fake imax B6 repair - Page 1
Forum section: electronics / repair

author: Matthew98
author_rank: Regular Contributor
timestamp: February 10, 2017, 12:41:27 am
content: Hello everyone. Let me introduce myself to this forum by asking for help.I bought a fake imax b6 charger half year ago, or so. Everything was OK, but it recently went horribly wrong in front of my eyes. One day i was measuring Lion cell capacity by discharging it through the unit, as many times before. The cell had big capacity. At least thats what the unit displayed. When i smelt a burn from the unit, i disconnected everything and started diagnostic.The interface is all right, but some dumb electronic must have failed, because there is stable 12V at output ! When i want to select for example Lion battery with nothing connected, it shows me over voltage error. Im feeding it 12V and enough amps from a Pc supply, but the output 12V have only around 250 uA, so its not directly connected. I checked only the n mosfet near output joins and as part its ok. I didnt saw any burnt parts, or bulbed electrolytic capacitors. I will check the other parts from under the unit, when the equipment for this will arriveAny idea what could that be ? I was thing of dickhead move of manufacturer, that it was supose fail after amount of time... it already have time built inincluding few photos for identifying the unit version.Thanks for any ideaMatthew

author: james_s
author_rank: Super Contributor
timestamp: February 10, 2017, 01:13:04 am
content: First thing I'd check is the mosfet, measure and see if it's shorted.I wouldn't spend too much time trying to fix a $20 charger though.

author: Armadillo
author_rank: Super Contributor
timestamp: February 10, 2017, 04:06:28 am
content: The VT13 P-mosfet should be defective. Take it out of the circuit and check it. It is not shorted, but offered high resistance from Vin to the output hence your low current.

author: Matthew98
author_rank: Regular Contributor
timestamp: February 10, 2017, 12:02:56 pm
content: Thanks for fast replies.I checked both N-mosfets. One is on photo, another is near output pins and is different brand. It is ok, when i apply VGS around 3.5 or 4 V, but according to datasheet VGS(th) should be MIN 2V MAX 4V. Is that a problem ? At 2V i get resistance 1600...Well, I spent a LOT, like really LOT of money this year, so im trying to save every dollar i canAnd fixing is fun, right ?Im sorry. I really couldnt find the VT13 P-mosfet no metter how hard i try looking. I guess i never even saw P-mosfet before* With the two N-mosfets desoldered i still get 12V at output.

author: sainter
author_rank: Regular Contributor
timestamp: February 10, 2017, 12:13:17 pm
content: I would advice against repairing something that you charge a highly flammable lipo batteries with. Fire extinguishers cost more than a new IMAX B6. Be safe and practice your knowledge safely.

author: Matthew98
author_rank: Regular Contributor
timestamp: February 10, 2017, 12:18:23 pm
content: I probably will buy the genuine imax charger, but for now I have no money to spend. So i have to get this charger fixed for half a year, or better full year. Untill i had this charger, i charged the batteries through power supply, so its nice stepup, i guessAnd as the charger is smart, it shouldnt let me overcharge lipo s and lions so easily...I was never much about safety, though...I know, when i get burnt (literally) Its just my fault

author: Armadillo
author_rank: Super Contributor
timestamp: February 10, 2017, 02:13:05 pm
content: Quote from: Matthew98 on February 10, 2017, 12:02:56 pmHello, it looks like attached.

author: Matthew98
author_rank: Regular Contributor
timestamp: February 10, 2017, 03:50:53 pm
content: Thanks a lot ! Im on itThe package really confused meSometimes it scares me how much i will have to know to actually do something... Im turning 19 this month, studying electronic at school for 4 years now and beying interested in electronics from earliest memories I have, I cant still do much...I hope High school will do little better

author: Matthew98
author_rank: Regular Contributor
timestamp: February 10, 2017, 04:15:03 pm
content: Armadillo : You were right.The P-mosfet is busted, but he doesnt have high resictance, instead he is shorted.* With P-mosfet desoldered and N-mosfets back in place i get 20mV at output with no current when shorted. I just wonder if that could help find the problem.

