Overcharge NIMH on a BC-9009

[squirrel]

I just bought a BC-9009 and a whole bunch of eneloops per lots of research on this forum.
Great betteries!

I got some older (1-2 year) Energizer AA and AAA batts that I used with the quick charger that came with them.
I have thrown away that quick charger.

anywhos, on a few of the energizers, the BC-9009 goes to 3.7AH on a 2300 mah AA and a 850 mah AAA.
charge current was 700 and 1000 (tried twice) on the AA.
500 on the AAA.

Even the discharge was upwards of 3AH on both of them before charging back to 3.7 AH which I think the BC cuts out at.

Can someone tell me whats happened to the energizers?

 

[drmaxx]

After reading the first part of your post, I would have answered: Easy, these cells just reached their end of life. The charger has a hard time to identify a clear termination signal and just continues until one of the safety limits are exceeded. In my experience these cells usually also have a very high self discharge, usually they are dead within 10 days.

However, this is really weired:

Even the discharge was upwards of 3AH on both of them before charging back to 3.7 AH which I think the BC cuts out at.

Don't know what to do with that. Sounds like the charger itself has a problem. There is no way that you can get 3 Ah out of a AA NiMH, especially not if it is an old one....

 

[TakeTheActive]

After reading the first part of your post, I would have answered: Easy, these cells just reached their end of life...

...However, this is really weired:

...Even the discharge was upwards of 3AH on both of them before charging back to 3.7 AH which I think the BC cuts out at...

Don't know what to do with that. Sounds like the charger itself has a problem. There is no way that you can get 3 Ah out of a AA NiMH, especially not if it is an old one....

You usually see statements like that when the poster is confusing ACCUMULATED Capacity with DISCHARGE Capacity (best AAA nimh batteries?), unless the charger is actually broken (in that manner, which I haven't read about here on CPF yet).

 

[MarioJP]

I only use the total charge as a an idea to how far the cells have been charged. But I don't really rely on it. For example the eneloops are rated 2000mAh on the label. The total charge that I see is around 2400 or so.

Something about some energy is being lost during charging.

 

[squirrel]

thanks everyone.
Lets ignore the whole discharge capacity.
Still, the accumulated charged capacity is still topping out at 3.7AH.
Clearly the charger is missing the - DV/DT or the cell is never going negative.

 

[TakeTheActive]

...Lets ignore the whole discharge capacity.
Still, the accumulated charged capacity is still topping out at 3.7AH...

1. At 1000mA, are the 'problem' Energizer cells getting hot?
2. What's the maximum voltage during Charge (that you see)?
3. How's their 'Self-Discharge'?
   i.e. are they worth 'Babysitting' during Charge or should they just be Recycled?

...Clearly the charger is missing the - DV/DT or the cell is never going negative.

How is the NEW BC-9009 handling the NEW Eneloops?

If it terminates properly at 1000mA, 700mA and 500mA, I say it's OK and something happened to the older Energizers. :thinking:

 

[squirrel]

Energizers,
Cells get warm, but never HOT.
termination voltage is about 1.41 ish
Ill have to let em sit for a month to find out the self discharge.

Eneloops,
I drained off 8 of them real quick (baby toys with motors in them) and charged them at 1000 ma. charge current went to zero for a tad. I believe the BC does this if the temp gets to warm. the cells were pretty warm borderline hot.
charging at 700 ma and the cells got warm, ditto on 500 ma.
Either charge current did terminate around 2.1 - 2.4 ah.

 

[TakeTheActive]

Energizers,
Cells get warm, but never HOT.
termination voltage is about 1.41 ish...

From the low termination voltage, I would guess that some of the chemicals have gone 'irreversibly' bad. I have some 'Low Cycle Count' Rayovac 2000mAh non-LSD NiMHs with low termination voltages (and low C9000 ICVs):

Rayovac 2000mAh AA               |  #1    #2    #3    #4
---------------------------------+---------------------------

09/xx/09 Superman 1AA Flashlight | 
09/xx/09 BC900 Discharge:  100   |

05/1x/10 BC900 Discharge:  350   | 

05/16/10 C9000 Impedance Check:  |  n/a  1.61  1.61   n/a VDC
05/16/10 BC900 Discharge:  250   |  n/a +2080  +2480  n/a mAh
05/15/10 BC900 Discharge:  100   |  n/a    60+   119  n/a <<<
05/15/10 C9000 Discharge:  100   |  n/a    45     0   n/a mAh

