Help with Testing new Eneloops

[grounder25]

I have read many posts concerning Eneloop testing and would like to make my own contribution.

I have just received 16 Eneloop cells (AA, 2000 mah, 1500 cycle) from Thomas distributing.
I won't be using these for a few weeks and would like to do some cycle testing to see what difference breaking in makes.

My initial thought is to separate the cells into four groups A1, A2, A3, A4, B1, B2 etc for C and D.

In deference to the "just use them crowd" I will Install the Group D cells into a cheapo led flashlight, turn it on, remove them when the light goes out.

Then perform the following operations using my Maha MH-C9000.

Discharge the cells from Groups A, B and C at 100ma and record the capacity of each cell.
Group A - just stick them in and let them charge automatically.
Group B - run three cycles using the cycle mode using 1000ma charge and 500ma discharge.
Group C - run three break-in cycles with the capacity set to 2000mah.
Group D - just stick them in and let them charge automatically.

After all this cell activity is complete I will discharge all cells at 100ma and record the capacity of each cell.

After all this testing is complete I will post the results.

The purpose of this is to determine what, if any effect breaking in or other operations will have on the capacity of these cells.

Any suggestions?

 

[awyeah]

I'd be interested to see your results.

I did a non-scientific test of some new eneloops I recently got. I discharged them, then charged them at .5C on my C9000, then discharged at .25C, and they were ~1800mah. After the break-in, they were all 1900+ mah, one was over 2000.

What I'd be most interested in is if they "break in" naturally after several normal charge/discharge cycles - i.e., will their capacity increase after you use them a few times.

 

[grounder25]

Awyeah
I have gotten a start on this testing but it is going to take a while to complete it.
I am also am interested to see if normal cycling will result in an increase in capacity. My biggest problem is trying to come up with a test that simulates a normal pattern of usage.
Do you think the multiple cycles of “Group B” will accomplish the normal charge/discharge cycles you reference or did you have some other testing methodology in mind?

 

[awyeah]

I think the Group B test is a reasonable way to do that. However, different lights draw different rates, so you may want to try discharging them more quickly or more slowly. In the end, though, 100mah probably won't make a huge difference, although obviously we flashaholics like to squeeze every last drop of performance we can get ;)

 

[Billspider]

I have read many posts concerning Eneloop testing and would like to make my own contribution.

I have just received 16 Eneloop cells (AA, 2000 mah, 1500 cycle) from Thomas distributing.
I won't be using these for a few weeks and would like to do some cycle testing to see what difference breaking in makes.

My initial thought is to separate the cells into four groups A1, A2, A3, A4, B1, B2 etc for C and D.

In deference to the "just use them crowd" I will Install the Group D cells into a cheapo led flashlight, turn it on, remove them when the light goes out.

Then perform the following operations using my Maha MH-C9000.

Discharge the cells from Groups A, B and C at 100ma and record the capacity of each cell.
Group A - just stick them in and let them charge automatically.
Group B - run three cycles using the cycle mode using 1000ma charge and 500ma discharge.
Group C - run three break-in cycles with the capacity set to 2000mah.
Group D - just stick them in and let them charge automatically.

After all this cell activity is complete I will discharge all cells at 100ma and record the capacity of each cell.

After all this testing is complete I will post the results.

The purpose of this is to determine what, if any effect breaking in or other operations will have on the capacity of these cells.

Any suggestions?

I also purchased a Maha C9000 and 10 AA 1500 Enelopps. Can't wait to see your results

 

[grounder25]

Progress report:

Group A, B and D testing is complete.Completed testing of the these three groups has produced an insignificant difference in capacity (less than 2% of total battery capacity).

I have begun testing of Group C (three break-in cycles with the capacity set to 2000mah).
Note: Group C cells have been discharged at 100 ma using the MH-C9000.

After examining my original test plan I realized the break-in testing would contain significant charging redundancy which would not contribute anything to the final data.

A break-in cycle consists of the following steps:
1. manual adjustment by the operator of C(manufacturer stated cell mah capacity).
2. 16-hour 0.1C charge.
3. one hour rest.
4. 0.2C discharge (cell voltage terminated).
5. one hour rest.
6. 16-hour 0.1C charge.
7. DONE

If three break-in cycles are performed back-to-back then between cycles two and three there will be a 16-hour 0.1C charge followed immediately by another16-hour 0.1C charge.

This procedure will result in the following.
1. (six cycles) 96-hour 0.1C charge.
2. (three cycles) 30-hour (approximate) 0.2C discharge.

I propose manually inserting a 0.2C discharge cycle after each of the break-in cycles which will yield the following.
1. (six cycles) 96-hour 0.1C charge.
2. (six cycles) 60-hour (approximate) 0.2C discharge.

The discharged cells will then be charged using the automatic charge function of the MH-C9000. Then a 100ma discharge cycle will determine the final capacity.

Any comments?

 

[SilverFox]

Hello Grounder25,

Welcome to CPF, and welcome to the world of battery testing.

Eneloop cells, as you have discovered, are new enough that they don't show much benefit from the Break In function. Other cells may have been in storage for an extended period of time. Those cells can benefit from the Break In. One way to look at the Break In function is that it can uniformly distribute the electrolyte within the cell. Things can get a little out of balance during storage. This is also needed if the battery manufacturer doesn't cycle the cells right after manufacturing. This additional cycling takes time and can add to the cost of a cell, so some simply don't do it.

Most of the damage to cells comes from overcharging, so you idea of adding a discharge between back to back Break In cycles is good. I always discharge a cell before running a Break In cycle.

To better understand the benefits of a Break In cycle, you should find a friend that has some old rechargable cells laying around and see if the internal resistance is low enough to be accepted by the C-9000 for charging. You would first do a charge and discharge using the defaults, then do a Break In to see if the capacity changes.

In light to moderate current draw applications, simply using the cell can produce the same results that a Break In does. The advantage of the Break In is that it follows a standard and gives you a benchmark to compare the cells health to later on when it comes time to think of replacing it. I use 80% as my replacement criteria. If a cell started out with 2000 mAh of capacity during a Break In, and it falls below 1600 mAh later on, it will be replaced.

Tom