author: james_s
author_rank: Super Contributor
timestamp: February 10, 2017, 04:33:23 pm
content: Quote from: Matthew98 on February 10, 2017, 03:50:53 pmThere is a learning curve, I was about your age when I finally started to get fairly good at repairing things. To be really good at repair, you have to have a significant amount of engineering knowledge as well as the troubleshooting and repair knowledge. That's one reason so few people repair things anymore, if you can repair things well you can probably make more money designing things. Keep at it though, it's a useful skill and it's enjoyable, fixing something is like solving a puzzle. Once you get good at it you hardly ever have to buy anything, I've never paid a dime for a TV for example and I've had more of them than I can count.

author: Armadillo
author_rank: Super Contributor
timestamp: February 10, 2017, 05:13:39 pm
content: Quote from: Matthew98 on February 10, 2017, 04:15:03 pmThere is a internal diode across the P-mosfet. If in fact p-mosfet is shorted then whatever V+ input you connect, you will have V+ - 0.6v strong output. Then it will be not the problem you described e.g. low current output. P-mosfet serves as a buck converter, there is another N-mosfet that serves as a boost converter... Anyway you should measure both direction again. Use ohm range and not diode range to measure both direction. Take it out of the circuit. I suspect the P-mosfet no longer switch. Also check the 2 diodes near the inductor.Imagine a buck converter, if the switch is shorted what will happen? and when is open  what will happen? And when the switch is removed out of the circuit, what will happen...

author: Matthew98
author_rank: Regular Contributor
timestamp: February 10, 2017, 06:16:30 pm
content: There is a internal diode across the P-mosfet. If in fact p-mosfet is shorted then whatever V+ input you connect, you will have V+ - 0.6v strong output. Then it will be not the problem you described e.g. low current output. P-mosfet serves as a buck converter, there is another N-mosfet that serves as a boost converter... Anyway you should measure both direction again. Use ohm range and not diode range to measure both direction. Take it out of the circuit. I suspect the P-mosfet no longer switch. Also check the 2 diodes near the inductor.Imagine a buck converter, if the switch is shorted what will happen? and when is open  what will happen? And when the switch is removed out of the circuit, what will happen...I used Ohm range this time and i got 5ohms at both direcions whatever i do. I had it out of ciruit before as well. It it kinda hard for me to imagine all of that, but i ll tryChecked all diodes i could find. the big one, 2 under tempeture (3pin) connector, one hidden under screen and one between add and entor switches. They all seems fine, i guess.Lets do your little quiz now.Shorted switch, input is directly on output. As its DC, inductor wont make any changes. Resistance should limit the measured current and with no switch, i will probably get only what inductor will "read" from near fields. Right ?Well, i struggled there a little, which is really shame ... Anyway i dont know what im doing wrong with measuring the P-mosfet If i am now...

author: Armadillo
author_rank: Super Contributor
timestamp: February 10, 2017, 08:57:44 pm
content: The P-mosfet is defective, if you have available, replace the P-mosfet. Because without it, its open circuited. There will be no output. Because even in Boost Mode, the P-mosfet needs to be ON. In buck mode, it will be switching. In off mode, it suppose to be High Impedance. The buck mode circuit is before the boost mode circuit, hence no buck no boost. I think the less than $20 fake should be the same as other fakes, I imagine.The other note you need to be aware is, finger static on the gate can turn a good mosfet on even when the finger is released. For that you can watch the recommended video below;The P-mosfet is a only a few cents, but I don't know how much it will cost in your country and whether it will be cost effective for you. Judging from your skills at removing the SMD, I think you are already good in electronics and you know where to get it.In future, if you need to get a fake charger, get the "Extreme balance charger x 605", the quality is way much better than the photos you showed but its not cheap.

author: Armadillo
author_rank: Super Contributor
timestamp: February 10, 2017, 09:13:29 pm
content: I was thinking why low amp if P-mosfet is not high resistance, it dawn upon me that there is another N-mosfet that need to switch the black output to ground through the current sense resistors. Can you check as attached.

