Possible overheating of BC-900 charger

[Flatshovel]

I have been using a BC-900 v35 charger to charge up some GP Industrial NIMH 2250mah batteries with. I have been charging them at 1000mah and they have been overheating and the charger will display 000. When this happens I am only charging 3 batteries at a time and have them inserted in slots 1, 2 and 4. I have read that the proper charger rate for NIMH is between 0.5c and 1c, well at the rate that I am charging them at is well under 0.5c. When I charge them at 700mah the batteries get warmer than I think they should be. My question is, If I charge them at under 0.5c than I risk overchargeing them and if I charge at 0.5c then it seems to overheat them. Also when chargin at 0.5c the bottom of the charger gets super hot but has not melted anything as of yet. This same thing happens when I try to charge different brands of NIMH batteries and different capacities as well. Does it sound like my charger is bad or would it be a good idea to add a fan to blow some air across the batteries as they are being charged? Would like to know what you think as I am seriously considering selling my charger and purchasing a maha one to take the place of this one. Any Ideas or suggestions?

 

[VidPro]

there you go.
get the 9000. keep the 900 for other stuff, and other testing.
mine locked up and destroyed my batteries, and melted the charger, and i am not so forgiving. it is a good idea and a nice charger , but burn me once . . . .

if you cool the CHARGER then the added heat of the charger itself wont go to the cells, that will just basically obsolete the poorly connected thermal probes, by cooling the thermal probes too.
If you cool the batteries the v-drop might not be AS strong and noticable then the microcontroller will not see the v-drop in a timely manner and will not terminate.
If you dont cool something down, you char the internals on the battery.
lose lose lose situation :-(

better question is how hot, for $20 you can buy a IR thermal probe that is a few degrees accurate. but with that thing bailing out due to heat, its a darn good indication that they are getting way to hot.
and how much is going INTO them as shown in the charge Ma ammount, is the quantity going in way high?

how well are the cells actually doing? as cells get worser over age and cycles more of the power going into them is wasted, which comes out as heat, when you discharge a cell, and read the ammount of energy it HELD, then charge it and read how much was sent in its general direction, just how much waste is occuring?

the rates your choosing, and the info you have is all good and well, you have done your job, the charger is probably working, it sounds like the batteries might be letting you down some :-( the 9000 would be quite different.

 

[Light Sabre]

LaCrosse's solution to all the overheating problems with version 3.5 was replacing the adapter. They were trying to meet a California specification or something like that. The adapters in question have a circled "IV" or "4" in the lower right hand corner on the back of the adapter. The adapters were only running 0.2V higher than the old versions.

I have version 3.2, supposedly the bugging over-heating version 3 or 4 years ago. I have never had any problems with it. I ran a couples sets of batteries at 1A and thought they got too hot, so I was only runing at 200ma to 700ma. Someone on CPF said that with 200ma the charger may not detect the small delta V when the battery became fully charged and may just never stop and overcharge your batteries. So I have nixed using 200ma as well despite the fact I have never had any problems at 200ma. At that rate with as many batteries I have, it just takes too long.

There are other threads on CPF (search for them) where people report over-heating and meltdowns and mostly with the 3.5 version of firmware and all were charging at 1A. IMHO the charger has 1A available (also has 1.5A and 1.8A available), but I don't think it was designed properly to handle that much current. Screw the 0.5A to 1.0A recommended by some people and other places and drop down to 700ma. I am probably gonna catch hell for that statement :duck:

And no, I'm not gonna buy a C9000. ~24 or so key presses to program 4 batteries to the same current is ridiculous. I also have a half dozen Duracell mobile chargers which only charge at 500ma and haven't had any problems with them either.

 

[MarioJP]

Funny how you brought this is up. I have 6 spare engizer rechargeables that was used in a electronic piano that took 6 AA's. That piano broke and end up with the spares. So anyways I started to do a refresh cycles on these cells. 500ma/1000mA ratio in my Lacrosse.

The energizers would get hot to the point I get the display 000. This never happened with my eneloops. Are energizers crap batteries?

 

[Russel]

I would venture to say the the internal resistance of the Energizer cells are much higher that the Eneloop cells.

My experience with Energizer NiMH rechargable cells is one of frustration and lessons in self discharge.

