BMS Battery Alloy Shell Charger Problems

[dnmun]

the pwm frequency is so high you would never hear it i think. do you have a picture of which big resistor that was and what the value is? the fan would be turning on when the op amp that controls the output is telling the front end to send juice to the back. so maybe the current is not getting through to the back end like it should. these with the TL494 are different from the newer designs, but the 5W resistor may be a clue.

[miuan]

the pwm frequency is so high you would never hear it i think. do you have a picture of which big resistor that was and what the value is? the fan would be turning on when the op amp that controls the output is telling the front end to send juice to the back. so maybe the current is not getting through to the back end like it should. these with the TL494 are different from the newer designs, but the 5W resistor may be a clue.

I recall I could hear the charger buzzing even before I had this problem, as soon as it started to taper down the current. But the 3rd led never lit before. So this is something to think about. For the record, I have the newer style charger with big heatsink, red LED display and Amp/Volt switch.

[dnmun]

i noticed there are two different chargers in the pictures. i have never seen either one.

[pradeepswain]

The capacitors right next to rectifier rated 200v are showing 166v on multimeter. Is that the starting point in the circuit?

[recumbent]

I have the EMC 600 model just as "rui_fujino" posted with the first three pictures. In fact they are identical inside except for the wire colors (inside) on the front end.

Just recieved it yesterday and it seems to work fine, the fan comes on as soon as the battery is connected. The 2 screws on each side of the charger where the heat sinks for the mosfets are STRIPPED, and have been painted black afterwards like it's been repaired.

My confidence level towards this charger is diminishing by the minute. Hope you guys figure what's wrong with your chargers. They might surprise us and actually work for a couple years.

[dnmun]

The capacitors right next to rectifier rated 200v are showing 166v on multimeter. Is that the starting point in the circuit?

yes, the 166V is the rectified RMS voltage output from the bridge. it is DC voltage, charge stored on the capacitors that is then pushed through the transformer at high frequency, to induce current to flow in the secondary windings of the transformer, and that secondary winding is what is connected to the back end through those 5-6 legs soldered on the output of the transformer.

several things can go wrong here. the switching transistor that pushes the current into the transformer can be bad, or the feedback circuit to the front end from the back end can be defective and not force the transistors in the front to switch.

in the back end the ground is negative and should be easy to find running from the transformer to the output wire. the big toroid in the middle of the current flowing to the back end helps reduce the voltage spikes in the back end as the current pulses come out of the transformer, then go through those diodes in the top of the picture and out through that big wire loop, which is called the shunt, to the positive output of the charger. the little black IC next to it, i think it has LM355 on it, is where the op amps live that tell the charger whether it should be running or not depending on the output voltage. those little blue trimpots next to the op amp help make the final adjustment of the voltage that turns on the front end, and the fan, and the other op amp in that package knows when there is too much current flowing through the shunt when the delta voltage drop across the shunt climbs above the set point, which is set by the other trim pot. so follow the traces for those and maybe you get some idea of which traces go to which function. those op amps drive the leds too, but not the same op amp usually.

so you should be able to find the output voltage across the diodes, all the way back to across the output cap. if you don't have voltage on the two traces coming off the diodes, they could be toasted.

the TL494 is the controller IC for the feedback from the back end to the front end. i am no so familiar with this older type, learned more about the newer integrated chargers myself. but one of the aussie guys knows them fairly well and may have some ideas too. this is essentially a self teaching thread, blind leading the blind sorta thing, so any help is appreciated.

[pradeepswain]

Thanks for the detailed information. Took a while to check the remaining circuit from following your comment.

I guess I've found the faulty part. The transformer YC-4803J does not show anything significant in output side. The input 4 legs show DC287v each. But voltage on the 6 legs on secondary side is 0.2v. I presume it should also have a fluctuating DC voltage. Or could it be the switching transistor that's feeding current.

[rui_fujino]

Here is another dead charger. this is BMS Battery Alloy shell 400w

[dnmun]

Thanks for the detailed information. Took a while to check the remaining circuit from following your comment.

I guess I've found the faulty part. The transformer YC-4803J does not show anything significant in output side. The input 4 legs show DC287v each. But voltage on the 6 legs on secondary side is 0.2v. I presume it should also have a fluctuating DC voltage. Or could it be the switching transistor that's feeding current.

the 287V on the capacitors is the DC voltage sitting on the output of the rectifier diodes. i once had the data sheet for that TL494 and tried to understand how it works to cause the switching in the front end. and if those were some kinda "push pull" transistor pair that were a balanced pnp and npn transistors that would switch on and off with the sawtooth pwm output of the TL494. all just guesses on my part, but somehow the signal from the 494 has to get up to the base on those transistors, or gate if they are mosfets. that's kinda stream of consciousness, about the best i have right now.

