[blr]

This was a bad one.
I knew the manual of my Sharp MT 866 says that no rechargeables should be used in the external pack. I could'n find any reason not to. However after using a NiMH cell in the external pack for about 4 months, which in my case amounts to about 10 cycles I removed the pack 2 days ago just to discover that my gumstick battery was nearly dead. After cycling it several times I could restore about 50 % of its initial capacity, that's all, so today I had to spend 20 USD on a new one, not a good start of the weekend. The conclusion, follow your manual.
What I think has happened at some stage was that my internal cell got overdischarged and went into a polarity reversal. Shame on me, I usually take good care about my cells.

 

[Superbaldguy]

I've often wondered why we're told not to use Nicads in the external packs, and that sounds like the reason. Fortunately, the gums last a LONG time, these days. The NH-14WM has become the standard and runs my MZ-R909, MZ-E707, and D-EJ925 portable audio toys.

 

[thomas]

Hmm, my sharp MD (MD-MT20) also warns to never use Nicad batteries, yet there is no external battery case and no danger of over-discharging the rechargeable batteries...

 

[Strogian]

Overdischarged? Is that possible? (I don't quite know what a gumstick battery is, actually

)

 

[pedxing]

if you buy a certain pcdp, it sometimes come with rectangular flat batteries that look like sticks of gum.

As I understand it, a batter over discharge is bad for the battery because it changes the chemical composition of the battery permanently. It cannot be reversed through the process of recharging it, hence the battery's capacity is diminished. NiMH are prone to over discharge. Further, I have read from non-technical sources that NiMH batteries should never ever be completely drained either. My friend has a bicycle headlight powered by NiMH and it says to recharge the battery as soon as the light starts to dim, not when the lights are very dim or dead. Certain electronic items in the market automatically shut down when there is not enough power in the battery, saving the NiMH from accidental over discharge.

 

[Duncan]

Yes, I must agree that NiMh gumsticks are prone to dieing...

My NH-9WM batteries, I was using them in the EJ825 (before I gave the PCDP to my brother)... and I let the batteries run flat, and then just left the player in a draw for about a month... went to use the player, nothing whatsoever... put external batteries on... nothing, attempted to put the player on charge... nothing, it wasn't until i removed the NH-9WMs and put in a pair of 14s that the unit would charge, and accept external batteries again...

The NW-9WM batteries refuse to charge even in my EJ1000.. so, in one charge cycle they've gone from being old, but still dependable, to just being stone cold dead... and I can't see that degredation happens THAT quickly??

 

[blr]

Yeah, that's real bad because these gumsticks are so damn expensive.
Besides, i couldn't find the Sharp version so i got the Sony 14 WM cell. They are absolutely identical, rating, markings on the body everything. Even the wrapping has the same colors. As expected, the cell charges and works just fine in my Sharp portable. I guess it is a company like Sanyo or GP that makes these cells and just brands them diffrently.