02/01/10 MQN06 Charge:  300      |  n/a     x     x   n/a
01/04/10 MQN06 Charge:  300      |    x   n/a   n/a     x
01/03/10 PS1   Charge:  200      |  n/a   ---   ---   n/a Terminated properly! (Topoff)
01/03/10 PS23B Charge: 1300      |  n/a   ---   ---   n/a Terminated properly! (WARM)
01/03/10 C9000 Impedance Check:  | 1.62  1.53  1.53  1.62 VDC
11/22/09 C9000 Impedance Check:  | 1.60   n/a   n/a  1.62 VDC
11/21/09 Sears Solar LED Lamp    |    x   n/a   n/a     x
09/22/09 C9000 DONE Voltage      | 1.41  1.40  1.39  1.41 VDC [LOW!]
09/22/09 C9000 Break-In: 2000    | 1553  1512  1401  1562 mAh#
09/xx/09 C9000 Impedance Check:  | 1.59  1.62  1.60  1.59 VDC
09/10/09 Sears Solar LED Lamp    |  ---   ---   ---   ---
09/09/09 BC900 Discharge:  100   |  ---   ---   ---   ---
09/07/09 C9000 Discharge:  400   |  n/a  1556  1459   n/a mAh
09/07/09 SAKAR Charge:  150      |  n/a   ~20   ~20   n/a Hrs
09/01/09 C9000 Discharge:  400   | 1570   n/a   n/a  1546 mAh
09/01/09 SAKAR Charge:  150      |  ~20   n/a   n/a   ~20 Hrs

07/17/09 C9000 DONE Voltage      | 1.39  1.38  1.38  1.40 VDC [LOW!]
07/17/09 C9000 Cycle10: 1200/ 400| 1504  1381  1333  1519 mAh
07/xx/09 C9000 Cycle9:  1200/ 400| 1524  1383  1338  1561 mAh
07/xx/09 C9000 Cycle8:  1200/ 400| 1516  1379  1327  1549 mAh
07/xx/09 C9000 Cycle7:  1200/ 400| 1527  1393  1335  1556 mAh
07/xx/09 C9000 Cycle6:  1200/ 400| 1541  1387  1332  1561 mAh
07/xx/09 C9000 Cycle5:  1200/ 400| 1530  1368  1317  1546 mAh
07/xx/09 C9000 Cycle4:  1200/ 400| 1543  1388  1332  1577 mAh
07/xx/09 C9000 Cycle3:  1200/ 400| 1543  1388  1327  1575 mAh
07/xx/09 C9000 Cycle2:  1200/ 400| 1515  1382  1298  1550 mAh
07/xx/09 C9000 Cycle1:  1200/ 400| 1548  1388  1314  1561 mAh
07/13/09 C9000 Impedance Check:  | 1.51  1.50  1.49  1.51 VDC
07/13/09 C9000 Discharge:  200   | 1367  1287  1188  1337 mAh
07/12/09 C9000 Charge: 1500      |  ---   ---   ---   --- >123°F
07/xx/09 C9000 Discharge: 1000   |  ---   ---   ---   ---
02/18/09 C9000 Impedance Check:  | 1.53  1.53  1.52  1.53 VDC
02/05/09 C9000 Break-In: 2000    | 1663  1459  1356  1600 mAh#
02/01/09 BC900 Discharge:  100   | 1850  1679  1498  1839 mAh
01/31/09 C9000 Charge:  500      |  n/a   n/a +1130*  n/a mAh
01/31/09 C9000 Charge: 1000      |  n/a +3600* +204   n/a mAh
01/31/09 C9000 Charge: 2000      |+1439  +169  +148 +1201 mAh
                                 |
01/31/09 BC900 Refresh:  200/ 100| 1770  1519  1371  1677 mAh**
01/30/09 BC900 Charge: 1000      |  ---   ---   ---   ---
01/30/09 BC900 Discharge:  100   | 1402  1180  1158  1404 mAh
01/18/09 C9000 Refresh: 2000/ 500|  n/a   n/a  1323   n/a mAh
01/11/09 C9000 Break-In: 2000    | 1540  1221   976  1364 mAh#
01/08/09 C9000 Discharge:  400   |  863   719   583   573 mAh
[Bought: mm/dd/yy - Came w/PS23-B, ?? months in storage]
 07/17-08/27/09:#1,4-GPS
 07/17-09/06/09:#2,3-RS 5-Day
 10/11-11/20/09:#1,4-GPS
>01/04/10:#1,4-Sharp SE-500 Mobile Organizer
 01/04-01/31/10:#2,3-Magellan GPS
>02/02/10:#2,3-Magellan GPS
]

...Eneloops,
I drained off 8 of them real quick (baby toys with motors in them) and charged them at 1000 ma. charge current went to zero for a tad. I believe the BC does this if the temp gets to warm. the cells were pretty warm borderline hot.
charging at 700 ma and the cells got warm, ditto on 500 ma.
Either charge current did terminate around 2.1 - 2.4 ah.

120% back in is 2400mAh, so that sounds right.

Next time, try charging only TWO cells @ 1000mA in slots #1 & 4 and see if it still goes into OVER TEMP shutdown.

 

[drmaxx]

Next time, try charging only TWO cells @ 1000mA in slots #1 & 4 and see if it still goes into OVER TEMP shutdown.

