Ni-MH BATTERIES (AA Size) - It's usage


Oct 12, 2008
35
1
0
Colombo, Sri Lanka
#1


When using AA size Ni-MH batteries in Speedlights it is always advisable to discharge them before recharging. My practice is to connect the four batteries to a 6v bulb in series until the batteries are fully discharged.

( 1 ) After an overnight's discharging procedure I have noticed 3 cells get fully discharged but one has little amount of charge left in it. Has anybody experienced this? How to overcome this?

( 2 ) Are there any 'Discharging units' available in the market?

Thanks if someone can answer these questions.
 

qystan

New Member
Jul 8, 2010
481
1
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#2
Your discharging method has a damage risk. You should discharge them individually not as a pack.

While discharging the whole lot in series, some cells will be flat before the others. No 2 cells are every the same.

The flat cells will be subjected to reverse charging while the remaining cells discharge. Effectively means it's getting damaged.

This is also the reason not to fully discharge your rechargeable batteries coz it is a pack of assembled cells.

Any battery with output more than approx 1.2v is a battery pack
 

catchlights

Moderator
Staff member
Sep 27, 2004
21,903
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48
Punggol, Singapore
www.foto-u.com
#3
Ni-Mh batteries have lesser memory effect, you need not to discharge them before each recharge,

there are some battery chargers come with discharge function, the Powerex MH-C9000 Charger - Analyzer, is the best charger money can buy.
 

Octarine

Moderator
Staff member
Jan 3, 2008
12,491
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48
Pasir Ris
#4

When using AA size Ni-MH batteries in Speedlights it is always advisable to discharge them before recharging. My practice is to connect the four batteries to a 6v bulb in series until the batteries are fully discharged.
Where did you got this misinformation from? Hope it's not one of your good friends / buddies who misleads you here. This procedure is completely useless since NiMH cells do not suffer from any memory effect as what the NiCd cells did. There is no need for any discharge. Secondly: uncontrolled discharge with some lamps will only damage the cells. If you need to discharge / charge the batteries this way (a process commonly named as 'refresh' or 'reformat') then do it in controlled way, which requires monitoring of voltage and current.
( 2 ) Are there any 'Discharging units' available in the market?
Almost all decent chargers out there in the market have this function. Get the usual suspects from Maha and other brands, skip cheap stuffs from uncle shops.
 

Oct 12, 2008
35
1
0
Colombo, Sri Lanka
#5
I know, it is a common saying only NiCd's have the memory effect and no problem with NiMH. It is not true, I have practically experienced NiMH also has it but not as big as in NiCd's.
 

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