I’ve got a nice little portable DAB radio (Tesco’s best Technica – usually surprisingly good quality stuff) and I want to use the battery option rather than always dragging a mains lead around.

It takes 6 AA batteries to give a 9V supply. I hear that DAB is a real battery muncher, so I don’t fancy using ordinary cells.

However, rechargeable AA batteries only kick out 1.2V, which would mean 7.2V in total.

Is it going to work with a 20% reduction in voltage? As it will cost £££s to buy the batteries and charger I’d rather know in advance.

Unsurprisingly, my local electrical shop owner says “It’ll be fine. That’s £22 please”.

I’ve got a few rechargeable NiMh AAs around with all different capacities. Do they all have to be matched, and what happens if some are 1700MaH and some are 2400?

It will work fine. However do yourself a favour and get some good batteries and a smart charger.
Sanyo Eneloop batteries are the best on the market and from Amazon or similar are not expensive.
A smart charger will charge each battery on its own circuit and avoid overcharging cells with kills them quickly.

The last batteries you will buy in a long time:

http://www.amazon.co.uk/gp/product/B004JL7JTQ/ref=s9_simh_gw_p23_d8_g23_i1?pf_rd_m=A3P5ROKL5A1OLE&pf_rd_s=center-4&pf_rd_r=0CZDPYERJY5VZRDWHM0V&pf_rd_t=101&pf_rd_p=467128133&pf_rd_i=468294

Right – I’ll order them then. Any links for a smart charger?

I still can’t get my head around it working with 7.2V though…

look at Ansmann chargers – I have an ‘Energy 8’ which has been fine for about 4 years and I’ve got dozens of AA and AAA batteries on the go.

However, rechargeable AA batteries only kick out 1.2V

Believe it or not, electronics manufacturers know about this 🙂

The only things that don’t work well with rechargeables are tihngs with very low voltages like clocks. It’s probably been designed for 7.2V and it regulates the 9V down to 7.2V

Anyway, you do know that the 1.5 and 1.2V numbers are just nominal, don’t you? The actual voltage varies loads depending on how much load you are putting on it and how charged it is. So these things have to handle different voltages.

Panasonic also do a version of the Eneloops called Infinium. I use them in my camera flash & they are pretty good.

Definitely worth getting this kind of battery and an intelligent charger like the Ansmann mentioned above, so you don’t cook them.

I hereby declare that my head is now around the voltage thing. 🙂

Thanks everyone.