In 2014, i installed a 200 Watt panel, feeding a MPPT T20 controller feeding two Deep Cycle Marine batteries (845 CCA, lead acid, circa 2015) feeding a 1500 watt inverter, NOW feeding a new 20 cubic foot deep freeze (531kw/yr). My question is, since this will be the first time I have powered anything from, it, I want to be sure the MPPT is set properly. See Attached file. Any help will be appreciated. If I can get this sorted, and it works, I plan to power two of these freezers, on timers, so they are not both powered at the same time. Like during a given hour, power one for 45 minutes, and the next hour power the other for 45 minutes, so there are gaps between the two charging events. It is my understanding, that if not opened, the freezers cycle 5 minutes per hour. Not sure if that is true or not. I am NOT a electronic genius, and 75 years old, so be gentle...
One 100W panel, two deep cycle marine batteries, 1500W inverter - trying to power a Freezer.
- Thread starter ww4cash
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Jim Burrow
Solar Enthusiast
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Note running with 845 CCM deep cycle Marine batteries will only buy you 30 to 45 minutes. I bought two 845 CCM deep cycle Marine batteries from Walmart a few months to test out my system. I also thought these batteries were good for around 80 ah. with a test load of 150 to 300 watts, the most I could get out of them was 20 to 25 ah.
6 weeks ago, I bit the bullet and bought the Ampere Times 24v, 100ah battery from Amazon and running a house load of on average, 500 watts, this battery last in the evening almost 6 hours. I'm differently getting the advertised ah (amp-hours) out of it. The price from Amazon was $1059 with free shipping. I'm totally happy with this battery.
Note that after the battery reached the voltage point of 23 volts (which I set it at), the power to the load switches to Utility power. The house runs off the utility until the first light when the Utility power kicks off and the battery starts supplying the load again. It takes about 2 hours for the sun to get high enough to take over and supply power to the load and starts recharging the battery.
6 weeks ago, I bit the bullet and bought the Ampere Times 24v, 100ah battery from Amazon and running a house load of on average, 500 watts, this battery last in the evening almost 6 hours. I'm differently getting the advertised ah (amp-hours) out of it. The price from Amazon was $1059 with free shipping. I'm totally happy with this battery.
Note that after the battery reached the voltage point of 23 volts (which I set it at), the power to the load switches to Utility power. The house runs off the utility until the first light when the Utility power kicks off and the battery starts supplying the load again. It takes about 2 hours for the sun to get high enough to take over and supply power to the load and starts recharging the battery.
Alphacarina
New Member
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Your lead acid batteries are 6 years old. With lead acid, you really don't want to run them below 50% SOC or they won't last very long . . . . and since they're already 6 years old, they probably don't have much left anyway. I strongly suspect your freezer will run them flat overnight and even if they survive the night, the first day or two with minimal sun will have your system completely flat!. Your set-up doesn't sound very viable to me. You need more solar, more battery power and some way to make sure you don't run your lead acid batteries down below 50% SOC
Don
Don
mikefitz
Solar Wizard
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All bad news, sorry. You dont have enough solar, suitable controller (and perhaps) battery to power even one freezer.
Regard the battery is suitable as store buffer for over night.
If my maths is ok, 531,000 watts per year is 1455 watts a day.
A 100 watt panel , assuming you could get the full yield for 12 hours a day, gives you 1200 watts over the day.
The solar controller is a fake MPPT, its actually a PWM. This means it will not get the full 100 watts, the maximum will be around 75 watts.
The batteries, you dont state the capacity , I will guess at 100Ah each, that's 200 x 12 = 2400 watts, full to empty. These only have to run the freezer over night ( around 700 watts over night). If you want the lead acid batteries to last they cannot be discharged more than 50%, and less is better. So for this and other factors the battery is only good for one freezer for one night.
Depending where you live, the number of good sun hours each day, time of year, you will need more solar, perhaps lots more.
I think you would need for one freezer a minimum of 400 watts of panels if you live near the equator, further north 3 to 5 times that.
You would need a quality solar controller true MPPT rated for the panels.
You would need batteries capable or taking the charge and having enough capacity for poor solar yield days.
