Laying a car up for the first time? Start with our long-term storage prep checklist — tires, fluids, covers, pests. This guide covers only what changes when the car has a high-voltage battery.
Storage advice written for collector cars assumes a combustion car: stabilize the fuel, put a maintainer on the battery, get the weight off the tires, walk away. Most of that still applies to a hybrid or an EV. But a combustion car in storage is a chemistry problem you solve once at layup. A car with a traction pack is a power budget that keeps running the entire time the car sits — and the battery that actually strands owners is not the expensive one.
Two batteries, and the cheap one is the problem
Every hybrid and EV has two electrical systems. The high-voltage pack moves the car. A separate low-voltage battery — nominally 12 volts, usually an AGM, increasingly a small lithium unit on newer EVs — runs the computers, body electronics, locks, telematics modem, and, critically, the contactors that connect the traction pack to everything else.
Those contactors are relays held closed by 12-volt power. If the 12-volt battery goes flat, the car cannot close them, which means it cannot draw a single watt from a traction pack sitting at 80% charge two feet away. You get a car that is dead in every visible way while holding enough energy to run a house for a day. It is the most common way a stored EV or hybrid fails, and the fix is a charge on the 12-volt battery, not on the pack.
That battery is also smaller than the one in a comparable combustion car. It never cranks an engine, so it is sized for electronics, which leaves less reserve to absorb months of parasitic draw. Everything in our post on battery tenders, flat spots and fuel stabilizer applies to it, with one addition: confirm your maintainer is rated for the chemistry actually in the car, and read the manual before connecting one, because some vehicles specify a particular terminal or procedure.
How long can you store an electric car without driving it?
Longer than most owners expect if it is set up correctly, much shorter if it is not. Two variables decide it: where you leave the state of charge, and how much the car draws while it sleeps.
A parked EV is never truly off. It wakes on a schedule to check in with the network, answer the app, run battery management, and top up the 12-volt battery from the traction pack through the DC-DC converter. That last one is the part people miss: an unplugged EV drains its traction pack partly in order to keep its 12-volt battery alive. With connectivity and monitoring switched off, idle loss on a modern EV typically runs from a fraction of a percent to a couple of percent of pack capacity per week. With camera-based sentry modes, scheduled cabin conditioning, or an app opened every day, the same car can shed several percent per day.
Do the arithmetic before you hand over the keys. Park at 50% with everything off and lose 1.5% a week, and six months later you are in the low twenties — fine. Park at 30% with sentry mode running and you can reach zero inside a month. Manufacturers generally warn that allowing the pack to fully deplete can cause permanent damage, and warranty language often excludes it. Everything else here is optimization; this is the failure that costs money.
What state of charge to leave it at
Lithium-ion cells age two ways. They age from cycling, which storage stops, and they age on the calendar, which storage does not — and calendar aging runs faster at a high state of charge, faster still when it is warm. A pack left at 100% in a hot building degrades measurably quicker than the same pack left mid-range in a cool one.
Manufacturer guidance varies, and the owner's manual for your model year is the authority here, not a forum thread. That said, published storage recommendations cluster around the middle of the pack, commonly stated as roughly 50% and sometimes as a band. If the car lets you set a charge limit, that is the cleanest way to hold it there.
Should you leave it plugged in?
"Plugged in" and "charging" are not the same instruction, and conflating them is where owners go wrong. Left connected with a charge limit set near the middle, the car manages its own 12-volt battery and thermal systems indefinitely with no involvement from you — the ideal arrangement, if the facility permits it. Left plugged in with the limit at 100%, the pack sits at exactly the state of charge you were trying to avoid. Left unplugged, the car is fine for a few months provided you ran the numbers above. The complication is that plenty of facilities do not allow unattended vehicle charging at all, which turns a question about your car into a question about your contract.
Hybrids: the case where you cannot plug in at all
A conventional hybrid has no plug. Its traction pack is charged only by the engine and by regeneration, so once the car is parked, nothing maintains it except the car's own management electronics — and those run off the 12-volt battery. The failure sequence is predictable: the 12-volt goes flat over a few months, the car stops managing anything, and you return to a vehicle that will not power up.
