On 02/02/2020 10:27, Andrew wrote:
On 02/02/2020 09:54, Andy Burns wrote:
Andrew wrote:

Out of the 4 batteries, two (inline) measured 1.29 volts
while the other two measured MINUS 0.094 volts !!??.

What's going on ?.

over-discharge

https://en.wikipedia.org/wiki/Nickel%E2%80%93metal_hydride_battery#Over-discharge


Ok, that means the Radio is at fault then, hence the odd faint drumming
noise it makes when it is 'off'.

Time to visit JL or similar for a replacement radio that runs on mains
(as this one did until I dropped it while doing some outside DIY and
it landed on a corner whereby the impact broke the internal mains
transformer away from the circuit board).


You have a device which has easily accessible DC power inputs, and is
capable of handing a wide range of DC inputs (4 to 6v).
This is the same range of voltage that 90% of mobile chargers spit out.
USB chargers spit out 5V and your average Nokia/Sony Ericsson
proprietary charger spits out somewhere betweeen 4.5 and 5.7v.

Either find an old charger, a mains USB charger+a 2 or 3m USB cable cut
off the old phone end connector, verify the polarity and solder the
wires onto the battery terminals. Cut a notch in the battery cover to
let the wire in - done.

If you want to get clever, either make 2 dummy batteries out of 10mm
dowelling and terminate the wires to screws, mark the + and - terminals.
or cleaner still - buy a 2.1mm panel mounting dc barrel connector and
matching cable connector. Open the radio, connect the tip of the
connector to the radio and battery +ve terminal, connect the sleeve
terminal to the radio -ve wire, and the switch terminal to the battery
-ve. Verify that inserting the (dead) plug into the socket turns the
radio off when running off batteries, then wire the plug to the charger,
and mount the socket in a freshly drilled hole in the case.

For the record - I've had a Sony Ericsson CST-60 charger powering an
Ikea Molgan PIR light (3xAAA) glued on top as a landing nightlight for
years...