Battery 'extenders' good or bad? UK source?

[Johnmcl7]

I'm considering one of these:

http://cgi.ebay.co.uk/Battery-Extender-Charger-Dell-Axim-x50-x50v_W0QQitemZ5823555779QQcategoryZ48674QQrdZ1QQcmdZViewItem

Unfortunately the cigarette lighter in my car doesn't work so I can't get any power that way, these extender devices seem to be the best alternative as they are cheaper and more powerful than an extended battery plus they work with the onboard battery. Are there any downsides to them? Does anyone know of any cheap UK sources?

Thanks,
John

[mikealder]

From looking at the link it looks fine, BUT the PDA needs 5,0 Volts to charge properly via the sync interface connector, you are therefore limited to using the normal disposable batteries (sugest Copper top type) -
NICAD or even the newer NI-MH units opperate at 1,2 Volts so as they run down it will fail to charge due to the inbuilt regulator not supplying the correct voltage for the PDA to charge (1,2V x 4 = 4,8V) so the rechargables are not a good option -

normal dry cells operate at 1,5V which equates to 6V as new condition -

I use eight NI-MH to produce 9,6V which is stepped down to the required voltage via a car charger lead, with 2500mAH AA cells I get an extra 8 hours (depending on what I am running) - Mike

[Johnmcl7]

I'm a bit puzzled now, why do these extenders specify that you can only use rechargeable batteries, not alkaline?

John

[mikealder]

John, the site will quote rechargable as they are cheaper to run in the longer term -
but the laws of physics (Ohms Law to be specific) give a different scenario - as stated previously - it will work with NICAD but not for too long Once the volts from the battery drop below the 5V required for the PDA the PDA will sense this and stop charging)

unless the device has a true DC-DC converter fitted which I doubt at the price offered as these cost considerably more as a single component - it will be OK for occasional usage but I would not want to trust it over say a four hour duration over and above the fitted battery,

give it a try and let us know how long you get before the internal PDA battery drops below 100%

- run tomtom5 and a gps reciever from the same pack to keep the similarity - Mike

[neil01]

Have you considered fixing the power socket in your car - it may work out cheaper if you can do it yourself (or even warranty on a new or recently purchased car).

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