[dnmun]

rui, can you tell what size that resistor is that burned up? maybe someone else has the same charger open and can read the label for you for the capacitor. it may be symmetric with another identical one there, also same with the resistor. i noticed they have identical circuits for each of those transistors, if these are in that loop.

[rui_fujino]

rui, can you tell what size that resistor is that burned up? maybe someone else has the same charger open and can read the label for you for the capacitor. it may be symmetric with another identical one there, also same with the resistor. i noticed they have identical circuits for each of those transistors, if these are in that loop.

sorry for late reply. it is 2.2ohm ±1% (red, red, black, silver, brown) position is R20.
Now, the cap is positioned C11
thanks

[GCinDC]

mine, from here.


worth replacing the cap, or is she toast?

[dnmun]

you coulda made toast with that one. what size cap? maybe someone watching here has a nichicon but i bet you have local electronic stores there who carry them. it was hot for a long time because the pcb has burned through too. easy when you can see the defective parts. this is the bulk charger for your lipo?

[recumbent]

Wow that looks like a lot of power went where it shouldn't have. Sorry i cannot help, just getting more worried about my 600 EMC, which is very similar to yours.

[rui_fujino]

i think you can replace the cap and see what it does... if you can buy the same rating capacitor then test it, as far as i know, the local electronic shop capacitor should be much better quality then the one from china...lol

[Spacey]

What I am doing with these chargers now is taking down the amps by 20% as like with everything you get from China it's always on the limit of what it can do. Bring the amps output down a bit by adjusting the correct potentiometer and get a lot longer life from them.

They do not like vibrations either.

[recumbent]

...snip... Bring the amps output down a bit by adjusting the correct potentiometer and get a lot longer life from them.

Can we hook-up an old "Cycle annalyst" between the charger and batteries to monitor it correctly?

[dnmun]

the doc puts an ammeter on the output of his charger, built in. you can use the ammeter in your voltmeter in line with the output to see how much current it puts out.

what happened to GC's cap looks like it just was poorly made, which can happen, and may have been running close to it's max voltage and then started leaking until it overheated from leaking charge internally until it failed. you can see that the heat was generated close to the legs end for a long time since it cooked the pcb underneath. i don't think it failed because of the current output of the charger. jmho.

[amberwolf]

@GCinDC: I can see that the inductor next to the cap also got so hot that it burned off it's enamel. You might want to re-insulate it, so that it can't accidentally short against something (or so you can't do any damage to it or yourself while you have it open while it's running, if you ever do that for any reason).

Can we hook-up an old "Cycle annalyst" between the charger and batteries to monitor it correctly?

I use my CA to monitor charging, so that I know if my pack actually got back in as much as I used up (in case the charger fails ot fully charge it for some reason).

[dnmun]

you can almost see how the flame was shooting outa the side of the capacitor and left all that soot on the inductor. even the fan cable has evidence of the scorching on the red insulating sheath, and i bet the side of the fan plug is almost melted. whatta blowout. examine the small cap next to it too in case it was damaged, but the inductor and trimpots should be ok, imo.

[pgt400]

Did anyone figure out which pots adjust current and voltage on these unit? I have been using one for over a year now with no problems.

[GCinDC]

Did anyone figure out which pots adjust current and voltage on these unit? I have been using one for over a year now with no problems.

don't have pic, but it's tiny, very close behind AC in i think..

you really think mine's fixable with the board like that?

[dnmun]

i would expect you can replace the cap and go with it. but the charred pcb may conduct electricity so it would still be shorted between the legs. if that is the only cap on those traces, you can measure the resistance between them when you take the cap off. but there is also gonna be a drain down resistor, about 5k usually across the traces somewhere, so unsolder that first and lift one end before measuring the resistance between the traces, if no short, then go with new cap.

[miro13car]

I am surprised that nobody mentioned here cooling issue.
China power supplies/chargers have often simply not enough colling, namely fans are too tiny for amout of heat components generate especially switching FETs/Mostets.
When you want to pump 18A amps at 43V you better make sure those semiconductors/cups/ colis have enough cooling.
In all of my China-designed chargers I changed factory blowers with much more powerfull. I had switching MOSFETs heat up so much that they desolder themseves from the board. I provided real blast of cool air which solved problem of overheating semiconductors.
Now if you have fake switching semiconductors in you China switch-mode charger problem of cooling is even more critical.
Even before first charging try determine if they are fake and if so replace with genuine ones to start with.
Don't just connect battery and start drawing like 20A from this thing before those mods.

[rui_fujino]

personally BMSBattery does not have this problem. from my experience with them (3 different chargers) mine was charged outdoor where average temp is around 10-15C and never charged for more than 2hrs. yet still cap blew up (fets never failed me so far)