Old fart, new to all this needs help to understand.

[CavPeter]

Hi everyone, Peter here.
I have health problems and keep myself isolated from the covid world.
Last year I built a shed, 10 feet by 10 feet and 12 feet tall with a 45 degree roof. The shed has a south westerly side where I have placed 4 120 watt monocrystlline panels in series to give me a total of 480 watts. Next I have a 60 amp solar charge controller with x2 12 volt 50 Ah LifeP04 series batteries wired in series to give me a 24 volt system. I also have a 1500w DC 24v to AC 220v inverter with a fuse inline on the in power cable to the inverter. so now you know what I have and yes it was a kit from Eco-Worthy.

I started and found the batteries had minimal charge and at the end of the first day my charger displayed

Time 17:30 Oct 14th

Main menu 26.5v
Panel volts 27.1v
Panel Amps 0.53a
Batter Volts 26.5v
Discharge 0.00 I have not used my inverter yet
Charge Ah 19Ah
Discharge Ah 0.00
Temp 23c
Load 16 I don't think I need to use the load side of the charger for anything
Error E0
and its on Bulk charge

This was after a good 8 hours of sunlight on my panels with some cloud

Today at 13:30 Oct 15

Main menu 27.8
Panel volts 28.6v
Panel Amps 8.35a
Batter Volts 28.0v
Discharge 0.00 I have not used my inverter yet
Charge Ah 43Ah
Discharge Ah 0.00
Temp 30c
Load 16
Error E0
and its on Bulk charge

So my questions are many to understand better but first I need to explain I want some heat in my shed as I spend a lot of time in it. Yes I do have mains power but that cost money and I wanted solar to save me this cost.

1/. How long to charge my batts on a nice day and a cloudy day.
2/. How high will the voltage go as its a 24 volt system.
3/ Will the Ah hit 50 Ah when the batteries are charged.
4/. Do I need a batter monitor so I know the charge level better.
5/. How many watt can I expect to be able to use in 24 hours daily.
6/. I understand I need to fully charge batts at least once a month for better batt life, so do I ned to add more panel to speed up the charge rate.
7/. if yes the to 6/. do I need another charge controller or can this one handle another 4 panels.
8/. Should I also be thinking of getting more batteries for cloudy days to hold a charge longer.

Last year I heated my shed with candles and flower pots, not ideal and not warm enough but I managed and looking forward to a better year this year.

I wish you all well and good health and thank you for any help you can offer, Peter

 

[chrisski]

1/. How long to charge my batts on a nice day and a cloudy day.

That’s a hard to answer question Which spends on your area and time of year. I can get 20 kwh on a sunny day, but have seen less than 1 kWh on a cloudy day.

Look at the solar calculator in my signature block to see an average local production for your area adjusted for weather.

2/. How high will the voltage go as its a 24 volt system.

The batteries should be charged IAW with the documentation. There’s a charge (Bulk/Absorption) and float value.

3/ Will the Ah hit 50 Ah when the batteries are charged.

Probably won’t read 50 ah.

The batteries probably had something in them when you charged them. My ah meter rests after each day. You had 19 ah day 1 and 43 ah on day 2. An inverter can have an idle draw. Mine is 1 amp. That’s 24 ah a day.

4/. Do I need a batter monitor so I know the charge level better.

Absolutely. Many are out there. On the high end I use a Victron BMV 712. Bit pricey but may adjustments and easy monitoring. On the low end I use a AI Li battery monitor.

5/. How many watt can I expect to be able to use in 24 hours daily.

Need a good power audit. A battery monitor will help that, along with a kilawatt meter. My power requirements are perhaps 1 kWh on a perfect weather day, and as high as 20 kWh when I turn the AC on.

For my area with my setup and on a sunny day, I can expect 2X the panel wattage in the winter, and 5x the panel wattage in the summer. So 480 watts of panels about 1 kwh in the winter and 5 kwh in the summer.