Mike
mikefitz and others:
Thanks for your comments. I had not used this in 6 years, since I set it up. I attached the freezer this AM at 8. The voltage was 12.4 in the batteries. At noon, I decided to top up the batteries with water, they were not low enough to see the plates. At 6, I decided to wash 6 years of crud off the solar panel. At 3 AM the voltage had dropped to 12.0 Volts. I am anxious to check it at 8AM or earlier. The inverter supposedly will work down to 10 Volts, when it will shut off. Not sure what the quality/specs of the electricity it can furnish below 12 volts... The temperature in the freezer has been holding at -10 degrees F, except when defrosting. If I had to rely on the solar setup at some point, I would disable the defrost bit. Based on testing at this point, it does not look like I could run two, not at the same time, on this setup.
Thanks for your comments. I had not used this in 6 years, since I set it up. I attached the freezer this AM at 8. The voltage was 12.4 in the batteries. At noon, I decided to top up the batteries with water, they were not low enough to see the plates. At 6, I decided to wash 6 years of crud off the solar panel. At 3 AM the voltage had dropped to 12.0 Volts. I am anxious to check it at 8AM or earlier. The inverter supposedly will work down to 10 Volts, when it will shut off. Not sure what the quality/specs of the electricity it can furnish below 12 volts... The temperature in the freezer has been holding at -10 degrees F, except when defrosting. If I had to rely on the solar setup at some point, I would disable the defrost bit. Based on testing at this point, it does not look like I could run two, not at the same time, on this setup.
It seems 11.9V was its low point. It is cloudy today, but it is holding above 12vdc. The freezer is empty, I am going to fill it mostly up from the 15 foot to the 20 foot and see if the duty cycle is shorter, by monitoring the battery voltage. I plan on putting a switch in to eliminate the defrost cycle for when the power out. Frigidaire tells me the compressor duty cycle is 85-90% of the time, and it seems to draw around 20 watts. The defrost cycle is 30 minutes, and the compressor is off, at about 60 watts. Another thing not in my favor is the sun does not get directly on the panel until around 9:30 or 10, and is blocked by trees at around 6 or earlier. The one solar panel and two batteries barely work on one freezer. I plan to run on house current except for outages, when I will run on Solar. So I plan on Two freezers. So I will probably do several things. One, put a switch on the freezers to defeat the defrost cycles, move the solar panel from on top of a flat enclosed trailer to the top of the pitch of the roof, maybe putting one or two on one side of the peak, and one or two on the other side. I am not sure what the limiting factor in my situation is, the panels or the batteries, some help there would be appreciated. Logically, if I added panels, I should have to add batteries. With 4 of the previously described panels, would doubling the number of batteries to four be advisable? Right now I have one panel, two batteries. Lets suppose I go to two panels and 4 batteries, would that be the right thing? Second, I am going to have to research how to link the panels in, so got some reading to do, unless you have some suggestions.
You need enough Wh (x2 for lead acid, you don't want to dip below 50% SOC) to go for two days without good sun.
You need enough solar power to recharge your batteries in 5 hours.
For 1500Wh per day, that means a lead acid bank of 6000Wh. To recharge that in a day (5 sun-hours) you need roughly 1200W of solar.
These numbers are very rough, and doesn't take into account inverter inefficiencies, nor the fact that the system will spend a lot of time at float (with the solar running the inverter directly, effectively).
The rest is just about finding the right equipment.
wibla, thanks. I do not understand how to calculate Wh (watt hours?). I have two 12 volt, 845 CCA lead acid batteries at present. Second, I do not understand what SOC is. Could you dumb it down for a cranky 75 year old guy? So far, and today is cloudy and it has rained once, and we are 30 hours into this use test case,, the Voltage has only dropped to 11.6 at most over that period. As I said, I may put half the panels on one side of the peak of my roof, and half on the other, to try to maximize the sun hours, rather than putting them on top of the enclosed utility trailer, where the one is now. Second, I will disable the defroster with a switch, to minimize the current needed to power one Freezer. Once the calculations are clear, I may double the number of panels and batteries to power the second Freezer. Thanks for any help.
Q-Dog
¯\_(ツ)_/¯
You have mentioned more than once now of the CCA of your batteries. That is a measure of how much amperage the battery can deliver to a starter. That is not a measure of how much energy storage capacity the battery has. In the case of storing solar energy, CCA is a useless number. You really need to know Amp Hours or Watt (or Kilo Watt) Hours.
rin67630
Solar Enthusiast
100W panels are designed to work best with PWM and 12V batteries.
