RV Power and Electrical Guide: Surge Protectors, EMS and Batteries
Your RV runs on two electrical systems: 120-volt shore power from the pedestal, and 12-volt battery power for lights, the water pump, the furnace fan and anything you run off-grid. Most expensive electrical damage comes from the first one, and most "my power died" stories come from the second.
Power gear we recommend
Match the amperage to your rig (30 or 50 amp). A basic surge protector guards against spikes and wiring faults; an EMS adds low/high-voltage protection.
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Why campground power is the real risk
People picture lightning, but the everyday problems are duller: pedestals with an open ground, reverse polarity or a loose connection, and low voltage on hot afternoons when the whole park runs air conditioning. Sustained low voltage makes motors like the A/C compressor draw more current and overheat — it is the most common way RV electronics get quietly damaged.
Surge protector or EMS?
| Protects against | Basic surge protector | EMS |
|---|---|---|
| Spikes and surges | Yes | Yes |
| Wiring faults (open ground, reverse polarity) | Better models detect them | Yes |
| Low voltage / brownout | No | Yes — cuts power |
| High voltage | No | Yes |
If you camp now and then at well-kept parks, a good surge protector that detects pedestal faults covers the likeliest problems. If you full-time or camp a lot in summer heat, an EMS's low-voltage protection is worth the extra cost. Some newer rigs have an EMS built in — check your panel or spec sheet first. Either way: plug into the protector, not straight into the pedestal. Our picks are in best RV surge protectors.
30 amp vs 50 amp
Buy the protector that matches your rig's shore power. A "dogbone" adapter lets you plug into a pedestal that doesn't match, but the protector itself should match your RV.
House batteries: the three types
| Type | Usable capacity | Typical life | Upkeep |
|---|---|---|---|
| Flooded lead-acid | About half the rating | ~300–500 cycles | Check water (distilled only), clean terminals |
| AGM | A bit more than flooded | ~500–700 cycles | Sealed, little upkeep |
| Lithium (LiFePO4) | Most of the rating | Thousands of cycles | Little upkeep; mind charging in the cold |
Lithium costs more up front but gives roughly twice the usable energy per rated amp-hour and lasts far longer, which is why it often works out cheaper over the life of the rig.
What kills batteries early
- Sitting partly discharged (lead-acid). Sulfate hardens on the plates and that capacity is gone for good. Recharge promptly.
- Freezing while flat (lead-acid). A full battery survives deep cold; a discharged one can freeze around 20°F and crack. Charge before winter storage.
- Charging lithium below freezing without a self-heating battery or a BMS that blocks it — it causes permanent hidden damage.
- Heat. A battery bay baking in desert sun ages much faster than one in a cool compartment.
Sizing a battery bank
Add up what you actually run overnight. Rough draws: LED lights 1–2 A total, a 12-volt fridge 3–5 A while running, the furnace blower 7–10 A when it fires, a CPAP 2–4 A. A modest night often lands around 40–60 Ah. Then make sure your charging (solar, generator, driving) can put that back each day — a bigger bank without enough charging only buys a slightly longer countdown.
Winter storage
- Charge fully, then disconnect the negative cable (or use the disconnect switch) to stop parasitic drain.
- Check monthly and recharge if it drops, or use a smart maintainer.
General information from RV owners' experience, not professional advice. Follow your RV and equipment makers' manuals, posted signs and local rules, and ask a qualified technician about your own rig.