How to test the shelf life of NiMHs?

[shobhitk]

Hi everyone,
i was wondering if theres a way to test the shelf life of nimh cells (2700 mah) using only the mh-c9000 charger?
i want to do this to check the health of my nimh batteries in terms of their charge retention capacity. this is useful to know otherwise the cells might look good when they r recently charged but when u want to actually use them after a few hours/days you may find that they have lost most of their useful charge.

it would be nice if someone could guide the correct procedure on the mh-c9000 to do this.

Thanks

 

[Mr Happy]

You want to know how long they stay charged if not being used?

First you label the cells so you can keep track of them. Then you put them them through a break-in cycle and record the capacity of each cell and the date. When they come off the break-in cycle they will be fully charged. Then you put the cells somewhere safe for a measured time like one month. After the month is up you put the cells on a discharge at 0.2C and record the results.

Compare the one month results with the original capacity and there you have your answer.

 

[shobhitk]

hello mr happy. thanks for the support. i'll give that one a try.
i have some more related quesions...

there are 2 capacities involed in a cell. first is the FULL capacity upto which the cell can be charged and the second one is the actual AVAILABLE capacity which is in it at a given point of time. so when i run a mode(except charging mode) to check the available capacity at the end of a full mode it shows the 'Available Capacity'. so i suppose this is the capacity which is ACTAULLY being held by the cell at that given point of time and not the capacity which the cell has potential to hold. but what if i want to know the FULL capacity upto which a cell can be charged(its full potential)? is Break-In the answer? by that i mean that after a break-in the charge which is being shown as 'available' is both the actual charge held in it and it is also the maxiumum charge which can be held by it for its full potential...am i getting it right?

also am a bit confused regarding the ACTUAL difference between the Refresh/Analysis and the Cycle mode...which one should be used at what time and for what specific situation?

thanks

 

[Black Rose]

R&A mode charges the cell, the discharges the cell to determine a working capacity (versus break-in capacity), and then charges the cell again.

Cycle mode does the same thing, but up to 12 times. Only make sense to use this mode if you want to do 2 or more cycles.

 

[shobhitk]

Hi Black Rose,
so u mean that theres absolutely no difference between these 2 modes and the only difference is the number of cycles in the cycle mode?

also i couldnt get u here-

black rose: 'determine a working capacity (versus break-in capacity)'

i coudnt get the 'versus break-in capacity' part of it..

 

[Mr Happy]

A break-in cycle estimates the full capacity of the cell, the maximum to which it can be charged. (To really get the best estimate you may have to repeat the break-in cycle more than once.)

On the other hand a normal charge will not typically fill the cell as fully as a break-in charge will. A normal charge therefore gives you a working capacity, which will typically be a bit less than the 'full' capacity.

 

[shobhitk]

fair enough Mr Happy, thanks. also as regards the difference between R&A and Cycle mode, are u of the same view as black rose?

 

[Mr Happy]

fair enough Mr Happy, thanks. also as regards the difference between R&A and Cycle mode, are u of the same view as black rose?

Yes. However, I personally find more benefit from running a break-in cycle than from running R&A cycles. I almost never use the R&A or Cycle features.

 

[shobhitk]

no doubt break-in is THE mode of charging...but u have to wait for around 40 hours for a single charge...

 

[Mr Happy]

no doubt break-in is THE mode of charging...but u have to wait for around 40 hours for a single charge...

But it's not a charge, it's a conditioning cycle. You don't run it every day (or even every week or month).

 

[Black Rose]

The only time I've gotten better results from using cycle mode over break-in was with some NiMh LSD cells that were not "broken in" at the factory.

Multiple break-in runs were not increasing the capacity. It wasn't until I put 12-15 charge/discharge cycles on the cells that things started to improve.