Newbie setup for backup power for freezer

[Hogheavenfarm]

Here is all I want to do - Run 1 chest freezer overnight, or if not possible, run the freezer during the day and let it coast overnight. We have blackouts often, 3 weeks was the longest, and cost of running a genny that long was enormous, even when gas was $1.99.
What I have - eight 100w panels - 5.5a 18v (typical panels) 2S4P(?) (2 in series 4 parallel sets)
(1) Renogy Rover Elite 40 amp 100v controller
(1) 200 amp hr SLA battery 12v (I am thinking I probably need another of these and then I would go 24v)
(1) 2000w no name inverter 12v (I am thinking I probably need another of these and then I would go 24v)
I get 3.8 hrs peak here, panels are south facing and get good exposure 10am to 6pm
Freezer stats are - 4 amps running 300w at 120v - surge is not listed but I am guessing about 10 amps. (This is a large freezer, 60"x28"x30")
My initial test of this system running a room a/c (for comparison, I cannot connect to the freezer at this time) was not very encouraging.
The little 2200 watt genny runs it ok.
We are old, so budget is pretty tight, and keeping food through these outages is very important to us.

Do I have all the required pieces? How can I arrange what I have to make the best use of this? Is this even possible with what I have? Any recommendations on different equipment?

 

[Sverige]

If you’re already considering buying another inverter, go for a larger one than 2000W if you can. Assuming we are talking about the high frequency Chinese made inverters which dominate the lower end of the market, you can safely halve the rating for the true continuous running capacity and fridge or freezer compressors draw a huge startup current initially, which can easily trip an inverter which you would think could cope based on its rating.

I have a 3000W 12V inverter run from a 272Ah lithium battery which copes with running a fridge and chest freezer, but I sometimes see over 1000W drawn for several seconds as one or other compressor starts up.

In any case, it’s the nature of off grid solar that your ambitions and needs tend to grow over time, so I really doubt you will have reason to regret buying a larger inverter than you currently think you need.

 

[Mattb4]

It would help if you have a meter like a Kill-A Watt to plug your freezer into and run for a typical day. That would give you all the numbers you need to then start sizing the things you need to power it.

 

[Hogheavenfarm]

I have a amp meter, but no killawatt device, so I guess I should get one. I was hoping since the little Honda 2200 watt genny ran it ok, the inverter would do the same. It did power the a/c unit for 1.5 hours which was 9 amps at 1150 watts, but that emptied the battery very quickly.
I would budget an inverter next if I know that battery is sufficient, otherwise the battery becomes a priority first.

 

[Mattb4]

I have a amp meter, but no killawatt device, so I guess I should get one. I was hoping since the little Honda 2200 watt genny ran it ok, the inverter would do the same. It did power the a/c unit for 1.5 hours which was 9 amps at 1150 watts, but that emptied the battery very quickly.
I would budget an inverter next if I know that battery is sufficient, otherwise the battery becomes a priority first.

You can not compare a gas generator to either a battery inverter for ratings or to a battery for amount of power. Battery Inverter ratings are much more overstated than a high quality gas inverter generator like Honda has. Heck the ratings for some of the cheap Chinese inverters seem to be pure fiction in a lot of cases.

Batteries do not have much capacity either in comparison to a fuel driven generator. A 100ah battery of 12v only has at most 1200wh to give and in a hour it is empty. Your Honda can give 2200watt each hour until the gas runs out. Likely 5-6 hours. Or 10,000 to 12,000wh.

 

[hankcurt]

You don't state if your inverter is modified sine wave or pure sine wave. If you want to run an inductive load like a freezer motor for any length of time, you really want a pure sine wave inverter.

I had a power outage a couple years ago and used a cheap Harbor Freight 3000 watt modified sine wave inverter to run fridge and a freezer. I used a 12 volt lead acid battery that I was charging off of my Chevy Volt car's DC to DC converter. It worked, but the battery would only last about 3 hours between having to run the car. The power from the modified sine wave inverter made the fridge compressor sound noisy and unhappy. I was worried about overheating it and ruining it.