author: Matthew98
author_rank: Regular Contributor
timestamp: February 11, 2017, 02:46:36 pm
content: I buy almost everything through ebay, so it takes about month to arrive, but i will try find some in school.The N-Mosfet does work, but the gate doesnt hold the voltage. When i was testing it (soldered out of curse), it showed short circuit for few moments (maybe half second, or less) and then it raised up quickly to disconnected circuit. Even my ohm meter couldnt measure anything.Left Resistor 0.2and right one 0.7

author: Armadillo
author_rank: Super Contributor
timestamp: February 11, 2017, 03:22:58 pm
content: The N-mosfet is suspected. I would suggest that you replace both the P-mosfet and N-mosfet.Below link, I have not bought from them before, don't know if its a fake. You should search around.http://www.ebay.com/itm/4pcs-Original-AO4468-4468-N-Channel-Enhancement-Mode-FET-Alpha-Omega-SOP-8-/261012270586?hash=item3cc58b2dfa:m:mI4KQW4YlRZ-vTvypNSWRWAhttp://www.ebay.com/itm/10pcs-New-AO4409-AO-4409-MOSFET-SOP-8-NEW-GOOD-QUALITY-/191674564293?hash=item2ca0b1bec5:g:ZnYAAOSwbqpT5gYn

author: Matthew98
author_rank: Regular Contributor
timestamp: February 11, 2017, 03:50:05 pm
content: Thank you for all your helpI have aredy learned more, than suspcted from this.Do you thing, that replacing the P and N mosfets will solve my problem, or it will just guide us towards the core of problem ?

author: Armadillo
author_rank: Super Contributor
timestamp: February 11, 2017, 04:25:32 pm
content: Replace the defective components as you have discovered.In repair, as long as the symptoms are answered by the repair logics, then you should develops confident in your repair. The symptoms are what you have described and yes I think the 2 mosfets should cover the repair.For me, I would just probe the mosfets drivers transistors and op-amps state changes to confirm they are healthy. Too lengthy to describe here though. Just change the 2 mosfets and cross your fingers.The rule of repair I learnt from this site.... "if it's working, don't touch it".... meaning.... no need to probe any further unless you have symptoms unanswered.

author: Matthew98
author_rank: Regular Contributor
timestamp: March 09, 2017, 01:35:46 pm
content: Today the components arrived. It works again and so far i didnt discovered any faultsThanks !

author: Armadillo
author_rank: Super Contributor
timestamp: March 09, 2017, 05:28:35 pm
content: Well done.

author: Matthew98
author_rank: Regular Contributor
timestamp: March 09, 2017, 05:53:40 pm
content: Quote from: Armadillo on March 09, 2017, 05:28:35 pmThats a little self-praise, dont you think ?its all your work

author: Armadillo
author_rank: Super Contributor
timestamp: March 09, 2017, 09:09:48 pm
content: thanks but it's all your efforts and electronics knowledge to troubleshoot based on those little pointers we gave.Well done! You own it.

author: hpapagaj
author_rank: Contributor
timestamp: September 19, 2017, 03:54:20 pm
content: Hi, I can't find any answer and I don't want to open a new topic for this one question:Can I charge NiCd/NiMh 14.4V (3A) battery (from cordless drill) pack with imax b6? If yes, the power supply for B6 must be 12V or greater, because of the higher charging at 14.4V?

author: Armadillo
author_rank: Super Contributor
timestamp: September 19, 2017, 04:05:08 pm
content: Quote from: hpapagaj on September 19, 2017, 03:54:20 pmOf course you can. Its a intelligence charger. Inside the voltage is boost up to match your NiCad battery.

author: hpapagaj
author_rank: Contributor
timestamp: September 19, 2017, 04:06:02 pm
content: Thanks for the fast answer.BTW: What a great forum.

author: Armadillo
author_rank: Super Contributor
timestamp: September 19, 2017, 04:12:04 pm
content: But of course, you need to press the Red button until the correct mode for the correct battery "NiMhBatt" or "NiCd Batt". and set to the appropriate charging current. You should know.Ohh 12V power supply is OK.

