Battery Tender Jr. vs. Noco Genius1

Feb 11, 2007
NorCal. USA
Anyone know if the Genius1 will actually desulfate a battery? I have (2) of the Genius1 that I bought on Amazon for $18.00 each with a Lightning Deal in June 2021, regular price $29.95. I bought the Battery Tender Jr. for $19.98 in May of 2019. The price doubled so I went with the Noco. They are still selling the Genius1 for $29.95, and in the answered questions, the mfg said that when you first plug in it, it goes to Desulfate mode. Here is the reply:

Flashing red on honda crv 12v lead-acid rc:85 (36ah) for 2+ days. voltmeter reads from 12.2 to 12.9v and back. is it really charging or desulfating?
Desulfation takes place at the beginning of the charge cycle. The Charge LED will go green when the battery reaches a full charge of 14.5-volts.
By NOCO Support MANUFACTURER on May 29, 2020

I bought a new battery and put the Noco on it to top it off, and the next day acid had leaked out the vent. I took it back to NAPA, and told him what happened, he got a new one for me. Did the same with the new one, no leak. So was the Noco desulfating the new battery? It may have been sulfated? Another instance, I had it maintaining my Montana, as it wasn't driven much. I disconnected it, not sure how long after, it wouldn't start. It was the 31st month of a 30 month battery, so I got a new one. Is there any way the Noco caused that battery to fail? It was still connected in the vehicle, so maybe didn't go to desulfate mode?

Why is the Battery Tender so expensive when the Genius1 does so much more?
Jun 15, 2003
I think there's an upper battery size limit to the Genius 1 that's smaller than your typical car-sized battery. It's in the specs somewhere. While it can trickle charge and maintain just fine, I don't think it has the oomph to properly desulphate something that big.