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monkeydeck
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# Posted: 16 Apr 2019 06:30
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im in the process of researching and designing a solar system for my off grid cabin. Im leaning toward a 48v chevy volt or nissan leaf battery bank. My location is in northern NY state and it gets cold. Ive read you shouldnt charge lithium below freezing. What are my options beyond bringing my batteries home between visits and keeping my cabin above freezing all winter?
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Nobadays
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# Posted: 16 Apr 2019 07:47
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We will be installing 1,500 watt system with 8kw of Chevy Volt lithium battery modules (4 × 2kw modules). I have been corresponding with Kelvin at Bobolink Solar (Creeky on here) about the same issue.
He says he uses a highly insulated box to hold both the modules and the inverter- which as he puts it is a 40 watt heater - I assume as long as it is switched on. He claims this is good down to about 20* F then the use of a battery blanket. He said this could be put on a thermostatic controller ( like an Inkbird) to come on at 40, off at 50. I was considering a seed warming mat under a piece of aluminum to both spread the warmth and guard the modules in the event of a problem with the mat over heating. These 10"×20" are 17.5w each so only a 35w draw when on.... I will use a thermostatic controller.
It is either something like this or switch to FLA in the winter if we are not there. It doesn't hurt the lithium to set in the cold just to charge them when they are below freezing.
If you come up with other solutions I'm all ears!
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Nate R
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# Posted: 16 Apr 2019 08:05
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Morningstar's Prostar MPPT controllers will allow to you program them to taper the charge amps down to no charging below a certain temperature. So you can have reduced charging at say 45 degrees, and 0 charging at 32 degrees if you'd like.
This would allow you to leave them hooked up, and only add charge when they are above freezing. (Along with a battery temp sensor.)
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Atlincabin
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# Posted: 16 Apr 2019 09:16
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Small pad heater (mine is about 30W) with a thermostatic controller in an insulated box has worked well for me over the last winter. I have 3, 24V Volt batteries (it's a rather small system).
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Nobadays
Member
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# Posted: 16 Apr 2019 09:22
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Nate... I've already purchased a Schneider 4048 inv/charge. I've read through the manual but don't see an option like that for my equipment. It does have a temp sensor but as yet haven't figured out if that can be used to shut off charging at a specified temperature. I think the battery temp sensor is normally used to tailor the charge so it may be possible if settings allow.
We won't be able to get into the cabin until May. I'm hoping to digest all the info I can find before then.
On holiday right now, start hi,ing the West Highland Way tomorrow!
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creeky
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# Posted: 16 Apr 2019 10:17
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The SW is a bit of a pain for lithium at 12S. I have learned this to my dismay this winter.
You have to be very careful with the charge parameters when using the SW charger. I had a customer set up for 48v max charge (the max the Volt modules like) and it went to 48 fine in testing. Once installed, and it may be the user fiddled with the settings reinvoking the defaults) the 48v was surpassed. Luckily the charge level did not reach a damaging level.
We rebuilt the LG chem pack to 14S as a result.
Heating the batteries is what most folks do. Inside an insulated box. I have my inverter inside the same box. Worked the ticket. THX Nobadays for explaining the process.
If you're using an SW for genny charging what I'm suggesting right now is use 120v only. And put a transfer switch that watches the battery voltage and disconnects the genny. OR charge manually.
I charge manually. It is so rare that I need to start the genny (haven't in two years and used less than 20 in gas the last season I needed to); that I check my voltages in the a.m. and if I need a charge I start the genny, make breakfast, turn off the genny/charge cycle. Then, at supper, I check the voltage, if necessary I start the genny/charge cycle and turn off after supper.
Everyone is different of course. But the great thing about lithium is you don't need to fully charge. Just enough to get through to the next sunny day and you're golden.
If you can find a Nissan pack they can be configured for 14S quite easily. The downside is the battery is unlikely to last as long as the LG Chem cells from the Volt.
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monkeydeck
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# Posted: 16 Apr 2019 11:05
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thank you for the replies, can you please explain what 12s and 14s is creeky?
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Brettny
Member
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# Posted: 16 Apr 2019 13:55
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14 cells in Series. 12 cells in Series. Every time you add cells in series they keep the same capacity but add to the voltage.
Series vs parallel circuit. Im sure theres a good youtube video about it.
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Steve_S
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# Posted: 16 Apr 2019 14:20
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Another possible option for you as your in build mode.
I built a separate Powerhouse / Pumphouse which not only has my well head & 50gal pressure tank in it but all the solar kit too. It is a small Hyper Insulate building in which I installed a recovered RV Furnace (out of a 20' Terry Taurus Trailer) that uses 12V and propane. The 12V is supplied by a separate Big AGM battery charged by it's own 100W panel but I have a line to my battery bank which has 12V if needed. The thermostat is set to the lowest setting it can @ 40F and is only on during winter months. Note I am near Algonquin Park, quite a bit further north, so winters can be serious.
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Nobadays
Member
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# Posted: 16 Apr 2019 14:50
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Steve_s..... thank you for another idea, hope this helps monkeydeck! Certainly made me think.... my solar "room" will be a small cubby under the stairwell, so easily super insulated and to top it off, the back of the propane fridge is exposed to the space. If the fridge is left on (not sure I would do that all winter while we are away...) it would throw off enough heat, if I seal up around it to perhaps heat the space. Maybe a 12v fan to help circulate the air.
Lots of ideas here! Thank you monkeydeck for starting this discussion!
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Steve_S
Member
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# Posted: 16 Apr 2019 15:41
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@ Nobadays, there are little devices which read temps and activate accordingly that could suit many folks as well. The idea is pretty simple, it's a fancy plug with temp sensor, once that temp is reached the circuit is activated and then you could have a small heater or whatever to generate heat in that area.
