What happened?

[Bates291]

I recently got my off-grid solar system working and have been running small devices off of it for the last month with no issues other than cloudy days. With the onset of summer and temps reaching 98° with up to 91% humidity, we decided we needed a bigger fan. Suddenly my system over discharged overnight. Here's what I have

2 - 200 watt bi-facial solar panels
VEVOR 50amp charge controller
1000 watt inverter
2 - 12v 100ah lifepo4 batteries

It's a very simple system that is growing as I can afford the parts.

I purchased an oscillating fan and ran it half of one day, overnight, and half of the next day before I suddenly had no power. That's ok, that's what the generator is for. But, why?

What I'm running on a daily basis is

3 LED USB rechargeable lights
1 small rechargeable water pump for a 5-gallon water jug
2 USB power hubs each running 1- 8" usb rechargeable fan, 1 - 4" USB rechargeable fan and a phone charging as needed.

The box my new 16" fan came out of states that it uses 0.5 amps and 60 watts.

Here is the most recent history from my charge controller app. What am I missing and how do I fix it?

 

[Andrewr05]

60W Fan x 36 hours = 2160Wh

12v x100Ah = 2400Wh


That left only 300ish Wh left to cover all your other accessory plus the inverters self draw usage.

I'd say that's a decent amount of time for that to run.

Edit:

I didn't see that you also have solar hooked up.
That's throws a wrench into the mix.

Your screenshots show very little charging yesterday and today, unless I'm reading it wrong.

 

[Daddy Tanuki]

60W Fan x 36 hours = 2160Wh

12v x100Ah = 2400Wh


That left only 300ish Wh left to cover all your other accessory plus the inverters self draw usage.

I'd say that's a decent amount of time for that to run.

Edit:

I didn't see that you also have solar hooked up.
That's throws a wrench into the mix.

Your screenshots show very little charging yesterday and today, unless I'm reading it wrong.

agreed you are simply using more than you are making and running the batteries down over a period of time. the charts showed that you only reached full charge 2x times andon a daily basis are only putting in about 55-60 aH's given time you will surely drain the batteries. that coupled with the new to you fan and you simply need more panels to reach full charge on the battery on a daily basis.

a small system like this you either conserve more, or you over panel so that they batteries get fully charged as often as possible.

are you shutting the inverter off when not activly using it? tare loads depending upon the inverter can be quite the killer...

 

[Bates291]

I'm not sure what you are referring to as "tare" loads. We are pretty much using the system 24 hrs. With the heat we need the fans just to sleep. With lows of 70°—75° fans are the only way to get enough relief to sleep.

I was unsure as to whether I should get another battery or another panel. Sounds like another panel is a better option than a battery at this time. At the moment we are in an RV and only running the minimum through an extension cord to the inverter. I'm trying to build up the system one part at a time while we build our cabin.

My next appliance I need to invest in is a small refrigerator. I know that I need to build up my system before I do that. Any suggestions on what I should be running on my system before I make that change? I know definitely more panels and batteries as well as a more powerful inverter. I'm asking more how much pv I should be bringing in and how many batteries. After the fan incident I'm less sure of what to shoot for in order to run a refrigerator. Atm I'm using my RV refrigerator as a glorified ice chest and that gets expensive in the summer...

 

[Bates291]

Also, since I have two 12v 100ah batteries, wouldn't that be 4800wh?

 

[CommandoJoe]

Also, since I have two 12v 100ah batteries, wouldn't that be 4800wh?

12v * 100ah = 1200wh * 2 = 2400wh

I'm not sure what you are referring to as "tare" loads. We are pretty much using the system 24 hrs. With the heat we need the fans just to sleep. With lows of 70°—75° fans are the only way to get enough relief to sleep.

I was unsure as to whether I should get another battery or another panel. Sounds like another panel is a better option than a battery at this time. At the moment we are in an RV and only running the minimum through an extension cord to the inverter. I'm trying to build up the system one part at a time while we build our cabin.

My next appliance I need to invest in is a small refrigerator. I know that I need to build up my system before I do that. Any suggestions on what I should be running on my system before I make that change? I know definitely more panels and batteries as well as a more powerful inverter. I'm asking more how much pv I should be bringing in and how many batteries. After the fan incident I'm less sure of what to shoot for in order to run a refrigerator. Atm I'm using my RV refrigerator as a glorified ice chest and that gets expensive in the summer...

