throbscottle
Well-Known Member
This is more for the benefit of others who may have similar problems, since I've "fixed" mine (read - modified slightly so it works) even though I still don't understand what's actually wrong.
I have a Karcher WV2 window vac. It came to me without it's original charger. Got a USB substitute cable as the chargers are pricey! Means it charges at 5v instead of 6v. It hadn't been used for a long time and would not charge it's battery. Light flashes for a bit, no current is drawn.
Replaced the battery and it charged once, refused to do so since.
Otherwise works correctly, turns on, motor will run, turns off, light flashes when battery starts to go.
Re-worked the charger board. Tried another battery. Tried the original battery.
Drawn a schematic of the charger board so I can understand what's supposed to happen. Not sure if it's 100% accurate. My initial sketch has a lot of crossings out on it!
Anyway, the first of the P-MOS transistors is supposed to get turned on by a signal to the transistor connected to it's gate, which is itself turned on by pin7 the ATTiny24A. That signal is missing. If I bypass the ATTiny with a resistor directly to the charger + input, it will charge, and once it's started charging it seems to latch and continue to do so without the resistor.
The 2nd P-MOS turns it off when the battery voltage gets too high. I think the FET is a J301 (marked !301)
When the charger is first switched on, pin7 goes high very briefly. So I think the ATTiny is sensing something it doesn't like, but I can't figure out what.
Q6 and Q7 form an interlock so the ATTiny can keep itself powered on when the motor's running, since the switch is momentary.
Then there's that weird arrangement with the TL431 type reference, set to 2.5v. All it seems to be doing is regulating the supply to a PD that has the low end tied to the battery side of a low-side current sense resistor. Is it just acting as a level shifter for the current sense voltage? Or something else?
At one point during my investigation it started working. Put it back together again - stopped working and refused to do so again.
The LED is supposed to turn green when charging is complete but it no longer does so.
So my "fix", based on the experiment turning on Q6 with an extra resistor, was to connect a bootstrap capacitor (100n) to it's base, directly to the charger + input. So far it's working, even after I put it back together. That's my entire weekend gone, better darned well keep working now...
I have a Karcher WV2 window vac. It came to me without it's original charger. Got a USB substitute cable as the chargers are pricey! Means it charges at 5v instead of 6v. It hadn't been used for a long time and would not charge it's battery. Light flashes for a bit, no current is drawn.
Replaced the battery and it charged once, refused to do so since.
Otherwise works correctly, turns on, motor will run, turns off, light flashes when battery starts to go.
Re-worked the charger board. Tried another battery. Tried the original battery.
Drawn a schematic of the charger board so I can understand what's supposed to happen. Not sure if it's 100% accurate. My initial sketch has a lot of crossings out on it!
Anyway, the first of the P-MOS transistors is supposed to get turned on by a signal to the transistor connected to it's gate, which is itself turned on by pin7 the ATTiny24A. That signal is missing. If I bypass the ATTiny with a resistor directly to the charger + input, it will charge, and once it's started charging it seems to latch and continue to do so without the resistor.
The 2nd P-MOS turns it off when the battery voltage gets too high. I think the FET is a J301 (marked !301)
When the charger is first switched on, pin7 goes high very briefly. So I think the ATTiny is sensing something it doesn't like, but I can't figure out what.
Q6 and Q7 form an interlock so the ATTiny can keep itself powered on when the motor's running, since the switch is momentary.
Then there's that weird arrangement with the TL431 type reference, set to 2.5v. All it seems to be doing is regulating the supply to a PD that has the low end tied to the battery side of a low-side current sense resistor. Is it just acting as a level shifter for the current sense voltage? Or something else?
At one point during my investigation it started working. Put it back together again - stopped working and refused to do so again.
The LED is supposed to turn green when charging is complete but it no longer does so.
So my "fix", based on the experiment turning on Q6 with an extra resistor, was to connect a bootstrap capacitor (100n) to it's base, directly to the charger + input. So far it's working, even after I put it back together. That's my entire weekend gone, better darned well keep working now...