#### virtualbeing

##### Newly Enlightened
how do you determine dead batts? charge them then check the volts? or read them at empty?

and i am guessing "fully" charged is all based o the charger used. but say we are talking about a AAA nimh is there a % of 1.2V that signals no good? or perhaps a time span that keeps the full charge? or what exactly is the best way to tell?

thanks

#### Mr Happy

##### Flashlight Enthusiast
What you need to do is charge them up and then do a run time or discharge test. This is to find out how much charge they hold (or how long they will run something) compared to what is expected of a good battery. Once the capacity is less than about 80% of normal you can consider them to have expired.

A second test would be for self-discharge. Charge them up and let them sit for a month, and then do the discharge test. Depending on how you use the cells, if they are flat after a month or less this might also tell you they have expired for your purposes.

#### virtualbeing

##### Newly Enlightened
so i would have to get both a "good"(control) bat and a "bad" (questionable) bat to full, then run them down to about 80%. meaning the time is the variable?

something like 1hour for each and test them- do the percent of 1.3v ?

2 hour etc. until 80% is reached?

80% being the mark of where i don't want to drain past right? but the control bat should have more volts than the dead at the same time frame....is that correct?

thanks mr. happy

#### Mr Happy

##### Flashlight Enthusiast
so i would have to get both a "good"(control) bat and a "bad" (questionable) bat to full, then run them down to about 80%. meaning the time is the variable?

something like 1hour for each and test them- do the percent of 1.3v ?

2 hour etc. until 80% is reached?

80% being the mark of where i don't want to drain past right? but the control bat should have more volts than the dead at the same time frame....is that correct?

Unfortunately you cannot tell much about the capacity or quality of a NiMH cell by measuring its voltage.

The standard measure of the capacity of batteries is mAh (milliamp-hours). This is measured for a single cell by starting out fully charged and draining it at a constant current until the voltage drops to about 1 volt. The time this takes multiplied by the drain current in milliamps is the capacity in mAh.

The best way to measure this value is with a battery analyzer such as the Maha C9000 charger. If you don't have one of those, the next best way is to measure the run time on a single cell flashlight. If you charge up a known good cell of the same kind and time it in the light until the light starts to go dim that gives you a reference point. If you now do the same test with the questionable cell you can compare the times. The length of time before the light goes dim is almost proportional to the capacity.

However, it is possible for a cell to be temporarily bad, so a single test like this is still not really enough to know. To be really sure you need to cycle the bad battery through a few charge/discharge cycles before testing it again to see if it recovers at all.

#### labrat

##### Enlightened
Open voltage readings of rechargeable batteries tells you little to nothing of the health of the battery/cell.
A NiMh AAA cell can read 1.5 Volts, a Lithium-Ion RCR123 can read 4.20 Volts, after charge and rested, and be completely empty of usable energy.
As explained above, with a battery analyzer such as the Maha C9000 charger, or a ZTS battery tester, an easy and quick state-of-health can be determined.
Or cycling the battery through a few charge/discharge cycles, doing accurate measurements, can give you an accurate readout of the health-state of the cell.
A quick test using your DMM and measuring the Amperes the cell can give in a brief moment of direct short through the meter is also a good indicator, just never keep the meter connected much more than a second! and remember also a good AAA NiMh can give out around 8 Amperes this way!
A RCR123 Lithium-Ion can push up to 19 Amps!
So this test is neither for use with a cell with a protection circuit.
Do not abuse this method, it does take it's toll on the cell, and should never last longer than a brief second!
If you get out less than one Amp from any cell after a charge cycle, the cell is done.

