Can I leave the batteries in the charger plugged into the wall? Will they stay charged and other than drawing a small amount of current, will it damage the batteries to leave them charging once they are fully charged?
asked by C. Gestal on February 25, 2011
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A
In most cases for a 'smart' charger, once it finished charging, the current is reduced to 5-10% of normal charging current. It is perfectly safe to leave your batteries 'trickle charged' for a few days.

- For ordinary NiMH cells, the trickle charge current cancels the effects of self-discharge. So your cells will remain in fully charged state the next time you need them.
- For low-self-discharge cells, trickle charge is not necessary. So you should remove your cells just to save some energy. But some people like to keep their cells trickle charge for a few extra hours, just to make sure that the cells are charged to 100%.

On the other hand, if you are using a dumb charging that never terminates, then it is a bad idea to keep cells in the charger for too long.
NLee the Engineer answered on February 26, 2011
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A
I have the Sanyo MQN06U charger and was wondering if it is a "smart charger" or a dumb one, i.e. does it switch to a trickle charger after the batteries have reached their full charge?
tom k. answered on December 9, 2011
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A
Was wondering this myself. NLee I have to say that you're the most informative person I've ever encountered on Amazon. If I buy the charger with four AA batteries and an extra set of AA batteries could i use one set of batteries one day and have the other set charging and then use the charged ones the next day? Or do I even need extra batteries. It's mainly for my new Fuji Finepix camera I just bought and it only takes two batteries. Would two batteries get me through a day while always carrying around the extra two and then charge them at night?
i don't know squat about this. I've bought chargers and things in the past but mainly on a whim and in target or best buy. I'd like to get a good reliable set. How long does it take to recharge the four batteries if they're completely dead? Also can I charge AAA batteries with this charger? Can I mix different types of rechargeable batteries with this charger? NLee you're my only hope!!!!
I need more engineers in my life and fewer artists.
Emma Dilemma answered on March 7, 2011
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A
Emma,
If your camera needs two AA cells, then you should get at least four. Keep one pair in your camera and one pair in the camera bag as spare. When the set in your camera is exhausted, swap in the spare set while the exhausted set goes in the charger. No down time, no waiting.

Note that this only works with low-self-discharge batteris (eneloop, etc). With ordinary NiMH cells, your spare set will probably be dead by the time you need it.

You should get the Sanyo eneloop MDR02 2-cell, plus another 4-pack of eneloop cells. This charger is better than the 4-cell eneloop charger (MQN06) because it is faster and handles individual cells. You can also use it to charge any brand of NiMH AA/AAA cells.

In general, it is not a good idea to mix and match different brands of rechargeable batteries. If one cell has a lower capacity, it will just drag down the capacity of the whole set.
NLee the Engineer answered on March 8, 2011
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A
How do I know if my charger is 'smart' or 'dumb'? I just took a look at it, read the label on the back, etc. and it doesn't say anything about trickle charging. It is a Synergy Digital model SB-252 rapid quick charger.
Hilda answered on June 22, 2011
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A
Normally it will state that it is a smart charger. One way to tell is it has a sensor that shows you via flashing lights or something like that, three or four lights counting up or red/amber/green. Honestly, it isn't a good idea to leave your charged batteries in the charger, even when a Smart charger. It can last a few days in there, but overall in the end it could damage the overall capacity of your battery. Best to charge them, remove them till used, used them all the way down, and recharge them to full...rinse and repeat. You can also damage the capacity of your batteries by only using say 50% of your battery life all the time, and then charging them again. Best to use them all the way down, till they need to be charged and charge them all the way up again.
Patrick Q. answered on June 21, 2013
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A
Normally it will state that it is a smart charger. One way to tell is it has a sensor that shows you via flashing lights or something like that, three or four lights counting up or red/amber/green. Honestly, it isn't a good idea to leave your charged batteries in the charger, even when a Smart charger. It can last a few days in there, but overall in the end it could damage the overall capacity of your battery. Best to charge them, remove them till used, used them all the way down, and recharge them to full...rinse and repeat. You can also damage the capacity of your batteries by only using say 50% of your battery life all the time, and then charging them again. Best to use them all the way down, till they need to be charged and charge them all the way up again.
Patrick Q. answered on June 21, 2013
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