MPPT needs a good voltage headroom above the max battery voltage that is not given with a 100W panel.
I think we already figured out that the controller he was talking about is actually PWM, so it should be fine... for some values of fine
Alphacarina
New Member
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SOC is 'State of Charge' and with lead acid batteries, you don't ever want to discharge them below 12 volts because 12 volts is roughly 50% of their capacity, or 50% SOC.
Can't picture an 'EverStart' battery actually being a true deep cycle - Another 'clue' is that they give a CCA rating for them, which true deep cycle batteries seldom do
Adding new batteries in parallel with 6 year old batteries is not a good idea. For what you're wanting to do, a pair of 6 volt golf cart batteries in series would be a good start . . . . of course, lithium batteries are the best thing in terms of how deeply you can discharge them without killing them and how long they will last. They cost more initially, but in the long run, they're actually cheaper because they should outlast 3 sets of lead acid batteries
You have a freezer that only draws 20 watts?? Check the plate on the back and it should give you the amps it draws - Multiply the amps by 120 and you will have the watts it needs for compressor start-up. Running watts will be less, maybe 1/2 of the starting watts . . . . but I'm betting both will be much more than 20 watts
Don
Can't picture an 'EverStart' battery actually being a true deep cycle - Another 'clue' is that they give a CCA rating for them, which true deep cycle batteries seldom do
Adding new batteries in parallel with 6 year old batteries is not a good idea. For what you're wanting to do, a pair of 6 volt golf cart batteries in series would be a good start . . . . of course, lithium batteries are the best thing in terms of how deeply you can discharge them without killing them and how long they will last. They cost more initially, but in the long run, they're actually cheaper because they should outlast 3 sets of lead acid batteries
You have a freezer that only draws 20 watts?? Check the plate on the back and it should give you the amps it draws - Multiply the amps by 120 and you will have the watts it needs for compressor start-up. Running watts will be less, maybe 1/2 of the starting watts . . . . but I'm betting both will be much more than 20 watts
Don
The first attachment is the label inside the freezer. The second MAY be the defrost cycle, the third MAY be the cooling cycle. The number have gone up, since I looked at them yesterday (20/60 or so).
Attachments
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![IMG_20210713_203042259[1].jpg](/data/attachments/56/56171-1a4ccc93870b11864a4456137ce0da48.jpg)
![IMG_20210713_195333290[1].jpg](/data/attachments/56/56172-3707ad6503328c9d8597087542d89e50.jpg)
0.45 is Amps, 0.62 is PF, 56.1 is VA. I put it back on house power last night, as the battery voltage dropped below 12, and I had read somewhere that was not good. Got the batteries on a charger. Also, the 1500 watt inverter alarms at 10.5 and shuts down at 10 Volts. Thats good, I guess, but if the batteries can be ruined below 12, that does not seem to be a good safety feature... Also, I saw, with interest, that Tesla is producing 420 Watt panels. Not sure if there is a proprietary controller, or if any would do. Any thoughts on that?
Attachments
![IMG_20210714_054057657[1].jpg](/data/attachments/56/56198-1ac99625814fc93252f44b80a6f9b364.jpg)
![IMG_20210714_054041997[1].jpg](/data/attachments/56/56199-39ff42c06e70d940d9ab809e85dd7a50.jpg)
![IMG_20210714_054028423[1].jpg](/data/attachments/56/56200-87846f47d6be35f14e21ad8025439aca.jpg)
rin67630
Solar Enthusiast
You ruin FLA batteries when you do not provide regularly a full charge at 14.4V.
Its OK to cycle a battery down to 10.5V as long as you let immediately a full charge follow.
400ish, or really any panel over 180W usually is a higher voltage panel, and would be incompatible with your pwm controller. Likely would set it on fire, or simply let out the magic smoke… or just waste most of the wattage as heat, not charging the batteries.
To keep the batteries charged you need the high watts, AND a good mppt controller capable of handling high voltage panels, or more of the panels you have, in parallel. Those two batteries will need over 20Amps charging current to achieve full state of charge, and the sun just cannot provide that through a 100W panel. Three would be minimum… with good sun.
To keep the batteries charged you need the high watts, AND a good mppt controller capable of handling high voltage panels, or more of the panels you have, in parallel. Those two batteries will need over 20Amps charging current to achieve full state of charge, and the sun just cannot provide that through a 100W panel. Three would be minimum… with good sun.
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