12v Dc to 240v Ac Inverter recommendations

[gra_farmer]

I need help from the collective here, I am going small ish power needs, really sort of caravan off grid power needs.

Can anyone help in relation to 12v Dc to 240v Ac Inverter recommendation, etc.

I would also love to see your setups.

 

[British Red]

The big question is what you want to run from it. Some items are sensitive and require a "pure sine wave" inverter. Other items are fine on cheaper "modified sine wave" models

 

[Broch]

Yep, as BR says, define what you're running off it first and the power consumption of everything added that you want to run together. Sensitive kit may need a more expensive inverter. Inverters are rated by peak power - 150w, 300w, 1,000w etc.

Remember the volts/amps/watts equations to work out how long you can run the gear.

W = V x A

A 100Ah 12 v battery gives you 1,200 wh (ignoring efficiencies) that means that when you convert it to 240v you will be able to run a 300w device for less than 4 hours at best.

I have 3 inverters: a cheap 150w one that will power lights; a 300w one that is better but not good enough to use on sensitive electronics; and a 1,000w pure sine wave one that I can use on most things but won't turn bigger motors like my water pump.

Having said that, a lot of electronic gear now comes with much better powers protection that can handle poor power - you need to check the kit you want to power. For example, I can run my laptop off the cheap ones through the laptop power supply.

Better inverters are in the 85% efficiency Mark; cheap ones may be as low as 65%.

 

[Robson Valley]

True, the inverter itself eats some juice to stay alive.
Common, modern motors have "universal windings" which means they look like a dead short when they start. The inrush starting current is about 2X the operating current in service. Most brands of inverters can take that momentary surge.

There's nothing in an inverter that you can fix. Blow up a few of them (filter capacitors) and you're away to buy another.
They go BANG! before you can hit the switch and they stink.

To which I advise running the inverter for an hour each week (no load) just to keep the filter caps properly polarized and loaded.

Where to buy:
1. Major brand name outlets for hardware and house-building materials.
2. Dealerships selling glamping RV units. Solar PV panels and all. If you find yourself jammed cheek to jowl in a car park, the silence of solar has its merits.
3. Ship's Chandler. While it's true many want to flog generators, some will have solar power equipment. All the boats, shrimpers, that I worked on had massive gen-sets and we were always tied up at night.

 

[Bongonaut]

Giandel pure sine wave inverters are good quality. I have the 600W and 1000W. I’d stay away from modified sine wave as they tend to be cheap and can let the smoke genie out and potentially burn your van down! I’d stay away from anything over 1000W unless your running 24/48v systems. If your on lead acid batteries you’ll soon run these down with big loads. Take into account wire gauge with big loads even a small kettle 800W will draw 60-80 Amps you need 6-8 Awg and fuses/circuit breakers to match…stay away from cheap circuit breakers as they don’t handle the rated current and reset way before the rated draw. I have a full solar setup in my van and have learnt that “buy nice or buy twice” is the way to do it..
I’d go for two 100ah Agm batteries and a 1000W pure sine inverter. And stick some solar in there with a Victron MPPT. Shore power/hook up can be used to top up using a 20-50A charger. Lifepo4 batteries are even better in the long run and last longer and work out cheaper over the years and are coming down in price….but they need looking after a little bit more…

 

[Bongonaut]

Also…if you have the cash look into the bluetti/poweroak units the Ac50s is a great little unit but only has 300W inverter. It’ll do for charging phones and laptops etc and can run led lights from the various outputs (I have one as a back up) it’s great for setting up outside and charges using solar or mains/12v car. £500 but cuts the hassle of installs..

 

[gra_farmer]

The big question is what you want to run from it. Some items are sensitive and require a "pure sine wave" inverter. Other items are fine on cheaper "modified sine wave" models

Two possible routes, for the home I was thinking about back up use, with 3 x 100ah agm batteries and a 2000w continuous inverter. The fridge will be the main use at home.

For caravan, I was thinking a single 12v 76ah lead acid battery, 300w solar panel, and 600w or 1000w inverter. The carvan has a back up 12v 22ah portable lithium phosphate, for just 5v applications.

The use will be purely charging and lights, maybe laptop?

Giandel pure sine wave inverters are good quality. I have the 600W and 1000W. I’d stay away from modified sine wave as they tend to be cheap and can let the smoke genie out and potentially burn your van down! I’d stay away from anything over 1000W unless your running 24/48v systems. If your on lead acid batteries you’ll soon run these down with big loads. Take into account wire gauge with big loads even a small kettle 800W will draw 60-80 Amps you need 6-8 Awg and fuses/circuit breakers to match…stay away from cheap circuit breakers as they don’t handle the rated current and reset way before the rated draw. I have a full solar setup in my van and have learnt that “buy nice or buy twice” is the way to do it..
I’d go for two 100ah Agm batteries and a 1000W pure sine inverter. And stick some solar in there with a Victron MPPT. Shore power/hook up can be used to top up using a 20-50A charger. Lifepo4 batteries are even better in the long run and last longer and work out cheaper over the years and are coming down in price….but they need looking after a little bit more…

Thanks for the recommendation, I was looking at this one for home EDECOA Power Inverter 12V to 240V 2000w, pure sine wave.

