Author Topic: fake imax B6 repair  (Read 11710 times)

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Offline Armadillo

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Re: fake imax B6 repair
« Reply #25 on: September 19, 2017, 04:12:04 pm »
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.
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Offline r-p

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Re: fake imax B6 repair
« Reply #26 on: February 07, 2020, 01:37:38 pm »
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 found here. (whole posting here)
- (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:
« Last Edit: February 07, 2020, 05:10:57 pm by r-p »

Offline r-p

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Re: fake imax B6 repair
« Reply #27 on: March 06, 2020, 11:11:21 pm »
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'...

« Last Edit: March 06, 2020, 11:42:41 pm by r-p »

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