Auto switching Inverter

Gundog · Guru

Auto switching Inverter

valiant81 · Guru

Hi all; There are quiet a few on the market. Some will also charge your house batteries while the mains power is connected and change over to the inverting mode when the mains power is disconnected. Not cheap and the inverter needs to be a pure sign wave version, easyer on sensitve equipment. I have had a good run with Victron and they have several models that may suit your needs. They can also be set up for AGM or Lithium batteries.

dorian · Guru

Would a UPS be cheaper? The only difference I can see is that a UPS integrates the battery/batteries.

rgren2 · Guru

UPS = Uninterrupted Power Supply.

Whenarewethere · Guru

I have UPSs (Uninterruptible Power Supply) for decades. From small 500VA units up to my current 3.0kVA unit, which has additional batteries.

Firstly UPSs are great.

Secondly a few issues:

The small units are extremely inefficient, usually around 70%.

Their components are cheap & not designed for regular switching to battery mode.

They use a 12v battery. The units a bit larger are 24v.

Their duty cycle is the life of the battery to run the equipment attached. From a computer point of view, to close apps & shut down the computer until you have 230 volts again.

They are not designed to add additional batteries, & if you did their duty cycle is not designed for extended running time.

My 3.0kWA (2700 watts output) is 90% efficient. A 15 amp circuit is required. The UPS is designed to have additional batteries to provide additional run time, which I needed for my computers to do 3d rendering. I have 2 additional battery units (4 maximum).

These higher powered UPS often run off 72v (6 x 12v batteries in series).

I replaced the fans in mine as the original fans were too noisy. I couldn't put the UPS in another room. The fans ran continuously, even at a low speed when the UPS was running on 230 volts.

Unless you buy a really top end UPS, if batteries have run down from extended use, they will take 24 hours of longer to charge up.

My 3.0kVA UPS with 2 additional battery units was $4,500 in 2007.

So unless you actually need a UPS, you are better to simply turn on an inverter when it is actually required, & turn it off as soon as it is not needed. They waste battery battery resources.

If the inverter like Victron has a standby setting, that is fairly low power vampire battery drain. But a UPS needs to be on all the time, it is a large battery drain if not running off 230 volts. They switch from 230 volts to battery instantly. Unlike an inverter which has a delay waiting for something to be turned on.

The really expensive UPSs are double conversion. They power everything by battery while at the same time continuously charging.

These are for really high end equipment.

Usually additional power filters are installed as well.

BarneyBDB · Senior Member

This is the one I use for the 230 volt fridge in the van, been working well for about 3 years now.

au.renogy.com/products/renogy-1000w-12v-to-230v-pure-sine-wave-inverter-with-ups-function

Ineedabiggerboat · Senior Member

Ive got a UPS to run my cctv and security system at home. It puts out a lot of heat.

Whenarewethere · Guru

Look up Eaton UPS, they have the high end stuff.

This is basically what I have, but 3 x the weight at it has lead acid batteries only back in those days. 6 batteries in the UPS & 12 in each of the extra battery units.

https://www.eaton.com/au/en-gb/catalog/backup-power-ups-surge-it-power-distribution/eaton-9px-li-ion.html

Techbuy is a good starting point. I have bought stuff from them over the decades. But not my UPS.

https://www.techbuy.com.au/searchcat/UPS_RACKMOUNT/3.asp

Bookleaf · Veteran Member

I think you are looking for/referring to an inverter with a "pass-through" function.

Not cheap, but this is what the Enerrive 2000W and one of the 3000W models do.

They are configurable
- When configured for it, when switched OFF, they will pass external 240V to the van. There is some very small parasitic current draw, and there must be 12V available at all times.
_ When configured for it, there is no external 240V, and when switched ON, they will generate 240V from the 12V for the van. 12V current draw is small,, but not insugnificant.
- When configured for (what has been referred to here as JUPS operation), they will pass external 240V to the van but instantly switch over to self 240V generation when the external 240V disappears. 12V draw is as for the above mode.
- When configured for it, with no external 240V, they will remain in a low 12V current draw standby mode with virtually no 240V generated, just a sensing level of 240V. When a 240V load of over 50W (I think it is) is turned ON at a power point, it immediately "wakes up" and produces all the 240V current required (up to the inverter max).

Other manufacturers have models that do similar, Enerdrive is not the only one.

-- Edited by Bookleaf on Friday 5th of September 2025 10:50:42 PM