I build electric bikes using Sealed Lead Acid (SLC) batteries. They are great and I've developed a love for them. You have to decide what you want to power (12v @ ampsXtime in hours) with this formula you can decide on what amp-hour rating (size) of battery you need.
Here is an example for overlanding use, at night at camp:
12v @ amps used for accessories X time in hours
12v @ 4amps X 4 hours = 16amp-hour battery to support 4 amps for 4 hours or 1amp for 16 hours. Keep in mind this is %100 depth of discharge so you will need to double (32 amp-hour) to be at %50 depth of discharge at the least. Most batteries, including the ones I use only like to go down to %20 depth of discharge. So for this example, we would need to have a 80 amp hour battery!!! <--(16ah divided by .20 = 80) An 80 amp hour battery is pretty big! Also, keep in mind that our example is also pretty small at only 48 watts
The best way to do off-grid is old fashioned deep cycle lead acid batteries that can be discharged to roughly %50, only necessitating a 32 amp-hour battery in this case, which is a lot smaller.
If you only want to power a few small lights for a little while then the John Deere batteries might work for you, and you can always wire them in parallel to double your amp-hours.
Mick