Bosch 10.8 LiIon charger not charging :(

[djmickyg]

Hi

My Bosch 10.8 charger (for the 10.8 power tool range) isn't working.
my question is, what are some things I can check on the board?

Visually nothing looks burnt/out of place, the mains fuse is ok and power is getting to the (dangerous) transformer in the middle.

I will check the capacitors (wanted to take the photo of the board before I removed them)

the PCB, the 2 transistors on the heat sinks are stth1602ct, psnk80z


where the battery plugs into, the 2 power wires and ribbon cable are fine


Top Right - lm324an & 6200cb1/mml


Top Left cny17f & can't read the other


Thanks,
Michael

[Psi]

Did you try pushing down on the battery to make sure that contact is being made between it and the charger terminals?

I've seen multiple chargers where the battery contact springs just aren't strong enough.

Also check the soldering for any dry joints

[djmickyg]

Did you try pushing down on the battery to make sure that contact is being made between it and the charger terminals?

I've seen multiple chargers where the battery contact springs just aren't strong enough.

Also check the soldering for any dry joints

thanks for the quick reply.

I tried jigling the batteries around, plus both the batteries aren't working.

the solder joints seem ok? (not an expert) I did retouch some of the joints, I can post a picture of the bottom if that helps?



EDIT: just checked the 2 caps near the realy, (bottom right) and they seem ok.. I used the ohms then voltage method on the multimeter

 

[M. András]

if i remember correctly from its manual if the red flashes or its on fully the battery has some problem and there maybe 1 state indicating incorrect connection, how long do you have that charger? btw its for the blue or the green tools?

[djmickyg]

if i remember correctly from its manual if the red flashes or its on fully the battery has some problem and there maybe 1 state indicating incorrect connection, how long do you have that charger? btw its for the blue or the green tools?

it for the blue tools.. If the red is on solid, it means the batter has overheated.

None of the LEDs are working, I've had both batteries on for days at a time and no lights at all.

[M. András]

how long did you have this charger? i have one too and im intrerested in its lifespan, you cant get anything from bosch cos they admitted it is not their design and they dont have anything for it on their bob forum lovely thing when you buy an expensive power tool and the charger or the battery dies years before the tool itself, you could look at the control chips cos this damn thing runs so hot it should have forced air cooling maybe the chips are toast and wont give the transistors the swithing signals, relay works or not etc

[djmickyg]

how long did you have this charger? i have one too and im intrerested in its lifespan, you cant get anything from bosch cos they admitted it is not their design and they dont have anything for it on their bob forum lovely thing when you buy an expensive power tool and the charger or the battery dies years before the tool itself, you could look at the control chips cos this damn thing runs so hot it should have forced air cooling maybe the chips are toast and wont give the transistors the swithing signals, relay works or not etc

I've had it for 2.5 years now.. I use it most weekend, so it's only charging a few times a week max.
I used to work for them too, I can't even use my contacts to get a new one or a replacement.
to buy a new changer is >$60 on eBay.

[M. András]

mine is new and still has 3 years warranty here,
you can still check if there is any activity on the control chips. or even they are getting power at all

[Paul Price]

You can build a charger for your drill battery with a very simple LM317 voltage regulator circuit and, a discarded wall-wart power supply and two resistors, two small capacitors  and and a piece of metal for a heatsink. You can attach your drill battery to the LM317 with alligator jumper clips. Setting the output voltage only requires setting a value for one resistor and the internal current limiting of the LM317 and the output voltage setting of the LM317 can be set so it will not damage the battery by overvoltage, overcurrent or overheating.

You can tell when the battery is fully charged by hand-checking the heatsink which will be cool at full charge.

[transistor12]

Same to me . Any suggestion ?

[KL27x]

First time mine died, it was the FET and FET driver that died. Replaced those, and it was fine for another couple years.

The second time, something else happened. I didn't look too close, because the first time it died was within a few weeks, so I already had a spare charger thru warranty. I just chucked the broken one.