Just about two weeks ago, I got a new set of equipment going for the same purpose. It is a 300ah 12 volt lithium battery running a 2000 watt pure sine wave inverter. I tested this running the freezer alone, which only pulls about 130watts, and it ran it for 3.5 days (with the freezer cycling on and off as it normally would). With both the fridge and freezer, I estimate it will do about a day and a half. The compressors sounded normal on the pure sine wave inverter. The freezer starts without a surge, but the refrigerator pulled about 170 amps from the battery for a second while starting.

The financial limitations may make this sort of set-up more than you want to spend, but investing in a pure sine wave inverter (if your current one is not) may prevent costly damage to your freezer.

 

[Hogheavenfarm]

Yes, the Honda is a great little genny, but a bit underpowered for what I would like, but it does run the freezer (but wont run the fridge, surge must be too high). So are you saying I need more battery? At 50% cap I have only 1200ah here.

 

[Hogheavenfarm]

Current inverter is pure sign wave as far as I know. I dont remember the brand , it was "EDO something" I think. It is on loan from a friend. We intend to buy an inverter if we can know with a little certainty that this entire setup will do what we need it to.

 

[Mattb4]

Yes, the Honda is a great little genny, but a bit underpowered for what I would like, but it does run the freezer (but wont run the fridge, surge must be too high). So are you saying I need more battery? At 50% cap I have only 1200ah here.

Your load will determine that. BTW room ACs use a lot more than most freezers do. My little 5000btu AC unit requires 583 watts when compressor is running, down to 56 watts when only fan running. Over a day where temps outside reached 93F, night low of 81F, indoor temperature of 74F, my total loading was 9.3kwh. In comparison, a 8cuft upright chest freezer that I own, the days power was 1.8kwh

If you know your freezers 24 hour watt-hour figures you can do some battery run time estimates.

 

[Hogheavenfarm]

First priority then seems to obtain some Kwhr measuring equipment.

 

[12VoltInstalls]

Battery Inverter ratings are much more overstated than a high quality gas inverter generator like Honda has. Heck the ratings for some of the cheap Chinese inverters seem to be pure fiction in a lot of cases.

That’s why you don’t buy cheap stuff. That’s greedy and doesn’t help anything.
A Giandel is inexpensive and at only 1200W runs my shopvac….

You don't state if your inverter is modified sine wave or pure sine wave. If you want to run an inductive load like a freezer motor for any length of time, you really want a pure sine wave inverter.

Never buy a modified sine inverter unless it’s just for a toaster, coffeemaker, or incandescent lights.

 

[Hogheavenfarm]

Ok, a bit more data - but actual Kwh still to be determined.
Freezer is 10.5 cu ft , 1.4 running amps, 161 watts, 115v, (surge not given)
I calculated Kwh as 1288wh/day plus 48wh/day surge.
The panels harvest 1521wh/day during peak
usable battery capacity is 1200wh, so looks like I need another.
Inverter is a "Edecoa" 2000w, manual says "pure sign wave" but I never heard of this inverter.
I don't plan on buying a cheap one, I want to buy one that works, but I have to be able to afford it or I don't get any.
With a second battery, would I be better off with a 24v setup?

 

[Hogheavenfarm]

ok, killowatt data says the freezer runs between 50-90 watts running, surge to 1757 watts (highest reading in 12 hrs), running time of the freezer was 4.3 hrs so from that I conclude the inverter should be fine, although when I buy my own it will be at least 3k.
So is it better to run a 24v system or should I stay with 12v and double my amp hrs?

 

[hankcurt]

I looked up the Edecoa inverter on Amazon to read some reviews. The 2000w pure sine wave version says it has 4000w surge capability, however, the reviews have a split between people who are perfectly happy with it and others who say it let the smoke out. It appears to be a generic chinese inverter, so I usually consider the stated capacity to be double of what the equipment can actually sustain in long term service. If your surge is only 2000w and your continuous is less than 1000w, it will likely be OK.

