HELP: Battery Voltage Quick Drop After Sundown

[LowVoltagw]

A little history, I am a complete PV Noobie, Have read a lot of information on the internet and different forums but no actual hands on experience until now. I have property that I am building a cabin on for full time living, but as of now we are living in our 5th wheel while we build. Grid power is a little over a quarter mile away and is the easy choice, except they require a well, septic and a min 500sq ft foundation in place just to come out and give an estimate for cost to run power to my place. Hence I decided to go off grid for now and more than likely always. System I have- 3 renogy 250 watt poly panels 24v 8.29amp wired in series connected to a sun mppt 5015a 50amp charge controller through 10 gauge wire at 20ft. 4 crown cr-430 batteries wired in series for 12v with 2 banks in parallel for 460amp hrs at 20hrs. All battery wiring including from charge controller is #1 gauge, all premade, all parts are new. Panels are mounted 10 feet off ground and adjustable with full sun all day, set at 55 degrees for my area for this time of year. N Central AR. Facing 3 degrees to the se from due south. Charging at full sun voltage is showing 13.6 to 13.8 and 50 amps. The problem I am having is most of the time I only get 80% to 90% charge and as soon as the sun goes down my batteries drp to 70%. The few times I have gotten 100% charge batteries drop to 80% and put any type of load and percentage drops as far down as 30% in a half hour of light use IE: cell phone charging, or tv and dvd player. I know my inverter is oversized for my set-up, 2000watt, but I am not using anything but above listed cell, tv and dvd. Everything else runs off rv batteries on 12 volt or propane. Also batteries drp voltage with inverter on or off. Sorry for the long read, but the more info I give the better for you to understand.

[mike3367]

you need to read sunkings are you klilling your battery's. i can tell ya 13.6 volts is to low to get your battery's charged. after reading his
post i know have my controller set at 14.8 and float is at 14 volts and im never down below 70% anymore

[LowVoltagw]

Thanks I will look at that as I am not sure of the settings. I know problem is something simple, but getting info over phone as I am on the road. Will look at system as soon as I get home.

[Bucho]

So first of all how are you determining how full your batteries are?

[Sunking]

I have- 3 renogy 250 watt poly panels 24v 8.29amp wired in series connected to a sun mppt 5015a 50amp charge controller through 10 gauge wire at 20ft. 4 crown cr-430 batteries wired in series for 12v with 2 banks in parallel for 460amp hrs at 20hrs..

OK your battery configuration makes no fricken sense at all. Crown CR-430 batteries are 6-volt 430 AH. If you wired them for 12 volts, huge mistake, is 12 volts @ 860 AH. If wired in series is 24 volts @ 430 AH is how they should be wired.

OK your first huge mistake is going with 12 volts, you are pissing a lot of money away and very inefficient. By wiring your batteries for 12 volts you cut 50% of their life time. With 12 or 24 minimum panel wattage is 1000 watts. Now here is where you really screwed up big time. If wired at 12 volts with 1000 watts requires a 80 amp controller. You only have 50 amps. With a 50 amp Controller the maximum panel input power is 650 watts ands you are trying to run 750 watts. You are throwing 100 watts away going 12 volts as you have already exceeded the maximum power Input.

If wired for 24 volt battery, you only need a 40 amp controller. Not only a smaller controller but a lot smaller inexpensive wire.

So first thing you need to do is throw away the 12 volt Inverter, get a 24 volt 1000 watt inverter, rewire the batteries for 24 volts, and add another 250 watt panel.
Then we can work and educate to forget what your SOC meter is telling you.

[LowVoltagw]

Sorry for the delay getting back on here, been a very hectic few weeks. First off, Mike3367 Thank you for info, told me what I needed to know. Second, Bucho, I am using a hydrometer and checking cell by cell after I got home to see what was happening for myself. And Third, Sunking, yes I know I should have wired for 24 volts and that was the original plan, but due to financial concerns due to moving and other things I have going on in my life, I chose to use a 12v inverter that I already had for a temporary time frame instead of spending the extra coin on a new 24v inverter. Also wire size was used as original placement of my panels was dictating a longer run from panels to charge controller, which I was able to change to a shorter run. The controller is rated for 700w of panels on 12v and 1400w on 24v, so I am only 50w over. After disconnecting charge controller and making sure bulk settings were at 50amps batteries are charging as the should, for now. I will be going 24v on the system within the next week or so, will not wait long to do so as I know it will be a stronger system. Then yes I will need to be educated on things. Only working on book knowledge here, so practical knowledge is what I am seeking

[LowVoltagw]

24v, 4 250 watt panels, 1000 watt 24v inverter. Panels are wired 2 in series and two strings parallel. Charge voltage goes as high as 27.8 and batteries show to be holding at 26.2 at full dark. I have not had a chance to ck open voltage or with hydrometer yet, but the seen to be holding better under use. Also should I consider a different charge controller, I am considering a hybrid system at a later point, combination wind and solar after the cabin is done as we will be living here full time and have a lot of cloudy days in the winter but good wind flow as well, I know I will be changing controller then but no definite as to if or when. So educate me please. And while your at it, give me a definitive answer why higher voltage at half the storage capacity is better. Thank you in advance for the help.

[Mike90250]

...... And while your at it, give me a definitive answer why higher voltage at half the storage capacity is better......

Current Density. The amps in low voltage wires increase beyond economic thresholds. Thick wire is expensive, heavy, hard to bend, won't fit connectors, requires expensive large lugs. Circuit breaker and fuse costs skyrocket over 80A (DC rated).
charge controllers - you need twice as much controller with low voltages. That can be a huge cost

[LowVoltagw]

Current Density. The amps in low voltage wires increase beyond economic thresholds. Thick wire is expensive, heavy, hard to bend, won't fit connectors, requires expensive large lugs. Circuit breaker and fuse costs skyrocket over 80A (DC rated).
charge controllers - you need twice as much controller with low voltages. That can be a huge cost

Quick, plain and to the point, Now I understand. So, What is the best way to add amp hour capacity for those of us who cannot afford 4 grand in 2v batteries all at once. I have read both add multiple banks and not to add multiple banks

[SunEagle]

Quick, plain and to the point, Now I understand. So, What is the best way to add amp hour capacity for those of us who cannot afford 4 grand in 2v batteries all at once. I have read both add multiple banks and not to add multiple banks

First off any type of battery system is expensive. If you go cheap in the beginning or decide to make it will all parallel wired components then you run a high risk of killing of one or more of the batteries. Going with high Ah low voltage batteries costs more up front but gets you a much higher chance they will last longer and produce more.

You have to do the math. Purchasing cheap batteries more often (every couple of years) may be higher in cost then purchasing high quality batteries every 5 to 6 years.

[LowVoltagw]

First off any type of battery system is expensive. If you go cheap in the beginning or decide to make it will all parallel wired components then you run a high risk of killing of one or more of the batteries. Going with high Ah low voltage batteries costs more up front but gets you a much higher chance they will last longer and produce more.

You have to do the math. Purchasing cheap batteries more often (every couple of years) may be higher in cost then purchasing high quality batteries every 5 to 6 years.

And this I do understand, which is why I bought what I thought would be a decent compromise in capacity and longevity. Only time will tell.

[SunEagle]

And this I do understand, which is why I bought what I thought would be a decent compromise in capacity and longevity. Only time will tell.

Keep us informed on how well your system performs. Thanks for the input.