Battery bank : lead acid

Try searching for or going to "", tab "Solar", "AGM Batteries" then find V6-225 on the page
A few thoughts to consider
1.) Harbor Freight is a terrible place to buy solar panels - You should be paying $1 per watt or less
2.) How many panels you need to recharge any battery bank is dependent on how much load the batteries are powering
3.) Lead acid batteries should never be pulled down to less than 50% SOC
4.) If your main load is a refrigerator, it won't be pulling the rated wattage 24/7 - It will cycle on and off and use much less
5.) A small 12 volt refrigerator will draw much less than a 120 unit running on an inverter - Don't buy a larger refrigerator than you actually need
6.) Peukerts Law has a lot to do with how much power you can draw from lead acid batteries - Not so much for lithiums
7.) No amount of calculation will give you accurate measurements of what you'll need in real world usage

I hate to mention it; however, I have 3@ harbor freight 100watt plug and play systems hooked up for a couple years now charging to a 1200+- ah battery bank and I have lights in 6 rooms and my controllers ar pegged at 13.2v.
I can't explain this.
Granted I have 2200watts of PV arriving today and I plan on immediately hooking up an additional 710 watts; but, my 200 amp service has been shut off for a week and I have continuous lights.
This link says 15A to 55A charge current, so about 0.07C to 0.25C

Thanks again.
Guess what.
I have decided to go to 24 v and wire the whole sh*t show to this animal:

MPP and a few other manufacturers now sell a "complete off grid system in a box" that has:

AC Inverter

Solar Charge Controller

AC Battery Charger

Automatic Transfer Switch (if grid power is available)

Circuit Breakers/ Temperature Protection/ Custom Charge Profiles

And they work! Instead of cutting/stripping/crimping wires for hours, and calculating fuse and wire gauge sizes, you can choose a package below and assemble it in minutes!

LoL ,you tried to tell me. 12 v is such an expensive headache!
Take care and thankyou for your help.
I assume others have mentioned this but let me add this. I ran the life cycle costs on LiFePo4 versus AGM batteries. The LiFePo4's came out significantly ahead as being the overall cheaper option. They do require a higher up front cost however.

They absorb and discharge more energy at any given moment. The have SIGNIFICANTLY more cycles over their life span. I have 3x 300 watt panels. Previously I had 10 200 ah AGM's connected to this system. At no point in that configuration did I see more than 600 watts going through the MPPT. I just installed (and am still fighting) LiFePo4's and BMS's in my installation. On a test run though I got a glimpse at the potential. I saw the full 900 watts running to the batteries at one point on a sunny day.

They are also much lighter and flexible in how you can mount them. The only issue I am fighting is that Im getting conflicting information (and experience) in running BMS's in parallel. This is the only issue I am still fighting. As of right now, I feel like I moved from a Model T (AGM) to a late Model A (LiFePo4). It takes a bit of a learning curve to move up, but well worth it overall.
Good luck with the install and congratulations on the upgrade. Those Li-ion BMS systems are very impressive. At the same time it looks like a wiring nightmare. Nothing to complicated you just cant get your wires crossed.
I took a look at the BMS Setup, very nice! This might help ya.

Personally, I am hoping I can move my 12v AGM to 24v; hopefully this will keep things cool; also, I have to setup 2k PV to 400ah AGM ( 4s2p 6v 225 ah) hopefully i can use them to maintain DC lights and a 12amp deep freeze. I wont know untill i try. With no doubt, I plan to save up for a Li-ion sys ;or, the next new technology available buy the time I get enough money.
Question, on your 10 atm battery sys did you allow for a ventilation sys? I am wondering and concerned about the 2k PV possibly boiling the battery bank. Is this possible or probable?
On my first system of 12 v 300ah (deep cell marine batteries) I filled the basement with ( rotten egg) gas.
I briefly researched the dangers of hydrogen ;but, it sounds to me like the buildup of gas in the basement is not good ofcourse yet the info I got led me to believe that the gas needs to be a very high concentration in a small enclosed area.
I was concerned that the pilot lights in the basement would be a danger.
Good luck with everything.
Be safe.
I did once overcook an AGM battery in a motorcycle using battery charger. It stank, and was swollen so difficult to pull out of the frame.

