AA Battery chargers vs 9 volt battery chargers - 39xx

[ipaqczar]

Hey gang,

I have an ipaq 3950, and a thumb keyboard that has a 9 volt battery charger hook up.

It is a bit flakey - and I've read conflicting reports that 9 volt chargers don't really charge the battery - they just give a little extra ooomph via a low level trickle charge or something similar.

Has anyone done any real world testing - and can someone explain why 9 volts doesn't help much, but 6 volts (1.5 * 4 AA's) charges just fine?

Also - I'm looking at getting one of the AA chargers - there are a couple models on ebay - one is square and has a plug that will work on a lot of other devices (but needs the funky connector for the 38xx/39xx that came with the cradle) or there is one that is more rectangular and has the 38xx/39xx connector.

Does anyone know of a cheap place to get more of the 38xx/39xx power adapter thingys?

[Menneisyys]

Does anyone know of a cheap place to get more of the 38xx/39xx power adapter thingys?

All the iPAQ's ever released use the same power supply (5V 2A). So, you can buy a second-hand 36xx power supply cheap.

A bit of warning: do NOT buy any 'travel power adaptor' from HAMA. They can't suppy the maximal 2A, which can be an issue when you use your 39xx with a sleeve that has an additional battery. (It did cause problems to my 3660 + PCMCIA sleeve)

[phs]

Also - I'm looking at getting one of the AA chargers - there are a couple models on ebay - one is square and has a plug that will work on a lot of other devices (but needs the funky connector for the 38xx/39xx that came with the cradle) or there is one that is more rectangular and has the 38xx/39xx connector.


I have a four-AA charger from sempsons that has a USB-like socket. Works great tohether with a retractable sync-charge cable.

[KimVette]

Hey gang,

can someone explain why 9 volts doesn't help much, but 6 volts (1.5 * 4 AA's) charges just fine?

9v batteries have a very low power density - due to the tiny packaging, current capacity (amp-hours) are sacrificed in order to squeeze six 1.5V cells into a tiny space - this does not leave much potential for total power capacity. 9V batteries were never really intended to be used in power-hungry applications. high voltage != high power capacity.

Total available power = ((v)(a))-(transmission loss). Typical AA batteries offer anywhere from .9 amp-hours to 1.8 amp-hours (some high-priced special-purpose AA batteries might put out 2.1ah) and a 9V battery's is much, much lower.