La Crosse BC-900 Charger Warning

[tacoal]

Hi SilverFox,

Thank you for the reply.

It is strange that the melting down happens even when charging current is 200ma.
In worst case, about 2V X 0.2A =0.4W heat will be generated in the battery,
supposing no energy is transferred into chemical one. I don't think such heat
will cause the melting down. It might be the malfunctioning of the CPU there or
the chemical reaction inside the battery.

I think the shutdown temperature could be changed by changing the resistors near
one of the holes where the thermal sensor is mounted. They are two 7.500K
precision resistors in parallel, 3.750K equivalent. Since the thermal sensor is
measured about 9K @70F, a 6K resistor will change the shutdown temperature to
about 120F, I think. Need to be confirmed by experiment.

So keep an eye on those 2500mah batteries and above when they are being charged.

I'll order another one as backup in case melting down happens on me.

 

[senna94]

I called LaCrosse today and was put on hold while the tech. helping me asked around. He was told that there had only been one unit overheat that they knew of. :thinking:

I guess until you know for sure if your unit is defective it would be prudent to take some precautionary measures.

1) Place unit away from walls and anything flammable.

2) Place unit on a metal tray or other non flammable surface.

3) If possible place near a smoke detector.

It is really a shame to have to take such measures but I guess it is better to be safe than sorry.

:sweat:

 

[Sigman]

I've not even used mine for the first time yet - and have to say that this info is certainly bothering me!

Maybe they are waiting for their first law suit?!

Is the loss of my house or worse yet - my family or a member of my family worth it?

Unacceptable!

 

[LeDfLaShEr]

Just to put in a word for the BC-900 charger- I use mine all the time and have yet to have a problem.

I've charged my cells at 1 amp and they barely even got warm. I've put them on refresh cycles at 500 mah that lasted several days and nothing got warm.

I've used good cells in them, I've used crappy cells in them.....never had a problem.

After using RC car chargers that make packs so hot that you can't even pick them up, I wasn't sure the BC-900 was working on the 1 amp setting until I used a multimeter to check things out. Sorry some people have had bad luck, but the charger has worked as advertised for me.

 

[wptski]

I posted in the Charger Comparison thread where I took a dual input temperature meter using two K-Type bead probe. I wrapped it around two of the cells enough times to insure contact.

The La Crosse BC900 at 1000ma charge rate on four 2000mAh cells reached 110F and at 1800ma charge rate on two 2000mAh cells reached 130F.

These were Titanium 2000mAh cells. On the other hand I've charged four MAHA 1800mAh 700ma and the unit shut down for high temperature! This makes me wonder if it's the cells. Has there been meltdowns with any cells other than 2500mAh Energizers?

I got some new "Made in China" 2300mAh Duracells that I'm trying to break in. I did one cycle on a Sirius Pro Former and tried a auto discharge on a Schultze 330d. It has four hour max limit for Ni-MH and at 3 1/2 hr is wasn't half way discharged. This could be due to these young cells being unstable or it didn't like my eight cell spring type holder. I just used the auto D/C cycle on a couple of DeWalt 14.4V Ni-CD packs with no problems

 

[regnim]

:thumbsdow The 2000mah La Crosse Tech cells that came with my charger melted down, so it is not just the 2500mah cells. I caught it in time and just the cells were damaged. Thomas replaced the cells, this was about 6 months ago, before I found out about the problems this charger has. Don't remember the charge rate, charger just went into a reset loop, displaying 32 then a blank display then 32.....

 

[SilverFox]

Hello Regnim,

Welcome to CPF.

La Crosse does not seem to be getting the information that these overheating problems are happening. I am not sure if Thomas Distributing is relaying the information to them.

If you don't mind, would you call La Crosse at 888-211-1923 and report to them what happened?

Thanks.

I would also ask that if anyone else has had overheating issues, they should contact La Crosse directly even if Thomas Distributing has already taken care of the problem. La Crosse can not remedy a problem they do not know exists, and I want to make sure they know about this.

Tom

 

[Pellidon]

Because of my days with RC car packs and melting one with a timer rapid cooker. I almost always use a secondary fan to blow on the cells. I just charged up some new 2000's on a Lacrosse with a fan and without. The cells without the secondary fan were warm but not overly hot. Less than a RipVan 4000 or my Maha 204 heats them up. They were stone cold room temp with the fan.

I'm using a Radio Shack 12 volt wall wart and a 12 volt DC 3" box fan. Soon I will make a bracket to hold it over the unit rather than have both sitting on their sides. I charged all cells at the 700ma rate.

I had an old Maxell charger that got cells very warm compared to my others. It also killed several cells due to it's overheating them. It now resides in a waste dump.

 

[photo2000a]

just wondering, don't the charger's turn off based on temp? if you cooled it (via fan) wouldn't the batt's maybee over charge???


[


QUOTE=Pellidon]Because of my days with RC car packs and melting one with a timer rapid cooker. I almost always use a secondary fan to blow on the cells. I just charged up some new 2000's on a Lacrosse with a fan and without. The cells without the secondary fan were warm but not overly hot. Less than a RipVan 4000 or my Maha 204 heats them up. They were stone cold room temp with the fan.

 

[regnim]

Silverfox, I have called La Crosse and they have advised me to send them my charger. It went out via Fedex today. We will see what they have to say.

 

[jtr1962]

I believe the power supply/reset problems are directly related to the overheating problem. Granted, poor thermal coupling and a high setting for shutdown temperature are poor engineering choices, but the problem boils down to the fact that the charger sometimes misses the end of charge signal. I attribute the BC-900 continuing to charge "full" cells directly to the power supply problem. In simple terms, the power supply is "noisy" due to poor decoupling. The small negative delta V exhibited by fully charged cells is easily lost amid all the noise. Once modified as described in this thread the charger should be less prone to meltdown. That being said, I've noticed other chargers with 700 mA or 1000 mA charge rates allowing cells to get uncomfortably hot. For that reason I'm now in the habit of having a fan blowing on any charger when I'm charging at 500 mA or greater. It can't hurt, and it might just prevent the kinds of meltdown problems we've been seeing. I'll also second Tom's recommendation to always charge away from combusibles.