The other option is to turn the charger to the side, so that the batteries are arranged vertically instead of horizontally. Benefits are, that the heat from the charger can better escape through the vents and that there is an increased airflow around the batteries (chimney effect).
It is a kind of silly how densely the AA batteries are packed on the BC-900x

 

[squirrel]

Thanks for the advice.
I ran 2 eneloops thru at 1000 ma on slot 1 and 4.
They both got a pretty warm, but the overtemp shutoff did NOT kick on.
I ran em thru at 700 ma in slot 1 and 4, and they were noticeably cooler.

I then ran the pesky energizers thru at 700 ma in slot 1 and 4, and had the same results.

All were warm and kicked out arond 1.9-2.2 AH.
termination voltages were around 1.51.

So basically, I need to put a fan over the unit if im to do all 4 slots?
This charger sucks.

Whats your guys/gals final diagnosis?

 

[Curious_character]

I've had a lot of charge termination misses with various Maha chargers. It usually happens with new cells or ones that have been stored for some time, and corrects itself after a number of full charge-discharge cycles or a break-in cycle. But it can happen with others, so I've learned to check on them not too long after the charge should have terminated.

c_c

 

[core]

I've had a lot of charge termination misses with various Maha chargers.

I thought we were talking about LaCrosse chargers here?

But really what I wanted to ask was: How do you have a missed termination with the Maha C9000 when the recent ones use voltage (in practice, not theory) as the primary means of termination?

 

[squirrel]

-dV/dT,
charger misses it.
dT is only so big.

 

[Mr Happy]

But really what I wanted to ask was: How do you have a missed termination with the Maha C9000 when the recent ones use voltage (in practice, not theory) as the primary means of termination?

Mostly, you don't. But some old design NiMH cells do not reach the trigger voltage for termination on max V and so the C9000 will still terminate by other criteria like - dV.

 

[Curious_character]

In fact, I bought some new Yuasa Eni-Time LSD cells a couple of weeks ago to test. The C9000 missed the termination the first two times they were charged. If the charge rate is high enough, the charger will terminate when the cells reach some temperature too hot to touch. 1A for AA cells (~C/2) seems to be right about at that limit -- the cells get really hot, but sometimes not quite hot enough for the charger to shut down.

c_c

 

[Mr Happy]

In fact, I bought some new Yuasa Eni-Time LSD cells a couple of weeks ago to test. The C9000 missed the termination the first two times they were charged. If the charge rate is high enough, the charger will terminate when the cells reach some temperature too hot to touch. 1A for AA cells (~C/2) seems to be right about at that limit -- the cells get really hot, but sometimes not quite hot enough for the charger to shut down.

What voltage is indicated for these cells when they reach that condition?

 

[TakeTheActive]

...I ran 2 eneloops thru at 1000 ma on slot 1 and 4.
They both got a pretty warm, but the overtemp shutoff did NOT kick on.
I ran em thru at 700 ma in slot 1 and 4, and they were noticeably cooler...

Warm is a relative term that varies between folks - OVER TEMP shutdown is absolute. Compared to the C9000, the slots on the La Crosse chargers are too close together. What's your ambient room temperature?

...I then ran the pesky energizers thru at 700 ma in slot 1 and 4, and had the same results.

All were warm and kicked out arond 1.9-2.2 AH.
termination voltages were around 1.51...

So the pesky energizers terminate properly @ 700mA (via -DeltaV), but just below the La Crosse MAX VOLTAGE point (~1.53VDC), when charging only 2 at a time in slots #1 & 4 and miss termination and trigger the OVER TEMP shutdown when charging 4 at a time?

Since the La Crosse appears to be operating within "its" design specs, you can either 'baby-sit' your pesky energizers or buy a Maha C9000, which has better cell spacing and a a lower MAX VOLTAGE (~1.47VDC).

...So basically, I need to put a fan over the unit if im to do all 4 slots?

A fan will cool the outside area of the cells AND the thermistors, thus raising the OVER TEMP shutdown point since the inside area of the cells will continue to heat up as long as Charge current is flowing. I have my BC-900 sitting on 2 wooden hexagonal pencils to increase airflow. My ambient room temperature recently has been ~78°F. Yesterday 1 of 4 (slot #3) 'Low Cycle Count' RadioShack 2000mAh LSD NiMH AAs went into OVER TEMP during a 700/350 REFRESH. When my C9000 'frees up', I'll check the ICV, but, I expect it to be low. Since I bought my C9000, I tend to use it (BC-900) mainly for my *CRAP* cells and only AAA VIBRANT cells.

...This charger sucks...

While not of the same quality as the C9000, it has its uses.

 

[Curious_character]

What voltage is indicated for these cells when they reach that condition?

I don't honestly recall, other than it was more than 1.4 and less than 1.5 volt.

c_c