With correct voltage and max current settings, and a temperature sensor, the batteries should never overcharge.
Maybe at end of life when some cells go bad and drop in voltage, then the remaining ones would be charged to excessive voltage. You would probably notice quite diminished capacity before then.

My 8x 6V AGM batteries are outside, under a deck, with a sheet of corrugated plastic roofing over them. No concern of gas buildup.

My PV capacity is large enough to charge at about 0.6C, but the system is configured to regulate that to 0.2C.
I am still waiting for my PV panels to arrive.
I was wondering about what you think of a 2 kw PV system and a 24v 4s2p 450 ah bank trying to run emergency DC light in 6 rooms a d also trying to keep a deep freeze on chill ( 120v 12 amps) and possibly a 115v, 1 amp refrigerator running.
Off the top of your head is that balanced?
Additionally, I am reworking the math. I can't seem to incorporate the concept of charging and c rate.
Is there some good info on this?

24V x 450 Ah = 10,800 Wh
2kW PV would be 0.2C, probably an OK charge rate.

120V x 12A = 1440W
115V x 1A = 115W

1500W (0.15C) is a perfectly acceptable discharge rate.

What matters is watt-hours. Look up a consumer energy label for the appliances.
If the deep freeze is already down to temperature (you didn't just pick up some road-kill on a 100 degree day and throw it in the freezer), then consumption might be 1500 Wh to 2500 Wh. That would be no problem for either PV or battery.

If you did just fill the freezer, then 2kW of PV x 5 hours = 10 kWh/day. The 1500W load will run about 6 hours each day. It can take a few days to cool a freezer full of food. Might be a couple of weeks only running 6 hours per day, better set up a smoker instead. Unless you're trying to age the meat.
Lol, I will have to focus on discharge and charge rate and try to wrap my head around that c rate of the vmaxtank.
Anyway. Thanks, I would probably just use the deep freeze and throw a couple bags of ice in it on a hot pull down.
I got some panels in today.
One of them had a blotch of rusty corrosion under the glass.
Do you think it will cause problems?


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Are you sure it's not on the surface, can't be removed?
How does contamination reach an area in the middle of a cell, sandwiched between glass and silicon?

I wouldn't consider that acceptable unless it came as a pile of cheap as-is junk.
If you ordered a pallet of panels, send a picture to the seller, maybe get a credit. But would your array be complete without it? I ordered extras.
Well it seems to be under the glass. I will have to contact san-tan.
The are new and under warranty so I will have to deal with it. I dont have the MPPT
Are hybrids anygood?
I want the all in one system but I think they will out of stock by friday:(.
So, I will have time to mess with the pannel.
There are top brands and off-brands of hybrids. I don't have first-hand experience with any.
All I've used is Sunny Boy and Sunny Island.
It depends on what you're trying to power, the environment it will be exposed to, quality you want and price.
How does one calculate the fuse needed to fuse a 5 foot 4awg positive wire from the MPPT to the 24 v battery bank?
I have 6 PV panels and I will run them in as 2s3p.
The 3 strings feeding the MPPT will max out at 32 amps each ?
So, does that mean I have an input of 96 amps ?

I have a :

PIP LV2424 MSD 24V 2.4kW, 120V Output, 2kW Solar Input 80A Mppt

For a single conductor in free air, 4 awg with 90 degree C insulation has ampacity (and maximum fuse) is 140A

If 4 awg in a cable, 95A

80 x 1.25 = 100A breaker.

Even if in a cable so 95A ampacity, I think you're allowed to round up to the next standard size (100A)

But that would be if you had a separate MPPT charger between your 2kW PV array and battery.
Using LV2424 hybrid, I think there's just one pair of cables between hybrid and battery, so it has to carry current for the inverter.

Manual says 2kVA unit, 109A and 4 awg.
109 x 1.25 = 136A fuse
Maybe you can wire with 4 awg 90 degree C in free air and fuse at 150A. Or better to use 105 degree C insulation (at full load the cable will be hot enough to burn you.)

Can you fit 2 awg wire instead?
I like 2awg because the setup is at the moment will need the positive and negative to be 3' long.