And a 500w or 600w model of some sort as the back up.

 

[Robson Valley]

The fridge compressor has an intermittent duty electric motor. That will require a pure sine wave inverter. What power does it consume?

A square wave inverter and a modified sine wave inverter will run lights and feed some devices with internal power supplies.
Look at the shape of a "sine wave." Sinuous thing. It rises + then falls through zero to some negative thing and back again.

Square wave jumps up quick to + then back to zero where it pauses for a split second. Like the thing is shut off. Then the neg. half of the cycle, back to zero and hold again. Modified sine wave does much the same thing. I can run a coffee pot on those.

What an electric motor sees is that every half AC cycle, the power is shut off. Shut off for just long enough, milliseconds, to demand the big inrush start-up current again and again and again. This suck is really hard on the motors and really hard on the inverter to make that surge power all the time.

Don't.

A pure sine wave inverter is the most costly of the three, but you get a lot for it. The power curve comes down from + and sweeps across zero like it isn't there to go negative. To a motor, the juice is always on. You don't get something for nothing. The inverter spends some power to generate the AC from 12VDC.

If I had security, I'd have a Honda 3500W genset. Quiet, economical, powerful and pure sine wave.

A few years back with big wildfires, our village was off the grid for 30+ days. Freezer vans came for everyone's food. We were OK, thanks to our village admin.

Best part? Somebody stole the generator from the Royal Canadian Mounted Police building here!

 

[Bongonaut]

Two possible routes, for the home I was thinking about back up use, with 3 x 100ah agm batteries and a 2000w continuous inverter. The fridge will be the main use at home.

For caravan, I was thinking a single 12v 76ah lead acid battery, 300w solar panel, and 600w or 1000w inverter. The carvan has a back up 12v 22ah portable lithium phosphate, for just 5v applications.

The use will be purely charging and lights, maybe laptop?



Thanks for the recommendation, I was looking at this one for home EDECOA Power Inverter 12V to 240V 2000w, pure sine wave.

And a 500w or 600w model of some sort as the back up.

Sounds good. I’d always recommend having more than one solar panel. If wanting 300W of panel, 2x150W or even 3x100W rather than a huge single 300W, my reasoning for this is, you have redundancy if one panel fails. Wired up in series the panels voltage (approx 21V) is doubled (for two panels) (42-45V) this higher Voltage with an MPPT solar charger increases output as it will switch on earlier and off later.

 

[grizzlyj]

Although a domestic fridge is a lot cheaper than a 12/24v compressor one, do you need to run the same big domestic fridge when running off the reduced voltage? Could a small 12/24v additional fridge keep a few bits cold from a couple of batteries? Or gas?? Or do you want a big fridge permanently running from batteries? How big for how long?
Check your laptop power supply, it may well be less than 20volts. Going from a 12v bank to 240v in the inverter to whatever the laptop charger outputs is silly and wastes. You can get 12v laptop chargers, some makes do their own or you can get ones with many plugs on one end, cigrette lighter plug on the other.
Normal caravan leisure batteries max at about 120Ah. The market may have a keen price point around there rather than going a bit smaller? You are supposed to limit lead acid discharge to 80%, ie skim off the top 20% only, if you want to maximise life. Fully discharged as their normal life then maybe they'll be out of life at a year. No direct experience of doing that with lead. We did have I think 225Ah AGMs paired at 24v which we did only skim off the top and they worked fine for three years full time in a camper, 2x110W solar only.
The solar charge controller MPPT starts to send charge to panels above a minimum threshold. Three 12v panels linked to 36v reach that minimum level sooner than one 300W 12v so you will get more charge time from a suitable MPPT, so I've read and set our current camper to do. That has diesel heating, gas cooking and 24v everything else which I thought was the best compromise.
Having had thoughts and experience of home power outage resources, we have a multi fuel stove we can cook on, we can do without the fridge and freezer (although we do have a 1KW genny but that can't run outside all the time) if we have to so I decided we just needed light. I bought one of the Poweroak type lithium all in one jobs when reduced which will run a couple of LED strip lights well enough, one 12v solar panel input.
Lithium can be discharged all the way and they are very light compared to lead if you need to move them but you pay a lot for the privilage. Maybe they won't last as long as a well maintained lead bank either.
My inlaws wrapped their chest freezer with blankets in the 70s with no power for more than a week.