author: r-p
author_rank: Newbie
timestamp: February 07, 2020, 01:37:38 pm
content: I know this is an old thread but posting here as the pics posted look the same (whereas many other links will have different version boards).I had the reverse polarity warning on my display and switched the charging-output-leads round. Why I did this is beyond me as the wiring was correct and I had charged a battery with it the day before...Now the N-FET AO4468 has released its magic smoke.Since I have an identical 80W B6 clone, I figured I would use that to:(1) measure the resistances under/next-to the AO4468, and look at the color-rings to make sure the discoloration in the broken one wouldn't confuse me.(2) confirm the posted solution to the initial fault (reverse polarity) is indeed correct for my case.Now I am running into several issues.- internet is broken. It won't give me a solution what value a black-green-silver-gold-black resistor should be. And I am fairly certain this is what the colors are.- (1) the resistors from my (at least when last used) working and my broken B6 chargers measure differently and vary from the values foundhere. (whole postinghere)- (2) there is no measurable short (so no PCB trace) between the ground-banana-plug and the ground-of-the-balanceport in my 'working' B6 (a fried PCB trace supposedly causes this "reverse polarity"message, see youtube link below)The two boards from my 80W B6's are shown below (I have a single 50W B6 too, which is better at e.g. measuring the delta-V of NiMH batteries, the 80W versions don't seem to measure this delta-V at all, but that is a different issue).Broken B6:Left resistor reads 45ohm (in circuit, so broken if correct value should be 0.05ohm)Right resistor reads 0.50 (after subtracting measurementlead resistance and offset, in circuit)Despite the pic not being perfect, you can see the crater where the magic smoke decided to erupt from on the AO4468.(When last used) functioning B6:Left resistor reads 57ohm (in circuit, so broken if correct value should be 0.05ohm)Right resistor reads infinite (in circuit)Next I should check if the 'functioning' B6 still functions, because it shouldn't when one of the current sensing resistors (for charging or discharging???) is fried.Then I think my best bet would be to try to get ONE functioning charger out of the TWO... But I am open for suggestions! (I have a couple of AO4468's, but a 3W(?) 0.05 ohm resistor will be harder to find unless I make it out of resistance wire.)Reverse polarity fix:

author: r-p
author_rank: Newbie
timestamp: March 06, 2020, 11:11:21 pm
content: Little follow-up.I removed the 0.5 and 0.05 ohm resistor to have decent access to the blown-up AO4468. Measuring them out of circuit, they were both OK. So now I am questioning my measuring equipment... but I guess I had the clamps too high up the leads of the resistor, where the enamel coating still extends onto the lead. Or I made some other error I have somehow missed...I replaced the AO4468 and placed back the 0.05 and 0.5 resistor.Meanwhile I also replaced the 0.5 resistor on the 'working' B6 (two 1ohm parallel). (Writing this, I forgot if I rechecked the 0.05ohm resistor and if it was OK, according to my previous post it wasn't, so I may have forgotten to replace this, this is what happens if you stop to walk the dog, stop to make dinner, stop to pick up the kids...)Then I looked into the schematics and decided that the "-BATT" of the balancing port should indeed be connected to the "-BATT" of the banana plug output. So I shorted them on both chargers.Then I wanted to use them on a NiMH pack (half of a 24V 10Ah pack), hooked one up and it immediately smoked the 0.5 resistor again. It turned out to be the 'working' one (so actually two 1ohm resistors, the fact it may have a blown 0.05 resistor should hopefully not matter as long as I didn't even have the time to select a setting).So I guess it is safe to say that this one was broken already and somehow has the IRFZ44N turned ON all the time. Why I missed the horible smell from the burned resistor first time round, I don't know. Or the shorting of the "-BATT" wasn't done correctly.The other one will be tested with probably a current-limited powersupply as a 'battery'...

author: kadolism
author_rank: Newbie
timestamp: January 19, 2022, 02:18:39 pm
content: Hello there. Registered here just for this problem.But my burned parts are transistors but I can find the values.But we have the same boards.I hope someone can help me knowing the values of these parts.Thanks. BTW, this thread is awesome.