 10 recharge cycles.

I ran the test, first for 3 hours, 180 “slates”, switched it off overnight, then left it running until the battery volts dropped to 4.8V, (1.2V/cell) measured when the display was off. The slate electronics will work down to about 4.1V, when the switched mode supply for the display doesn’t switch any more.

Time        no load        full load
0                5.36            5.20
30 min     5.30        5.12
1hour        5.25        5.12
1hr30      5.22        5.06
2hr            5.20        5.03
3hr            5.16        4.95

Over night rest

0            5.19        5.02
1hr        5.14        4.98

Off to the street cafe for breakfast, more later.

2hr        5.11        4.96
3hr        5.10        4.93
4hr        5.08        4.92
5hr        5.07        4.91
6hr        5.07        4.89
7hr        5.06        4.86
8hr        5.05        4.85
9hr        5.05        4.85

Getting boring.

10hr        5.05        4.86

Take Two, 5 seconds on each minute, duty cycle 8.3%

Time        No load        Full load
Start        5.33        5.18
30min    5.27        5.13
1hr          5.20        5.06
2hr         5.11        4.96
3hr         5.04        4.91
4hr         5.02        4.88

bedtime

Re start   5.09        4.93
1hr        5.01        4.86
2hr        4.99        4.85
3hr        4.97        4.82
4hr        4.96        4.81

etc.

10hr        4.84        4.69

Conclusions

The software hasn’t crashed, and it looks as if 18 hour battery life  might be attainable

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