ICA 681b UPS fixing


Hello, i have an old UPS (ICA brand) type 681b, the MOSFET inside is burning (fire came out from it). it's uses 8x IRF540N, but my local store ran out of it, so i intend to use IRF3415 to replace 'em, my question is that can i do that (use IRF3415 instead of IRF540N)?.
History before: the UPS already been service about 2 years ago, and they said that the MOSFET is broken (IRF540N) so the changed it with the new one. and right now beacuse of some unstable current it blow off again.
so , any opinions?
The UPS uses :
2X 12v Sealed Lead-acid battery (in serial)

then, after i changes eight of them to IRF 3415, and try to turn it on, some smoke came ot from one of the resistor (22ohm). what am i doing wrong here ...?

if i have to, i will wait till the IRF540N back to store and change em' again ...


so in other words, i need help here in fixing the UPS... Thanks