Anyone know where to find service info for this shaver?

The online reviews suggest that battery longevity isn't so good, but I got
it on a free recycling group, so the rechargeable cell should have been
cycled to its peak condition by now.

While the heads were in the ultrasonic cleaner - I removed the "pan" under
the heads, but all I got at was the comfort adjustment mechanism, it not
obvious how to split the case and examine the battery, it was pretty fiddly
as far as I got, so I'd like to get the service info before delving any
deeper.

Thanks for any help.