 

[Lynx_Arc]

Funny how you brought this is up. I have 6 spare engizer rechargeables that was used in a electronic piano that took 6 AA's. That piano broke and end up with the spares. So anyways I started to do a refresh cycles on these cells. 500ma/1000mA ratio in my Lacrosse.

The energizers would get hot to the point I get the display 000. This never happened with my eneloops. Are energizers crap batteries?

the energizer 2500s are notorious for being HSD cells with high internal resistance. I have had their 2200s that come with chargers go bad losing a lot of capacity or giving errors on chargers that normally charge everything. the 2300 energizers are good, I have heard better reports on the 2450s so far but IMO the verdict on them isn't settled yet. IMO the energizer nimh cells are risky at best I would say try and catch some duraloops on sale or even hybrids on sale instead of energizers.

 

[MarioJP]

Seems like these cells are new. The wrapping feels new can't tell for sure. I did notice one thing is 2 cells out of 4 are labeled 2500 while the rest are 2200. I am guessing this is not recommended to have in series???. Does appear these cells were not used often either. They were almost dead when I took them out of the piano.

 

[Lynx_Arc]

Seems like these cells are new. The wrapping feels new can't tell for sure. I did notice one thing is 2 cells out of 4 are labeled 2500 while the rest are 2200. I am guessing this is not recommended to have in series???. Does appear these cells were not used often either. They were almost dead when I took them out of the piano.

I wouldn't run the 2200s with 2500s as the 2200s would run out of juice first and be overdischarged too low voltage and get damages or even reverse charge and there is a good chance if left set for a month the 2500s would self discharge to about 1v while the 2200s would have half capacity and the opposite would happen ruining the 2500s. I use 2200s for junk and 2500s for a headlamp that drains batteries in 2+ hours as you have to constantly charge cells for it when I use it heavily and the 2500s give me a little more runtime than LSD cells off the charger plus I fast charge on a 1 hour charger not worrying about damage while I charge the LSD cells at slow to moderate rates. Otherwise the verdict on 2500s is to toss them if you have any trouble usually they develop HSD (high self discharge) and/or high internal resistance so you either have to charge them every time you want to use them or chargers complain about them and not charge them at all.

 

[Mr Happy]

Are energizers crap batteries?

Do bears sh*t in the woods?

 

[MarioJP]

Awww they were free batteries. I knew it was good to be true. and here I was going to use them in a battery pack

 

[Apollo Cree]

And no, I'm not gonna buy a C9000. ~24 or so key presses to program 4 batteries to the same current is ridiculous.

To charge AA's, all you have to do is stick them in. No button presses needed. For AAA's, you "should" change it to 700 mA, but it's not really necessary. If you want to do something special like a recycle/analyze, discharge, breakin, yes you do have to push a lot of buttons.

 

[Conan]

To charge AA's, all you have to do is stick them in. No button presses needed. For AAA's, you "should" change it to 700 mA, but it's not really necessary. If you want to do something special like a recycle/analyze, discharge, breakin, yes you do have to push a lot of buttons.

I was just about to post the same thing. It takes ZERO KEY PRESSES to charge four pieces of AA Eneloops at 1000 mA on the Maha C9000. You can even charge them at 2000 mA safely without overheating the batteries or the charger. But you know some LaCrosse owners vow to never "cross over" to the Maha C9000 no matter how badly designed the LaCrosse is, go figure.

 

[NutSAK]

It appears to me that your BC-900 is working as designed, but it would be nice to know exactly what temp your cells are reaching when the charging pauses due to high temp.

 

[TakeTheActive]

I have been using a BC-900 v35 charger to charge up some GP Industrial NIMH 2250mah batteries with. I have been charging them at 1000mah and they have been overheating and the charger will display 000. When this happens I am only charging 3 batteries at a time and have them inserted in slots 1, 2 and 4...

I'd guess that your 2250mAh cells have developed HIGH Internal Resistance.

With a C9000, you could easily check their 'Impedance Check Voltage' (Interpreting Maha MH-C9000 Impedance Check Voltage). Without one, you'll need a DMM and a resistor - CLICK on my Sig Line LINK for the LINKs to how to do this.

For now, I would only charge 2 cells at a time, in slots 1 & 4. I would also place your BC-900 on a fireproof surface *AND* raise it up (with something like 2 hexagonal-sided wooden pencils) to improve airflow. I would not use a fan.

• What's the CAPACITY of your 2250mAh cells @ ~0.2C?
  .
• How old are they?
  .
• Have they always been properly treated and/or charged with the BC-900?

