Help: Correct strategy with C9000

[shobhitk]

Hello everyone,
i have a few questions regarding the usage of C9000 along with some underperforming GP Nimhs (4 x 2700s). these are absolutely new and have been used only 4-5 times before been conditioned on C9000. now the situation is like this:-

i bought these new batteries a few weeks back and felt that they were underperforming and were not living upto the promised 2700 mah tag. so i decided to put them under the acid test (the breakin of C9000) to determine the true capacity and health of these batteries.

Stats:
set breakin cell capacity @ 2700 mah
impedance check: 1st-1.51v, 2nd-1.62v, 3rd-1.43v, 4th-1.42v
after around 40 hours of break-in, the absolute capacity of the batteries was as under:

1st- 1660 mah
2nd- 1552 mah
3rd- 1902 mah
4th- 2010 mah

a pretty disappointing revelation . anyhow, now as the eletrolyte was evenly spread i decided to do 2 cycles on all 4 of the batteries @ 0.33C charge and 0.2C discharge. the results are as under-

1st Cycle

1st- 1770 mah
2nd- 1634 mah
3rd- 2000 mah
4th- 2050 mah

2nd Cycle

1st- 1710 mah
2nd- 1680 mah
3rd- 1810 mah
4th- 1860 mah

End

now i have a few queries:

1) how did the 1st cycle give more capacity than that shown after the break-in as the capacity shown by break-in is absolute and as far as i know it is the upper ceiling for that battery.

2) now even if the capacity got increased after the 1st cycle, how come the battery capacity at the end of the 2nd cycle is LESS than the capacity in the 1st cycle. i thought that mutiple cycles helped IMPROVE the battery health and capacity and not REDUCE them :ironic:

it would be nice if someone could tell me where am i going wrong...why is the new GP battery so severely underperforming and why isn't the above method working. what steps need to be taken to atleast achieve 2200 mah?

Thanks everyone.

 

[SilverFox]

Hello Shobhitk,

Crap cells often display erratic behavior.

If I were trying to recover those cells, I would do a number of Break-In cycles and log the capacities you get. If they are going to recover the capacities should continue to increase.

After 4 - 5 Break-In cycles you can speed things up by doing 1000 mA charges followed by 500 mA discharges.

You may be able to exercise them back to life.

Keep in mind that the GP 2700 cells are actually rated for about 2500 mAh when you are going through this recovery process.

Tom

 

[shobhitk]

Hi Tom. Thanks for the observation. have some questions:

1) i referred to that pdf link. i was wondering whats the difference between nominal capacity, minimum capacity and typical capacity. also no where did i got to see 2700 mah....so why do they write it on the battery when its actually 2500 mah?

2) should i set the break-in capacity to 2500 mah or keeping in mind my break-in results should i keep it to 2000 mah to be on the safer side?

3) on the given pdf link, what is meant by TCO - 45-50'c and how is it different from DT/dt

Thanks

 

[45/70]

I'll try to help out here.

i was wondering whats the difference between nominal capacity, minimum capacity and typical capacity.

Good question. Nominal and typical capacity, should be the same, in my book or, what you obtain under normal use. Minimum capacity should be the value that you should be able to obtain from the worst cell in a batch. Yeah, I know, looking at the chart in the .pdf, that doesn't make any sense.

also no where did i got to see 2700 mah....so why do they write it on the battery when its actually 2500 mah?

This is a marketing strategy. If you saw two packs of cells side by side on the shelf, with the same price, which would you buy, the ones labeled 2500mAh, or the 2700mAh?

should i set the break-in capacity to 2500 mah or keeping in mind my break-in results should i keep it to 2000 mah to be on the safer side?

I would go with 2500mAh. This would amount to a 0.1C charge rate, the proper rate for "break in/forming" of NiMH cells of 2500mAh capacity.

on the given pdf link, what is meant by TCO - 45-50'c and how is it different from DT/dt

This is a reference as to how the cells are terminated during charge. Temperature (TCO = Temperature Cut Off), or delta temperature/delta time, which figures in the temperature changes in relation to time, rather than just a maximum temperature at which the cell charging will terminate (TCO). Also, there is negative delta V, which terminates the charge when the voltage drops a specified amount.

Hope this helps,

Dave

 

[Mr Happy]

Many first time owners of the C9000 are shocked at how poorly their batteries perform. The C9000 is ruthless at exposing sub-par batteries; perhaps even a little too ruthless for some tastes.