The 12 volt vs 24 volt question is a little difficult to answer. Higher voltage allows for use of smaller wire diameters at the same power and usually results in better efficiency. I have never looked to buy 24 volt equipment, but I think it is a little less common than 12 volt or 48 volt equipment.

Of course if you are trying to stay on a budget, you already have a 12 volt inverter. Another consideration is that you have one lead acid battery with some use on it. @Will Prowse has commented that he saw short life back when he tried to put older lead acid batteries in series with newer lead acid, or if they were different. So you might be able to buy a second battery and put it in parallel with you current one, staying at 12 volts, and do OK. But if you try to put them in series to get 24 volts, you might destroy one of the batteries in a relatively short time.

Considering the equipment you have, there is very little risk in getting a second battery and some heavy copper cable and keeping the system 12 volt. On his https://www.mobile-solarpower.com/ website, Will has links to some reputable cable vendors, which I have used and been happy with. (you have to be careful not to get CCA (copper clad aluminum) instead of pure copper, it will not perform well)

Hopefully someone with 24 volt experience will comment.

 

[Hogheavenfarm]

Thank you for the reply. I am considering another battery in parallel, but shouldnt to a problem in series as this current battery is only a few weeks old and has only been cycled a few times. I can always balance them first I suppose. The current inverter I have is just borrowed,so I have to pick up one myself anyway, so thats the reason for asking about the 25v versus 12v. I have avoided then CCA wire whenever possible,I dont believe I am running any at the moment. The Edecoa inverter pulls 14w and 1.5a by itself, I wonder if that is normal,it is probably not very efficient.

 

[hankcurt]

Considering all of the circumstances you outlined yesterday, I really don't have a strong opinion on whether 12v or 24v would be better for your situation. I did happen to see a three year old video by Will Prowse today on this very subject.

When it comes to inverter efficiency, I don't think the standby power is important for your use case, where you will only turn the inverter on when you need to power appliances in a power outage. I did check my 2000w 12volt inverter's standby current and found that without a load it was consuming 0.45 amps at 13.2 volts, which is about 6 watts. I have a rough idea that the efficiency of the inverter under load is around 90% or so, but I haven't really gotten crazy about trying to figure it out exactly.

When looking at inverters, you essentially have a choice between low frequency and high frequency inverters. The low frequency inverters use heavy transformer coils, sometimes verrry heavy. While this can affect the portability of the system, the low frequency inverters have a reputation of being better at handling surge loads. High frequency inverters use capacitors and rapid switching to convert the electricity and thus they are much lighter weight. I chose a high frequency inverter because I wanted the portability for camping and such in addition to backup of my freezer. Which ever you choose, I think @Sverige had an excellent suggestion in his comment to get a 3000w inverter if you think you need a 2000w.

 

[george57]

Here is all I want to do - Run 1 chest freezer overnight, or if not possible, run the freezer during the day and let it coast overnight. We have blackouts often, 3 weeks was the longest, and cost of running a genny that long was enormous, even when gas was $1.99.
What I have - eight 100w panels - 5.5a 18v (typical panels) 2S4P(?) (2 in series 4 parallel sets)
(1) Renogy Rover Elite 40 amp 100v controller
(1) 200 amp hr SLA battery 12v (I am thinking I probably need another of these and then I would go 24v)
(1) 2000w no name inverter 12v (I am thinking I probably need another of these and then I would go 24v)
I get 3.8 hrs peak here, panels are south facing and get good exposure 10am to 6pm
Freezer stats are - 4 amps running 300w at 120v - surge is not listed but I am guessing about 10 amps. (This is a large freezer, 60"x28"x30")
My initial test of this system running a room a/c (for comparison, I cannot connect to the freezer at this time) was not very encouraging.
The little 2200 watt genny runs it ok.
We are old, so budget is pretty tight, and keeping food through these outages is very important to us.

