Converting Dewalt DCB101 battery Charger from 110v to 220V - Page 1
Forum section: electronics / repair

author: dark_hawk
author_rank: Regular Contributor
timestamp: September 08, 2020, 06:18:50 am
content: Hi,I'm attempting to convert a Dewalt DCB101 battery Charger from 110v to 220V.The Power Transistor is a 6R229P, which can withstand 600V so I don't think I need to change it.https://datasheet.octopart.com/IPP60R299CP-Infineon-datasheet-49156.pdfThe Current Mode Controller is 3845p. I think it would work fine but I'm not sure.https://www.onsemi.com/pub/Collateral/UC3844-D.PDFWhat I came with so far is this:1- Replace the 200V 220UF cap with a 450V 100UF2,3- Install a varistor between points 2 and 3 (One Live and the output of the fuse). The two I have are 10V471K and S10K300.Which would be better?4- Replace the 4A Fuse with a 2A fuse5- Remove the small choke number 6 and move the bigger choke number 5 in it's place.6- Install to thermistors in place of the bigger choke number 5.The ones I have are: NTC 5D-9 (5 ohm/3A), SCK 053 (5 ohm/3A) and SCK 2R55A (2.5 ohm 5A). Which would be better?7- Install a 4x4 cm fan plowing in the direction of the power transistor and the Schottky rectifier (STPS20150C)Would that be enough or are there anything more I can do?Thanks

author: magic
author_rank: Super Contributor
timestamp: September 08, 2020, 07:00:31 am
content: What's the deal with swapping chokes?The secondary rectifier will now see more voltage across it (secondary output voltage plus rectified mains divided by turns ratio).What's that yellow box in the middle and all the primary circuitry near it?

author: coromonadalix
author_rank: Super Contributor
timestamp: September 08, 2020, 08:00:20 am
content: Why simply buy a 220v to 120v transformer ?Not sure this model is modifiable easily, you need the capacitor and you're supposed to add / change some power resistors value to drop the voltage.The smps ic need to have its supply adjusted too ?, unless the circuit can do it automatically ?The DCB105 is hackable with 2 resistors and the main capacitor, youtubes videosThe DCB101 in EspaniolSeems doable, i think you overthink a few things

author: dark_hawk
author_rank: Regular Contributor
timestamp: September 08, 2020, 08:01:55 am
content: Quote from: magic on September 08, 2020, 07:00:31 amI need a place to put the thermistors with a gap on the pcb, since there are to filtering chokes I thought (Not an electrical engineer here) to keep the large choke, and replace the smaller one with the thermistors.The yellow box looks like a transformer, the transistor on top is ST BV42:https://np.infinity-electronic.hk/datasheet/a8-STBV42G-AP.pdf

author: coromonadalix
author_rank: Super Contributor
timestamp: September 08, 2020, 08:02:48 am
content: Quote from: magic on September 08, 2020, 07:00:31 amThe yellow box is a coupling transformer for the smps ic to the main power circuit, it provide isolation too

author: dark_hawk
author_rank: Regular Contributor
timestamp: September 08, 2020, 08:07:05 am
content: Quote from: coromonadalix on September 08, 2020, 08:00:20 amI already have a step down transformer for this charger, but the other day I wanted to have the charger out on a job and it's not easy dragging a step down transformer around, so I thought I try to modify it.I think the smps ic will adjust automatically, since I've found on some Russian forum people just change the capacitor and the charger works, but some complain than the power transistor and the current mode controller blows up after a while, so I'm trying to avoid that.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 08, 2020, 10:11:16 am
content: Dont change parts if you're not sure of the long terms effectsI've seen many people badly sliding the battery in Dewalt chargers, they dont push the batteries all the way down. some Dewalt chargers will try to charge but it will be badly done, i've seen many people storing them in bad weater / in cold weater, dropping them too low in the voltages or storing them for a long time period without a full charge ...I have many 20v batteries and some of them are in the first generation when they came out, and they are still working fine.I had the chance to poke in the Flex series 60volts, they are badly designed, the bms is not good enough to equilibrate the 3x5 cells pack in them, and they eventually fails over time.When you pay over 100$ for a battery ... i want them to last. So i stayed in the 20v models ...

author: Haenk
author_rank: Super Contributor
timestamp: September 08, 2020, 11:22:57 am
content: Did you check outhttps://www.elektroda.pl/rtvforum/topic2695442.htmland even betterhttp://www.78294.ru/forum/5-2-1

author: dark_hawk
author_rank: Regular Contributor
timestamp: September 08, 2020, 11:40:44 am
content: Quote from: Haenk on September 08, 2020, 11:22:57 amI checked those links yes.The second link is informative and most of my suggested modifications are his ideas, but the model of the pcb differs from the one I have, so I'm asking for directions here.His model has an empty place to install the thermistors for instance, and the overall layout of the pcb is different.

author: magic
author_rank: Super Contributor
timestamp: September 08, 2020, 03:09:45 pm
content: Thermistors, fans? I suspect that the modded chargers blow up because of marginal derating rather than temperature, you are probably wasting time with that stuff.Do you have a scope? Post the waveform on the secondary winding, before the rectifier, and report voltage on the primary capacitor (don't blow it up, don't kill yourself, yada yada). This will help estimate turns ratio of the transformer.Is the secondary rectifier that STPS20150C diode that you mentioned earlier? What's the maximum secondary output voltage?The primary switch may need an upgrade, because it sees rectified mains plus secondary voltage multiplied by turns ratio plus inductive kickback from the transformer's leakage inductance.I'm still not sure what to think about the circuit in the center, and yes, I too think that box is a transformer. Not sure what the whole thing is doing, maybe an auxilliary PSU for some secondary circuits?editThere is likely a high value (1Meg or so) resistor which pulls UC3845's VCC up before the converter starts working and produces its own supply voltage. This may need checking for proper power and voltage rating. Or just desolder one end and add an identical resistor in series.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 08, 2020, 04:37:59 pm
content: the yellow box is a signal coupling transformer between the smps ic and the power / main section, you can see some pinouts idea in the smps ic datasheet, if the power stage blows, it wont go further in the circuitry

author: magic
author_rank: Super Contributor
timestamp: September 08, 2020, 08:04:16 pm
content: Which datasheet?The "power stage" is the UC3845 with its associated MOSFET and I think it gets its control signal through that lone optocoupler IC35.

author: dark_hawk
author_rank: Regular Contributor
timestamp: September 09, 2020, 02:38:42 am
content: Quote from: magic on September 08, 2020, 03:09:45 pmUnfortunately I don't have a scope.Here is a closeup to the UC3845 circuitry, did you mean R9 which is a 100K 2W resistor?Here's the blue transformer in the middle with the surrounding circuitry.I also found this photo of the 220V version of the board, the input ciruct seems different, they have 2 5W 0.33ohm resistor instead of the bigger choke and what looks like a bigger choke instead of the smaller choke.Maybe I should move the bigger choke in place of the small one and add those 2 5W resistors.

author: magic
author_rank: Super Contributor
timestamp: September 09, 2020, 05:46:42 am
content: R9 is not connected to the chip's VCC. R9, D1 and the polyester cap are the snubber, leave them alone. I think their operation is only affected by peak primary current, and that's going to be the same regardless of input voltage in a fixed frequency converter like the UC3845. The chip's VCC and GND comes from somewhere else though those 0Ω resistors.The input circuit is a filter which reduces EMI injection into mains. There is no way to improve it without testing. You don't even know if the "big" and "small" inductors on different versions of the board are the same.