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Troubleshooting Bosch al1411dv NiCd charger

JordanSunday

Apr 5, 2022
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Apr 5, 2022
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Hello! I was recently given two chargers for possible repair, but with a neglected battery that holds no charge. I'm not sure that the chargers are even broken. As far as I understand the charger stops charging as soon as it detects a certain voltage drop in the battery which can't hold more than 4V
and apparently, I need the battery connected to detect the voltage in the charger. So the charger has 3 legs(4 but the 4th seems to be for the drill) a Positive leg a negative leg and a T leg for the thermoresistor which gets connected between the T and Positive Leg. With no battery attached, I have 5V on the T leg and 0V between the Positive and Negative legs on the charger. My question is that normal. How exactly can I be sure if the charger is working or not without a known good battery? The LED indicator seems to be working!
 

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73's de Edd

Aug 21, 2015
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Sir JordanSunday . . . . .
Where did your supplied schematic come from ?
Is there even a 1% possibility that linear battery controller IC is legibly labeled and you can pass it's numbering info to us ?
Also a GOOD close up photo of both sides of the PCB may be required . . .as we are being totally blind here.
What devices battery is attempting to be charged . . .you say a a drill ? . . .or other ?
What is the battery voltage written on that devices battery and what voltage are you presently reading from it, while being out of the charger..
As you can see the main power supply is being derived by the 4 diode FWB and is feeding pulsating DC to the the battery via a controlled switching SCR . . . . .TYN208..
There is a secondary voltage boost supply configured with D1 and C1 to feed the auxilliary SCR driver and sense transistors..
I found no linear battery controller I.C.'s that match your units pin-outs, so we are heavily dependent on that ? I .C.? units numbering.
There is a bit more fulfilling info in this additional schematic . . . . .

LE SCHEMATIQUE . . . .

upload_2022-4-6_23-19-39.png


73's de Edd . . . . .

upload_2022-4-6_23-23-10.png
.

 
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JordanSunday

Apr 5, 2022
2
Joined
Apr 5, 2022
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IC is 6HKB 07801758 but, there is no datasheet or anything on google. Just a couple of aliexpress listings from which one uses a Driver IC in the description. The Schematic came from one of 2 on google two, but since I already inspected the board I can confirm it's the same. Thank you for your's though much more understandable actually and interesting for me. The battery is a 12V NiCd battery that can't hold more than about 2V. When I put it on the charger which is rated for 7.2 to 14.4V it recognizes the battery via a blinking LED but then the LED stops blinking indicating full charge. Tried individual cells and only one had a little over 1V. I have 2 of these chargers which are almost identical and they react the same. All of this makes me believe that the chargers are working and know that the battery is faulty. Nevertheless, I want to be 100% sure the chargers are working and maybe learn something. If this can't be achieved without the IC datasheet then I just wouldn't pursue it. All components seem to be working. Couldn't remove the thyristor to check it without other components, but the reading seems to indicate it's working. No camera for pictures, unfortunately. Thank you!
 
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