AA cells Vs custom 'power pack'

[Simon C]

Wanted a portable digi radio, bought the 'Pure One' from Comet whilst browsing but stupidly didn't read the spec well enough. Sign said 'mains or batteries'.. turns out its 'mains or custom/rare/expensive propietary power pack bought seperately'.

The spec of the 'pak' is below. Would 3 AA rechargables in series give the same output and capacity? Sure they'd fit, just need to contruct some sort of holder for them. If not do-able I'll take the radio back, but then I'll still be looking for a compact digi radio... grr.

From the Pure website; ============================ ChargePAK A1 features include: Easy to install ? can be fitted in seconds Easy to use ? just fit and forget Charges inside the radio, no separate charging unit required Increased battery life per charge over standard rechargeable batteries Replaces the need for throwaway alkaline batteries Provides up to 18 hours wireless listening

Specification: lithium-ion 3.7v 2100mAh. ======================

[Andy Burns]

I have a Pure Evoke3, I also had the original NiMh (or was it NiCd?) chargePAK for it, the radio cooked the batteries within the space of a year. I did replace the battery pack with the LiIon version, which has been fine ever since.

Anyway, I disassembled the old pack and it had a PCB with charging circuitry on it, so it's not just a case of physically getting some AA cells to fit ...

[Old Codger]

Three rechargeables should operate the radio just fine, nominal 1.2 volts per cell giving a nominal 3.6 volts. Three alkaline however would probably damage the radio (nominal 1.5 volts per cell). However, is the charger in the radio or in the battery pack? Also a charger for lithium ion may have different characteristics to a charger for NiCad or NiMh so might not charge properly or might damage standard rechargeables.

[Tabby]

You can always - or usually - fall back on the old approach by just fitting a resistor to the charge circuit. Then no matter what the charger does it wont kill anything. The downside of course is slow charging, set it to charge in over 24 hrs IIRC.

NT

[Terry Fields]

If you like the radio itself, get the battery pack that goes with it.

I bought a Pure Evoke Flow about 18 months ago, and it was (and still is) a good radio.

However, when I got around to getting the battery pack for it, it transformed the radio into something I take all over the house and garden at any time I want, greatly increasing its use. Seven watts of rock-n-roll while having a shower is just great, especially when streaming one's own music over the Media Player. I also use it sometimes in conjunction with the separate speaker for improved audio from the LCD TV. Getting the remote control was also a good idea as it gave simpler access to the radio functions.

TF

[Theo Markettos]

There's two issues: getting sufficient voltage and current to power the radio, and tricking the battery management hardware into accepting the battery. With LiIon there's probably a management circuit in the battery - I wouldn't be surprised if the radio won't turn on until it can read plausible battery status from the battery's controller.

Whichever, don't try to charge the batteries in the radio as the charging circuit (particularly end-of-charge detect) will be completely wrong for it.

What you could try and do is take apart the radio and just inject 3.6V into the power supply, cutting out the charging and battery controller. You might need to fit a hardware switch as the battery switching might be software controlled.

Theo

[Dave Liquorice]

Li-ion chargers are smart not dumb. What a Li-ion charger will do if it can't "talk" to the battery I wouldn't like to say. It might work it might not... The battery has protection circuitry and "knows" how charged it is. This can get out of sync with reality though.

How much is the proper Li-ion battery?(*) How much faffing about will you have to do with AA cells to get 'em to fit? Looking at web images it looks to be about 3/4" sq and a couple of inches long, might be a bit of a squeeze?

(*)=A315.00 plus or minus.