Offgrid system not powering up -- batteries too cold?

PorkChopsMmm · February 2012

Some of you may remember when I installed an Outback VFX3648, a string of 6 240 watt panels hooked up to an Outback MX60 MPPT controller, Outback MATE, etc. All of this is hooked up to 8 225 amp our 6V golf cart batteries purchased new in August 2011. Everything was working well and I got some warnings from you guys about the batteries getting too cold in the winters here in Michigan since I have everything installed in a shed that is not heated or insulated.

Well, I haven't been out to our cabin for a few months and was just out there today. What I found was less than ideal. Although I left everything powered up I arrived to find the inverter, charge controller, and MATE off. I checked the acid in a few of the batteries and they weren't frozen, although using a hydrometer I think the battery acid was less than 30 degrees, but again not frozen solid or even icy. I fired up my generator to try and get everything up an running and I was surprised when the inverter didn't come on with the external AC source.

Any idea why the inverter wouldn't power on with the external AC power? I know my batteries may not have enough juice to power everything up but I thought the inverter would power up with the generator input since it is an inverter/charger. Any advice?

BB. · February 2012

Re: Offgrid system not powering up -- batteries too cold?

What was the battery bank voltage before charging?

-Bill

westbranch · February 2012

Re: Offgrid system not powering up -- batteries too cold?

"I arrived to find the inverter, charge controller, and MATE off."

Can you expand on this statement?.
thanks

Cariboocoot · February 2012

Re: Offgrid system not powering up -- batteries too cold?

Default on Outback inverters is "invert". Even with an AC IN source they will not click over to "charge" without sufficient battery Voltage to run the circuitry. If the bank was less than 40 Volts it will shut down.

I'll hazard a guess that your panels super-conducted in the cold temps, raisin the Voc above the MX60's 150 Volt maximum causing it to shut down. It would not reconnect on its own. Deprived of a charge source, the batteries went dead shutting down everything else.

When you leave a remote system like this, keep the charge controller connected but physically disconnect the inverter. That way even if the charging fails the batteries will only be subject to self-discharge, which ironically is less in cold temps than warm.

Check out the array configuration and see if its Voc * 1.3 exceeds 150.

PorkChopsMmm · February 2012

Re: Offgrid system not powering up -- batteries too cold?

Do you mean before I turned on the generator today? Not sure -- I didn't have a voltmeter with me and since the MX60 and MATE were dead I couldn't check it that way.

A few months ago it was getting up to 49 + volts when I left, sun was shining. So I figure it go up to full charge.

westbranch · February 2012

Re: Offgrid system not powering up -- batteries too cold?

do you have a plain old 12v charger out there? you could give each 12 v set a quick charge to get above the minimum or at least try.

TnAndy · February 2012

Re: Offgrid system not powering up -- batteries too cold?

PorkChopsMmm wrote: »

Some of you may remember when I installed an Outback VFX3648, a string of 6 240 watt panels hooked up to an Outback MX60 MPPT controller, Outback MATE, etc.

If you literally "A" string, as in ONE string of six 240w panels, then I'd second Cariboocoot's theory.....too much voltage in for an MX60 even before it got real cold, or you hit a nice clear cold day with bright sun on snowpack.....even 2 strings of 3 might have done it considering the local conditions and VOC.

icarus · February 2012

Re: Offgrid system not powering up -- batteries too cold?

The cold isn't going to hurt the batteries per se. If they are allowed to go dead that is another matter.

Tony

PorkChopsMmm · February 2012

Re: Offgrid system not powering up -- batteries too cold?

westbranch wrote: »

do you have a plain old 12v charger out there? you could give each 12 v set a quick charge to get above the minimum or at least try.

Wish I did have a 12V charger -- I do not. Come to think of it... I have no idea how I am going to fix this other than to pull all 8 batteries back to my house, hook them up in sets of 2 to make 12v, and buy a 12v charger. Not awesome.

Thanks for the info!

Cariboocoot wrote: »

Check out the array configuration and see if its Voc * 1.3 exceeds 150.

