Battery Power Off at 22% ??

Is it normal for the Clip+ to power down when the battery is at 22%. And if not, then why is mine doing it?/Thanks

There are a few issues with battery monitoring, so it’s probably just that.  I believe sandisk have said they’re looking at it so they’ll probably fix it in the next firmware.  No timescale.

Mine powers off at approx. the same level (18 - 23%). This is a safeguard against dangerously depleting the battery. Whether this will be adjusted in a future firmware update is anyone’s guess, but since battery issues have been a major sore spot among users here, I would assume it would.

So just what is the current firmware #?? Thanks

It’s what you have on your player–SanDisk hasn’t issued a firmware upgrade for the Clip+ yet.

I have a little experience with batteries and I can tell you it’s very difficult to measure the state of charge accurately.  There are many factors including temperature that can affect the reading.  Also the reading is affected by the state of use - if it’s in standby mode vs playing music it is consuming different amounts of power and that can affect the reading as well.   Also if it’s charging, or has been resting for a long period of time, that can have an effect on the reading. So giving you a battery % reading is not an exact science.  I’m not surprised they’re having some difficulty with this and it will be interesting to see if they can make it work better with a firmware upgrade.  For me, I notice that the last bar on the battery almost never shows full.  I can plug my player in the USB for several hours and it still has the last bar empty.

I think the voltage delivered by the battery gradually drops off as the charge reduces. It follows a curve, and if you know the shape of the curve, you can measure the voltage, find that point on the curve, and work out how depleted the battery is.

You could find a function to calculate the curve, but it’s probably easier to store a lookup table with (say) 20-30 values: you could then look up the nearest value to the present voltage, and read off the (approximate) percentage used.

I suspect that the Clip+ firmware uses a curve (or a table) that doesn’t match the battery’s performance, either because the battery is slightly different, or because the same battery now behaves differently with the new hardware.

So (and I’m making up the numbers here just to convey the idea) when the firmware reads a voltage of 3.5V and assumes the battery is 10% depleted, it may be that the voltage actually drops off more graduallly than this so that 3.5V really means 20% gone.

Then by the time we get down to an indicated 45% (supposedly about half-way along the curve) we’re really near the right-hand end where the battery is almost completely depleted. That’s when we see the percentage falling minute by minute over the next half-hour, and we’re rapidly down to < 8% remaining.

Then the battery icon doesn’t properly reflect the (incorrectly calculated) percentage anyway.

My Clip+ still shows a full icon after 90 minutes, when a 15-hour capacity would imply 10% used. The percentage (shown in System Settings -> Info) at this point is usually 93-94%, which is why I think the calculation is off by some margin.

Message Edited by njd on 01-07-2010 12:27 PM

The battery percentage reading is not linear currently, as you may have seen.  No doubt, the meter will be addressed in a future firmware update.  Mine go boink at the 20-or-so percentage point too, and the last hour of playback exhibits a rapid meter change too.

The Clip+ has a slightly different battery than the previous Clip as well, so some meter tweaking is in order.