I have personally seen way too many of these threads. If my charger dies, again, and it's not something obvious, I will be making my own charge circuit with the housing and contacts of this POS.

[boogieman]

I know that the topic is old but this here seem still the best place for my findings.

I had the same problem. I fixed it by replacing the broken resistor(see image), the big one that powers the UC3842B Current Mode Controller from the high voltage (ca 310V). I dont know why but i had to lower the resistance to 330kOhm to make it run again. The UC3842C VCC is around 18V now. The resistors get pretty hot (70°C), but as far as can see it runs stable.

[Rick Law]

You can build a charger for your drill battery with a very simple LM317 voltage regulator circuit and, a discarded wall-wart power supply and two resistors, two small capacitors  and and a piece of metal for a heatsink. You can attach your drill battery to the LM317 with alligator jumper clips. Setting the output voltage only requires setting a value for one resistor and the internal current limiting of the LM317 and the output voltage setting of the LM317 can be set so it will not damage the battery by overvoltage, overcurrent or overheating.

You can tell when the battery is fully charged by hand-checking the heatsink which will be cool at full charge.

Having ran across a few bad 18650 LiIon that merely convert charging-power to heat...  I suggest adding some HW to do some current/heat limiting.

I have a decent charger, but I experimented with the LM317 setup for learning purpose.  Encountering that battery-as-heater condition, I limited the current to below (whichever is lower) 500mA or 1/3 C somehow at the minimum  I would limit the current to no more than 500mA or 1/3 C, whichever is lower.  Preferably, add a temperature sensor and shutdown north of (conservatively) 120F to 150F.  The rather conservative number here is because (unless the battery has provisions made) you can only measure the exterior temperature  but internal temperature could be much higher than external temperature.  So, better safe than sorry.

Those cheap-ish TP4056 boards may not be bad.  Some has the thermo-sensor connection already broken out to the connectors, some don't.  For those without, it is rather easy to adjust the TP4056 current limit.  At lower current, it gives you more time to manually check the battery heat.

[Edit: Corrected the hard to read sentence.  That sentence was probably written when I was possessed by some evil demon who happen to have no idea how write a readable sentence.]

[KL27x]

500mA or 1/3 C, whichever is lower.

That would be quite conservative. The 1.3Ah battery is 'posed to charge in 60 minutes. And IME, as close as I have ever paid attention, that is accurate. The last third of the charging takes up more than half of that time. So the charger probably has a current limited phase something like

2/3 *(1.3Ah)/0.5hr = 1.73 A

in the least.

[Monkeh]

500mA or 1/3 C, whichever is lower.

That would be quite conservative. The 1.3Ah battery is 'posed to charge in 60 minutes. And IME, as close as I have ever paid attention, that is accurate. The last third of the charging takes up more than half of that time. So the charger probably has a current limited phase something like

2/3 *(1.3Ah)/0.5hr = 1.73 A

in the least.

Very conservative. Their current chargers do 2.5Ah in 65 minutes.

[rekorden]

I know that the topic is old but this here seem still the best place for my findings.

I had the same problem. I fixed it by replacing the broken resistor(see image), the big one that powers the UC3842B Current Mode Controller from the high voltage (ca 310V). I dont know why but i had to lower the resistance to 330kOhm to make it run again. The UC3842C VCC is around 18V now. The resistors get pretty hot (70°C), but as far as can see it runs stable.

My charger was completely dead and I could see the voltage over the main condensator did not drop when charger was disconnected. The mosfet and all diodes measured fine and no burn marks was found.
When I found this post it was pretty obvious that the resistor on my charger also was broken. I replaced it with a 330kOhm and 20kOhm resistor to get closer to the original 357kOhm resistor that was there.
Charger now works fine. I haven't checked the resistors for heat, but believe I used 2 watt resistors, so most likely they will not face any heat issues.