Strange battery behaviour in portable radio?

[crutschow]

I put it in the 20A socket first to be on the safe side just in case I happen to get a reading greater than 1A that might damage the my multimeter?

That would be the safe thing to do.
The lower current input may have a fuse in the multimeter for protection.

obviously the radio needs to be on when I test but should I keep the volume at the same loudness as I would normally listen to it?

Yes.

 

[73's de Edd]

Sorry, the black lead is the one that goes into the multimeter which usually lives in the COM socket
And that is where the black lead STAYS.

There are 2 other sockets to the left of the COM socket for measuring current one is (20A 15 sec max the other is for mA) im guessing I should plug the black lead into the mA socket as I am expecting a reading of less than 1A or should I put it in the 20A socket first to be on the safe side just in case.

NO . . . your RED meter lead gets unplugged and then goes into the 20A socket.

Then somewhere in the radio / battery power circuit you OPEN the circuit, so that your meter leads then can be inserted into that NOW opened circuit to complete it again.
The meter then will read the amps / milliamperes of power being consumed. ( Unless you have a dumb meter which requires a reversal of leads to get an upscale meter reading )
If you then initially see that 1A scale readings will be permissible, move your RED lead to that 1A socket.
Try at no volume, to see what the actual smart electronics is pulling and then at normal / or / and high volume to then see what the audio portion is burning up, at different volume settings..

 

[David B]

Ok, I hope I did this right, I put the leads into my meter as instructed above (perhaps I should have read the meters instruction manual first) and lifted out the positive end of the first battery and put the red probe on the positive end of the lifted battery and the black probe on the connector on the radio (where the positive end of the lifted battery should normally be). With the meter set to the 2A range and the red lead in the mA socket I got these readings:
Volume turned down.... 0.111 A
Gradually increasing as I turned the volume up 0.2 A at max volume.

 

[David B]

Thanks, I dont want to use non-rechargeable batteries (too expensive). I dont have any brand new rechargeable batteries but I do have a different make I could try in the radio (some Instant 2500mAh). I'll see how these fare in my radio.

Ok, I have ran the radio until it ran out of steam using my newer 2500mAh Instant rechargeable batteries.
I got 14 hours of radio with the newer 2500mAh batteries.
And only 8 hours with the older Uniross Ultra 2100mAh batteries.
With the Instant batteries 3 of them ran down to approx 1.17 v but 1 battery went down to 0.060v
I assume the low reading of that last battery tell me more about the state of the battery than it does about the radio?
So from what I have learned on this thread do I conclude the radio is quite power hungry and needs the very best rechargeable batteries available to get a reasonable amount of radio play?

 

[crutschow]

I assume the low reading of that last battery tell me more about the state of the battery than it does about the radio?

Yes.
It means the one battery has slightly less capacity than the other two and completely discharges first.

I conclude the radio is quite power hungry and needs the very best rechargeable batteries available to get a reasonable amount of radio play?

Yes.
For a nominal 0.15v (150mA) drain the battery life would be a maximum of (bat mAh / 150).
Thus a 2500mAh battery would last for about 2500 / 150 = 16 hours maximum, which is reasonably near the 14 hours you measured.

You might consider C size NiMh rechargeable batteries which can have a 5000mAh rating, to give you a run time of about 30 hours, or D size which have double that rating.

 

[David B]

Update: I have just checked the current draw of my old Roberts R862 portable radio using the above method.
Volume turned down.... 0.006 A
Volume on half 0.03 A
Quite a reduction in power consumption compared with the Crypto radio!

 

[Martaine2005]

Massive difference.
6mA vs 111mA
30mA vs 200mA.
Perhaps that’s why the Roberts only has two AAs and the other needs four!.
Quite a hungry little radio!

Martin

 

[Audioguru]

if the DAB radio draws its rated 500mA from a 6V battery then it heats with 3W and it would probably burn your hand if you held it.