As for changing the reset temperature on the BC-900, I'm going to look into it. The temperature sensor is a simple PTC thermistor, meaning that the resistance goes down as the temperature increases. My idea is to measure the resistance at 160°F and 130°F, and then put a shunt resistor in parallel with the thermistor so that the charger "sees" 160°F when the actual temperature is only 130°F.

Overall as I've said already the BC-900 is a great idea in concept, but has so many rough edges that it's more like a pre-production prototype. Hopefully if LaCrosse ever releases a BC-900 version 2 it will address all the issues we've seen.

 

[senna94]

I just recieved my BC-900 and am running the test cycle on 4 2500mah Energizer cells at 1000ma. I decided to put my charger on top of a glass to provide extra ventilation underneath. I will be monitoring the temp closely and keep my fingers crossed.

Paul

 

[tacoal]

Hi regnim:
Is the charger works fine after the melting down?


I just read some documents from Panasonic dated August 2005.

In the document, the thermal cut off temperature is recommended to 55C(131F) for A, AA and D; 50C(122F) for AAA http://www.panasonic.com/industrial/battery/oem/images/pdf/Panasonic_NiMH_ChargeMethods.pdf So the BC-900 is set to high for it. Other related documents can be found at http://www.panasonic.com/industrial/battery/oem/chem/nicmet/index.html

Another finding is when temperature is high and charge current is small, the -delta V is hard to detect, even no -delta V at all, esp. for those high capacity batteries So keeping batteries cool by a fan is a good idea to allow BC-900 to get that -delta V more easily.

Battery with high internal resistance is another factor for the melting down case.

 

[wptski]

I don't know! Is there a right or perfect point in temperature to shut down the cycle? Could the -deltaV point be lost if the cycle is stopped just prior to that point and restarted several minutes later??

 

[mccavazos]

I called LaCrosse today and was put on hold while the tech. helping me asked around. He was told that there had only been one unit overheat that they knew of. :thinking:

I think that this might be my charger. LaCrosse was a pleasure to deal with. They had an excellent customer service program. I was just told that my new charger arrived in the mail. As soon as I get my hands on it, I will send back the melted one so that they can figure out what went wrong.


Chris

 

[tankahn]

What a regret. With so many kind people here having favorable experience, decided also to get one last Monday. Its too slow, takes me almost 24 hrs to test my batteries. With 2 charging cycle I can't be attending to it all the time.

Since I can't sell a potential fire-hazard away in full conscience. I don't know what I can do with it.

Flame me if you want. The BC-900 unit is made in China. I am Chinese but would avoid buying any China made electrical stuff if I can. QC must be an alien concept there. Was in Shanghai when I forgot to brought my charger with me. Went to a store and every piece they show me is broken. I got a camera with german words stamped on it and the film cover just popped off. In Singapore where I lived, many Chinese made aquarium pumps went up in smoke.

I bought Triton charger at the same time. Its a pleasure to use. Its flying off the shelves here.

 

[SilverFox]

Hello Tankahn,

Are you aware that in the test mode you also have control over the current setting?

If you have 2500 mAh capacity cells, select the test mode, then select a current of 1000 mA. It will take roughly 5 hours to do the discharge, then roughly 2.5 hours to charge them back up. This works out to only around 7.5 hours for a full cycle.

I will also point out that there have been no reports of fires, only plastic melting. If you place your charger inside a baking dish, or on a platter, or on a plate, or on a ceramic tile, or on a silicon hot pad, you should be well protected against hot plastic.

On the other hand, I agree that the Triton is an excellent charger. I would also advise you to charge on a non combustible surface while using the Triton as well.

Tom

 

[tacoal]

By google's translation, I found a German page to change the thermal shutdown temperature. The link is http://www.digicamfotos.de/index3.htm?http://forum.penum.de/showthread.php?id=24339

By replace a 7.5K resistor with a 10K one, the thermal shurdown temperature will drop 5C(9F) to 53C(127F).

From the page, it seems the shutdown temperature for BC-900 is bellow 60C(140F)(FW 33?), rather than 71C(160F) here.

They also point out that the melting down happens on 200ma changing current might be the bad thermal contact, bad battery .....

 

[senna94]

How prudent would it be to modify a unit that is already known to have a problem that the manufacturer is as of yet unwiling to acknowledge. If the manufacturer ever does decide to recall these units, it is unlikely they will accept one that has been modified. Not to mention that this would probably void your warranty. :thinking: Lets say that after you modify the unit it still fails and heaven forbid it melts and causes damage to your property. Then you have really exonerated LaCrosse from any liability by virtue of having modified the unit.


Just a thought.

Paul

 

[jtr1962]

Thanks for the info, tacoal. You saved me a lot of work! I'll be doing that mod on my chargers right away. I'll just point out that by replacing one of the 7.5K resistors with the 10K one, the net result is a resistance of 4.286K instead of 3.75K (two 7.5K resistors in parallel). Apparently the BC-900 compares the resistance of the two thermistors to this reference value, and shuts down the channels where the thermistor resistance is lower. BTW, I measured room temperature (70°F) resistance of the thermistors at around 12.2K.

Since I have 4.7K resistors handy, I'm going to be removing both 7.5K resistors and replacing them with the 4.7K one. My cutoff temperature should be another 5°C or so lower than their modified temperature, or around 48°C. I feel a lot more comfortable with it there.