Solar system dead after cold winter

[Cavesson]

Help! My off-grid solar system is dead! Last November, I finally finished installing my system and had it working nicely. In late December, I left the country for a 2 ½ month vacation and returned a few days ago to find the whole system down and batteries severely depleted.

The equipment I have is as follows. A True South tower holds 3,825 watts of panels (15 Silfab panels x 255 watts each) and runs 75 feet on AWG 3 cables to the house. Batteries are a rack of 8 Fiamm AGM 12 volts/135 Amp-hour wired to give me 48 volts. It’s all tied together with a prewired Magnum 4448 PAE Power Center with a Midnite Classic 150 charge controller purchased from Wholesalesolar.

I left the system up and running in late December and flew off to Thailand for 2 ½ months to stay warm. Temperatures in Southern Ontario dipped to record low temperatures while I was gone and snowfall was heavy. There was no heat in the house so batteries could have gotten down to as low as 0 Fahrenheit but I wasn’t too worried as they were fullly charged when I left. The only utility I left running was my sump pump as I often have trouble with water in the spring in my crawlspace. The crawlspace now has two feet of water in it so I’m thinking that possibly the pump discharge froze and split and the pump kept running incessantly recirculating the water until the batteries got discharged (assuming that on several days that the solar panels would have been snow-covered, failing to recharge the batteries.)

Yesterday, I measured the voltage on the solar panels and there was a reading of about 100 volts coming in to the house so I don’t think there’s any problem there. I measured a couple of batteries and they were reading around 5 volts. The charge controller has a couple of lights on the lower left that flash every 15 seconds or so but the information panel is dark. It flashes on for a split second when I turn the DC disconnect on and off but then dies. The inverter switches are also dead and don't respond at all.

The temperature in the house is now about 22 degrees F. so the batteries would still be frozen. I’ve left home today to visit friends in Florida for two weeks and when I get back to Ontario, I hope the air will be above freezing. Any advice on what to do next?

[Naptown]

Look at the sump pump and rule out anything out of th ordinary.
What type of battery are you using?

[Sunking]

Something had to drain the batteries down, and something went wrong with the CC.

That said your batteries are toast and need replaced, and you will have to replace them to find out what failed. It was not cold weather other than the possibility the panels got covered in snow, and the sump pump drained the batteries down before the snow covered panels thawed out.

[Johann]

The pump or something else drained your batteries and you have to check into this first and fix it if needed.

Looks like that the system shut itself down to protect itself from self destruction.
Some charge controllers and/or inverters will not operate if the battery is not within a specific range/voltage. If the battery voltage is way out of range the charge controllers and/or inverters may see the batteries as over charged...under charged... or may even see a battery as damaged and they may shut the system off. 5 volt per battery is very low and a battery bank that should have around 48 volts would measure 20 volts now, yes I can see that a charge controller shuts down to prevent further damage, since it is set up for a 48 volts system.

You may have to disconnect the batteries from the system and charge those batteries with an external charger first before you are able to get this system running again. It may take 1 day or more to charge those really dead batteries so be very patient; and when you start charging the amp draw may be very low and may look like that the batteries are not charging.

[Cavesson]

Dead batteries

The pump or something else drained your batteries and you have to check into this first and fix it if needed.

Looks like that the system shut itself down to protect itself from self destruction.
Some charge controllers and/or inverters will not operate if the battery is not within a specific range/voltage. If the battery voltage is way out of range the charge controllers and/or inverters may see the batteries as over charged...under charged... or may even see a battery as damaged and they may shut the system off. 5 volt per battery is very low and a battery bank that should have around 48 volts would measure 20 volts now, yes I can see that a charge controller shuts down to prevent further damage, since it is set up for a 48 volts system.

You may have to disconnect the batteries from the system and charge those batteries with an external charger first before you are able to get this system running again. It may take 1 day or more to charge those really dead batteries so be very patient; and when you start charging the amp draw may be very low and may look like that the batteries are not charging.

Thanks for the advice. I'll charge the batteries slowly, one at a time. They're Glass Mat batteries so perhaps they didn't sustain any permanent damage. I'll let you know how things turn out.

[SunEagle]

Thanks for the advice. I'll charge the batteries slowly, one at a time. They're Glass Mat batteries so perhaps they didn't sustain any permanent damage. I'll let you know how things turn out.

You may be able to get a little life out of those batteries if they charge to test and maybe find out where the electrical drain problem is but they really have no true life and need to be replaced.

Maybe having someone come by and check your system every couple of days when you are gone would be cheaper than replacing the batteries next year.

[ChrisOlson]

I've brought several stone dead off-grid systems back online in my day. Here's how you do it.