6/. I understand I need to fully charge batts at least once a month for better batt life, so do I ned to add more panel to speed up the charge rate.

More panels are always better, as long as the max charge rate of the battery is not exceeded and the max input of the SCC is not exceeded. You may be able to double your panels. After you use the system a little, you’ll see if this is right for you.

7/. if yes the to 6/. do I need another charge controller or can this one handle another 4 panels.

You have a 60 amp SCC, so if you add like panels, than no. A 60 amp SCC likely can exceed the charging rate for your 50 ah battery pack. The caveat to this is once you put different sized panels in, best to put these on a different SCC.

 

[CavPeter]

That’s a hard to answer question Which spends on your area and time of year. I can get 20 kwh on a sunny day, but have seen less than 1 kWh on a cloudy day.

Look at the solar calculator in my signature block to see an average local production for your area adjusted for weather.

The batteries should be charged IAW with the documentation. There’s a charge (Bulk/Absorption) and float value.

Probably won’t read 50 ah.

The batteries probably had something in them when you charged them. My ah meter rests after each day. You had 19 ah day 1 and 43 ah on day 2. An inverter can have an idle draw. Mine is 1 amp. That’s 24 ah a day.

Absolutely. Many are out there. On the high end I use a Victron BMV 712. Bit pricey but may adjustments and easy monitoring. On the low end I use a AI Li battery monitor.

Need a good power audit. A battery monitor will help that, along with a kilawatt meter. My power requirements are perhaps 1 kWh on a perfect weather day, and as high as 20 kWh when I turn the AC on.

For my area with my setup and on a sunny day, I can expect 2X the panel wattage in the winter, and 5x the panel wattage in the summer. So 480 watts of panels about 1 kwh in the winter and 5 kwh in the summer.

More panels are always better, as long as the max charge rate of the battery is not exceeded and the max input of the SCC is not exceeded. You may be able to double your panels. After you use the system a little, you’ll see if this is right for you.

You have a 60 amp SCC, so if you add like panels, than no. A 60 amp SCC likely can exceed the charging rate for your 50 ah battery pack. The caveat to this is once you put different sized panels in, best to put these on a different SCC.

Thank you for a fast reply and help, I just ordered a Victron Energy MPPT Control - SCC900500000 from Amazon. My charge controller now shows BOOST not BULK and my panels shows 41.8 volts but the Amps shows 0.00 Amps and I have 46 Ah showing, I take it the batts are now charged or will it go higher and end up on EQUATIZE.

 

[Doggydogworld]

4 120 watt monocrystlline panels in series to give me a total of 480 watts.

Four panels in series sounds very wrong to me.

It'd help to know panel specs, but I'll guess these have an optimum working voltage (Vmp) of ~18V and can deliver ~6.67A of current in full sun. Four in series would be 72V @ 6.67A = 480W. But 72V is way too high for your battery. A PWM controller in bulk mode simply direct-connects the panels to the battery. There is no voltage conversion. When directly connected panel voltage will drop to nearly equal the battery voltage. Current will increase, but only a tiny bit. So in full sun, ideal conditions your 480W array is actually putting out something like 28V * 7A = 196W. You'll generally get fewer Amps due to lower sun angle this time of year, clouds, shading from nearby trees or structures, sub-optimal panel orientation, etc. So maybe 28V * 5A = 140W when the sun is directly facing your panels, even less before and after that.

I'd immediately switch the panels to 2S2P. That should deliver almost twice the power through your PWM controller to the battery.

An MPPT controller should do even better because it can convert voltages. So the array will operate near the ~72V optimum and in ideal conditions the MPPT will feed the battery something like 28V * 17A = 476W. But the Victron SCC900500000 is not an MPPT controller. It's just a monitor that works with their controllers. Unless I'm mistaken you should cancel that order ASAP.

