Best battery setup with 7 12v 100ah batteries?

[Teyrex]

Hi guys and gals, I'm brand new to the forum and solar systems so please go easy on me with my beginner questions.

I have a small cabin on a lake that gets used mainly during the summer months, we currently have a very very novice solar system setup and working but I feel it needs to be tweaked in order to run the appliances we'd like to when it's hot outside and we have the entire family visiting.

Currently we have 7 100ah 12v AGM batteries in parallel as our battery bank. (we were given these batteries as they came out of service at a local communications company, so I don't fully know the state of the batteries).
-200 watt solar panel ( about 5 years old now)
- cheapo 30amp charge controller
-1500watt modified sign wave inverter

The issues we seem to be constantly running into is that when we have a full cabin and it's ho outside we're running 4 x flood standing house fans, a couple usb style baby noise devices overnight and we're running the batteries down through the evening. This seems so odd to me since if I understand the battery setup we have 700 amp hrs or 8400 watt hrs of battery which should be more then enough no?

A couple things to also mention, when I woke up and saw that our bank was down to 11.6v I ran the generator all day with a 30amp ac to dc charger on the batteries and the charge controller never showed that it when into "float mode" does that indicate we might have bad batteries that aren't able to take on a full charge?

Things that we'd like to be able to run:

- Around 12 LED bulbs but never on all at once or on for very long right now.
- TV for the news in the morning (2 hrs) LED tv and satellite box
- A movie in the evening every now and then
- 4 or 5 fans when it's hot in the evenings
- 12v for the logic on our RV style propane fridge
- run the oven which has a glow plug that flips on and off to start the propane and regulate temperature. (pies are important okay!) haha

THANK YOU to your help!!
Mike

 

[sunshine_eggo]

Hi guys and gals, I'm brand new to the forum and solar systems so please go easy on me with my beginner questions.

I have a small cabin on a lake that gets used mainly during the summer months, we currently have a very very novice solar system setup and working but I feel it needs to be tweaked in order to run the appliances we'd like to when it's hot outside and we have the entire family visiting.

Currently we have 7 100ah 12v AGM batteries in parallel as our battery bank. (we were given these batteries as they came out of service at a local communications company, so I don't fully know the state of the batteries).

700Ah of AGM should be charged at 70-140A. charging at significantly lower currents encourages sulfation and capacity loss.

-200 watt solar panel ( about 5 years old now)

200W/12V = 17A - way under 70A

- cheapo 30amp charge controller

Way under 70A.

What charge controller?

What 200W panel?

-1500watt modified sign wave inverter

MSW inverters can be way less efficient. Some devices consume more power on MSW vs. PSW.

The issues we seem to be constantly running into is that when we have a full cabin and it's ho outside we're running 4 x flood standing house fans, a couple usb style baby noise devices overnight and we're running the batteries down through the evening. This seems so odd to me since if I understand the battery setup we have 700 amp hrs or 8400 watt hrs of battery which should be more then enough no?

Battery capacity determines how much you can use between charges. Your solar determines how much you can use sustainably for one day.

Your 200W panel MIGHT be able to produce 1000Wh/day with fantastic solar conditions with full solar exposure from sunrise to sunset (facing due south, proper tilt and zero shading).

A couple things to also mention, when I woke up and saw that our bank was down to 11.6v I ran the generator all day with a 30amp ac to dc charger on the batteries and the charge controller never showed that it when into "float mode" does that indicate we might have bad batteries that aren't able to take on a full charge?

Maybe, but more probable that you're just using way more than your solar can provide on a daily basis.

700Ah / 30A = 23 hours to charge from empty assuming you use absolutely no power for those 23 hours.

8400Wh / 1000Wh/day = 8.4 days to charge purely from solar assuming you use absolutely no power for those 8.4 days.

Things that we'd like to be able to run:

- Around 12 LED bulbs but never on all at once or on for very long right now.
- TV for the news in the morning (2 hrs) LED tv and satellite box
- A movie in the evening every now and then
- 4 or 5 fans when it's hot in the evenings
- 12v for the logic on our RV style propane fridge
- run the oven which has a glow plug that flips on and off to start the propane and regulate temperature. (pies are important okay!) haha

Unfortunately, the list is meaningless until you establish the daily Wh requirement for each item and sum the total.

Based purely on your battery size, healthy charge rates and assuming you have fantastic solar conditions, you need to immediately add:

(70Ah - 17Ah) * 12V = 636W of solar (round up to 800W).

Assuming you can utilize the remaining 13A of your 30A controller, you'll need to add another 50A of MPPT charging to accommodate the larger array.

Recommend replacing MSW inverter with PSW. Possibly an inverter/charger, so you can charge directly with the generator.