Keep in mind I'm a noob to the diesel world,,,,, So twice now the batteries have run down on my Duramax from lack of use. I'm starting to look for an inexpensive tender that I can mount to the vehi...
Since you are charging two batteries, I would use the 1.25 amp model. Battery Tender has an extension cord that would be a better solution. Just connect when you plug in and the a Battery Tender will be out of harms way and available for other uses when not connected.
If you have had severly discharged batteries, they may well be on their legs.