Do I have all the required pieces? How can I arrange what I have to make the best use of this? Is this even possible with what I have? Any recommendations on different equipment?

With the SLA batteries, you are sort of limited to 50% capacity discharge in order to extend the life of the battery. If you were to go with a Lifepo4 you could generally use far more of the capacity without shortening the life cycles. Buy since the cost is a factor, getting another 12v 200ah battery and putting it in parallel to double your ah to 400 or 200+ usable would be more economical. That way you can keep your 12v Renogy controller.

I would also put your panels in 4s2p. 2 sets of four in series, then 2 sets of four in parallel. Your Rover can handle up to 100volts. https://www.renogy.com/learn-series-and-parallel/ You must have a massive window ac. A smaller and more efficient window ac that draws about 450-500 watts might be better, a Midea uses an inverter compressor that can draw down to less than 50 watts while still cooling. You could certainly run it with your Honda. If you plug in a small AC smart battery charger and connect it to the battery terminals, it can put up to 20 amps when the sun goes down to keep the batteries from running down during the night. And probably have a nearly full charge by morning.

 

[Hogheavenfarm]

Thank you. I am debating how best to link the panels. The SCC could handle the 72v even with very low temps, so that was an option. I see my SCC has a max pv input of 520 watts at 12v, and my thought was to go to a 24v system to take advantage of the second string, but then I would have to get a 24v inverter (not a big issue as I need to get an inverter anyway), and 3k was what I was looking at.
I just finished the killowatt metering on both freezers, both use about 85w when running, and about 10X that at surge. Over 24 hrs the large one sees 1.75Kwh.
Ideally I would like to run both, but if I cannot, I will only run the meat freezer (large one) as the other one is mostly just frozen non-meat food (I could always use the little genny on the small one).
So it still looks like I need more battery, even two will certainly be pushing it.

BTW, the a/c unit I was using as a test is a 1972 GE "Carry-Cool" window unit. I couldn't find any tags on it, but it not that large, just an energy hog I guess. (looks just like this Hotpoint) - Still works great!

 

[george57]

You can generally over-panel your Renogy Rover, just keep your voltage under 100v. The controller will only accept the wattage it needs, any more will be clipped off. I finally got rid of my 40-year-old Amana side x side refrigerator. I kept it because it still worked fine and a new refrigerator was going to cost $3K+. I knew it was using a lot of electricity when running. 450watts.

It started to make noise from the compressor. It was time to get rid of it. I bought a big Samsung with an inverter compressor. It is far more efficient with electricity. So I am glad for the lower overall consumption.

Are your freezers frost free? If they are, they go through a defrost cycle every 8-12 hours. They will draw a lot of current for 15 minutes to power the defrost heaters. That may be the reason your battery can't make it through the night. If they pull a heavy startup current, you can install a hard start kit with a start capacitor to lower that surge. Sometimes you save money getting rid of old inefficient appliances. You should be able to get a propane conversion kit for your Honda to save on gasoline costs and a 20lb tank of propane lasts far longer than the small tank of gasoline on the Honda.

 

[Hogheavenfarm]

The freezers are not frost free. The smaller one is about 5 years old, was an energy star model at the time. Killowatt says it uses about 103w, startup is about 1kw . The larger one is a year old, uses 83w, surge is about 800w. I do prefer to keep the older appliances as they seem indestructible, but they are all grid connected. The only ones I would like to keep running during these outages are the freezers, we can live without everything else for an extended period of time, we have done it before. I do believe the Rover is overpaneled somewhat, the manual says 520w PV, I have 800w up at the moment, but I have an old PWM controller I could use on the second string if I need to. The wind turbine isn't hooked into this system at this time, That runs some small equipment in the barns, and it has its own controller for the dump loads.
I am ordering another battery today, and will place that in parallel (since I dont have a 24v inverter yet), so my Ah should be 400 with that added.
I will be testing the system with a 100w load this weekend, maybe that will give me some indication of runtime for the freezer. I had thought the a/c wattage would have been close to the freezer, but it wasnt.