Yup, that's right.
We're not in hyperinflation. The currency isn't worthless. It's just not worth as much as it was a year ago. Or two weeks ago: I found out today that AR$11890.99 is no longer about US$58 as it was two weeks ago, but more like US$55 now. The annual inflation rate is about 50%, which is about 3.4% per month. If it's 50% per year over the next 12 months, the total value of those 12 monthly installments will be about US$46, which you'll notice is still more than the US$42 offered by the other seller without an installment option. So unless inflation goes higher in the next year, or the buyer defaults on the loan, the installment vendor is still making a pretty decent profit on the battery. They may not be "charging interest" but offering "interest-free" installments enables them to charge a sufficiently higher price that it's a profitable thing to do.
They are taking the risk that inflation suddenly explodes three months from now and 9 of their 12 installments are much smaller than they had planned on. And the buyer is taking the risk that inflation suddenly stops six months from now, which would make their final installments are just as onerous as the first few.
There have been a lot of loans pegged to the inflation rate in the past, as well as things like pensions. Unfortunately, since the government was the creditor for most of these, and also the government publishes the official inflation rate, they solved the problem in the early 02000s by faking the inflation rate statistics. Some economic consultancies published statistics showing the real inflation rate so the government prosecuted them for "commercial disloyalty". Retirees rioted in the streets and got tear-gassed by the police until the government agreed to raise their pensions faster than the fake inflation rate. Bondholders weren't so fortunate.