Dead Battery?

[michele]

I left my Sony MZ-NH700 in its bag for three months without using it and with its rechargeable battery in. Now I try to charge the battery and after hours of charging it is still death. What's going on? Help this dummy boy!!

[greenmachine]

The charger may not recognize the battery as it seems to be deeply discharged. Try to charge it in a conventional charger without any 'smart' automatic controls for the first time. If you're lucky, it'll recover itself within a few charge-discharge cycles. If not - NiMH AA's are not that expensive nowadays.

If rechargeables are not used for a longer period, it's advisable to discharge them and not to leave them in the unit.

[MDX-400]

The charger may not recognize the battery as it seems to be deeply discharged. Try to charge it in a conventional charger without any 'smart' automatic controls for the first time. If you're lucky, it'll recover itself within a few charge-discharge cycles. If not - NiMH AA's are not that expensive nowadays.

If rechargeables are not used for a longer period, it's advisable to discharge them and not to leave them in the unit.

←

Yep, the above is the way to go Greenmachine is right, NiMH AAs aren't expensive, and the NH700 actually came packaged with an AAA-inside-AA-casing NiMH meaning it has about 1/3rd the capacity of a standard NiMH AA!

If you replace it with 2100-2500mAh AA NiMH battery, Play times of 4/7/9/7/9/10 hrs (PCM/Hi-SP/Hi-LP/SP/LP2/LP4) should be increased to more in the neighbourhood of 10/21/25/20/24/27 hrs instead, which is an appreciable jump

[MichaelBeardy]

Personally, I would look upon it as the fates prompting you to upgrade your battery.

A couple of 2000mAh or better AA batteries are so cheap nowadays, you'll be wondering why you didn't replace the original Sony battery ages ago.

BTW Greenmachine, my understanding is that it's better to store NiMH cells charged, and cycle them down and then back up to full charge every few months. The thing a NiMH cell hates the most is being discharged too far - which is what can happen if they are stored in a discharged state, as they tend to have a higher rate of self discharge than the older NiCd cells.

Peace,

Michael

[greenmachine]

Seems like none of us is right, battery university says:

"Performance degrades if stored at elevated temperatures - nickel-metal-hydride should be stored in a cool place at 40% state-of-charge."

I think i've read the same for li-ion batteries somewhere.

[michele]

Thanks guys! No problem to get new batteries ... I just wanted to ask if it was normal. BTW some of you reccomended an Ni-MH AA in the 2000 -2100 mAh variety ... as I looked at the original Sony battery inside I discovered it's a 700 mAh ... what does it means?

Thanks again!

[greenmachine]

It's the capacity - generally speaking - the higher, the better. You'll get significantly extended operation times with higher capacities. It's really cheap from Sony to deliver it with such a weak battery.

[MDX-400]

BTW Greenmachine, my understanding is that it's better to store NiMH cells charged, and cycle them down and then back up to full charge every few months.  The thing a NiMH cell hates the most is being discharged too far - which is what can happen if they are stored in a discharged state, as they tend to have a higher rate of self discharge than the older NiCd cells.

This isn't entirely correct from my knowledge of battery chemistries. To store either an NiMH or NiCd battery, the best way to do it is in the discharged state and disconnected from any equipment/load. Furthermore it should be stored at a lower temperature (as in the fridge or freezer). While it is true that being discharged too far is not good for the battery, this is because of the danger of voltage reversal--literally the positive terminal becoming negative and vice versa. If you get a battery in that state (which is caused by such things as leaving a discharged battery connected to a device or load) then it may not be recoverable.

Storing cells in a charged state, particularly at room temperature or higher (as in summertime temps), will result in "rock"/crystal formation in the battery which will only result in such things as commonly referred to as "memory". However, batteries that have rock formation can often be recovered using deep discharge/charge/repeat cycles to refresh the battery.

As greenmachine says, the same is true of Li-Ion batteries in terms of storage conditions, though with Li-Ion you'd usually want to keep about 30-40% charge on the battery before low-temp storage. Also deep discharge is never desired for this chemistry type and Li-Ions which lose capacity because of room or higher temp storage while fully charged can never be recovered.

[MDX-400]

Thanks guys! No problem to get new batteries ... I just wanted to ask if it was normal. BTW some of you reccomended an Ni-MH AA in the 2000 -2100 mAh variety ... as I looked at the original Sony battery inside I discovered it's a 700 mAh ... what does it means?

Thanks again!

Sony essentially put an AAA NiMH battery inside the casing for an AA battery. That is why the capacity is so low. A move to save a few cents on every MD unit with this type of battery packaged with it--and obviously a stupid move by Sony.

Also, if you are going to be recharging the battery in the unit (via plugging it into the wall and hitting the stop/charge button) expect charge times approximately 3x longer than it used to take to charge the Sony-provided battery as a higher capacity AA will require more time to charge to full capacity.