#### virtualbeing

##### Newly Enlightened
thanks mr happy- at leat i was getting the "time" sense right

thanks labrat.

about how much is the Maha C9000 charger ?

sounds like a good deal (i am assuming it runs tests?????) but the other point of having another charger is good enough reason to get on. i ALMOST got the sanyo (i think it was) at Costco. i remember it coming up afew times here on CPF. not sure if it runs diagnostics.

not sure if there might be an advantage of 1 over the other. right now i just have a cheapy 4AA or 4AAA energizer charger from wallys. works fone for \$20 or whatever it was. but they don't last forever. we have had 1 die, and a D size charger that never seemed to work right.

so i guess...having premium flashlights justifies a premiuim bat charger:thinking:

LOL

thanks for the help. any link or comparitive info on the costco charger and the Maha C9000 charger would be helpful.:thanks:

#### Black Rose

##### Flashlight Enthusiast
None of the Sanyo chargers available at Costco are able to perform tests.

The C9000 is currently available at Thomas Distributing for \$59.97.

#### virtualbeing

##### Newly Enlightened
thanks man.

i guess that settles that

#### Bonky

##### Banned
or a La Crosse, essentially the same, at \$32-39.

#### Mr Happy

##### Flashlight Enthusiast
The cheapest way to approach dead rechargeables is to recycle them and replace them with new high quality cells as soon as you suspect they are under performing. Compared to the cost of expensive chargers and time spent analyzing them, replacing old cells is far more economical than testing them and trying to revive them.

#### Bolek

##### Enlightened
how do you determine dead batts? charge them then check the volts? or read them at empty?

and i am guessing "fully" charged is all based o the charger used. but say we are talking about a AAA nimh is there a % of 1.2V that signals no good? or perhaps a time span that keeps the full charge? or what exactly is the best way to tell?

thanks
As a NiMH cell is not dangerous if not severly abused, it's dead when the runtime in the device in which you want to discharge it is lower than what YOU consider as a USEFULL runtime
As long as it gives me light, pictures, flashs, you name it, for a reasonable amount of time I keep it.
Be carefull dead Li Co can be dangerous. I use new ones for hi curent lights, not too old in low courent lights, and I do not use the bad ones.

#### virtualbeing

##### Newly Enlightened
bolek :tinfoil: LOL

one of the problems i was running into with the energizer charger i have was say 4 aa or aaa are in it. it would charge.....but i wouldn't know which bats were good or not. Now i have a MM.

but i can see i would drop 4 bats in it and then it's a guessing game as to which were good or not. the charger would just charge. leaving a sense of ambiguity. then i would drop bat 1/4 and maybe 3/4 in a device and it might be half azzed. then try to add 2/4 and 4/4 etc. etc
:mecry:

i see some of the chargers you guys recommend say they wont charge dead bats. good! that takes the above scenerio out of the picture :bow:

#### virtualbeing

##### Newly Enlightened
btw the couple chargers recommended...they don't charge the CR123 since they are a dif dimension right?

also if i want to go to other 18650 Li-ion what do i need to charge them & the 123?

i haven't used the 18650's before. so that will open up some flashlight options :twothumbs

#### Bonky

##### Banned
Compared to the cost of expensive chargers and time spent analyzing them, replacing old cells is far more economical than testing them and trying to revive them.

Keeping in mind that the aforementioned La Cross charger is \$30something and includes 4 AAs and 4 AAAs with it.

I'm not a shill for the company, I just don't understand why more people here don't have this charger. It takes all the guesswork out of which batteries are good and which aren't. And it will tell you just how good (or bad) they are. And I've used it to recondition batteries that have fallen under 0.5v so that they're indistinguishable from new ones.

Once you throw in the cost of the included batteries (around \$20 retail), you're getting a top-of-the-line charger for around \$15.

#### Black Rose

##### Flashlight Enthusiast
Keeping in mind that the aforementioned La Cross charger is \$30something and includes 4 AAs and 4 AAAs with it.

I'm not a shill for the company, I just don't understand why more people here don't have this charger.
Earlier versions of the BC900 had a reputation of actually melting down if precautions are not taken...that's one reason I opted for the C9000.

The lower cost BC700 seems to have avoided it's big brothers problems.

Also, the C9000 has a 3 year warranty vs 1 year for the LaCrosse models.

#### Bonky

##### Banned
ok fine, but you have an equally high-end if not better product. I should have said:

"I just don't understand why more people here don't have this charger or another high-end charger."

The difference of course is that the C9000 is pricier.