Firstly, none of your equipment is going to start on only 5 VDC, including the inverter. So you can't use the genset and inverter/charger to bring the batteries back.

Flip off all the combiner breakers on the arrays. Pull the PV input wires out of the Classic 150 and wire nut a couple wires to them. Hook the other end of the wires to the battery bank + and -. Make absolutely certain you do not have any frozen cells by physically inspecting each one. A frozen cell could cause a battery explosion. Flip on the combiner breakers with the arrays hooked direct to the batteries and use the arrays to bring the batts up for a day.

Safety considerations:
Keep explosion-proof covers over the batteries (like in a wood case) because the possibility of a battery popping a top is pretty good if you have a shorted cell someplace. If one pops off you'll have acid everywhere so it's best to have it contained instead of being sprayed all over your equipment.
DO NOT handle any loose connections from a 100 VDC array. You'll have a nice blue welding arc about 2" long that will easily melt lead battery terminals. Make sure all connections are tight before you turn on the combiner breakers.

If you have a DC voltmeter I'd hook that up so you can monitor the voltage on the bank while it charges. If it skyrockets past 60 volts right away, flip off the combiner breakers and go buy new batteries. They're junk. If it slowly starts coming up then things are looking good and just leave the panels hooked up until the batteries get gassing good and your voltage gets up to 58V or so. Then shut the arrays down and see if you can start your equipment. If the inverter and Classic fires up, then you can hook everything back to normal, absorb charge and equalize the batteries and assess what you have left for a battery bank.

[ChrisOlson]

They're Glass Mat batteries

Oh. I was assuming flooded when I wrote my previous post. Same difference, just that you can't really check for frozen cells and you're not gonna gas 'em. All you can do is warm them up to make sure the mats aren't froze, then hook the arrays up direct and see if you can bring 'em back. AGM's can sometimes thermal-runaway if you got a problem with them. But I expect fairly poor performance from your solar arrays being hooked direct, so I don't think you'll get enough amps going to them to drive them that hard.

[mapmaker]

If your theory (sump pump ran the batteries down) is correct, it could have been easily prevented by setting the low voltage disconnect on your Magnum to 48 volts.

--mapmaker

[Johann]

Can a battery freeze?

The only way that a battery can freeze is if it is left in a state of partial or complete discharged. As the state of charge in a battery decreases, the electrolyte becomes more like water and the freezing temperature increases. The freezing temperature of the electrolyte in a fully charged battery is -92.0oF. At a 40% state of charge, electrolyte will freeze if the temperature reaches approximately 16.0oF.

[ChrisOlson]

If your theory (sump pump ran the batteries down) is correct, it could have been easily prevented by setting the low voltage disconnect on your Magnum to 48 volts.

The sump pump obviously didn't do it. Most 48V inverters won't even run much below about 40 volts, no matter what you have the LBCO set at. I'm guessing the Classic went belly up and sacked the bank out. The Classic will run fine on the PV input alone, without the batteries even hooked up. I've run mine on PV alone with the DC breaker to the bank shut off many times. From what was described it sounds like a dead controller. That's why I'd bypass it and use the arrays hooked direct to bring the bank back up. Once you get power so you can fire equipment up, then you can properly assess the situation.

[Cavesson]

I'm happy to report that my frozen system is now up and running and there doesn't appear to be any damage or loss of performance yet. I first disconnected the eight glass mat batteries and gave them each a four hour charge (bringing them from 5 volts up to about 11.5 volts) with a car battery charger and a long extension cord to the neighbor's house. Then I reconnected everything and started the system up. I measured 45 volts coming out of the battery bank. The inverter and charge controller turned on and the solar panels charged the batteries up over the next couple of days to 54 volts. I found out that my system automatically shuts down at 40 volts so the snow-covered panels and a running sump pump, must have drained the batteries and shut the system down. Then the batteries continued to discharge to 5 volts each. So far, so good. Thanks for the advice, guys!

[Johann]

I'm happy to report that my frozen system is now up and running and there doesn't appear to be any damage or loss of performance yet. I first disconnected the eight glass mat batteries and gave them each a four hour charge (bringing them from 5 volts up to about 11.5 volts) with a car battery charger and a long extension cord to the neighbor's house. Then I reconnected everything and started the system up. I measured 45 volts coming out of the battery bank. The inverter and charge controller turned on and the solar panels charged the batteries up over the next couple of days to 54 volts. I found out that my system automatically shuts down at 40 volts so the snow-covered panels and a running sump pump, must have drained the batteries and shut the system down. Then the batteries continued to discharge to 5 volts each. So far, so good. Thanks for the advice, guys!

I am so glad that you got it work again.