Possibly a basic electrickery question

ParkerNorris · Post by **ParkerNorris** » Thu Jun 14, 2007 1:35 pm

Last time we did an overnighter, we took our household DAB radio with us (BBC 7), running off a set of internal Duracell batteries.

However, after about 1.5 hrs of comedy, the duracells were exhausted...

How can I connect the DAB to the leisure battery circuit, bearing in mind that the power requirements are 9V/1200mA (I've looked at some cigar lighter plug in adapters, but they only seem to be rated at 800mA...).

Is it as simple as connecting a resistor, in series, to bring the voltage down ? If so, can it be calculated from Ohms Law ?

Help ...

pippin · Post by **pippin** » Thu Jun 14, 2007 2:57 pm

No, you cannot do that with a simple resistor. It is a bit technical, so you will have to trust me on that one.

The power requirement is probably based on the peak current draw if the radio is playing very loudly.

Basically, unless you can find a higher rated 12V-9V adaptor I would cautiously experiment with an 800mA version.

Running it with no volume is the first test. Keep feeling the adaptor, if it gets more than just warm then it is not man enough for the job.

If it is Ok then try listening at your normal volume and testing the temperature. Again, unless it gets very hot the odds are that you will be OK to run it at lower volumes.

RADAR · Post by **RADAR** » Thu Jun 14, 2007 6:10 pm

What about using a couple of sets of rechargable batterys and a charger that runs off ciggy lighter..

Dave up north · Post by **Dave up north** » Thu Jun 14, 2007 6:13 pm

exactly my view too.
I have shedloads of AA batteries and a 8 battery charger. I just precharge 16 batteries before departure and pack the charger just in case.

All t best,

BUD

ParkerNorris · Post by **ParkerNorris** » Thu Jun 14, 2007 6:44 pm

Thanks all...

Pippin; excellent advice, and very precise as expected

Dave up north and Radar: valid suggestions, but I'm trying to limit as much as possible the things I have to remember to pack... Also, I've got this great big leisure battery installed, so I want to use it.

Anyway, ebay has come up trumps, a multi volt adapter, giving up to 1500mA, see item 140110381143 if you're interested...

pippin · Post by **pippin** » Thu Jun 14, 2007 9:52 pm

That should do the biz.

Double check then check again that you get the output centre pin polarity correct.

Oh, then check again BEFORE you connect it to your DAB

smartmonkey · Post by **smartmonkey** » Fri Jun 15, 2007 9:48 am

Good to hear you are sorted but I will just stick with rechargable batteries. I have a 30 minute charger and get the batteries from liddle or aldi. They now sell nickel metal hydrides at £2.50 for 2.1ah (4 x aa). They should last twice as long as duracell and 30 minutes later they are brand new again. I have so many adaptors allready I am getting a phobia about them.

mikeonb4c · Post by **mikeonb4c** » Fri Jun 15, 2007 12:33 pm

smartmonkey wrote

I have so many adaptors allready I am getting a phobia about them.

As posted on another thread this has turned out to be a real benefit of having an inverter and 4-way gang lead i.e. everyone carrys on using the chargers / powersources they have rather than getting (more) 12v adapators to use household devices in a 12v environment.