its trash now.. its a core.. turn it in when you buy a replacement.

recharging deeply discharged batteries require some skills and NOT overcooking them with too much amperage.

i actually learned from a boss a long time ago about current limiting adjustable voltage power supplies for bringing back deeply discharged batteries without damaging them as long as nobody had tried to jump them .. nobody had tried to start the car with them that low.. and that nobody had attempted to recharge them

sulfate crystals grow as the battery slowly discharges.. also as the battery wears. this is what causes the ends of the battery to swell outward like a ball park frank when you cook it.

my current limited settings are 17 volts DC with the leads disconnected. without them touching the battery. then i touch them together and turn the amps up to 0.3 or 0.5 amps for mid size batteries.. 1/3 of an amp at 17 volts current limited will slowly dissolve the NON Hardened sulfate crystals and recharge the deeply discharged battery over several days..

invest in one of these.. https://www.ebay.com/p/Hiltex-40531-10-Amp-30-Volt-DC-Digital-Power-Supply/1323975107?iid=283320709537&chn=ps

they come in so handy for powering things too..