Start winter fully charged. Everything else on this page follows from that one rule.
Research — built from manufacturer guidance and published owner documentation. This page is general guidance only; it does not describe any specific routine used on the owner's rig.
Affiliate disclosure: Links marked as affiliate links on this page may earn us a small commission at no extra cost to you. You pay the same price either way, and you buy directly from the retailer.
The rule that drives everything on this page: a fully charged battery resists freezing far better than a discharged one. A discharged lead-acid battery can freeze, crack, and die in a cold snap. Winter battery care is really just two jobs — keep the charge up, and stop the slow drains.
As a lead-acid battery discharges, the acid in its electrolyte turns to water — and water freezes. The commonly cited figures tell the story: a fully charged lead-acid battery resists freezing down to around −70°F, while a fully discharged one can freeze at around 20°F — an ordinary winter night. A frozen battery can crack its case, buckle its plates, and short internally. Once frozen solid, it is usually scrap, not a recharge job. This is why "start winter fully charged" is the single most important step on this page, and why every option below is really a way of staying charged.
Illustration only, using the commonly cited figures from the guide: charge state decides whether a battery survives a cold night.
Your three options
Leave them in, on a maintainer. A smart battery maintainer (not a plain trickle charger) holds the battery at full charge without overcharging. This works if the rig has power available where it is stored. Easiest option, and the best one if you have power.
Disconnect and check monthly. If there is no power at the storage spot, disconnect the negative terminal so parasitic loads — detectors, radios, control boards — can't drain the battery over months, and check the charge every four to six weeks, topping up as needed. Note: disconnecting stops parasitic loads, but it does not stop self-discharge, which is why the checks still matter.
Pull them and store them somewhere warmer. Batteries stored above freezing, on a shelf (not on a cold concrete floor), and checked monthly will come through winter in the best shape. Label the cables before you pull them so spring re-installation is painless, and take a photo of the wiring before you touch anything.
Know what type you have
Flooded lead-acid — check the water level before storage and top up with distilled water if it is low. Never let the plates sit exposed to air. Check specific gravity with a hydrometer if you want a real read on charge state — voltage alone can mislead on an old battery.
AGM (absorbed glass mat) — sealed, no water to check, but still needs its charge maintained and still suffers if left discharged. More tolerant of vibration and tipping than flooded, and slower to self-discharge.
Lithium (LiFePO4) — different rules: many manufacturers say to store at a partial charge (often around 50%), and most will not accept a charge below freezing. Follow the battery maker's storage guidance, not the lead-acid rules above. Lithium also has a battery management system (BMS) that can disconnect the battery entirely when it gets too cold or too low — if your lithium battery reads dead in spring, check whether the BMS has simply shut it down before assuming it's failed.
Storage rules compared
Flooded lead-acid
AGM
LiFePO4 lithium
Store at
Full charge
Full charge
Partial charge, often ~50% (per maker)
Self-discharge
Fastest — several percent per month
Slower — roughly 1–3% per month
Slowest — roughly 1–2% per month
Water checks
Yes — top up with distilled water before storage
No — sealed
No
Charging below freezing
Possible, but a frozen battery must never be charged
Same caution as flooded
Most will refuse below ~32°F / 0°C
Freeze risk
High when discharged (~20°F); very low when fully charged
Same pattern as flooded
Low — different chemistry, but follow the maker's cold limits
Biggest winter mistake
Left connected to parasitic loads, drained, frozen
Same as flooded
Stored at 100% or charged while frozen, against maker guidance
Maintainer vs. trickle charger: not the same thing
This distinction kills more batteries than cold does:
Smart maintainer — monitors voltage and charges only when needed, then floats or shuts off. It can stay connected all winter safely. This is what you want.
Plain trickle charger — pushes a small constant current whether the battery needs it or not. Left on all winter, it overcharges, boils off water (in flooded batteries), and damages plates. Fine for a weekend top-up; wrong for winter storage.
