Help me understand how the c9000 breakin mode does not the batteries

I have been reading about the break in mode of the c9000 and also the skyrc nc25000 that does the same thing.

They charge the battery for 16hours at .1C and rest for one hour, discharge it at .2C rest another hour and then charge again for .1C and its done.

What I dont understand is how charging at .1C for 16 hours doesn't hurt the battery because for example a 2000mAh rated battery, charging at 0.1C would put in 3200mAh.

So what happens after 2000mAh is put in the battery? Does it just converts the remaining 1200mAh into heat? What happens to that extra current?

With todays cells is this mode still necessary?

You're probably right, and it's overkill for today's quality cells. I certainly wouldn't charge Eneloops 16 hours at 0.1C on a regular basis, as I think it would damage the cells (Eneloops are sensitive to overcharging and trickle charging).

I assume that for an older cell with higher internal resistance, 16 hours at 0.1C is necessary to guarantee a full charge, since some of the charge on older cells is lost to heat. Since new Eneloops do not need any break-in, this mode is best reserved for old cells that are suffering, or non-LSD cells that have been sitting unused for a year. Otherwise, just don't use it.

I think the break-in is more useful for cells that haven't been used in a long time and often times will think the cell is full. For an example the Enercells i got was originally around 0.5 volts but only took 15 to 30 minutes to charge so i ended up having to trickle charge them (since i only had the La Crosse charger with me) for 15 hours or so. So far for 2500mAh cells, i got roughly about 1800-2200 (the newer cells did better) and they are pretty well useful.

I don't see any reason to use the break-in on Eneloops since they are LSD. A general test should give you an idea of what capacity Eneloops have and for the most part don't need refreshing.

I think for the most part if you are choosing the right capacity of the battery, ie: 2000mAh for a battery that will perform at 2000mAh it won't severely overcharge the batteries and any overcharging won't kill the cells because it's an extremely low current that you should not be doing all the time. You shouldn't refresh or drain your cells all the time either, but if you don't mind the cells degrading quicker...

I think that the break in function is a means for you to verify that you actually got what you paid for when you purchased the batteries. Attempting to read the DOM off of a battery that may have sat for years in storage before sale can be an issue.

The break-in assures that you are starting out with a fully charged battery.

NoNotAgain said:

I think that the break in function is a means for you to verify that you actually got what you paid for when you purchased the batteries.

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Precisely
The C9000 Break-In Mode is a close approximation of the standard ANSI C18.2M procedure for determining rated capacity of rechargeable batteries:
1. Discharge cells at 0.2 C to specified end voltage (1.0 V for NiMH).
2. Charge cells at 0.1 C for 16 hours.
3. Rest cells for 1 hour.
4. Discharge cells at 0.2 C to specified end voltage (1.0 V for NiMH).

Unfortunately, the C9000 does not do the first step automatically; you should run the Discharge Mode manually before the Break-In Mode.

Hello Hammerjoe,

To understand what is going on with the 0.1C charge for 16 hours you need to do some studying of coulometric charging efficiency.

With NiMh chemistry the coulometric charging efficiency is in the range of about 65-85%. The lower efficiency is observed at low charging rates. The higher efficiency is observed at high charging rates.

As an example let's arbitrarily define 0.1C as a low charging rate, and 1.0C as a high charging rate. If we have a fully discharged 2000 mAh cell we would expect to have to put in 3077 mAh at a low charging rate, or 2353 mAh at a high charging rate.

With a 2000 mAh cell the 0.1C charging rate is 200 mA. To put 3077 mAh into the cell you would need to run the charge for 15.39 hours. The battery test standard rounded that up to 16 hours giving the cell only a little over 36 minutes of overcharge. Since the charge is terminated by time, this small amount of overcharge does no damage to the cell.

To monitor against overcharge when charging at 1.0C with the same cell and once again starting with an empty cell you would set your timer for 1 hour and 11 minutes and check to make sure the charge has terminated.

Tom

Silverfox thank you for the lesson.

I think I got what you are saying.
For those that dont have the c9000 like me can simulate the breakin mode by following these steps:

- Assume 65% efficiency for the cells both AA and AAA.
- Calculate capacity for 100%. Example 2400mAh battery 100% efficiency would be 3692mAh
- Charger lowest charging current is usually 200mA so to charge 3230mAh it would take over 18hours
- If charger has a timer charge at 200mA for 19 hours otherwise set up an alarm to warn that times up.
- Rest for at least one hour
- Discharge at the lowest setting (usually at 100mA).
- Rest at least one hour
- Repeat charge steps again.


Did I get this right?

Hello Hammerjoe,

That looks pretty good...

Tom

what's a "c9000" ???

lumen aeternum said:

what's a "c9000" ???

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MAHA MH-C9000 AKA "c9000".

Apparently the venerable charger has a legend large enough for Google to grok as the first result links of a Google search for C9000 turn up the MAHA charger, not the Samsung C9000 high definition television.