I have a 2019 Express diesel with two batteries. I store this van for a few months during the winter. If I put a battery maintainer on one battery will it charge both batteries? I assume both batteries are connected via the starter, but does the second battery need to be connected to the charger.. or charge it separately?

 

It depends on how they were hooked up. See if there's a schematic on gmupfitter.com

 

buy or borrow a VO multimeter w a d c amp measure option. write down voltage in #1 and #2. then hook up the battery maintainer to bat #1, then turn on maintainer. then measure what charging amps are going into bat #1 and then measure charging amps going in to bat #2. check voltages of both bats against the start voltages you measured after an hour or 2. if both bats show increased volts after 2 hours of maintainer being hooked up to only bat #1, you have your answer.

 

You can typically connect the battery maintainer to just one of the batteries, and it should charge both. Most modern vehicles, including vans like yours, have a system where both batteries are connected in parallel. This means that when you charge one, it should effectively charge both. However, it's always a good idea to consult your vehicle's manual or reach out to the manufacturer to double-check the specific setup in your van, just to be sure. And if you ever need a replacement battery, I suggest you check out the 96R battery – it's a popular choice for many vehicles.