I started and found the batteries had minimal charge and at the end of the first day my charger displayed

Time 17:30 Oct 14th

Main menu 26.5v
Panel volts 27.1v
Panel Amps 0.53a
Batter Volts 26.5v
Discharge 0.00 I have not used my inverter yet
Charge Ah 19Ah

This was after a good 8 hours of sunlight on my panels with some cloud

19Ah does seem low, but SW orientation means you won't get much production in the morning hours. Then if you have some afternoon clouds....

Also, even a little shade on one panel can kill output for an entire series array.

Discharge is usually what goes out the controller's "Load" port. The controller doesn't know what goes out the battery to your inverter. The inverter consumes power 24x7 even when it just sits idle.

Today at 13:30 Oct 15

Main menu 27.8
Panel volts 28.6v
Panel Amps 8.35a
Batter Volts 28.0v
Discharge 0.00 I have not used my inverter yet
Charge Ah 43Ah

This is usually cumulative, so 19 Ah the first (partial) day plus another 24 Ah the second.

So my questions are many to understand better but first I need to explain I want some heat in my shed as I spend a lot of time in it. Yes I do have mains power but that cost money and I wanted solar to save me this cost.

It's hard to save money with solar + storage unless you have extremely high rates and/or get very generous subsidies.

Heating with solar is especially difficult, because you need the most heat early in the AM when the panels are not yet producing. Heat pumps give you about 3x as much heat per kWh as resistance heaters (less when outside temps are far below freezing). Passive solar gives you about 5x as much as resistance heat, but like panels doesn't help much around dawn when you really need it.

1/. How long to charge my batts on a nice day and a cloudy day.

PVWatts can estimate panel production for your exact location and configuration.

2/. How high will the voltage go as its a 24 volt system.

"24V" LiFePO4 is nominally 25.6V. It has a "flat curve", so resting voltage should be close to that across a wide range of SOC (e.g. 15-85%). The curve has "knees" at both ends -- voltage increase rapidly as you approach 100% SOC and decreases rapidly as you get near 0%.

You have to apply additional voltage to force it to charge, so expect 27V or so while charging (depending on where you measure, there's a little voltage drop along every wire and at every connection).

3/ Will the Ah hit 50 Ah when the batteries are charged.

Like I said, I think that's cumulative. And your controller doesn't really know about battery discharge except via the Load port (which is only good for tiny loads like a light bulb).

4/. Do I need a batter monitor so I know the charge level better.

Yes.

5/. How many watt can I expect to be able to use in 24 hours daily.

PVWatts mentioned above can estimate panel output. It's up to you to move those watts efficiently through your system.

6/. I understand I need to fully charge batts at least once a month for better batt life, so do I ned to add more panel to speed up the charge rate.

You should have enough panels for a full charge, even in winter, unless you're pretty far north.

7/. if yes the to 6/. do I need another charge controller or can this one handle another 4 panels.

Your PWM can send 60A to the batteries, which is more than I'd do. But a 2S4P array of 120W panels would only produce ~27A, well under your controller's limit and probably no problem for the batteries.

8/. Should I also be thinking of getting more batteries for cloudy days to hold a charge longer.

Let's fix the other problems first.

Last year I heated my shed with candles and flower pots, not ideal and not warm enough but I managed and looking forward to a better year this year.

It's hard to beat combustion for heating. I'd look at small wood stoves, or maybe propane if in a desert area.

You might also be able to find some old solar heat collectors cheap or free on Craigslist. Pretty fiddly, and not productive at dawn when you most need heat so you have to rig up storage somehow.

Another way to warm up in the early morning is with a stationary generator. You won't generate economically useful amounts of electricity, but you will be warm!

 

[Geokilroy]

Two 50ah batteries in series still only = 50ah. If an inverter uses about 24ah a day, that leaves about 14ah useable (Drawing batteries down to 20% remaining). Not very much for what he wants to do.

I think more batteries is a top consideration. And then compute panel needs for charging more batteries.

The price of LiFePo4 is coming down. Two more 50ah batteries in 2s2p would put him in a much better situation. 24v 100ah would be about 65ah useable after inverter draw.