Sangean DPR-99 Plus Operating Instructions Manual page 24

If you use the radio powered from the batteries, the battery light will
be off. When the batteries are exhausted, the radio will switch itself off.
It does this in order that the batteries are not excessively discharged.
This would otherwise damage the batteries and shorten their life.
If you use the radio powered from the mains with rechargeable batteries
fitted, the charging process is suspended until you switch off the radio.
When you switch off the radio using its On/Off button charging will then
resume. If the batteries have already been charged then they will only
charge for a few more minutes before the battery charge indicator goes
turns off.
If you only listen to your radio for short periods, you do not need to
connect your radio to the mains to charge the batteries every time that
you use it. However, if the radio is not to be used for a few weeks we
recommend that the batteries are fully charged before the radio is put to
one side (charge until battery charge light turns off).
If you intend not to use your radio for some months, then we
recommend that the batteries are removed and put away, keeping them
in a cool place out of reach of children, away from moisture and such
that no metal object can contact the battery terminals.
With care, rechargeable batteries can last a long time and can operate
for many hundreds of charge and discharge cycles. When your
rechargeable batteries can no longer power your radio adequately,
please dispose of them thoughtfully.
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To avoid danger and risk of injury, please follow these
guide lines
Improper use of batteries may result in leakage of fluid, overheating
or explosion. Battery fluid is corrosive and may also be toxic.
Battery fluid can cause skin burns, can damage the eyes, and can be
harmful if swallowed.
1. Keep batteries out of the reach of children.
2. Do not heat, open, puncture, mutilate or dispose of batteries
by burning.
3. Do not mix different battery types or old and new batteries.
Always replace all the batteries at the same time.
4. Do not carry or store batteries such that metal objects may contact
the end caps.
5. Remove batteries from the radio if they are worn out or if you are
storing it for a long time.
6. Remove old or worn out batteries promptly, and recycle or dispose of
them according to the regulations applicable to your location.
7. If a battery does leak, remove all batteries from the product,
taking care to avoid directly touching the leaked fluid. If the fluid
contacts skin or clothes wash with water immediately.
Before inserting new batteries, thoroughly clean the battery
compartment with a damp paper towel, or follow the battery
manufacturer's advice for clean up.