maintainers

Anyone out there have a recommendation for a battery maintainer/tender? We just took our coach out for the weekend, but it had previously been sitting for nine months with nothing maintaining the batteries. They were OK, but the chassis batteries were getting fairly low, the chassis batteries...

I have a new 2025 Grand Design Lineage on the Sprinter chassis and had to replace the chassis battery 10 days later to goon a trip. Would someone please recommend good battery maintainer that has an automatic storage mode that you have used and liked? Thanks!