NiMH rechargeable batteries PROBLEM

[ahmed osama]

NiMH rechargeable batteries PROBLEM

i have a NiMH rechargeable batteries Energizer AA 1.2V
My problem that the battery get discharge so fast if i didn't use it ib about 1-2 week it get empty (my digital camera don't even run for a moment !! )


any tips ???

 

[flatulent]

The self discharge rate you give is too fast. Try removing the battery from the camera when not taking photos and see if the charge lasts longer.

 

[ahmed osama]

The self discharge rate you give is too fast. Try removing the battery from the camera when not taking photos and see if the charge lasts longer.

i have 4 batteries , 2 was in the camera & 2 was out and both get empty about in the same period
?????

 

[flatulent]

In this case there are two possible problems.

1. Your charger is defective and not charging the batteries fully.

2. Your batteries are defective. Normal NiMH batteries will hold most of their charge for a year.

There are several things you can now do.

1. Buy new NiMH batteries and see if this fixes the problem.

2. If this does not fix it, buy a new charger.

 

[Mr.Cool]

that is good advice flatulent.

i would only add that possible both batteries and chargers WERE good at one time.. but maybe the batteries were discharged to zero volts by accident once and now they are ruined. (this may not apply to NiMH technlogy, see member posts below)

remember that the label voltage (12V sealed lead acid battery, or 1.5AA battery for example) indicates the DISCHARGED voltage. so.. if you have a AA battery and it reads 1.5 volts, it is dead. if it reads 0.9V it is likely to be worthless forever.

Mr.Cool

 

[ahmed osama]

my batteries voltage now about 950 mV !!!! is it only dead or it is damaged ????


indeed what i recalled that it was storaged for 3 days in a hot place about 38oC , i guess this may be the reason for it is fast discharge ???



About the charger indeed i used an old one ,it is charging current is low about 125 mA & i charge my batteries 140% C (140% of 2500 )

so 1.4*2500/125 give 28 hr of charging and i stop the charging when the voltage rise more than 1.45 V and be about to decrease again (delta V)

by the way while charging batteries temp. almost doesn't rise at all !!!


any tips ?????

thx all

 

[turttle]

As far as I know:

- SLA batts shouldn't go below 1.8V/cell (high risk of permanent damage).

- NiCd/NiMH batts don't have a discharge limit, indeed it's commonly advised a periodical full discharge to avoid battery depresion effect (sudden voltage fall similar to memory effect for old NiCd but not permanent). Nevertheless for multicell packs (x times 1.24V/cell nominal) full discharge must be avoided because of the effect of fully discharged cells (faster discharge) together with partially discharged ones. 0.9V/cell uses to be taken as practical indicative of fully discharged cell but not of a definitely lost one.

About charging (NiMH):

delta-V End-Of-Charge uses to give early EOC (in few minutes) on deeply discharged cells. delta-Temp is supposed to be more effective but I doubt if it works as expected at slow charging.

1.4-1.6x C rate charging it's usually refered for C/10 charging current and 14-16 charging hours and, since it's related to charging efficiency, I don't know if it could be applied for very slow charging.

On my experience auto-discharge is greatly reduced keeping batteries protected from regular air exchange (ie enveloped inside a drawer with few changes of moisture and temperature). It's also a lot cheaper than a real climatic chamber.

Cheers ;-)

 

[hermin]

probably you bought a low quality battery...i have rechargables AAA, and they work fine even if i dont use them for 5 days,

 

[ahmed osama]

probably you bought a low quality battery...i have rechargables AAA, and they work fine even if i dont use them for 5 days,

it is NiMH rechargeable batteries Energizer AA 1.2V

but old charger with 125 mA charging current

 

[fedejofa]

probably you bought a low quality battery...i have rechargables AAA, and they work fine even if i dont use them for 5 days,

it is NiMH rechargeable batteries Energizer AA 1.2V

but old charger with 125 mA charging current

well, that charging current is not the problem...and the other things u ay arent either..
i guess they have some 'accident'.
If u want, use a multimeter and check charger current while charging the battery.

 

[ahmed osama]

i guess its high temp.

i left them for a week in a high room temp. about 38 oC !!! i guess this is the problem