...I have read that the proper charger rate for NIMH is between 0.5c and 1c, well at the rate that I am charging them at is well under 0.5c. When I charge them at 700mah the batteries get warmer than I think they should be. My question is, If I charge them at under 0.5c than I risk overchargeing them and if I charge at 0.5c then it seems to overheat them...

Healthy, vibrant cells charged at 0.5-1.0C do NOT get super hot.

Also, "...warmer than I think they should be......" is SUBJECTIVE; a reading from a thermometer is OBJECTIVE. If the BC-900 is switching the MOSFET off and displaying '000', the thermocouple(s) sensed an OVERTEMP (127°F V33+ [was 160°F V32-] (2 sensors)). That's too hot and the safety feature is kicking in.

If you're interested, you can try some 'Experiments'. With the same 2 2250mAH cells in slots 1 and 4:

1. Run a DISCHARGE @ 1000/500 - Record the ACCUMULATED CAPACITY
2. Run a TEST @ 1000/500 - Record the DISCHARGE CAPACITY
3. Run a DISCHARGE @ 700/350 - Record the ACCUMULATED CAPACITY
4. Run a TEST @ 700/350 - Record the DISCHARGE CAPACITY
5. Run a DISCHARGE @ 500/250 - Record the ACCUMULATED CAPACITY
6. Run a TEST @ 500/250 - Record the DISCHARGE CAPACITY

Please post your results.

Do you own any NEW (Healthy & Vibrant) Eneloop 2000mAh AAs? If so, you can repeat steps 1 & 2 with them and note the results.

...Also when chargin at 0.5c the bottom of the charger gets super hot but has not melted anything as of yet. This same thing happens when I try to charge different brands of NIMH batteries and different capacities as well. Does it sound like my charger is bad or would it be a good idea to add a fan to blow some air across the batteries as they are being charged? Would like to know what you think as I am seriously considering selling my charger and purchasing a maha one to take the place of this one. Any Ideas or suggestions?

It doesn't sound like your BC-900 is bad. It DOES sound like your cells are. An 'Experiment' with NEW 2000mAh AA Eneloops will help determine which.

No fan...

...if you cool the CHARGER then the added heat of the charger itself wont go to the cells, that will just basically obsolete the poorly connected thermal probes, by cooling the thermal probes too.
If you cool the batteries the v-drop might not be AS strong and noticable then the microcontroller will not see the v-drop in a timely manner and will not terminate.
If you dont cool something down, you char the internals on the battery.
lose lose lose situation :-(

- for the reasons VidPro pointed out above.

Charging 'Non-Vibrant', HIGH Internal Resistance (~2000mAh) cells @ 1000mA (~0.5C) in the C9000 is still going to cause the cells to heat up. The OVERALL effect may be less since the C9000 has better airflow. Also, once the 'Impedance Check Voltage' of the cells reaches 2.10VDC, the C9000 will refuse to charge them. So, to continue using *CRAP* cells, you're going to need a 'more lenient' charger.

LaCrosse's solution to all the overheating problems with version 3.5 was replacing the adapter...

That was with the BC-9009 v35; although there have been random reports of BC-900 'Meltdowns', I don't recall reading about ANY problems with the AC Adapter on the BC-900 v35. IMHO, the entire circuit is so close to being MAX'd out, a BC-900 AC Adapter slightly plus of tolerance, combined with a slightly plus AC outlet voltage 'could' push it 'Over-the-Edge'. :thinking:

...They were trying to meet a California specification or something like that. The adapters in question have a circled "IV" or "4" in the lower right hand corner on the back of the adapter. The adapters were only running 0.2V higher than the old versions...

Flatshovel,

Please read:

La Crosse BC-700/BC-900/BC-9009 Charger 'Meltdown' Reports - La Crosse Responded​

and report back with the output voltage of your AC Adapter.

...get the 9000. keep the 900 for other stuff, and other testing...

I agree. I have both and I feel that they compliment each other well. I also maintain a high number of *CRAP* cells, so that too affects my judgment.

 

[TakeTheActive]

...For AAA's, you "should" change it to 700 mA, but it's not really necessary...

800mAh AAAs -> 400mA (0.5C) or less, noting the unavoidable "100mA for 2 Hours" Top-off charge after 'Done'; just monitor the heat.