inverter not working in extreme cold

Re: inverter not working in extreme cold

Joe94 wrote: »

I've been out working on my place the last couple weekends and the overnight temps have been in the single digits. When I wake up in the morning my inverter is not working, by about 10:00am everything is working fine again. I have 500 watts of panel charging a 440ah bank with a suresine inverter. I can't imagine I'm over taxing the system I'm only running few lights in the evening and charging my iPad. Probably a few hundred watts tops. Every thing that is wired for 12v runs fine but no inverter. It's only happened to me twice on very cold nights. I probably just need to get my volt meter out and test some things but I thought I start here for some pointers.

Having had two Suresine 300 watt inverters running for about 5 years, one 24/7, the other on power-save, waking up when it's loads turned on, and both located in an unheated outbuilding where the temps regularly dropped to minus 20C (0F) and sometimes minus 25C, I've never had a problem with the inverters shutting down other than when I grossly overloaded the tough little buggers. I've since replaced them with higher wattage inverters due to ever increasing loads.
My first thoughts about your situation is - - - battery voltage, especially with the days getting ever shorter and stormy this time of year as Winter approaches, resulting in less and less charge going into the batteries each day. Friend of mine recently ran into the same problem and killed his year old batteries. Deficit charging situation gradually brought his batteries to a lower and lower state of charge until finally the inverter started shutting down on low voltage.
Don't forget, the inverter if running continuously is also a load on your batteries. A load you don't see and therefore may not be aware of. If you don't need it running at night, shut it off. But first things first, and that's to try to salvage your batteries, hope they haven't sulfated and that they will take a full charge.

Re: inverter not working in extreme cold

My guess is that you re using more power than you think, and/or your batteries are/have been chronically undercharged, such that the inverter goes to disconnect. I would do a real evaluation of your loads and charging, and look at the basic health of your batteries. The fact that you state "Tht I can't imagine I'm over taxing the system" suggests that you have no real idea how you are loading and charging these batteries.

Good luck and keep in touch,

Tony

Re: inverter not working in extreme cold

Chronically undercharged/overdrawn batteries will get to "full charge" even though they have little capacity.

I suggest you do a good charge cycle, and then a load test.

I'm not sure you understand the difference between watts and watt/hours since you mention only running "95 WH". Are you saying that you routinely run 300 watts of load, or 300 WH total per day? 300 WH out of a 12 v battery bank is ~ 25 ah. The point is, try to get a real handle on your loads ( and charge regimen) and then figure out if you are really living within your means, so to speak. Also charge and load test the bank.

As for the cold, 0F is not that cold for batteries. If the cell temps are really that cold, you have a capacity significantly lower than at 70f. But will still be above ~60%. It is also unlikely the batteries are as cold as the ambient, unless they are subjected to wind. 0f overnight, might warm to 15 above during the day, and if they are inside the building will give them some heat, and they will develop some heat from PV charging. So your battery temps are likely to be several degrees F warmer that 0.

Good luck and keep in touch,

Tony

Re: inverter not working in extreme cold

The classic has a meter on it for the battery voltage. Whats it reading evening, and morning ?

A dumb pump sounds the same on 12V as it does on 11V, it's NOT a good indicator of charge.

Re: inverter not working in extreme cold

And that takes us back to failing batteries...

Re: inverter not working in extreme cold

Joe94 wrote: »

Both times I've noticed that the inverter is not on it has been 9:30 or so in the morning when the sun is out. .

What time does the sun strike your panels in the morning? How long has the sun been on the panels before you notice the problem? This time of year there is normally very little output from panels at or before 9 AM. At least in my part of the world.

Re: inverter not working in extreme cold

Will be very interesting to see what the volt meter shows. WXboy could possibly be right. The inverter shuts down when the DC input reaches a high of 15.5, or a low of 10 volts, although I seem to remember the low voltage cutoff being user selectable between 10 volts and perhaps 11.5 volts. I've had overvoltage shut down happen a few times, but only during extreme cold. It would however be unusual for such voltages to be reached so early in the morning unless the batteries were already almost fully charged, or have lost their capacity so APPEAR to the controller to be almost fully charged. The volt meter and WHEN the shutdown actually takes place, will tell all.

Re: inverter not working in extreme cold

Joe94 wrote: »

Update, I spent the weekend out at the house. The inverter did not shut down at all this weekend. It was about 20 degrees warmer this weekend then last. Last night I ran more loads on the system then normal and this morning at about 8:45 I put a volt meter on the breaker panel and was showing 14 volts. I ran things all day long today, and checked the battery voltage sometime after the sun went down. The Voltage was 12.95v. I usually don't draw down the batteries more then few hundred watts per night so its very likely they are mostly charged going into morning. Anyway, I just wanted to report back.

Well it's beginning to look like Wxboy may well be right when he said:

Wxboy wrote: »

My vote is for high voltage from temperature compensated charging shutting down the inverter.

But to verify, you'll have to see what the volt meter is saying on those cold mornings when the inverter shuts down. If it's reading 15.5 or higher - - BINGO!
But still, 15.5 is a long way from the 14 you found in the morning. And the next time it shuts down, disconnect the panels from the controller, allowing battery voltage to drop. Inverter should come back on when the voltage drops back to roughly 14, IF the shutdown was caused by over voltage.

This problem of my inverter shutting down due to high voltage in cold weather has really become a PITA. It has been very cold here recently and my battery bank has been sitting around -20C, and due to temp compensation my Suresine 300 is always shutting down (when the sun is shining), as voltage is limited to 15.5 volts. I have been considering how to improve this situation. If this system was used on a daily basis it would really be maddening, but it is only occasionally and lightly used.
My batteries are in an insulated box, in the tool shed, with the rest of the system. The box is somewhat over sized, so I could add some more insulation, that may help. I could move system into the cabin, but I don't really want to, as this would be a ton of work.
The Suresine 300 is a great little inverter but it has it's limitations. (15.5v max in this case). I have looked at some at the bigger "real" inverter/chargers, but for my purpose can't really justify the cost, as my power requirements are small. Looking at the other smaller inverters on our hosts site, ie; Exeltech, Samlex, they both list max voltage as 16.5v, which would address my problem I think. The Exceltech is rated to operate in temps as low as -25C, the Samlex is 0C. (The Suresine is -40C). Xantrex models I looked at were only 15 or 15.5 volts.
If I go the new inverter route I would probably switch to 24volt while I'm at it, as I would only have to rewire the battery bank.
Just sharing some thoughts as this potential problem did not occur to me when planning things out.