Battery capacity setting for IP40 Charge Controller

[mapmaker]

These batteries are only 2 years old (gel type - 24 x BAE 2v 6 PVV 660 Secura solar) and I would have though with our moderate usage (general indications in previous post), and the large 48v battery bank, we would get more than 2 days worth. Any thoughts?

Generally speaking, gel batteries are not suitable for solar applications, but these specific ones are an exception... they can handle the higher currents that are needed in RE. I don't know much about your batteries, but the specs seem to require a minimum of I₁₀ for charging current. I don't know what I₁₀ means.

Regardless, as has been mentioned, you don't have enough solar panel to charge those batteries.

could you hazard a guess as to why if the batteries are fully charged and then the clouds set in for days, we only get 2 days battery power before needing to use the generator?

Why do you think the batteries are fully charged? I'm not saying they're not... I just don't know and I wonder how you know.

--mapmaker

[Solar40]

Thanks again Mapmaker, I'm in the process of determining KwH/day usage. It will take some time.

In the meantime, could you hazard a guess as to why if the batteries are fully charged and then the clouds set in for days, we only get 2 days battery power before needing to use the generator?

These batteries are only 2 years old (gel type - 24 x BAE 2v 6 PVV 660 Secura solar) and I would have though with our moderate usage (general indications in previous post), and the large 48v battery bank, we would get more than 2 days worth. Any thoughts?

[mapmaker]

The system was installed 23 years ago. We've had it for the past 16 years and have only used it occasionally.

That was typical back then... batteries were cheap and panels were dear. Now that has been reversed. Living off grid is all about keeping your batteries happy.

Soon we'd (two of us) like to live in it full-time.
<snip>
What would you recommend?

Design a system on paper and then figure out how much, if any, of your current system you can use.

We can help with the design, but engineering is about hard numbers. We need to know your loads, climate, resources.

If you asked me which pickup truck to buy I would ask you to tell me your load (how many lbs you intend to carry or tow). Same goes for power systems... what are your loads?

To know your loads, you must know your daily kwh use, your peak wattage draw, and the time of day that you draw these loads. Give me numbers and I will give you a plan.

--mapmaker

[Solar40]

Thanks Mapmaker, indeed, at best these panels only bring in 15 - 20 amps.

The system was installed 23 years ago. We've had it for the past 16 years and have only used it occasionally. Soon we'd (two of us) like to live in it full-time.

We're off grid and run 2 medium sized fridges, tv, lights, 24hr 71w air pump for sewerage, water pump to pump from rainwater tank, 24hr inverter, so our power consumption isn't over the top.

We're coming into winter here (Sydney Australia) and get about 4-5 hours sun on the days of least light.
It would be great if the fully charged batteries supplied enough power to last 7 days without having to crank up the diesel generator.

What would you recommend?

[mapmaker]

are you suggesting that the solar system at 1.44kw isn't adequate for the 660Ah batteries?
We are having some problems with this system.

In a properly designed 48 volt system with a C/10 charge rate you would be able to push at least 66 amps into those batteries.

If your panels were producing 1440 watts (rare event) and your charge controller were 100% efficient (it's not) and your batteries were up near absorb (about 58 volts), you would be pushing only 1440 ÷ 58 = 24.8 amps into the battery.

--mapmaker

[Solar40]

Thanks Sunking, are you suggesting that the solar system at 1.44kw isn't adequate for the 660Ah batteries?
We are having some problems with this system.

[Sunking]

C/20 charge current is way too low for a solar application. Typically if designed properly the charge rate will fall between C/12 on the low side up to C/8 on the high side for flooded batteries. So for a 48 volt battery system with 660 AH battery minimum panel wattage required is 2750 watts with 55 amp charge current.

Only way to see a charge current of C/20 on a solar application is if you are using 8 or more days of battery autonomy. But for 5 days C/12 to C/8 is where it falls.

[Solar40]

Hi, does anyone know if the current BCAP setting - 660Ah - is correct?

48v battery bank (24 x 6 PVV 660 - BAE Secura PVV Cell solar)
Charge Controller (Plasmtronics PL40)
Solar panels ( 24 x 60w)

My concern is that it should be set to the C20h setting of 596Ah.

Thanks