 

[shobhitk]

hi 45/70. thanks for clarifying the doubts

Mr Happy: thats true!

 

[SunFire900]

High capacity AA rechargeable cells..

I read this thread and many others like it and it only adds to my loathing of AA rechargeable cells with a rating of more than 2000-2100mAh. I only bought some of the best cells available in the 2500-2700 range and had nothing but disappointing results. The capacity would almost always be off by 100-200 mA in every 4-pack and the cells nominal capacity would never improve with break-in and additional charge cycles. This is why the LSD, like eneloops have become so popular. Even with their relatively low mAh ratings, they seem to match, balance and last longer than the higher rated cells.

This is also the reason why I would not buy a light that uses more than 2 AA cells. Forget about 8 cells.

Ahhhh.........I feel better already.

Moral: It's not the chargers that fail you, it's the batteries that fail you!

 

[SilverFox]

Hello Shobhitk,

Basically, what Dave said...

I generally go by minimum capacity, and sometimes get surprised.

Set your Break-In for 2500 mAh cells.

Very few chargers use temperature termination as a primary termination, but if you had one that did the TCO value would be important. I believe TCO is a maximum temperature cut off where dT/dt involves the slope of the temperature curve.

Tom

 

[shobhitk]

SunFire900 i think i am going to join the same bandwagon... i mean we are paying for 2700s and we are getting 2500s...which are actually around 1800s !??! :shakehead and yes its the poorly built batteries that acually fail us.

Tom: yes tom, i appreciate dave's explanation....clears most of my doubts. and i think DT/dt is a much better cutoff than a simple TCO.

 

[shark_za]

wow wow wow.

Eye opener since I got my own Maha C-9000 as well.
Same 2700 GP's being charged for a few times on a dumb time based charger showed 1800mAh on discharges with the Maha.
I did one or two refresh-analyses and both showed very different values, 2000 and 1800.

I did a long break in on them and they are responding well to this. 23xx for both.

I am exposing my new Hybrio's as junk as well as confirming my old (at least 2 years) Hybrio's as being proper 2000mAh LSD's.
GP Recycko also showing good results.

Energiser 2450 cells giving constant 23xx results. I'll use these when I know I need the cells that day, for my camera.

Hybrio and Recycko for everything else.

My latest Hybrio/Safeways are definately LSD but low capacity 1600mAh.
They are for kids toys, remotes, clocks etc.

Viva Maha C-9000 Viva !!!!

 

[shobhitk]

hi shark_za....those are good stats...thanks. but hey that was a nice resurrection of those GPs....what mah setting did u input for getting them upto 2300 in the break-in mode? because when i did my first break-in on them they gave me very poor results as u can see in my first post above...

 

[shark_za]

hi shark_za....those are good stats...thanks. but hey that was a nice resurrection of those GPs....what mah setting did u input for getting them upto 2300 in the break-in mode? because when i did my first break-in on them they gave me very poor results as u can see in my first post above...

Break in set at 2600mAh.
It takes so long though !

I also did the cycles at low discharge, 2A charge and 500mA discharge.
The only reason I have these GP2700 is because my wife loaned 2x Hybrio's to her sister and she threw them away thinking they were Alkalines.
She then bought me these as payback. Could not refuse and ask for Recycko's, she would think I'm being difficult.

I am seeing the one cell has dropped to 2000mAh retention again, grrrrrr !
I have then on cycles now, don't seem to be reliable.

The energiser 2450's are solid and returning almost the same values but nothing beats the charge on charge performance of the GP Recycko and squat top hybrio's.

I must start labelling and keeping a spreadsheet.

 

[shobhitk]

hmm 2600....i see. i read the battery printing and it said that the forming charge(break-in) needs to be done at 250 ma for 16 hours, which means that the capacity need for the break-in should be 2500 mah...the same is recommended here: http://www.gpbatteries.com/pic/GP270AAHC-r0.pdf

i'll try them at 2500 mah...lets see how much do they resurrect.

and sorry to hear about the disposal of those rechargeables taken to be as alkalines...u definitely took the 'correct step' mate

also, many people have appreciated the GP Recykos...will give them a try some time!

 

[TakeTheActive]

hmm 2600....i see. i read the battery printing and it said that the forming charge(break-in) needs to be done at 250 ma for 16 hours, which means that the capacity need for the break-in should be 2500 mah... ...i'll try them at 2500 mah...lets see how much do they resurrect...

