Join the conversation on the friendliest most helpful DIY solar energy forum
Greetings from the "Hillbilly" state!
I have a question that I believe I know the answer to but need some verification
First, I have not put together my system just yet. I am awaiting my Kill a Watt meter on Monday and will go from there.
What I want from this system is the ability to run my refrigerator and two chest freezers from the solar system in the event of a long term power outage. If I do it right with plenty of capacity, maybe just run them all the time even when still on the grid.
I currently have a 7000W (12,500 surge) gasoline generator and about a 50 gal supply of gas readily available so I probably would be OK for a while, however, If we had a long term outage, I would want to keep my freezers going so I don't loose all that food.
With that being said,lets make a couple of assumptions. Lets say I will have powerful enough solar cells / Controller and ample batteries.
My question is two fold. I believe I should use pure sine wave inverters to be sure I am not risking damage to these three freezers. Is this correct?
My second question is.....should I use three separate inverters, one for each freezer? My thoughts are if two or three of the motors just happen to try to start up at the same time, one inverter may not be an option for me.
So, if I use three inverters (one for each freezer), and hook them all up to the same battery array, would you foresee any issues?....assuming I have enough capacity in the batteries
If I did use three inverters, would that require three battery arrays isolated from each other? If this is the answer, I am assuming I can supply power to all three battery arrays with the same solar panels?
Hope I have not confused anyone...or asked a stupid question for my rookie post
Thanks for any info in advance
Hey Dan, welcome to the forum.
All panels to the same battery bank.....no problem.
All 3 inverters off the same battery bank......no problem.
All 3 freezers/frig off the same inverter.....no problem as long as it's a HUGE inverter. 3 individuals might be more practical.
First thing first though, the math. How many watts does each appliance draw?
Second, how much available credit do you have on your credit card? ;-]
Thanks for the info!
I have a Kill A Watt meter coming on Monday and I will see what they actually use.
At that point, i will do my math to see what is needed. I do understand that I want to be able to grow the system and it is always best to have more capacity than you need.
As soon as I get the wattage info, I will come here and we can hash it out.
I have some money put back to get started but I may have to build to the level I described in my original post.
I am thinking I have enough to get good and started and add to it as I go along.
My concern is not for the panel controller and inverter but more about the batteries and their cost. I may have to start out with a few 12V I already have. I have two large capacity car batteries and one large capacity deep cycle 12 volt right now
I may have to pick up the 6 volts one at a time
I am a man of many trades so making the mounts and doing the electrical configuration wont be a problem. I also have about 20 of the 175 yellow fork lift electrical connectors and 25 feet of #1 wire that I am using on another project.
Thanks again for the help!
If it were me, I'd have each freezer on it's own inverter, and you can tie all three inverters to the same battery bank....
Now, that said, be prepared to have a rather LARGE battery bank to do the job, in the event all 3 freezers come on at the same time...and...a LARGE array of solar panels to charge that battery bank...
I also have a 3500 watt generator dedicated to a long outage, but as of late, my "Bug-Out Jeep" would easily run my one refrigerator/freezer (and everything else in the house to boot), using an 1100 watt inverter, driven by the Jeep's 140 amp high output alternator...
So, that's MY plan, should I exhaust the solar battery bank, the Jeep does the power work until the sun comes out again...
It looks like the questions have been answered already. I would agree with them but would add a few things.....
One thing that I don't really see discussed that much is running a battery charger with a small generator to keep your battery bank going. I do have a large generator but I have not had to use it at this point. Once your battery bank has a good base, lets say 6 to 8 of the 6v batteries you can keep them charged during a heavy use period with one of the 800w generators from Harbor Freight and a good floor battery charger. I have supplimented my power sources in the winter when mother nature has not cooperated on providing me the energy I needed.
The battery bank will have a good base of power to start with and if you connect a good battery charger, one that can handle extended periods of running you are able to supply the needed energy with much less gasoline. The 800w generator runs my floor model battery charger for many hours from a single gallon of gasoline. The charger can be set to the 200 amp start charge setting. If you are familiar with the chargers they only provide what is being drawn at the battery side, so if you set it to 200 amps it will provide what is being drawn up to 200 amps. The generator is not going to provide 200 amps, but it will run the battery charger it around 50 amps with no issue. This is a quick way to provide 50 amps of DC power to your battery bank, when this is combined with the power that is in your bank already you are able to sustain the fridge and freezers for a long period without much gas being consumed.
I have ran my little 800w generator for a few days at a time supplimenting my bank. This has worked out very well and is easy to sustain.
The inverter question is a good one. Many here use the MSW inverters without issue. I am an advocate of PSW inverters for everything. I then have zero worries of incompatibility or damage to anything I run. I have purchased many inverters and settled with the PSW units and have not looked back. If you buy one at first there is no wasted money. I have spent money on MSW unit because I did not think I should spend the extra money on a PSW, only to replace them later with a PSW. So I am out the original money spent, I would have been ahead in the long run if I had only saved a bit more and only bought one unit.
There are many ways to build a robust system, read out eveyones setup and scavenge the best elements to build your system.