A maintainer solves it. On most hybrids the 12-volt battery lives in the trunk or under a rear panel, and there is a designated jump-and-charge post under the hood so you do not have to go digging — use whichever the manual specifies, and never attach anything to the high-voltage system. Do not disconnect the battery instead of maintaining it unless the manual says to: you lose stored settings, and some vehicles want a relearn procedure afterward.
The fuel side gets no pass. A hybrid burns less fuel per mile, but the fuel in its tank ages on the same schedule as anyone else's, so it still wants a full tank and stabilizer at layup. Plug-in hybrids add a wrinkle: several run a fuel maintenance routine that starts the engine periodically to burn off aging gasoline, and that cannot run on a car asleep with a flat 12-volt battery. Treat a PHEV as a combustion car for fuel and an EV for everything else.
What six months does, system by system
| System | What a six-month layup does | What to do |
|---|---|---|
| High-voltage pack | Calendar aging continues; charge drifts down through self-discharge and 12-volt top-ups | Leave near mid-charge and cool; never leave it near empty |
| 12-volt battery | Discharges under parasitic load — the usual cause of a "dead" stored EV or hybrid | Maintainer matched to the correct chemistry, or a car left plugged in |
| Telematics and monitoring | Sentry modes, cabin conditioning and app polling multiply the drain rate | Switch them off at layup; ask the facility not to wake the car |
| Tires | Flat-spotting, more pronounced on a heavy EV, plus the usual pressure loss | Inflate per the prep checklist; roll or move the car if the term runs long |
| Brakes | Rotors corrode as on any stored car, and regeneration means less pad contact to clean them off | Dry air in the bay; deliberate friction braking on the wake-up drive |
| Fuel (hybrid and PHEV) | Ages normally; PHEV fuel maintenance modes will not run while the car sleeps | Full tank, stabilizer, circulate it before shutdown |
The effects that hit every stored car — brake fluid absorbing water, A/C shaft seals drying out, rodents — are covered in our guide to storing a car for six months.
Six questions for the facility
This is where an EV or hybrid stops being an ordinary storage customer, and the answers vary far more between buildings than pricing does.
- Do you accept EVs at all? Ask before you tour. A small number of buildings do not, usually for insurance reasons.
- Is there power at the bay, and may it run unattended? A 120-volt outlet is enough to hold a car at a set charge level, but allowing a 12-volt maintainer and allowing vehicle charging are separate permissions.
- Level 2 charging: available, metered, or extra? If it exists, ask how it is billed and whether it is shared.
- Will staff plug and unplug on a schedule? Some concierge programs will. Get it written into the agreement.
- What is the written EV policy? Battery fires are rare but difficult to extinguish, and a facility that has thought about it will have real answers on detection, suppression and where EVs are parked.
- What temperature does the building actually hold? Not "climate controlled" — a number.
That last question is not a formality. The 55–70°F band collector facilities target for combustion cars sits close to ideal for lithium storage too, which is a real argument for a proper building over a home garage in a hot market like Scottsdale. Cold is comparatively benign for a parked pack — it slows aging — but charging a cold pack is not, so a car that winters in an unheated space should warm up first. EV-dense markets such as the Bay Area and Los Angeles have the highest concentration of facilities that have already worked this out.
Waking it up
- Charge or replace the 12-volt battery first, before trying to power the car up.
- Wake the car and check pack state of charge and stored fault codes.
- If the building was cold, let the car reach shop temperature before charging.
- Charge to the level you actually need, not to 100% by reflex.
- Set tire pressures, then drive gently and use the friction brakes deliberately — regeneration alone will not clean the rotors.
- Turn monitoring and connectivity features back on.
Finding storage that will take the car
Storage costs the same for these cars as for anything else — see our storage cost reference for tiers and ranges — but the shortlist is shorter, because power at the bay and a written EV policy are not universal. Browse your market from the city index, ask the six questions above, and check the answers against our verification standards. The right building answers with a number and a policy document, not with "we can probably work something out."