The accessory battery for an EV "energizes" the electronics that manage the rest of the car. It's critical to keep the 12v battery healthy. A battery tender is highly recommended (not a trickle charger) as it maintains the battery at a safe level and doesn't try to push more electrons into it as time passes.
The main pack would be best placed at a storage voltage level, approximately 50 percent discharge or remaining power. Many of today's EVs will charge to 80% to reduce the stress on the pack at the top end of the charge. Our Rav4EV charges to 80% but allows "extended range" at the press of a few screen buttons. It also advises to not do this frequently.
Drive your EV half the usual distance, pop on a battery tender and you should not have to worry about the 3 month charge. If it does get charged, you'd have to also have it driven to drop off the top fifty percent to place it back into storage.
Alternatively, have the 3 month charge interrupted at a 50 percent full point.