Here are my specs... so 36*1.3= 46.8. I am guessing you multiply 46.8*3 to reflect the panels are in a series... so 140.4? To clarify -- I have 2 series of 3 240W panels.
Rated Power (Max) 240W
Tolerance +- 5%
Voltage at PMax (Vmp) 30.0V
Current at Pmax (Imp) 8.0 A
Open-Circuit Voltage (Voc) 36.0 V
Short-Circuit Current (Isc) 8.96 A
Nominal Operating Cell Temp (NOCT) 45 +- 2 degrees Celcius
Maximum System Voltage 600VDC
Maximum Series Fuse Rating 15A
Operating Temperature -40 to + 85 degrees Celcius
Fire Resistance Class C
Cell Technology Poly-Si

Blackcherry04 · February 2012

Re: Offgrid system not powering up -- batteries too cold?

You could go to a Golf Cart Shop and see if they'll loan you or rent you a 48 V charger for a couple days. They are kind of lonely this time of year. Once you give the inverter some power it'll fire up. I have just hooked a 12 V battery with Jumper cables to the first two batteries in the string and that was enough to start them. You'll probably need around 42 V, disconnect all the loads from the inverter. Since you don't know how much Voltage you have, it hard to say. I guess you have a generator ??

PorkChopsMmm · February 2012

Re: Offgrid system not powering up -- batteries too cold?

icarus wrote: »

The cold isn't going to hurt the batteries per se. If they are allowed to go dead that is another matter.

Tony

I will check with my voltmeter tomorrow. I know the hard way that the Outback inverter will shut off at ~45 volts or so.

Besides taking the batteries home and charging them up -- is there away to force the Outback inverter to start up even though the battery voltage is/may be low?

Cariboocoot · February 2012

Re: Offgrid system not powering up -- batteries too cold?

Yes that's right: three 36 Voc panels in series = 108 Volts * 1.3 means a potential Voc of 140.
Now here's what I forgot to mention first time: different revisions of the MX60 have different V-max shutdown points. The 150 Volts is the "point of no return" - do not exceed this or things fry. But if you look at Page 9 of the manual http://www.outbackpower.com/pdf/manuals/mx60_pv_mppt.pdf you see the latest revision shut-down Voltage is 141. I believe some of the earlier models will turn off before this. Once off, they don't restart on their own. Some people will say that the 1.3 cold temp factor is too high for Michigan, but they probably don't live in Michigan.

It still seems entirely likely that this is what happened: all the factors came together to cause the MX to turn off.

Even so, you still would have been all right if there was no load on the batteries. Even when turned "off" the VFX draws current. If you have to keep the system running under these circumstances you may need to re-think the design (three parallel strings of two panels in series won't work because the Vmp will be too low for a 48 Volt system) or change the controller to a MidNite Classic 150 or 200 (the Hyper Voc function on those is meant to deal with just such a situation).

Wouldn't it be easier to carry a 12 Volt battery charge to the batteries & generator rather than carry the batteries to the charger?

I think the default low Voltage for the 48 system is 42. Once the battery bank is above that the VFX should operate again.

PorkChopsMmm · February 2012

Re: Offgrid system not powering up -- batteries too cold?

Blackcherry04 wrote: »

You could go to a Golf Cart Shop and see if they'll loan you or rent you a 48 V charger for a couple days. They are kind of lonely this time of year. Once you give the inverter some power it'll fire up. I have just hooked a 12 V battery with Jumper cables to the first two batteries in the string and that was enough to start them. You'll probably need around 42 V, disconnect all the loads from the inverter. Since you don't know how much Voltage you have, it hard to say. I guess you have a generator ??

Good idea -- if I can't get magic to happen tomorrow I will call around to some nearby golf courses. I have a 2000 watt Coleman generator -- I had it running for ~30 minutes but nothing happened with the inverter. I can see why -- it wasn't charging the batteries. Worse case I will try what you said with the 12V charger.

