La Crosse BC-900 Charger Warning

[wptski]

Hi wptski,

My BC-900 has the firmware 32. It is possible they changed the algorithm in 33.

As for the waveform, you could refer to http://www.digicamfotos.de/index3.htm?http://forum.penum.de/showthread.php?id=17111. They inserted a 0.1 ohm resistor to measure the waveform. You could tell the cycle time (10ms/div) and current (in red 1.6=174mv/0.1ohm) in those photos. Theses photos may be based on firmware 32.

According to my measurement, the BC-900 does have 1s cycle to measure the temperature. After the measurement, it has full one charging cycle (19.6ms) sporadically even in 200ma charging mode. I think this is a firmware bug.

tacoal:

That's 19.6ms ON time at 200ma?

EDIT: I get 2-3ms at 200ma, v33 has to be different in more ways than one! I gave my contact at ESI a 101 class in the BC-900. They seem to think that the probe is reading correctly at this point unless they change their mind and can't understand how La Crosse's manual could be so misleading!

 

[tacoal]

19.6ms is the cycle time including a ON and a OFF interval. This means the charger will ON/OFF at the rate of 51 times per second. As I said in previous post, every second, there is a interval to measure the temperature. So it is supposed the charger controls the duty cycle in one 19.6ms cycle 50 times and uses one cycle to measure temperature in one second.

EDIT:

I get 2-3ms at 200ma

the average current will be ON_CURRENT *2~3ms/19.6=200ma, so the ON_CURRENT is about 1.3A~2A.

 

[wptski]

19.6ms is the cycle time including a ON and a OFF interval. This means the charger will ON/OFF at the rate of 51 times per second. As I said in previous post, every second, there is a interval to measure the temperature. So it is supposed the charger controls the duty cycle in one 19.6ms cycle 50 times and uses one cycle to measure temperature in one second.

tacoal:

That's right, I forgot we get the exact same frequency, 51Hz!

 

[tacoal]

tacoal:

That's right, I forgot we get the exact same frequency, 51Hz!

We get the point!:buddies:

 

[wptski]

19.6ms is the cycle time including a ON and a OFF interval. This means the charger will ON/OFF at the rate of 51 times per second. As I said in previous post, every second, there is a interval to measure the temperature. So it is supposed the charger controls the duty cycle in one 19.6ms cycle 50 times and uses one cycle to measure temperature in one second.

EDIT: the average current will be ON_CURRENT *2~3ms/19.6=200ma, so the ON_CURRENT is about 1.3A~2A.

tacoal:

Back to the original quiz now! Clamp current probe only shows about 1A amplitude.

 

[tacoal]

tacoal:

Back to the original quiz now! Clamp current probe only shows about 1A amplitude.

From the waveform you posted before, it is not the issue of clamp response time. You could see the ON and OFF clearly in ms scale. The only thing I could say is the resistance inserted although you think you contact them well. From the example of that German site, only 0.1 ohm will reduce the current from about 2.5 A (my measure) to 1.6A. You could measure the voltage between battery and charger's negative side and do the same on positive side by a digital voltmeter. You may get about 0.2 volt or more there.

As for the correct reading on other chargers you mentioned, I think those charger can regulate the voltage to keep the current unchanged, just a presumption. Another reason is the PSU. I think those charger use 12V DC or 120V AC, 0.1 or 0.2 ohm in the charging loop does not bring big interference on charging current but 3V PSU does.

 

[wptski]

tacoal:

Measure the voltage drop across my connections? Good idea! My standard connection is lame at best but there's hardly any other way to make a connection and leave your hands free. The better connection, battery clamped up good and holding short heavier wire to the contacts made no diffeerence in the waveform at all, so I think that the coonection isn't the problem. I will do the voltage drop anyway.

Not sure about the power supplies used on the other chargers and I'm away from home now and can't check them. I do have one of those 3.3V supplies mentioned in other threads but never tried it. You mentioned that it may generate more heat as others have too.

 

[wptski]

tacoal:

Checked the voltage drop across the negative wire, 0V but I did get maybe .02V across the magnet connection at the positive end. So, I tried the clamped cell with short heavier wire again and sure enough I must have goofed somehow the first time as I got the this screen below at 200ma charge rate. Whew! Glad to get this figured out! Thanks for the pointers! :rock:

 

[tacoal]

tacoal:

Checked the voltage drop across the negative wire, 0V but I did get maybe .02V across the magnet connectionat the positive end. So, I tried the clamped cell with short heavier wire again and sure enough I must have goofed the first time as I got the this screen below at 200ma charge rate. Whew! Glad to get this figured out! Thanks for the pointers! :rock:

Yeah, you got it!:twothumbs

 

[Handlobraesing]

I just bought one from Thomas Distributing and mine's a "33" version.