If you're going to be running a fridge, more panels and more batteries. If you're on a tight budget, check Facebook Marketplace for used panels - I see often see 300w+ panels as low as $20-40 each, and $50-70 more frequently. When you get one or 2 small panels online and shipped, you're paying a lot more...

If the fridge is the one that came with your RV, it's probably not very efficient (Mine wasn't) and you might consider replacing it with a residential unit that fits the same space. I replaced mine with a $200 apartment size fridge from Walmart and it uses less than half the power of my old one, and when you're just starting out with a small system, that is a huge difference.

 

[Solar Guppy]

Your inverter is likely 50-60 watts ( tar load ) just turned on, so that's a 1440 Wh a day doing nothing.

 

[Chispas]

I'm asking more how much pv I should be bringing in and how many batteries. After the fan incident I'm less sure of what to shoot for in order to run a refrigerator.

Try an online calculator to do an energy audit using the sticker Watts consumption of the appliances x the number of hours you want to run them.Then you can size your inverter, taking into account the surge current for items like pumps.
The PV Watts online calculator will tell you what to expect in terms of production from your location according to the amount of watts you have in panels. This is enough to be getting on with, IMO.

 

[OhYou_]

I blame the Vevor by default.
I had an outage on a similar older setup was just 2x300w panels, 40a charger, 12v280ah battery. thing went dead unmonitored randomly during some super hot weather.
all I was running was a 60w fridge, and some networking equipment.
I determined the overall discharge was spread out over several days, pulling just a little more out than what came in and it eventually dipped below the cutoff. The issue was while they were 600w total of panels, my sun angle was bad and so they were producing very little.

I would start first with the panels, make sure they are clean and pointed correctly for your area.

 

[SunDave]

Your inverter is likely 50-60 watts ( tar load ) just turned on, so that's a 1440 Wh a day doing nothing.

Indeed. Even if it is half of that the math doesn't work out. The charts show approx 800 watts of solar daily. So it's just a classic case of not enough input for the amount of use. You were likely draining your battery over time even before the new fan.

 

[Chispas]

I blame the Vevor by default.

An interesting anecdote, but the key to correct diagnosis is not starting out with preconceptions.

 

[SunDave]

Try an online calculator to do an energy audit using the sticker Watts consumption of the appliances x the number of hours you want to run them.Then you can size your inverter, taking into account the surge current for items like pumps.
The PV Watts online calculator will tell you what to expect in terms of production from your location according to the amount of watts you have in panels. This is enough to be getting on with, IMO.

Good advice with one issue. That works for larger systems when idle draw, and general inefficiencies are a single digit percentage of the total system. When a solar system is very small, and these factors are significant, it is best to make sure you have plenty of input power. More than you think you need.

 

[OhYou_]

Your inverter is likely 50-60 watts ( tar load ) just turned on, so that's a 1440 Wh a day doing nothing.

what inverter do you have? mine pulls 1.5W at idle

 

[Chispas]

Your inverter is likely 50-60 watts

That sound like a lot to me, a comparable Victron uses 9 W . I would expect a more economical brand to use more but 5 to 6 times?

 

[Chispas]

it is best to make sure you have plenty of input power. More than you think you need.

Good advice, but run the numbers ! I have been stone broke in the past, where €100 seemed like a lot of money, so just chucking some extra panels on wasn't possible.

 

[SunDave]

You have a 1000 watt inverter that pulls 1.5 watts at idle?

Even the idle draw rating is not an in-use rating. So imagine a load of 200 watts even on a top notch 1000 watt inverter. The base load draw, plus about 20 watts of conversion at 90% efficiency.

Its easy to get into the weeds on technical discussions but that doesn't help with the original problem.

The reality is that some possible solutions are

• more panels
• less usage, including shutting off the inverter at times

 

[Solar Guppy]

That sound like a lot to me, a comparable Victron uses 9 W . I would expect a more economical brand to use more but 5 to 6 times?

Budget brands are known to have high idle draw and the larger the inverter the bigger the idle power consumed. Victron is likely 4-5x more in cost than a budget / no name 1000 watt inverter and yes Victron are known for very low tar load.

