Problems using a battery extender

TC · Posted: Wed Nov 10, 2004 7:31 pm Post subject: Problems using a battery extender

I'd like to hear from anyone who has used a battery extender to keep their PDA (Ipaq) topped up while out in the wilds.

Initially my experience of a battery extender was quite good, I bought one with a female USB connector so that I could charge my Clip-on GPS and my Ipaq. Admitedly I only used one for a couple of hours two to the times to get me home as it were.

However I've just tried to use 4x2300 AA and 4x2500 AA mAh NiMH batteries and found that at the very best when fully charged I can only charge my Ipaq once and not the 2-3 times others have found in these forums. I use the extender when the Ipaq has about 15% remaing battery life I've tried multiple sets of these batteries and checked their voltages before and after use and they never get anywhere near charging may Ipaq 1.5 times let alone 2-3.

Anyone any ideas?
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lbendlin · Posted: Wed Nov 10, 2004 8:03 pm Post subject:

Don't forget that rechargeable batteries have only 1.2v whereas Alkaline batteries have 1.5V. To be really successful with your rechargeables you would need to use five of them, not four.
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Lutz

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TC · Posted: Wed Nov 10, 2004 11:32 pm Post subject:

Hi Lutz

thanks for your comments, but if use 4 Alkaline batteries equalling 6v then I will be charging at voltages outside that recommended for both the Ipaq and the Clip-on (both requiring 5v), as would five NiMH batteries.

One of the really bad things about the extenders is that if when the batteries are exhausted you leave leave the extender connected to the Clip-on and the Ipaq then charging reverses, and the extender drains the very device you are trying to charge. Worse still while it's doing this the Ipaq and the Clip-on both say they are being charged, whereas in reality they are being discharged.
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Ipaq 2210
Fortuna Clip-on [Xtrac V2]
Tom Tom Navigator 3
Memory Map

lbendlin · Posted: Wed Nov 10, 2004 11:55 pm Post subject:

A simple diode can help - and has the additional benefit of dropping the voltage a bit.
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Pc-Mobile · Posted: Thu Nov 11, 2004 2:15 am Post subject:

Have you checked the conditions of the batteries/charger?

There are many brands of rechargeable batteries out there and many are cheap. Some are not very good. If only one of the four batteries is not fully charged it may not work even if the other 3 are in top condition.

Also the efficiency of the charger also affects the result.
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TC · Posted: Fri Nov 12, 2004 5:47 pm Post subject:

lbendlin · Posted: Fri Nov 12, 2004 7:26 pm Post subject:

They don't include one because it adds cost.

I'm out of the component business for too long to give you precise recommendation as to what diode to use. It needs to be able to transport a 2A current. Maybe someone else can recommend one.
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Lutz

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