Cariboocoot · February 2012

Re: Offgrid system not powering up -- batteries too cold?

Question; can you re-initialize the MX60? Once it is back up the panels should bring the batteries up to usable Voltage in a couple of days. Unless the batteries have been destroyed by this mishap.

PorkChopsMmm · February 2012

Re: Offgrid system not powering up -- batteries too cold?

Cariboocoot wrote: »

When you leave a remote system like this, keep the charge controller connected but physically disconnect the inverter. That way even if the charging fails the batteries will only be subject to self-discharge, which ironically is less in cold temps than warm.

I did this once, but then stopped. In Outback's literature they have you attach the Remote Temperature Sensor to the 1st device on the HUB, which they recommend is the inverter. When I turned off the inverter it turned off the RTS for the charge controller (I think). I should probably reconfigure this to the charge controller.

Cariboocoot · February 2012

Re: Offgrid system not powering up -- batteries too cold?

If the charge controller is the "main charging device" (usually it is) have the RTS on that. Or switch it between Winter (only charge controller connected including RTS) and Summer (everything hooked up).

Right now, if the batteries won't fire up the MX you can bypass it completely and feed the panels directly to the batteries to get some charge into them. Don't have anything else connected to the batteries, and remember to take the panels off the controller first then disconnect the batteries.

PorkChopsMmm · February 2012

Re: Offgrid system not powering up -- batteries too cold?

Cariboocoot wrote: »

Question; can you re-initialize the MX60? Once it is back up the panels should bring the batteries up to usable Voltage in a couple of days. Unless the batteries have been destroyed by this mishap.

How do I do this? After looking at page 9 I think 1.3 is a little much... for this winter. We have had extremely warm temperatures. We hardly have an inch of snow on the ground and temps have been in the twenties at night.

I saw this in the manual:
The controller will automatically restart operation once the PV array’s open
circuit voltage falls to a safe level (141 VDC). The amount of time required to reset is dependent on the
module type, ambient temperature, and the amount of sunlight directly on the PV array. Normally, the
controller starts in the morning within a few minutes of the PV array being in direct sunlight.

PorkChopsMmm · February 2012

Re: Offgrid system not powering up -- batteries too cold?

Cariboocoot wrote: »

Right now, if the batteries won't fire up the MX you can bypass it completely and feed the panels directly to the batteries to get some charge into them. Don't have anything else connected to the batteries, and remember to take the panels off the controller first then disconnect the batteries.

Awesome advice! I didn't even think of this. Thank you!
So... I would disconnect the inverter and temporarily hard wire my full array of panels panels to my buss bars -- charging up my full 48V array? It is supposed to be sunny tomorrow so this this should work well.

Cariboocoot · February 2012

Re: Offgrid system not powering up -- batteries too cold?

Again, cold temps and bright light ... something turned it off. The particular Voltage point is an issue of the revision; mine (old) shuts down somewhere around 136 Volts and will not restart. But Outback has made changes over the years.

It could also be a case of the inverter drawing over too many days of not enough sunlight. In any case, your batteries seem to be dead and that's what has to be dealt with.

To reset the MX, disconnect the panels first then disconnect everything from the batteries. Unplug the controller from the HUB just to be sure. Then go through the install procedure: connect the batteries and see if the screen lights up. You'll have to reconfigure it (defaults to 12 Volts). If the screen doesn't light up, the batteries are probably too low to activate it - which is unlikely since it only needs about 10 Volts to do this. If there isn't 10 Volts in a 48 Volt bank you've got to buy new batteries.

Let's just hope it isn't something worse that happened and has fried everything.

Cariboocoot · February 2012

Re: Offgrid system not powering up -- batteries too cold?

PorkChopsMmm wrote: »

Awesome advice! I didn't even think of this. Thank you!
So... I would disconnect the inverter and temporarily hard wire my full array of panels panels to my buss bars -- charging up my full 48V array? It is supposed to be sunny tomorrow so this this should work well.