Edited a wee bit.

 

[British Red]

for the home I was thinking about back up use, with 3 x 100ah agm batteries and a 2000w continuous inverter. The fridge will be the main use at home.

Okay so as noted, you need a pure sine inverter for motors. 3 x 100ah batteries is 3,600 watt hours storage. You should not exceed 80% use so 2,880Wh.

The inverter could use that up in an hour and a half.

A small fridge is 150 watts. Multiply that by 24 hours =3,600Wh. Too much. This is just scribbled calculation but you get the idea

 

[Great egret]

Yep, as BR says, define what you're running off it first and the power consumption of everything added that you want to run together. Sensitive kit may need a more expensive inverter. Inverters are rated by peak power - 150w, 300w, 1,000w etc.

Remember the volts/amps/watts equations to work out how long you can run the gear.

W = V x A

A 100Ah 12 v battery gives you 1,200 wh (ignoring efficiencies) that means that when you convert it to 240v you will be able to run a 300w device for less than 4 hours at best.

I have 3 inverters: a cheap 150w one that will power lights; a 300w one that is better but not good enough to use on sensitive electronics; and a 1,000w pure sine wave one that I can use on most things but won't turn bigger motors like my water pump.

Having said that, a lot of electronic gear now comes with much better powers protection that can handle poor power - you need to check the kit you want to power. For example, I can run my laptop off the cheap ones through the laptop power supply.

Better inverters are in the 85% efficiency Mark; cheap ones may be as low as 65%.

you might be able to charge your laptop on DC via the USB C port. It will be a little more energy efficient because you are not changing DC > AC > DC.

 

[Bongonaut]

Okay so as noted, you need a pure sine inverter for motors. 3 x 100ah batteries is 3,600 watt hours storage. You should not exceed 80% use so 2,880Wh.

The inverter could use that up in an hour and a half.

A small fridge is 150 watts. Multiply that by 24 hours =3,600Wh. Too much. This is just scribbled calculation but you get the idea.

 

[Bongonaut]

Generally a fridge will not use all its rated wattage all the time. When at the set temp and the power goes bye bye the fridge will cut in say for 10mins every couple of hours max on your “back up power” Of course if your in and out of it like a yo-yo it’ll be on most of the day…I’ve happily ran a small compressor fridge for a week on 120ah agm (I have solar but I’m UK and it ****** it down all week!)

 

[British Red]

Generally a fridge will not use all its rated wattage all the time. When at the set temp and the power goes bye bye the fridge will cut in say for 10mins every couple of hours max on your “back up power” Of course if your in and out of it like a yo-yo it’ll be on most of the day…I’ve happily ran a small compressor fridge for a week on 120ah agm (I have solar but I’m UK and it ****** it down all week!)

Very true, it's most likely enough, but also potentially a large domestic fridge - or even a huge American one !

 

[Bazzworx]

In our van we run a 200w solar panel with an MMPT controller, 2 100ah LiFePo4 batteries and a Sterling power inverter which is 1000w pure sine wave. The system works well but the solar panel is well undersized for the system and our weather, we don't stay in the same place that long though so the batteries are replenished when the engine is running. I don't often use the inverter to be honest as everything runs off 12v. The times I have used it though is when I'm working away from a power source and I want to use power tools or charge batteries.

Another thing we do to save power in the van and at home is when we want to defrost something is to put it in the fridge, it takes a lot longer to defrost but is saves the fridge having to cut in so often.

 

[gra_farmer]

Another thing we do to save power in the van and at home is when we want to defrost something is to put it in the fridge, it takes a lot longer to defrost but is saves the fridge having to cut in so often.

Brilliant, I have done that too from time to time....but have not joined the thinking in a while, thank you for the reminder

 

[Nice65]

Brilliant, I have done that too from time to time....but have not joined the thinking in a while, thank you for the reminder

Rather than use the little icebox in our van fridge to make ice, we pack it with pre-frozen gel packs. When we’re hooked up they refreeze, and when we’re not, they keep everything in the fridge cold for if the leisure battery needs conserving.

We’re kitted pretty much the same as @Bazzworx, 200W solar on the roof and 1000W inverter.

 

[grizzlyj]

If you did only want to keep a few bits cold in a fridge an alternative could be a super dooper cool box. Yeti in the US are suposed to be mega, we bought an Iceytek in the UK with their big cool blocks for the weekly shop since thats 45 mins away.

 

[Broch]

TBH cool boxes just don't hack it in really hot conditions IMO. They struggle above 25C and in desert conditions are useless. They also consume a lot more battery juice than compressor fridges so, if you're static for a few days, you run the risk of running the battery flat. I bought an Engle some 15 years ago; it's expensive but still going strong and superb.