First Off-grid setup

[brackstone]

Hello All
I am looking at starting my first off grid set up. This will be small at first as I get more gear and learn to get better setup.

My first project will be to run the check freezer we have on an inverter. Solar and MPPT batteries etc I am Ok with for now, but i need some advise on the inverter.

The freezer pulls around 200W normal use but this does not take into account the start up power, I also do not want an inverter on all the time the freezer is not running as this is waste of energy

So two questions

1, will a 1500 pure sine wave inverter cope ok starting a domestic 200W chest freezer.

2. If I put a relay on the 12v side controlled by a freezer thermostat so it switches on the inverter when the freezer needs to run will this burn out relay contacts with the inverter inrush current. Is this a bad idea as this will be large currents and could be large arcs, or is there a remote way to put the inverter to off when not needed I can do this by a relay

 

[sunshine_eggo]

1. If you can get an AC clamp ammeter with an INRUSH function, you can measure the actual surge of the unit.

1500W will likely cover it, but a 1500W unit only providing 200W is going to be less efficient and have higher idle consumption.

If you think you might want to use the 1500W for additional power in the future, go for it.

2. If you get the right inverter with a low idle power consumption, then this solution is unnecessary. It's also another point of failure.

 

[Bobert]

1, will a 1500 pure sine wave inverter cope ok starting a domestic 200W chest freezer.

I wouldn’t guarantee it but it probably would

If I put a relay on the 12v side controlled by a freezer thermostat so it switches on the inverter when the freezer needs to run will this burn out relay contacts with the inverter inrush current. Is this a bad idea as this will be large currents and could be large arcs, or is there a remote way to put the inverter to off when not needed I can do this by a relay

I don’t believe is is good for an inverter to startup with a load on it is probably not good for the freezer either. This means you need to devise a way to power up the inverter and then power up the freezer a minute or so afterwards. Some inverters turn on and then apply voltage to the loads and if that’s the case you could save a step. The biggest issue to be certain of is what your actual wattage draw will be over your worst case 24 hour day. Figure out how much the system will cost to setup first. If you have grid power available you might be able to use a all in one unit and have grid power available to subsidize your setup should you have multiple cloudy days in a row. Batteries are very expensive sometimes it is cheaper to buy newer more efficient equipment than to size your solar to meet your present demands. You may have already figured all this stuff out but I thought I would mention it.

 

[brackstone]

Thanks for tips. This will be hopefully a bigger project as time goes on so could power the hole garage off an inverter in future. I will look at calculating the inverter to be on all the time rather than switching on/off. As a start up there are a lot of expensive components was was looking to do some small projects at first (the freezer) and will upgrade this over time. I have done solar before on my camper which is lithium setup so will hope to go this route in the future

 

[SeaBear]

I also started small (window panels) and now in a position to go a bit bigger. Researched YT videos and will do a treated 2x4 3-panel rack to provide power for a medical device (CPAP) for 7-8 hrs, two adjustable beds, two tower fans and a full size refridge/freezer (alternating every hour) when power fails. I have the following: Renogy 12v 100ah agm battery X-1, Renogy 12v 100w starter kit panels x-2, , 900w Power Bright 12v inverter, a Volt Works 1500w psw inverter with inline bolton fuses to connect. Charger controllers is my issue being a newby. Will be getting MC4 connectors and was looking at an additional battery-Chins LifePO4 12v 100ah to complete a 24v system. Am I on the right track? Appriciate you inputs. Thanks in advance.

 

[Bobert]

900w Power Bright 12v inverter, a Volt Works 1500w psw inverter

A 12v inverter cannot be used in a 24v system

 

[SeaBear]

A 12v inverter cannot be used in a 24v system

Will it have to stay as a 12v system or just change to a 24v inverter?

 

[Bobert]

You could go either way. The amount of wattage that you were thinking of running off of the inverter around 1000 W would work fine with 12 or 24 V just double the amperage for 12 V.

 

[SeaBear]

You could go either way. The amount of wattage that you were thinking of running off of the inverter around 1000 W would work fine with 12 or 24 V just double the amperage for 12 V.

Thanks. When you mentioned double the amperage is that to include more solar panels?

 

[Bobert]

Thanks. When you mentioned double the amperage is that to include more solar panels?

No if you use a 12 volt system it takes twice as many amps to push 1000 watts of power to an inverter as the same number of watts to 24v inverter. You get the same amount of power out and the same amount of power in but your wires and fuses must be larger.

 

[Bobert]

If you have never read Will’s book “Mobile Solar Power Made Easy” it’s super cheap on Amazon right now

Mobile Solar Power Made Easy!: Mobile 12 volt off grid solar system design and installation. RV's, Vans, Cars and boats! Do-it-yourself step by step instructions.: Prowse IV, William Errol: 9781546567110: Amazon.com: Books

Mobile Solar Power Made Easy!: Mobile 12 volt off grid solar system design and installation. RV's, Vans, Cars and boats! Do-it-yourself step by step instructions. [Prowse IV, William Errol] on Amazon.com. *FREE* shipping on qualifying offers. Mobile Solar Power Made Easy!: Mobile 12 volt off...

www.amazon.com

 

[SeaBear]

No if you use a 12 volt system it takes twice as many amps to push 1000 watts of power to an inverter as the same number of watts to 24v inverter. You get the same amount of power out and the same amount of power in but your wires and fuses must be larger.

I so much appriciate this explination.

 

[SeaBear]

If you have never read Will’s book “Mobile Solar Power Made Easy” it’s super cheap on Amazon right now

Mobile Solar Power Made Easy!: Mobile 12 volt off grid solar system design and installation. RV's, Vans, Cars and boats! Do-it-yourself step by step instructions.: Prowse IV, William Errol: 9781546567110: Amazon.com: Books

Mobile Solar Power Made Easy!: Mobile 12 volt off grid solar system design and installation. RV's, Vans, Cars and boats! Do-it-yourself step by step instructions. [Prowse IV, William Errol] on Amazon.com. *FREE* shipping on qualifying offers. Mobile Solar Power Made Easy!: Mobile 12 volt off...

www.amazon.com

I bought it and the information is awesome. I'm just getting stuck on the amps power which you explained very well. So to my project, in your oppion is the equipment I currently have, increase the guage wiring and fuses and getting an additional battery for the setup should work?