Yes: array directly to battery buss bars. Like connecting them through a PWM controller in Bulk stage. Since the potential 90 Vmp will be dragged down to around 70 it won't be efficient, but I'm not suggesting you run it this way. Ought to suffice temporarily to get some charge in the batteries, if they'll take any.

PorkChopsMmm · February 2012

Re: Offgrid system not powering up -- batteries too cold?

Cariboocoot wrote: »

To reset the MX, disconnect the panels first then disconnect everything from the batteries. Unplug the controller from the HUB just to be sure. Then go through the install procedure: connect the batteries and see if the screen lights up. You'll have to reconfigure it (defaults to 12 Volts). If the screen doesn't light up, the batteries are probably too low to activate it - which is unlikely since it only needs about 10 Volts to do this. If there isn't 10 Volts in a 48 Volt bank you've got to buy new batteries.

Let's just hope it isn't something worse that happened and has fried everything.

Dude, this scares me. I have breakers/disconnects set up for the panels and power coming from the panels. The MX did not fire back up when I had the panels and power disconnected and then reconnected... which means either my batteries are less than 10V or parts of my set up are fried, right? Bah!

Cariboocoot · February 2012

Re: Offgrid system not powering up -- batteries too cold?

You need that DMM. Nothing like it for getting through the "disconnect and inspect" process.

First thing you must check is what the battery Voltage is. Remember that if they got too low and too cold they can freeze. Any signs of bloated cases or cracks? By now the water that may have leaked out could easily be evaporated. Water levels okay? Without battery power you aren't going to get any further.

PorkChopsMmm · February 2012

Re: Offgrid system not powering up -- batteries too cold?

Sorry, DMM? I am slow.

westbranch · February 2012

Re: Offgrid system not powering up -- batteries too cold?

digital multi meter

icarus · February 2012

Re: Offgrid system not powering up -- batteries too cold?

DDM=DVM=Digital Multi Meter.

Tony

niel · February 2012

Re: Offgrid system not powering up -- batteries too cold?

actually a dvm is more specialized as it is only a digital volt meter.

icarus · February 2012

Re: Offgrid system not powering up -- batteries too cold?

True dat!

Tony

PorkChopsMmm · February 2012

Re: Offgrid system not powering up -- batteries too cold?

Cariboocoot you were right! Well... unfortunately

I tested the batteries and at first came up with 6V!!!! Later tests showed 8V, but still too low for the MX60. I tried your trick of hooking the solar panels to the buss bars (after disconnecting everything else) and was able to fire up the MX60 a few minutes later. I put the RTS on the MX60 and left the inverter off. We had some good sun today. Below are some pictures.

Got everything hooked up and charging the bank. I think I was averaging ~1150 watts.

Notice the High VOC and the High Watts? It doesn't look like it recorded a high enough VOC to shutdown the MX60... but if it did have a spike and shutdown would it record it before powering off?

My humble temporary set up. Lots of funny weather these days. 45 degrees in February!

westbranch · February 2012

Re: Offgrid system not powering up -- batteries too cold?

78% of STC as panel output is not too bad

Cariboocoot · February 2012

Re: Offgrid system not powering up -- batteries too cold?

Oh my; a 48 Volt battery bank dragged down to 6 Volts?

That is not good. I hope you have a hydrometer ... and a lot of luck.
Unfortunately there's no way of telling when the High Watts and High Voc were recorded. We still don't know if the Voc did exceed 141 and shut down or if it was a very long stretch of cloudy weather that couldn't keep up with the inverter draw (if it's full on that's 23 Watts or 552 Watt hours per day) leading to hopelessly dead batteries.

So the next step is to see if the batteries will come up to full charge, and hold that charge.

PorkChopsMmm · February 2012

Re: Offgrid system not powering up -- batteries too cold?

westbranch wrote: »

78% of STC as panel output is not too bad

Thanks! I am sure I can gain some efficiencies with better wiring and the like. This is a temporary setup until I can properly mount them this summer.

Offgrid system not powering up -- batteries too cold?

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