Thanks. I just ordered the CTEK charger you posted earlier (-865). Will arrive Tuesday. Will try it out then.
The picture there indicates it does de-sulphation (stage 1).
Is that not what you have? Wondering if i should cancel and buy one that does the desulphation also, if this one does not.
But I did connect the jump starter to the car battery and measured its voltage with a multi-meter (after disconnecting the jump starter).
It was at 9.70 V originally. After 5 mins, it went up to 10.40 V.
But 10 more minutes, it was back to 10.2V and after an hour or so, back to 9.92V with nothing attached to it.
As you confirmed earlier, the electric cars need the 12V battery even while driving, so it seems risky to put it back.
Besides, wife won't drive the car with the old battery in it.
Edit on CTEK 865:
So the video indicates it has 6 stages. The description shows 8 stages (adsorption and soft start and recondition ectra stages).
Wondering how important the recondition stage is. Important enough to change the order?