DMX Power Catalog
Introduction to mobile power inverters
What an inverter does, how to pick the right waveform and design, and what to check before you buy.
The basics
What a power inverter does
A power inverter turns the DC energy in your batteries into the AC power your tools, appliances and electronics expect — so you can run them anywhere you have a DC source. Air compressors, drills, air conditioners, microwaves, TVs, computers and anything else within the inverter’s rating all work the way they do at home.
Unlike a generator it does that quietly, with no fuel and no exhaust.
Decision one
Which waveform do you need?
Inverters produce one of two AC waveforms: pure sine, the same shape the utility supplies, or modified sine, a cheaper approximation of it. Anything designed for AC will run on pure sine; some equipment tolerates modified sine, which brings the cost of the inverter down.
As a rule, the more sophisticated the device the more likely it needs pure sine. A computer will usually run on either, but monitors and laser printers often will not.
Waveforms explained covers the difference in full, and lists which DMX Power inverters use each.
Decision two
High frequency or low frequency?
Beyond the waveform you choose between two inverter designs. High-frequency units are sold everywhere, cost less and take up less room. Low-frequency units are built around a heavy transformer, and that transformer is what gives them their surge capacity and their working life.
If everything you run draws steadily, a high-frequency inverter may be enough. If you need to start motors, pumps, air conditioners, refrigerators or power tools — or you want a unit that will survive years of heat and vibration — you need low frequency. Most DMX Power inverters are low-frequency designs. Inversion methods explained goes into how each design works.
High frequency (HF)
- Costs less. The least expensive way to get AC power on board, and the easiest to find.
- Smaller and lighter. A compact package that fits where a transformer-based unit will not.
- Limited surge. Enough for loads that draw steadily, but not for starting a motor.
Low frequency (LF)
- High surge capacity. Starts motors, pumps, compressors and air conditioners, which can pull five to ten times their running current for a moment.
- Longer working life. Far more durable under the heat and vibration a vehicle puts an inverter through.
- Handles a mixed load. Sized once, it copes with demand that changes through the day rather than one steady draw.
Decision three
Sizing your inverter
Capacity is chosen from the largest load — or largest combination of loads — the inverter will ever have to carry, plus the surge if you are starting motors.
- Add up the wattage of everything you will run at the same time. If you use tools one at a time, take the highest single draw instead.
- Allow for loads you expect to add later. Headroom now is cheaper than a second inverter afterwards.
- Check the surge requirement. Motor-driven equipment can pull five to ten times its running current at startup, so match the inverter’s surge rating to the horsepower you need to start.
- Pick a unit slightly above that figure from the inverter catalog, or higher again if larger loads are coming.
The inverter is one of three things that have to match the load: the battery bank and the cabling are sized to it as well.
Efficiency. Efficiency is how much of the DC power an inverter draws actually reaches the AC output. The more efficient the unit, the longer your bank runs it — a typical inverter is better than 80%.
DC input voltage. The inverter’s DC input has to match your system. Most vehicles are 12VDC; some service vehicles run 24VDC.
Before you order
Options to look for
Battery charger. Some inverters include a charger, or offer one as an option. Plugged into shore power while the vehicle is parked, it recharges the battery bank. Decide on it before you choose a model — it is not something to add later.
Transfer switch. An internal transfer switch moves the load from the inverter’s output to shore power when the vehicle is plugged in. The inverter drops into standby, and if it has the charger option it starts charging. Available on most of our inverters.
Cable kits. The DC wiring and fusing are as much a part of a working installation as the inverter itself. The 12VDC cable and fuse guide gives the sizes for a given run, your owner’s manual carries the specifics for your model, and we can supply the matching kit.
Not sure which inverter, options or cable kit suit your application? Get in touch and we will help you work it out.