how quickly will it inflate a queen sized air mattress?

Its an inverter, not a compressor, so it will inflate your air mattress at the same rate that an overripe banana would... ie, it wont. It cant. So eat the banana and purchase an inflator. Now, if you are using this inverter it to *power* an inflator, then the inflator will work at the same speed as it would plugged into a wall socket. But I’d still eat a banana because its clear you have a potassium deficiency (but I’m not a doctor so you may want a second opinion).

is this a three phase inverter?

500W Three Phase @ $60? In what world is that?

I'll be attaching a relay on the (+) connector, so I'll keep the switch in the ON position all the time, is there a problem with this setup?

Max power draw is very close to 40 amps (34-38 depending on battery voltage). The relay would have to be a 50 amp rating MINUMUM, and higher if you can get it. I believe the next common rating is 70 or 75 amps.

What size are the posts on the inverter? 5/16 or 3/8?

It is neither. The posts on my unit are 3/16, which is adequate for the loop connectors and any load I'll be creating while using the unit.

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BESTEK 500W Pure Sine Wave Power Inverter DC 12V to AC(2 Outlets) 110V Car Charger Plug Inverter Adapter Converter with 4.2A Dual USB Charging Ports, ETL Listed

Product ID: 177529791

Details

Battery Capacity
12
Brand
BESTEK
Power Source
DC
Recommended Uses For Product
Vehicle
Wattage
500 watts

⚡500W Pure Sine Wave Output

🔌2 AC Outlets + 2 USB Ports (4.2A max)

🛡️Multi-layer Safety Protections

540.14 DT

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Description

🔋 Power your journey with pure sine wave precision—never settle for less!

COMPACT TRAVEL READY DESIGN - Lightweight (2.2 lbs) and portable with ETL certification—your perfect off-grid companion for work, road trips, and emergencies.
FLEXIBLE POWER SOURCE OPTIONS - Plug into your 12V cigarette lighter for convenience or use alligator clips for full 500W capacity directly from your car battery.
SEAMLESS PURE SINE WAVE POWER - Delivers clean, grid-quality AC power for sensitive electronics and cordless tools—no interference, no compromise.
ROBUST THERMAL ELECTRICAL SAFETY - Built-in fan, aluminum casing, and replaceable fuses protect against overheating, overload, and voltage spikes for peace of mind.
DUAL AC OUTLETS FAST USB CHARGING - Power multiple devices simultaneously with 2 AC outlets plus dual USB ports that auto-detect and deliver up to 2.4A each.

The BESTEK 500W Pure Sine Wave Power Inverter converts 12V DC from your vehicle into clean 110V AC power with two outlets and dual USB ports delivering up to 4.2A total. Featuring advanced thermal management, multiple safety protections, and flexible connection options, it supports sensitive electronics and heavy inductive loads with minimal interference. ETL listed and compact, it’s ideal for professionals on the go who demand reliable, high-quality power anywhere.

Specifications

ASIN	B082MDRC64
Antenna Location	Vehicle
Battery Capacity	12
Best Sellers Rank	#7,210 in Automotive ( See Top 100 in Automotive ) #19 in Power Inverters
Brand	BESTEK
Built-In Media	500W Pure Sine Wave Power Inverter DC 12V to AC 110V Car Plug Inverter Adapter Power Converter with 4.2A Dual USB Charging Ports and 2 AC Outlets Car Charger
Color	1 Red
Customer Reviews	4.5 4.5 out of 5 stars (3,363)
Electrical Output Waveform	Pure Sine Wave
Energy Specifications Met	ETL
Frequency	60 hertz
Input Voltage	12 volts
Item Dimensions L x W x H	8.7"L x 4.3"W x 2.4"H
Item Weight	2.2 pounds
Manufacturer	BESTEK
Mfr Part Number	MRZ5011BU
Model Name	MRZ5011BU
Model Number	MRZ5011BU
Number of Outlets	4
Output Power	500 watts
Output Voltage	110 volts
Power Source	DC
Standby Power Shutoff	90
Unit Count	1 Count
Voltage	110 volts
Warranty Description	2-year Warranty
Wattage	500 watts

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540.14 DT

Duties & taxes included

In stock

Sold byAmazon TunisiaDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

Buyer Protection · Full refund if your order doesn't arrive as described.

Desertcart purchases this item on your behalf and handles shipping, customs, and support to Tunisia.

Secure transaction

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