Sharp 190: No NiMH AA's?

[Breepee]

I'm using the Sharp MD-MT190 and have been using it's external AA-case in combo with old NiCd AA's for a long time without a hassle. Recently I purchased a couple of NiMH AA's which (at least I hoped) would provide longer playback time. They are 1700mAh to be precise.

After 5-10 minutes the unit says they're empty and shuts down. During these few minutes the status bar that indicates how full the battery is, goes up and down like a rollercoaster. On minute, is says it almost empty the next it entirely full. When I put these batteries into a searchlight or something, they work perfectly and also my battery-indicator says there pretty much fully loaded.

What's wrong here? I've tried a set of completely different NiMH's and the give the same problems. I'm 100% positive there's nothing wrong with the batteries, in other machines they work fine, for a long time...

[Mystyler]

I know it states in the Sharp manual not to use rechargeable batteries in the external AA case. :rasp:

This is your problem, from my secret Sharp FAQ:

Q Can I use rechargeable NiCd batteries ?

A With regard to the use of Ni-Cd rechargeable batteries, the simple answer to this question is one of a suitable power supply.

Most rechargeable AA cells will provide 1.2v only, whereas non-rechargeable cells offer 1.5v per cell. This is required to power the unit.

The external 1.5v battery pack is not used in isolation to the internal 1.2v battery, as can be seen from the operation manual.

The external battery is connected in parallel with the internal battery during use and provides charge for the internal battery. The internal battery acts as a ballast for the external battery and power is taken from both at the same time. This arrangement means that the external battery can cope with instantaneous power demands that exceed its capability if used in isolation. This arrangement will not work if both batteries have the same potential i.e. 1.2v and internal resistance, it could be possible that the internal battery could end up providing charge for the external battery hence not recommended !

Yes, I know it relates to NiCds, but NiMH cells are the same, and you can get away with using rechargables sometimes. But it seems that your unit really doesn't like the idea, and cannot get enough juice (which makes sense), so decides to shut itself off. Also, using rechargeables in the external battery case will shorten the lifespan of the "internal" rechargeable, as it will try to charge the external battery pack, when the reverse is meant to happen! :smile:

[Breepee]

I know it states in the Sharp manual not to use rechargeable batteries in the external AA case. :rasp:

This is your problem, from my secret Sharp FAQ:

Q Can I use rechargeable NiCd batteries ?  

 

A With regard to the use of Ni-Cd rechargeable batteries, the simple answer to this question is one of a suitable power supply.

Most rechargeable AA cells will provide 1.2v only, whereas non-rechargeable cells offer 1.5v per cell. This is required to power the unit.

The external 1.5v battery pack is not used in isolation to the internal 1.2v battery, as can be seen from the operation manual.

The external battery is connected in parallel with the internal battery during use and provides charge for the internal battery. The internal battery acts as a ballast for the external battery and power is taken from both at the same time. This arrangement means that the external battery can cope with instantaneous power demands that exceed its capability if used in isolation. This arrangement will not work if both batteries have the same potential i.e. 1.2v and internal resistance, it could be possible that the internal battery could end up providing charge for the external battery hence not recommended !

Yes, I know it relates to NiCds, but NiMH cells are the same, and you can get away with using rechargables sometimes. But it seems that your unit really doesn't like the idea, and cannot get enough juice (which makes sense), so decides to shut itself off. Also, using rechargeables in the external battery case will shorten the lifespan of the "internal" rechargeable, as it will try to charge the external battery pack, when the reverse is meant to happen!  :smile:

I've used the external AA with the internal battery removed. Also with a near-empty internal battery inserted, same problem. And also with both full batteries, but it seem to use the internal up leave the external full.