Does anyone know if the Sharp GF boxes that use 15v (or 10x D batteries) will work on a 12v supply from a leisure battery?

I know that the car voltage can vary from about 11v to 13v and could just try it but don't want to cause any damage (although I assume under-volting shouldn't cause an issue)

I think, it wouldn't make a problem. You can check the battery level, if the VU has a battery check mode and see that it is within the range.

Even otherwise, what happens when the battery goes low, if you are running on D cells? Voltage gradually drops down and the boxes are made to work like that?

Good point - the highest voltage is not going to be above 15v and if too low, it's no worse than when the D cells go flat ... I'll give it a whirl. Thanks

Mines are working normal on rechargeable d cells ＝ 10x1,2V ＝12V. Even the fat HK-9000. So it shouldn't be a problem.

maybe it wont hurt it, id say be careful....one time i let a friend of mine plug in my conion to his car...and it blew out my conion couldn't turn it on for nothing....i was in tears i now that we're on the subject i wonder why did it blow out since cars are 12volts...this was in the 80s............even though he told me he always plugged his JVC m70 to his car and played fine so thats  why i let him....not sure what coulda of happened then............but i ended up buying another conion then....it was a c100ff...the first one was a c100f

Just adding a bit more, which was missing in the above discussion.

Voltage is not the only concern while using car batteries. The Car batteries carry a lot of current, sufficient to turn the starter motor for starting a V8 engine. e.g. a 100 amp-hour, 12-volt battery will run a 5-amp motor (or a 60 watt) for 20 hours. Or a 100A motor for  1 hour, theoretically (that is 1.2 kilo Watt motor = 1200 watts!). That is too much current.

If the protection circuit (you can say the current control resistance) within the boombox is not proper, all this current will pass through the box's circuit unrestricted, blowing it. This is what might have happened with the Conion.

Normal boomboxes have a transformer of maximum 1 to 3 Ampere rating at 12V. While using D cells, the current drawn will depend on the boombox demand. If you are using a 12V DC adapter, the adapter will supply only its rated current maximum (1 or 2A as the rating may be). Whereas, when connected to car battery, the current drawn depends on the current control resistance of the power supply circuitry. If the circuit is not designed to connect to high current sources (like car batteries), it may end up in disaster.

Hence I now wonder whether my earlier comment is correct or not - "no problem with car batteries". Experts' opinion sought!

The radio only takes the current (amps) it needs. So even if there is a high capacity car battery, there is still no problem.. It will play for a very long time on one charge 

Thanks all ... was speaking with a local electrician and he said the only thing you need to be careful about is ensure you don't have it connected whilst cranking the engine (as you can get spikes/ surges that could damage the electronics, although he did say even this is unlikely with moden cars/ alternators). The other thing is two ensure it's correctly fused .. with a 12v 3A fuse. I think this aligns with most of what people have recommended above so I'll sort that and give it a whirl.

One more important point missed. Check the polarities thoroughly (+ - ), before connecting. Common polarity for DC jack is center pin +ve, and th outer ring -ve. But many Japanese Panasonics (and some other too) have the center pin Negative!

This was a good call - hadn't thought of checking the polarity as assumed that the tip would be +ve. When I checked it's definitely the other way round on the Sharps.

This raises another issue in that you need to take care that the outer ring of the 12v lead does not touch the bodywork or anything metallic on the car - things will go pop.

Finally thought I'd share a tip - as discussed, some of the larger GF sharps use 15v rather than 12v. By pure fluke I noticed that a Trust 12v laptop converter I had does voltage conversion from 12v to anything from 15v to 24v - can support 6A/ 120W, easily enough for the box. Tried this with the reversed power connector and worked a treat. This is the laptop supply I'm using ...

http://www.trust.com/products/...uct.aspx?artnr=14129