Repair of 8A pb-battery charger. Unkown part?

[Snake____1]

Good evening people.

I'm at a loss trying to repair a charger. It's based off a switch mode power supply, and output just pulsates. I have checked all diodes, main resistors, optocoupler and more...
I get 350v DC on the main side, but on the secondary side it pulsates up to ~3v...

I have a TO-220 component on the secondary side I can't identify, hope someone can pitch in here... (See photos) "markings are: T410 BV4715 (Google search renders nothing)

[0xfede]

Hi Snake,

it is an AOT410L from Alpha & Omega semiconductor (100V 150A MOSFET)
You can find the datasheet here:
http://www.aosmd.com/pdfs/datasheet/aot410l.pdf

Best,
0xfede

[Inverted18650]

http://www.aosmd.com/res/markings/AOT410L.pdf

[Snake____1]

Thank you @0xfede!

Strange circuitry, seems power goes straight from the SMPS transformer via a relay, to the battery, back through this mosfet and back to the transformer...

Almost seems like they are using the mosfet just for the diode...

[0xfede]

You are welcome.

I can't say for sure if this is the case but MOSFETs are often used as reverse polarity protection. A good texas instruments application note is here:
http://www.ti.com/lit/an/slva139/slva139.pdf

Best,
0xfede

[Snake____1]

Found the faulty component! The OP-AMP on the bottom, the LM324. Changed it and now it's fully functional again