@Bill .... That PBR is the most important thing in your picture. While the jeep is providing the power that you have preplaned for, you can sit back and enjoy the nice cold PBR while everyone else is scrambling around wondering if someone is going turn the grid back on for them.
You have a very good point that I briefly thought about which lead me to the question..."why shouldn't I just build it to run them all the time and the ability to grow" instead of having it sit idle until needed. Batteries don't like that.
So I think that is where I am headed with this project.
One note....my big generator is wired to an isolation panel and it pretty much runs the house when I have to use it.( actually had to use it for a few hours last week when we had a bad storm)
The generator also has a 12V charger built in so anytime I have it running, I can top off the battery bank.
Your comments on a small generator are actually a good idea, I will look around for one that is a gas "sipper"
I also am going to order a propane conversion kit for the generator that will allow me to use gas or propane. That should give me more fuel time before I may have to be 100% dependent on the cells to keep the food frozen
Thanks for all the info
You have a pretty sharp set of eyes, there, the PBR was not intended to be in the picture, but, oops, there it was....I often go out to the Jeep after the sun begins to set, and sit and sip and listen to some classic rock on the satellite radio...the air is cool and so is the music, and after all, in a power outage, the cooling of the PBR's is first on the list! :)
Well I received my Kill A Watt meter. I put it on one freezer for 96 hours (4 days) and it said it used 2.5 KW over that four day period
Does that seem right? that would be .625 per day
I know I'm late in the game here with some thought, sorry! However, as usual I see things a bit different then some of the fellows.
First, on stand by back up power, be carefull storing gas for all the obvious reasons but keeping in mind it gets old and wet!
Second, I have never figured out why everybody fire's the 110 volt light plant to run a battery charger. Things get a lot more efficient and cost effective using the big take out truck altranators driven by the take out briggs!
Third, Be very careful running multiple inverters. No one is addressing the day things go wrong and your now potentialy dealing with 300 Plus volts, things like grounding become very critical for safety. Personally one inverter speced for the job will do it and the batteries don't no anything but load. One big inverter also may run cooler and be more efficient.
And yes, for compressor effiency, life and start capacitor life pure sine wave is the way to go.
As to price, I'm about as cheap as they get! My one big inverter came in very close to what two would have cost me.
Thanks for the info,
I do rotate out my gas, I have three 6 gallon jugs that I used for my race car, I put it in a 55 gal plastic drum but only fill it about 1/3 to half way at a time. I use gas from the drum for lawn and other gas items around the house and back fill with new gas as I use it
I also keep the three jugs full and use Staybil marine. So far no problems with it going bad, I also keep it in a separate garage away from the house.
I am pretty handy with electricity so hopefully I wont zap myself. I can do basic house wiring and wired up my transfer switch. If it gets real bad, I have a friend down the street that works at the electric company :)
If one large inverter can do the job, that is probably the way to go......my only concern is if the one unit goes, all 3 freezers are affected vs if they are all on separate ones, I still have freezers running.
I also believe Pure Sine is the way to go if I can get them big enough
Thanks again for the input.
My only concern is that I am measuring the freezer power usage correctly with my new meter.
It seems to be a pretty low number for a freezer
I'm not real sure about the freezer usage, but I would go with the Kill-a-Watt. They have always given me good numbers.
On the inverters Bill (from the woods.. not Bill K.) and I disagree. I would split the load between two inverters. I would have each inverter large enough to handle the entire load. That way if one does fail you are still covered. I used to have the stance that one large inverter was all that I needed. That was until my one larger inverter failed and I then did not have power to my home. I now have the load split between two units and have a third as a back up.
Bill does have the most efficent charging method with the alternators, but I perfer not to break down my charging system to that level. I'm fine with using a small generator and a big battery charger. It is everyones why of thinking that will drive their system design. I have been very frugile in the past, but as items failed or let me down, I have found that I have spent less by going larger the first time instead of replacing items mulitple times.
Question, I have measured the one freezer and the wattage is about .75 per day
so, do I multiply that by 30 to get the number I need for sizing?
I know I have to do all three units, I am just practicing since I have only one measured at this time.
I have to go out of town all this week so I wont know what the second freezer draws until I get home on Friday and them to measure the third one over the weekend.
So, lets say I was only going to run the one unit, what formula do I use to get the info I need to size a system just for that one freezer?
I am just trying to get a quick "guesstimate" on what panels, controller and inverter I need and the associated pricing
Any help with that is appreciated
"Well I received my Kill A Watt meter. I put it on one freezer for 96 hours (4 days) and it said it used 2.5 KW over that four day period
Does that seem right? that would be .625 per day"
Yes, that looks very close to my usage (625 watt hours) for my refrigerator/freezer, so yes...however, the KAW meter will not measure (for better words, show up on the meter read out) the 1500 watt, nano-second surge that the compressor uses during start up, that surge is a killer on the battery bank, as brief as it may seem...the inverter always needs to see a voltage above the alarm/shut down voltage point, so a significant sized battery bank is needed, for 3 freezers, triple that in the event that all 3 come on at once...insufficient voltage will just shut down the inverter(s)...