Problems so far:
1. Poorly built. The #3 button on mine was busted upon arrival. It looks to be punched in. The toothpick sized rod that pushes the button was broken.

2. Running a "test" cycle in +1000mAh/-500mAh, it reported many of my 600mAh AAA cells as having ~1100mAh ish. Something is not right.

3. During discharge cycle, the voltage readout is is 100mV lower than actual cell voltage. 100mV is quite significant when NiMH exhibits ~1.25v during regular use and shows you're nearing the end of useful capacity when you see 1.15v.

4. LCD has a painfully lousy contrast and flickers.

 

[wptski]

I just bought one from Thomas Distributing and mine's a "33" version.

Problems so far:
1. Poorly built. The #3 button on mine was busted upon arrival. It looks to be punched in. The toothpick sized rod that pushes the button was broken.

2. Running a "test" cycle in +1000mAh/-500mAh, it reported many of my 600mAh AAA cells as having ~1100mAh ish. Something is not right.

3. During discharge cycle, the voltage readout is is 100mV lower than actual cell voltage. 100mV is quite significant when NiMH exhibits ~1.25v during regular use and shows you're nearing the end of useful capacity when you see 1.15v.

4. LCD has a painfully lousy contrast and flickers.

Hmm, my replacement BC-900 has a broken #3Slot button too but I don't seem to have the other problems that you mention! Send it back.

 

[Tremendo]

I got a new one last week from Thomas distributing and it has worked absolutely fine, version 33. Buttons are OK, not super high quality, but after reading posts here, just as I expected. You just learn how to push them better, everything works correctly. I have refreshed about 12 batteries or so (still working on 1 now), it found a dead cell I had paired with a good one. I've been doing the refresh at 1000mAh charge, 500 mAh discharge. It has brought back some AA's from about 800-1200 mAh upto 2,400+mAh.

I'm very happy with the purchase.

 

[kiwi]

I bought a BC-900 a month ago on Amazon. Version 32 firmware!

I contacted La Crosse via e-mail asking if v32 was endorsed by them and safe to use. No answer....

I followed up a week later to their tech support line. Female operator claimed to have no knowledge about the the issue and went away to ask their 'expert'. Funny I wasn't connected directly to him, eh? She came back and said that "they were aware of the mis-information being put out on internet forums", however, the expert assured me that there were no differences between the v32 and v33. "They are identical". Sounds fishy based on observations on this thread.

Since previous posts indicate that version 33 appears to be a safety-related fix, should I send it back or is it safe to use? Sigman - How did you get on sending your v32 back (posts #102 and #106)? Did they send you a v33?

I guess a seperate issue from safety is longevity. Not much use if it fails just outside of warranty, notwitstanding safety measures such as charging in a non-flammable container.

 

[SilverFox]

Hello Kiwi,

Welcome to CPF.

The "official" word from La Crosse is that the BC-900 was designed and is made in China. The technical people in China have not been able to get the charger to malfunction, so they do not see any problem at all.

I was also told that there are several thousand units in Europe, and there has not been a single failure reported to them from Europe.

At any rate, it seems that we are having all of the problems and our numbers are so small that it is statistically insignificant...

Tom

 

[Sigman]

Sigman - How did you get on sending your v32 back (posts #102 and #106)? Did they send you a v33?

After calling them and receiving a return authorization number - sent the charger (only) back to them and they sent me a new charger (only) with version 33 indicating in the window when plugged in.

BTW, I've not used it at all...still using my CCrane charger as primary.

 

[rycen]

How do you tell what version you have?

 

[Sigman]

Plug it in and see what's in the window upon startup...

 

[coppertrail]

I believe I have Ver. 33. When I power on the unit, I see "12 11 33" briefly on the display.

I've charged my PowerEx 2500s at different rates; haven't had a problem yet.

 

[Flash007]

I've received my Lacrosse BC-900 (v32) today.

I have putted 4 used Ansmann 2300 mAh to refresh mode (700/350 mA).
Hope the charger will not melt. I work during this night, and I'll not be at home to supervise the charge process.

I have 2 years warranty on the product.

 

[Christoph]

It's not a good idea to charge while you are away. imho
is there a warranty on your house?

Chris