SAI/UPS y protección eléctrica para POS y cajeros: tipo, VA, autonomía y qué enchufar
Una guía de compra de protección eléctrica para sistemas POS y cajeros — SAI vs protector de sobretensión, tipos standby vs line-interactive vs online, dimensionar VA y vatios con factor de potencia y margen, autonomía, y qué proteger.
La respuesta rápida
A momentary power blip can corrupt a transaction, jam a mid-print receipt, or knock a till offline at the worst moment. A UPS prevents all of that — but only the right type, sized correctly, with the right gear plugged in. The essentials:
| If you need… | Choose | Why | |
|---|---|---|---|
| Spikes only (lowest cost) | Surge protector | Clamps surges — but nothing for outages/brownouts | — |
| A standard retail till | Line-interactive UPS | Surge + brownout (AVR) + battery; the usual choice | — |
| ATM / critical / dirty power | Online (double-conversion) UPS | Continuous clean power, no transfer gap | — |
| Single low-criticality PC | Standby UPS | Basic battery backup at the lowest UPS price | — |
Qué hace la mala energía a un POS o cajero
“Bad power” isn’t just blackouts. Three power problems hit POS and ATM hardware, and a UPS addresses all three where a surge strip addresses only one:
| Power event | What it does | Surge strip | UPS | |
|---|---|---|---|---|
| Surge / spike | Can damage electronics & PSU | Clamps it | Clamps it | — |
| Sag / brownout | Resets/instability, stresses PSU | No help | Corrects (AVR) | — |
| Outage | Lost sale, corrupt transaction/DB | No help | Battery rides through | — |
The cost of skipping protection isn’t hypothetical: a power loss mid-transaction can corrupt the day’s data, an ATM that drops power abruptly can fault its modules, and a surge can take out a power supply or mainboard outright. A UPS is cheap insurance against all of those.
Tipos de SAI: standby, line-interactive, online
Three UPS topologies, in rising order of protection and price:
| Standby | Line-interactive | Online (double-conversion) | |
|---|---|---|---|
| Brownout handling | Switches to battery | Corrects with AVR (saves battery) | Always regenerated |
| Transfer gap on outage | Small | Small | None (zero-transfer) |
| Power cleanliness | Basic | Good | Best (continuous clean) |
| Cost | Lowest | Moderate | Highest |
| Best for | Single non-critical PC | Most retail POS | ATMs, critical, dirty power |
Dimensionar: VA, vatios, factor de potencia y autonomía
Size on both VA and watts, then add headroom. The method:
| Term | What it means for sizing | |
|---|---|---|
| Watts (W) | Real power your gear draws — the UPS watt rating must exceed it | — |
| VA (volt-amps) | Apparent power; VA = watts ÷ power factor (≈0.6–0.9) | — |
| Headroom | Add 20–30% so the UPS isn't at its limit | — |
| Runtime | Typically ~5–20 min at POS loads; lighter load = longer | — |
| Surge rating (joules) | Higher joules = more surge energy absorbed | — |
Elegir según el despliegue
A short path from your site to the right unit:
- 1
How critical is uptime?
ATM or a site that can’t tolerate any gap or dirty power → online (double-conversion). A standard retail till → line-interactive. Just spike protection on a non-critical device → a surge protector. - 2
Add up the load
Total the watts of the terminal, monitor, receipt printer and network gear, convert to VA via power factor, and add 20–30% headroom. - 3
Decide runtime
A few minutes for safe ride-through/shutdown is enough for most. Need longer (ATM, card processing through long cuts)? Choose a model with external battery packs. - 4
Plan the outlets
Battery-backed outlets for the terminal, critical printer and network gear; surge-only outlets for non-critical loads. Keep heavy loads off the UPS.
Qué proteger, y mantenerlo sano
A UPS is only protection if its battery is healthy and the right things are on it. Two rules:
| Practice | Detail | |
|---|---|---|
| Plug in the right loads | Terminal + critical printer + network gear on battery; heavy/non-critical on surge-only or elsewhere | — |
| Don't overload it | Stay within VA and watt ratings, with headroom | — |
| Replace the battery | Consumable — typically ~3–5 years; degrades silently | — |
| Test periodically | A worn battery can pass a quick test but fail under real load | — |
| Keep it cool | Heat shortens battery life — ventilate, avoid hot spots | — |
Browse power supplies and protection in our power supplies category, related parts in terminal repair parts, and cooling in cooling parts. If a terminal is already showing power faults, see our power supply failure diagnosis and overheating & cooling guides. Tell us your equipment list and we’ll help size the right protection.
Preguntas frecuentes
¿Qué diferencia hay entre un SAI y un protector de sobretensión para un POS?
¿Qué tipo de SAI debe usar un terminal POS?
¿Cómo dimensiono un SAI para mi POS — VA o vatios?
¿Cuánto mantendrá un SAI mi POS funcionando?
¿Qué debo enchufar realmente al SAI?
¿Con qué frecuencia hay que reemplazar la batería de un SAI?
Fuentes y lecturas complementarias
- UPS Buying Guide: Selecting a Battery Backup System — Schneider Electric (APC)
- UPS and Power Management Fundamentals Handbook — Eaton
- Different Types of UPS: A Comprehensive Guide — Comms Express
- Small Business UPS Guide: Protect Servers & POS Systems — EcoFlow
- Which UPS System Is Right for You? — Batteries Plus
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