 

[Bates291]

12v * 100ah = 1200wh * 2 = 2400wh


If you're going to be running a fridge, more panels and more batteries. If you're on a tight budget, check Facebook Marketplace for used panels - I see often see 300w+ panels as low as $20-40 each, and $50-70 more frequently. When you get one or 2 small panels online and shipped, you're paying a lot more...

If the fridge is the one that came with your RV, it's probably not very efficient (Mine wasn't) and you might consider set replacing it with a residential unit that fits the same space. I replaced mine with a $200 apartment size fridge from Walmart and it uses less than half the power of my old one, and when you're just starting out with a small system, that is a huge difference.

Thanks for clarifying my ah q

The refrigerator in the RV is not operational. I am going to need to buy a small apartment size refrigerator once I have my system set up to handle it. What would you recommend as a total watts to bring my system up to a realistic size for my needs? Batteries I can figure out now.

 

[Bates291]

Try an online calculator to do an energy audit using the sticker Watts consumption of the appliances x the number of hours you want to run them.Then you can size your inverter, taking into account the surge current for items like pumps.
The PV Watts online calculator will tell you what to expect in terms of production from your location according to the amount of watts you have in panels. This is enough to be getting on with, IMO.

I'm not versed enough in the technical aspects to understand how to use that calculator. Do you know of a "solar calculator for dummies"?

 

[Chispas]

Budget brands are known to have high idle draw and the larger the inverter the bigger the idle power consumed. Victron is likely 4-5x more in cost than a budget / no name 1000 watt inverter and yes Victron are known for very low tar load.

A renogy 1000W is 150 euros here & a victron 1200 is 250. Im not sure if I would try my hand at a70 or 80 euro no name inverter.One thing I fing frustrating about Renogy, LiTime etc. is the lack of a decent datasheet.

 

[littleharbor2]

I am curious why your current is so low the last few days now if you turn your fan on and note that low current and then go turn your fan off and see if it goes back up to normal that could start to explain it. Actually turn your fan and your inverter off and check the incoming current

 

[Chispas]

What would you recommend as a total watts to bring my system up to a realistic size for my needs?

You need to do the calculations mate.

 

[CommandoJoe]

Thanks for clarifying my ah q

The refrigerator in the RV is not operational. I am going to need to buy a small apartment size refrigerator once I have my system set up to handle it. What would you recommend as a total watts to bring my system up to a realistic size for my needs? Batteries I can figure out now.

At a bare minimum I would double your current battery bank, but 10kwh would be better. For panels, 1000w-2000w.

 

[Bates291]

At a bare minimum I would double your current battery bank, but 10kwh would be better. For panels, 1000w-2000w.

Thank you! I didn't need an exact amount, just a ballpark figure and I didn't understand the calculator previously suggested. I appreciate you taking the time to give me some approximate numbers to shoot for. Not knowing how to do the calculations myself yet makes it difficult to figure out myself. I appreciate the help.

 

[Andrewr05]

Thank you! I didn't need an exact amount, just a ballpark figure and I didn't understand the calculator previously suggested. I appreciate you taking the time to give me some approximate numbers to shoot for. Not knowing how to do the calculations myself yet makes it difficult to figure out myself. I appreciate the help.

Take every device that you're running and look at the label.

It should say how much watts it uses.
(if it doesn't, then you just have to multiply it's voltage by it's stated amperage; Watts ARE Volts x Amps)
Then figure out how many hours you are going to run that device.
That's is WattHours.

Add up every single conceivable thing that you think you will ever run.

Then multiply that number by 1.25 and that should be a great ballpark figure of where you need to be for your total amount of battery capacity needed.


THEN

You have to figure out how much solar you need to refill that battery.

Solar panels work in the same way.

You just multiply their wattage by the number of hours you are going to get peak sunlight.
That will be how many WattHours you can put back into your battery bank each day.

Each geographical area is different, so you need to look up how many solar hours you get every day

(you also need to take into consideration that the value that is on your solar panel for its total wattage output is only in the absolute best conditions, The amount that you will get out of it is likely only about 75% of that value. That number is a bit high, but it factors in all possible losses.)