Battery charger - STIHL AL 300

[petehall347]

Re: Battery charger - STIHL AL 300

L6599AD

Supply Voltage Min: 8.85V


Supply Voltage Max: 16V

[stj]

Re: Battery charger - STIHL AL 300

pin12 look for connected capacitors

[YellowJacket]

Re: Battery charger - STIHL AL 300

OMG, I feel dumb, mistake like I am newbie beginner. Sorry for wasting your time.

So, I was digging around, and find out something - simplified schematic of powering the IC in attachment. The zener diode should be MMSZ5245 ( zener voltage = 15V ), and it is working fine ( tested out of the board, there is stable 15V if I apply more to a protective resistor in series with it ). So, if there is 12V on colector of a transistor, 12V should be also on its base, right? Why there is only 6.9V then? I tested also a transistor, onboard, with diode mode - I can see 0.7V at base-collector and base-emitter. So I believe, it is good. Any ideas? ( I tested also an electrolytic capacitor, which is connected to collector, and I measured 0.18R ESR / 47uF ; capacitor is 47uF/50V ).


// EDIT: tried to replace the transistor FMMT2222A for BCW66G ( little bit underrated, but just for test its fine ), no change. Then I tried to lower 22k resistor, to 10k resistor and then I got around 9V at emitter of the transistor! ( still only 8.18V at VCC of the controller ). Does it mean, that the zener is bad after all?

[petehall347]

Re: Battery charger - STIHL AL 300

voltage in at collector . zener and base fed by the resistor .. the zener sets the base value and emitter should be approx 600 mv lower .
the zener cant magically make extra voltage . you need to get it higher at the collector . more than 15v . not sure how much more though .

[YellowJacket]

Re: Battery charger - STIHL AL 300

Well, I know, that zener can not make any extra voltage, but if the voltage at the resistor ( and collector ) is less, than zener voltage, then that voltage should be also at cathode of the diode.
And I know, why its not there - there is an optocoupler ( its transistor side ) in parallel with zener diode. That's why there is less voltage ( there is around 1V on LED side ). And that means, I probably waste time with this, since LED side of optocoupler is connected somewhere to battery circuitry, so this charger probably start switching only when you connect a battery ( at least it looks like it works that way ).

I will try to search more, but chances for me are less now.

[petehall347]

Re: Battery charger - STIHL AL 300

yes the battery starts the charger up well it wont start without it .. you sure the connections from battery ok ? what is the battery voltage out of the charger and installed in the charger ?

[YellowJacket]

Re: Battery charger - STIHL AL 300

I gave up, already gave the charger back to customer. Thank you all anyway, for trying to help me.

Have a nice day.