Sennheiser A 200 Notice D'emploi page 13

Rechargeable accuplugs have a „charging cycle"
Depending on how long your receiver has been in use, you must
also recharge the BA 151 accuplug for a certain amount of time.
A simple rule of thumb will help you to decide how long is
necessary:
Example:
1 hour listening
1.5 hours recharging
Operation with a second accuplug
By using a second accuplug, you can increase the listening
time with your A 200. The second accuplug should be kept in
the charging compartment of the L 200 charging unit to ensure
that it is ready and fully charged when needed.
If you use your system with only one accuplug, you must
stop after about 12 hours and recharge the accuplug for
about 18 hours.
Listen
3
With a second accuplug, you can listen for more than twice
the time. Simply place the discharged first accuplug back
into the charging compartment. After the (partial) recharge,
there is an additional (partial) amount of power available:
2
Listen
1
3 6
Operating time x 1.5 = recharging time
2 hours listening
3 hours recharging
Recharge
6 9 12 15 18 21 24 3
Listen
Recharge
9 12 15 18 21 24 3
6 9 12 15 18 21 24 ...
Listen
6 9 12 15 18 21 24 ...
3 hours listening
4.5 hours recharging
13