IMHO, 2700 (100%) or 2600 (96%) or 2500 (93%) isn't going to make any measureable difference.

You'll see / understand this the longer you use the MH-C9000 (and read the CPF 'Batteries Included' Archives).

 

[shobhitk]

TakeTheActive, shark_za said:

I did a long break in on them and they are responding well to this. 23xx for both.

he did this at 2600 break-in.

i was concerned because my batteries on the first break-in showed poor results, all 4 below ~2000 mah and whereas shark_za'a GPs reached ~2300 mah...
then is there something else i need to do? like shark_za's 2A charge and 500ma discharge or something?

 

[TakeTheActive]

...he did this at 2600 break-in.

i was concerned because my batteries on the first break-in showed poor results, all 4 below ~2000 mah and whereas shark_za'a GPs reached ~2300 mah...

His cells are somewhat healthy - your cells are *CRAP*. Either they arrived new as *CRAP*, or something you did to them caused it. (i.e. Encore 2700mah Cell reversed?; overdischarged?; dropped?

...then is there something else i need to do? like shark_za's 2A charge and 500ma discharge or something?

...Crap cells often display erratic behavior.

If I were trying to recover those cells, I would do a number of Break-In cycles and log the capacities you get. If they are going to recover the capacities should continue to increase.

After 4 - 5 Break-In cycles you can speed things up by doing 1000 mA charges followed by 500 mA discharges.

You may be able to exercise them back to life...

If you're interested in experimenting and learning with these *CRAP* cells, SEARCH the recent CPF 'Batteries Included' archives for my experiments. Long, slow charges followed by long, slow, deep discharges might help - nothing is certain though. What's their 'C9000 Impedance Check Voltage'?

Also, if you log the cumulative data in my TEXT style format, and post it between CODE tags, it'll be much easier to follow your progress...

 

[lrp]

After reading this thread I just brought back 4 Sanyo 2500 cells using the Maha 9000 charger via break-in cycle....amazing! First time I ever used that setting but won't be the last.

 

[shobhitk]

congrats lrp!

hi TTA, the impedance check is as follows: 1st-1.51v, 2nd-1.62v, 3rd-1.43v, 4th-1.42v

nope, no overdischarge, no dropping...
TTA i have a query...its always said that slow charges on NiMHs encourages crystal growth and are bad for the health of the cell as it increases internal resistance and lowers the under-load-voltage, then how does Break-In help? i am confused as Break-In consists of very low charging rates and 'tired' cells with very high internal resistance would take even a bigger hit due to such low charging rates(ie. 0.1C) as the crystal growth would be further encouraged.

btw i was trying to bring back to life one more 2100 NiMH with 2000mah typical capcity which showed an impedance of 1.82v. so as per the suggestions i did a break-in on it and when i came back after 40 hours i saw the 'Available Capacity' being shown as 0 mah ...i was taken aback! how did this happen?? i then removed the cell and checked its impedance on C9000 and to my great disappointment it was now showing it @ 2.62V and the charger switched to HIGH message. there was however a peculiarity during the process...the cell was at all times showing 1.50v during the charging process(sometimes 1.49v), which is kinda weird. so, wasn't the cell well off without a break-in? did break-in do more harm than good?

TTA do these results confirm the fact that a break-in might increase the impedance of a poor battery instead of decreasing it? should break-in be performed only on brand-new or 'healthy' cells which have been kept in storage for long time?
please correct me if am wrong. trying to learn...

Thanks

 

[Mr Happy]

The break-in process can wake up tired and under performing cells, but it cannot rescue bad or damaged cells. In simple terms the break-in or conditioning charge "mixes up" and "activates" all the chemicals inside the cell.

A break-in charge does not normally harm a bad cell any more than it already is (as long as you use the correct charge settings), but if the cell has for instance been overcharged so that electrolyte has been lost or chemicals oxidized, then that kind of damage cannot be reversed by conditioning.

From the descriptions you give, it seems your batteries are just somehow bad and beyond rescue. You could perhaps buy some new and good quality batteries for comparison so you can get a feel for how healthy batteries behave.

 

[shobhitk]

i agree with u Mr Happy. next time am going in for a Sanyo, Duracell kind of a battery...even better a low-self discharge version, because so far the break-in or R&A has not been able to do any good or bring back to life any of my cells :shakehead