Desulfation / recondition modes — some maintainers include a desulfation cycle for lead-acid batteries. It can help an aging battery, but it is not magic: a sulfated, dead battery is usually still dead, and high-voltage desulfation pulses should never be used on AGM or lithium unless the maker explicitly allows it.
Never charge a frozen battery. If a battery is frozen solid — case bulged, no voltage, ice inside — do not connect a charger to it. Charging a frozen battery can crack the case, vent gas, or worse. Let it thaw slowly somewhere safe and have it tested before deciding anything.
The monthly check schedule
Whichever option you picked, the checks are the same. Put a reminder on your calendar:
When
What to check
Before storage
Full charge; flooded water levels topped with distilled water; terminals clean and tight; cables labeled if pulling
Every 4–6 weeks
Voltage (12.6V+ is roughly full for lead-acid at rest; 12.0V or below means charge now); maintainer still connected and indicating properly; no swelling, leaks, or corrosion
After any deep cold snap
Same voltage check — cold snaps are when a marginal battery dies
Spring, before first trip
Full charge, load test if the battery is more than a few years old, water levels (flooded), terminal cleaning, and a check that everything disconnected in fall is reconnected
Mistakes that kill batteries over winter
Leaving the battery connected with parasitic loads draining it for months.
Using a plain trickle charger instead of a smart maintainer, and overcharging all winter.
Letting a flooded battery's water drop below the plates.
Assuming a battery that survived last winter will survive this one without a check — capacity fades with age, and an old battery freezes sooner.
Storing lithium at 100% or charging it below freezing, against the maker's guidance.
Storing batteries directly on a cold concrete floor. (The old "concrete drains batteries" story is mostly myth with modern cases — but a cold floor still keeps the battery cold, and a shelf in a warmer spot is simply better.)
Forgetting what was disconnected. Label cables and photograph the wiring before you pull anything, or spring re-installation becomes a guessing game.
Products that fit this job
[AFFILIATE LINK: smart battery maintainer — product to be confirmed]
[AFFILIATE LINK: battery terminal cleaner / disconnect switch — product to be confirmed]
[AFFILIATE LINK: battery hydrometer (flooded batteries) — product to be confirmed]
Our take, honestly
If you have power where the rig sits, a smart maintainer is the easiest good answer. If you don't, disconnect and check monthly — and actually check, because "disconnect and forget" is how a battery quietly dies by February. Either way, start winter with a full charge: that one step does more than anything else on this page.
Frequently asked questions
Should I leave my RV plugged in all winter?
If your rig's converter is a modern multi-stage charger, leaving it plugged in is usually fine — it maintains the batteries like a maintainer does. If it's an old single-stage converter, it can overcharge and boil batteries dry over months. If you don't know which converter you have, check the model: that one detail decides whether "plugged in all winter" is safe or a slow battery killer.
Can I just disconnect and forget about it?
No. Self-discharge continues even disconnected — fastest in flooded batteries. A disconnected battery still needs a voltage check every 4–6 weeks and a top-up when it drops. "Disconnect and forget" is how a battery quietly dies by February.
What voltage means "charge now"?
For a lead-acid battery at rest (no load, no charging for a few hours), about 12.6V or above is roughly full, 12.4V is roughly three-quarters, and 12.0V or below means charge it now — it's already in the zone where freezing risk climbs fast. Lithium voltages read differently; follow your battery maker's chart.
Is it true concrete floors drain batteries?
Mostly myth with modern plastic cases — the real problem with a concrete floor is temperature, not discharge. A cold floor keeps the battery cold. A shelf in a warmer spot is still the better choice.
My lithium battery reads dead in spring. Is it ruined?
Not necessarily. Many lithium batteries have a BMS that disconnects the battery when it gets too low or too cold, and it can look dead until it's woken with a compatible charger. Check the maker's recovery procedure before replacing it.