Questions about my off-grid 1kW system in southern India

[sakthi]

Here is my setup located in southern India:
1. Four 250W 24 volt panels in parallel
2. Phocos CXN 40 charge controller
3. 8 Batteries 24 volts total (four 12V 100 amp-hour in parallel in series with four more 12V 100 amp-hour in parallel)
4. Single 220V Inverter that is offgrid

Here are my results:
1. Get about 32Volt open circuit
2. Get about 28Volt with load (connected to battery bank)
3. Maximum instantaneous current ever collected is 28 amps
4. Maximum panel teperature is about 105 degrees Fahrenheit

Usage:
1. Adjust panels every month and now (November) at 20 degrees off zenith
2. Dust off the panels from any bird dropings and dust every morning
3. Check batteries for distilled water level
4. Use power from solar for the all of the lights and ceiling fans and computers
5. Use solar power from 8AM till the battery bank reaches 30% charge left (around 8PM)

Questions:
1. Am I getting enough power from my current setup?
2. If I am not getting enough how can I maximize my investment?
3. What is the proper way to use my battery bank to maximize long life of the batteries

I would greatly appreciate your advice and suggesions.

[Sunking]

Not real clear what you are saying about the panel specs, something is not right. A typical 250 watt 24 volt panels would have Voc = 44 volts, Vmp = 36 volts, Imp = 6.9 amps.

A1. Cannot tell as I do not know your panel specs. Something is not right because you should 36 volts Vmp. I suspect the voltages you have given are taken with a PWM controller.
A2. Get a MPPT Charge controller. If the maximum charge current you have ever seen is 28 amps sounds right using standard 250 watt with a Imp of 7 amps x 4 = 28 amps. But here is the catch. A PWM controller will turn a 1000 watt array into about 670 watts is what you are observing with 28 amps x 24 volts = 672 watts. Use a MPPT charge controller and you will see the charge current up around 40 amps.
A3. There is no way to maximize your battery life. You did everything you could possible do to get the least amount of battery life using 4 parallel string. You want to use only 1 single string. So if you wanted a 400 AH battery you should have bought 400 AH batteries. At that AH level you are looking for 6 volt L16 type batteries with 4 of them in series to make 24 volts.

[sakthi]

Clarification

1. The panels are made in India (Banglore to be more specific).
2. I measured each panel without any load with a multimeter and I get 32 Volts.
I have been suspecting that these panels may not be of good quality. I did order a MPPT controller and should I arrive shortly.
My question about the battery bank is, how much can I drain it everyday before going to grid? My current bank takes about 2 hours to get to reach 100% from 30%. Can I drain it even further by taking it down to 5% every night without compramizeing battery life? and I do understand it will take longer to charge in the morning.

[inetdog]

My question about the battery bank is, how much can I drain it everyday before going to grid? My current bank takes about 2 hours to get to reach 100% from 30%. Can I drain it even further by taking it down to 5% every night without compramizeing battery life? and I do understand it will take longer to charge in the morning.

For maximum battery life you should not discharge them to below 80% on a routine basis, with 50% as the threshold for unusual situations like several days without sun combined with a grid outage.
If you will be switching to mains power or using mains power for charging, you should try not to go below 75-80%.
If you use batteries on an a less than daily basis, such as an average of one power interruption per week, the number of discharge cycles in the batteries will become less important and you can justify discharge to a lower level.
If you go down to 20% your battery life will be short, and if you go as low as 5% you are killing your batteries.

[Naptown]

How many individual cells are in each panel? That voltage sounds like 60 cell grid tie

[Wy_White_Wolf]

...5. Use solar power from 8AM till the battery bank reaches 30% charge left (around 8PM)....

How are you determining this?

If by battery voltage then you are getting false readings. Batteries have to be at rest for at least 2 hours before voltage can have any reflection on SoS.

WWW

[Sunking]

If by battery voltage then you are getting false readings. Batteries have to be at rest for at least 2 hours before voltage can have any reflection on SoS.

+1 WWW. Battery voltages are just about completely useless while under discharge or being charged. Even after being rested for several hours is only a ball park guess. Only true measure of the SOC is a temperature corrected hydrometer reading.

[sakthi]

How many individual cells are in each panel? That voltage sounds like 60 cell grid tie

Yes, each one is a 60 cell grid tie panel.

[sakthi]

+1 WWW. Battery voltages are just about completely useless while under discharge or being charged. Even after being rested for several hours is only a ball park guess. Only true measure of the SOC is a temperature corrected hydrometer reading.

I agree with you that battery voltage is not a pure surrogate for the SOC (State of Charge?) but that is what available for my setup. The voltage readings are from the Phocos CXN 40 charge controller software which I independently verified with a multimeter.
In case, if you are wondering, why am I using it extensively, where I live, we have power outage of close to 10 hours per day intermittently and I am paying about 20 cents per unit kWh.

[Naptown]

Yes, each one is a 60 cell grid tie panel.

You are not feeding enough voltage to the batteries with those in parallel. I did not check the charge controller for top end voltage or type but you need to make 2 series strings of 2 panels with the strings in parallel. You will also need to make sure your charge controller is a true MPPT controller capable of handling the open circuit voltage.
That controller is a PWM controller you need to replace it.

[Wy_White_Wolf]

I agree with you that battery voltage is not a pure surrogate for the SOC (State of Charge?) but that is what available for my setup. The voltage readings are from the Phocos CXN 40 charge controller software which I independently verified with a multimeter.
In case, if you are wondering, why am I using it extensively, where I live, we have power outage of close to 10 hours per day intermittently and I am paying about 20 cents per unit kWh.

You need to compare the voltage readings to that of a temperature corrected hydrometer to have any idea of SOC. Comparing it to a multimeter is worthless.

I'd bet your not getting the batteries fully charged and/or only running on the top 25%. If you are truely draining the batteries to 30% SOC, they will be short lived and need replaced within the first year.

WWW

[Wy_White_Wolf]

...8 Batteries 24 volts total (four 12V 100 amp-hour in parallel in series with four more 12V 100 amp-hour in parallel)...

8 batteries * 12V * 100AH = 9600WH

...My current bank takes about 2 hours to get to reach 100% from 30%. ...

9600WH * 70% = 6720WH

There's no way 1000 watts of panels can do that. Either your numbers are so far off they are meaningless or you've already lost over 70% of the batteries capacity due to abuse.

WWW