AA 3600mah

[mp3hot]

yes yes i know AA batteries cant reach 3600mah , but i just bought them to test .

i read that ni-mh would get permanently damaged if discharged below ~0.9VDC . so may i Ask which option to choose to charge these batteries for the first time and know there exact capacity ?

i know if i charge them normally the bc-9009 would start charging the battery from 000mah , so lets say if they already have 1000mah of charge inside and u charge them for the first time and charger would display they are fully charged at 500mah that means that the battery is 1500mah .

& if i do Charge&test the battery would get charged and then totally discharged and charged again ... i ask when it gets totally discharged it would permanently damage the battery?since its totally discharging it & ni-mh batteries cannot get totally discharged

 

[45/70]

Welcome to CPF mp3hot! :thumbsup:

Your BC-9009 will not completely discharge your cells, regardless of which mode you use. There is sometimes confusion when the term "completely discharged" is used. For practical purposes, "completely discharged" is an open circuit (OC) voltage of 1.20 Volts with a NiMH cell, not necessarily 0.00 Volts. Your BC-9009 will only discharge your cells to 0.90 Volts under load, and the voltage will recover to ~1.20 Volts (OC) (or should, with healthy cells) when removed from the charger.

If you want to check the capacity of these new cells, simply stick them in and set the charger to "Test". I would use something like a 700mA charge/350mA discharge for the test, that way the charger shouldn't have any problem with termination of the charge portion with the new cells.

Dave

 

[SilverFox]

Hello Mp3hot,

Welcome to CPF.

The danger with over discharging is more from the potential of being reversed charged by other cells. You can discharge a single cell below 0.9 volts for a short time, and it will recover.

On the other hand, if the cell self discharges below 0.9 volts damage can occur.

This is a grey area, so it is best to limit the discharge to 0.9 volts under load. Keep in mind that when the load is removed, the cells voltage will rebound to around 1.2 volts.

The reason we use a cut off of 0.9 volts is that at that point there is virtually no capacity left in the cell. With NiMh chemistry 0.9 volts under load is empty.

The capacity of a cell is the discharge capacity. While charging, you usually put more in than you get out. While it is interesting to see what you put in, run time is based upon what you get out of the cell.

Your charger stops the discharge at 0.9 volts, so this is a normal cycle and it does not do damage to the cell.

Labeled capacity is supposed to be based upon standard testing. The standard charge is a 16 hour charge at a charge rate of 0.1C. If your cells were really 3600 mAh, they would be charged at 360 mA. After this charge the cells rest for an hour, then are subjected to a discharge that drains the cells in 5 hours. This is referred to as discharging at 0.2C. In the case of the 3600 mAh cells, the discharge rate would be 720 mA.

The BC chargers skip the rest time, so the discharge capacities are a little optimistic, but close.

Tom

 

[TakeTheActive]

mp3hot,

...While charging, you usually put more in than you get out. While it is interesting to see what you put in, run time is based upon what you get out of the cell...

As cells age, it's important to also regularly monitor what you put IN (ACCUMULATED Capacity) vs what you 'could' take OUT (DISCHARGE Capacity) to ensure that your charger is terminating properly.

If you SEARCH the CPF 'Batteries Included' Archives, you'll find folks actually stating / believing that their 'Not-Brand-New' AAs *ARE* yielding 3200+ mAh DISCHARGE Capacity, since they always carefully 'Slow-Charge' them @ 200mA. In truth, they're confusing ACCUMULATED Capacity with DISCHARGE Capacity *AND*, by charging at so low a Charge Rate, their charger is missing the -DeltaV termination and overcharging their cells (and terminating on MAX Time).

So while TEST and REFRESH are good to determine DISCHARGE Capacity, DISCHARGE every-so-often is also good to determine if your charger is terminating properly (i.e. ACCUMULATED Capacity not over ~130% of DISCHARGE Capacity). When that happens (ACCUMULATED Capacity > ~130% of DISCHARGE Capacity), you need to up the Charge Rate until it drops back down. If the cells then get HOT at the new, higher Charge Rate, their Internal Resistance has increased to the point where they should probably be recycled. (Unless you're like some of us 'frugal' types, who'll then 'nurse' EVERY LAST DROP of energy out of them in digital clocks, thermometers, remotes, etc... )

 

[mp3hot]

Welcome to CPF mp3hot! :thumbsup:



If you want to check the capacity of these new cells, simply stick them in and set the charger to "Test". I would use something like a 700mA charge/350mA discharge for the test, that way the charger shouldn't have any problem with termination of the charge portion with the new cells.

Dave

thanks guys for your warm welcome . ok ill try the TEST option , i never tried it before since i always charge my batt's @ default mode .

Within this 8-second time from inserting the batteries the user may first select the
operating mode by the MODE key. "Charge", "Discharge", "Refresh" and "Test" mode
may be chosen.
Then within 8 seconds from the last key pressing, user may select the charging/
discharging current by pressing the CURRENT key.
Note:
 The mode key shall first be pressed and held for about 1 second to activate the mode
change. The subsequent pressing of the mode key will toggle between the "Charge",
"Discharge", "Test" and "Refresh" mode.
 There is an 8-second time allowed for choosing further functions after each key
pressing. If no more keys are pressed, the LCD will blink one time to indicate the end of

 

[TakeTheActive]

TTA's "Summarized" La Crosse BC-700 / BC-900 / BC-9009 Charger/Analyzer Instructions

:help: TTA's "Summarized" La Crosse BC-700 / BC-900 / BC-9009 Charger/Analyzer Instructions​