Battery charger - STIHL AL 300

[YellowJacket]

Hi friends,

I got to fix STIHL AL 300 battery charger, for mower machines, which works fine only when the battery is discharged ( haven't tried it already, since I got only fully charged battery, but that's why I have been told ). When the battery has some % of voltage, the charger doesn't work. In this case, the red LED starts to flash 10 times, and there is no voltage at the output. The customer tried more batteries, and it worked like this with all tried batteries ( so looks like not a battery related issue ).

I would try to discharge the battery ( with few 12V lightbulbs in series, since I don't have any device to fit it in ), and would try to confirm that claim, but I would try to diagnose the charger so far.

Between the charger and a battery, there are three power supply wires ( one for positive and 2 for negative voltage ), NTC BAT wire and DATA wire. On the first picture, you can see the communication between devices ( green is DATA, yellow NTC BAT ) right after plugging in a battery. I wonder, if the issue is related to DATA communication and if so, if I am able to identify it somehow ( maybe compare the communication between charged and discharged batteries with logic analyzer? ). Or if it is related to battery voltage itself ( some voltage comparator on the board, etc ).

Does anyone have any experience with this weird fault? I would be thankful for any hint. If you need some more info, feel free to ask. Thank you in advance.

[CapLeaker]

Re: Battery charger - STIHL AL 300

One piece of advice:
Don’t go in diagnosing and breaking your head about something that you didn’t confirm, tried and couldn’t replicate.
Why is this important? Because a hot battery will not charge in any state for example. In theory your customer could have tried to charge a hot battery and told you the thing isn’t charging. Same if things are too cold.

[petehall347]

Re: Battery charger - STIHL AL 300

always best to read the instructions first with these things .. i do some 80v stuff as said the pack might be too hot .

[petehall347]

Re: Battery charger - STIHL AL 300

the clue is on page 11 . https://cdn.badcaps-static.com/pdfs/...0c459ad215.pdf
i have had to change a few temp sensors in the packs to get them to work .. also some chargers are picky about the battery packs . say if a pack wont work in one charger doesn't mean it wont work in another and visa versa .

[YellowJacket]

Re: Battery charger - STIHL AL 300

Thank you all for your replies.

As I mentioned, I have only one battery, and it is fully charged. When I tried to plug it in, the charger immediately started to flash red LED with some error code ( which says actually nothing useful according to manual, just to visit authorized service - the customer sent it there, and they said "buy a new charger"... I believe, they tested totally different battery packs, not this one ). The communication in attachments runs though, all time.
So battery is in my room, where is around 25 degrees Celsius, its not hot, nor cold, during testing. I am trying to discharge it at the moment, with 4A load ( lightbulbs ), and will try to plug it in with various voltage levels ( I will let it cool down after discharging ). I will let you know, what I discovered.

[CapLeaker]

Re: Battery charger - STIHL AL 300

The NTCBAT is the temperature for the battery.

[YellowJacket]

Re: Battery charger - STIHL AL 300

Yes, I know. Actually, I don't know, why its value changes during communication with the charger ( yellow color in the first scope picture ).

[petehall347]

Re: Battery charger - STIHL AL 300

check the connections .. it will flash red if it cant see the battery properly . maybe a bad solder connection or resistor gone high etc . do the light on the battery do anything ?

[petehall347]

Re: Battery charger - STIHL AL 300

i have discharged packs with a 240v 600w lamp . its a bit slow but works .. best thing i found is a leaf blower to discharge them .

[YellowJacket]

Re: Battery charger - STIHL AL 300

I am on 32V ( 36V stated on the pack ), LED status on the battery shows 1 from 4 and it flashes ( so its fully discharged ), and I am unable to make it charge - customer said, it is charging only when a battery is discharged, so its not working at all now.
I have already made some brief visual inspection, for bad solder joints, etc, but haven't found anything suspicious. Will give it another try, more precisely this time.

( discharging in my case is really fast, four 12V/55W light bulbs for a car )

[stj]

Re: Battery charger - STIHL AL 300

about that scope-shot.
why is a logic signal 14v?
and did you zoom in to see if that was data packets or just pwm?

[stj]

Re: Battery charger - STIHL AL 300

also does it try to charge? is the charger outputting power for a second?
maybe the mosfet is dead if it's not

[YellowJacket]

Re: Battery charger - STIHL AL 300

- 14V is directly on wires coming from the charger. I traced the connection to pin of some uC, and there is exactly the same waveform, but with max voltage around 4.5V
- yes, I zoomed out, and its for sure some digital data
- yes, it does try to charge, but only for very brief time ( fan starts to spin, LED on the battery starts flashing ), less than one second. I have voltage on the secondary side of a transformer. It starts to fall after the charger decides to stop charging though ( after plugging the battery in again, voltage on the secondary rises again for a brief time )

[stj]

Re: Battery charger - STIHL AL 300

any idea how old it is?
maybe small caps are dried out

[petehall347]

Re: Battery charger - STIHL AL 300

i just remembered that the ones i work on behave like this if the battery pack is too far out of balance or too low voltage . they are supposed to go into a balancing program but i have never seen that happen yet .
also they do same if the temp sensor in the pack is faulty/broken .
sometimes you can jump the pack off a good battery and then charge it hopefully .
dont take much notice of the state of charge led.s as they can tell lies .

[CapLeaker]

Re: Battery charger - STIHL AL 300

Try a known good battery for sanity sake.

[sam_sam_sam]

Re: Battery charger - STIHL AL 300

What type of batteries are in this device

[YellowJacket]

Re: Battery charger - STIHL AL 300

any idea how old it is?
maybe small caps are dried out

I have no idea, and customer aswell.

@CapLeaker: this is a known good battery, I got from customer, he used it with different charger perfectly fine.

Anyway, I observed a new fact - when I connect the charger to power source, there is no output voltage at the secondary side of a transformer! Before, I measured there voltage, but it was due fact, there is N-channel mosfet, between secondary and positive VBAT voltage, so after plugging the battery in, battery voltage appeared on secondary side via internal diode in that mosfet.
So either, there is some problem on the primary side of a transformer, since there is no switching, or - I don't know, maybe it should start switching only after some condition is met? ( in my opinion - there should be switching right in a moment, when I connect the charger to power source, what do you think? ).
I am going to dig around primary side now. Thanks for hints so far.

[stj]

Re: Battery charger - STIHL AL 300

time to fix the psu section - start with the caps

[YellowJacket]

Re: Battery charger - STIHL AL 300

Main switching controller is L6599AD. I am afraid, I wont be able to diagnose anything without schematic - this controller is really complicated. It has 6V on VCC pin, but it looks like there are so many conditions, that have to be done, to make the controller start. It won't start switching at all, by the way. Without or with battery plugged in. Mosfets are fine.
Measured voltage ( no battery plugged in ) at all pins are 0V, except:
7 = 1.2V
12 = 6.2V
16 = 4.2V

Am I understanding datasheet correct, when I say, that after VCC, there should be ramping up some other voltages? Datasheet page 25.