REF to one example of many. If you look on Amazon there is a huge assortment with various temp settings and some which are adjustable.
https://www.globalindustrial.ca/p/hvac/controls/thermostats/tempro-freeze-protection- plug-in-thermostat-tp526?infoParam.campaignId=T9F&gclid=EAIaIQobChMIttyavq7V4QIVD_5kC h0LIA9EEAQYASABEgKgWPD_BwE
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Nobadays
Member
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# Posted: 16 Apr 2019 15:55
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Steve_s... see my first post... I use Inkbird temperature controllers for managing temps of fermenting wine and a Johnson Controls one for my kegerator. The only issue would be running an electric space heater on solar...if snow covers the panels and there is not enough energy produced to keep up with demand ( assuming we left it on during the winter months) lots to think about. I'm still leaning toward seedbed warmers on a thermostaticly controlled outlet since the draw would be quite low and would only heat the batteries. I am may have the satellite internet on all winter with camera feeds so could likely get some kind of device that would tell me if the temps are dropping too low or the heater has failed. (I'm 9 hours away so no running up to save the system...) I didn't opt for network system controller because we are not certain we will leave the satellite internet on and if it will be reliable in the winter with snow on the dish.
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monkeydeck
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# Posted: 17 Apr 2019 00:10 - Edited by: monkeydeck
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lots of great ideas here, thank you everyone, I like the electric heat ideas but I worry about the panels getting covered and running the cells down. What if i had more panels than i need and orient them close to vertical in the winter when im not there to keep the snow off?
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Nobadays
Member
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# Posted: 17 Apr 2019 01:12
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Monkeydeck..... snow covering is my worry as well, like the idea of near vertical panels. Mine will be fixed at 45* and though not impossible to get at in the winter it will require climbing a ladder affixed to a metal roof. I have a much flatter porch roof below the main array... might be able to mount several near vertical panels there for winter generation.
Ground mount just isn't an option at this time.... how do others deal with snow? Or do you just take your batteries and go home in the winter?
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neckless
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# Posted: 19 Apr 2019 10:19
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i was thinking to make a ground bunker 3 ft deep well insulated top ....or like a root seller even for my flooded battery's because i have no solar for nov. and dec i have to take battery's home so they dont freeze i might just build a root seller but would not like to store food with battery's ...
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NorthRick
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# Posted: 19 Apr 2019 15:32
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Quoting: neckless even for my flooded battery's because i have no solar for nov. and dec i have to take battery's home so they dont freeze
A fully charged FLA battery won't freeze until it hits -92F. Even at 85% charged, the freezing point is -62F. In cold weather the rate of self-discharge slows down so they will maintain their charge for a good while if you fully charge them and then disconnect them from any load.
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razmichael
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# Posted: 19 Apr 2019 18:44
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As NorthRick states. I leave mine connected all winter (minimal draw - motion sensor/flood light and couple of game cameras). I know the panels get lots of snow on them but still enough to keep them topped up with no far. In Quebec so it gets really cold! I have only ever gone up once in the winter and checked them - fully charged. Lots of advantages with lithium but this is the one area where FLA wins.
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Ontario lakeside
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# Posted: 19 Apr 2019 21:18 - Edited by: Ontario lakeside
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We left our lithium pack disconnected at about 75% all last winter. Unheated cabin in Ontario so plenty cold. The pack lost a small fraction of its charge and performed perfectly all the following year. We also own a Chevy volt, it sits in extreme cold weather unplugged with no ill effects. I say charge it, disconnect and forget about it until spring!
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creeky
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# Posted: 20 Apr 2019 13:10
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It is okay to store batteries at very cold temps. However if you're actually trying to use them. All batteries must be kept warm.
The amount of power a well insulated box needs to stay above 0 degrees? Not much. Full time/winter users heat battery boxes.
A recent install I saw put the batteries in the second washroom. A small direct vent propane heater plus a well insulated small space. Perfect. And, as a bonus, the washroom is warm upon arrival.
Popular is monitoring via phone/home automation. And actually turn on and off with temp gauge, timer or manually.
Ontario. Here's to many years to come!
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Wilbour
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# Posted: 20 Apr 2019 19:15
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Quoting: creeky Ontario. Here's to many years to come!
Is that on our new auto plates?
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monkeydeck
Member
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# Posted: 20 Apr 2019 23:31
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good stuff,
any thoughts on vertically orienting panels to keep snow off?
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Nobadays
Member
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# Posted: 21 Apr 2019 01:35
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I have to pay year-round (the first 2 years) for satellite internet so want to instal a camera or two so we can check in during the winter.
Quoting: razmichael Lots of advantages with lithium but this is the one area where FLA wins.
Right now have a 12v FLA system for the water pump, might convert that to keep the internet and cameras going in the winter.
Quoting: monkeydeck any thoughts on vertically orienting panels to keep snow off?
I have a railing on the south side of the house that gets a lot of winter sun....shading in the morning and late afternoon... but I'm thinking of mounting maybe 2 or 3 - 250w panels vertically to that railing... no snow will stay on those. Can't see why it wouldn't work.
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spoofer
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# Posted: 22 Apr 2019 23:09
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My problem on the Tug Hill of NY is keeping snow off my panel. Even vertical it picks up to much snow and ice. I have 2 six volt golf cart batteries wired together and am afraid they will freeze over winter. We usually get over 20 feet a winter. The most east of the rockies.
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monkeydeck
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# Posted: 23 Apr 2019 10:12
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Spoofer im on the east side of the hill, I wonder if it could be coated with something to repel the snow
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