Off Grid Wisconsin

[Photowhit]

Just the insulating will help keep them warm, the charging warms them and the insulation will help them stay warmer. I don't draw much in the winter so don't worry too much.

Heating uses a good bit of energy, but if you must, hunt the internet for an article about using a AC heat strip, I can't recall it all, but basically they will work with thermostat on DC if you reduce their length in relation to the voltage. Still this is heating with solar, and we all should avoid if possible.

Maybe survive this winter and build a berm shelter for the batteries for next winter.

[cpm]

Just like Photowit says,

The process of charging will result in surplus heat,
The batteries themselves have a *lot* of thermal mass
So, just get them into an insulated box, and you should
be just fine.

no need for additional heat, really.

[TomW]

Just to affirm what the others are saying, unless you are in an arctic situation of deep cold for months you probably are fine installing them in an insulated & ventilated box.

Vents are essential to let the outgassing escape so it does not create an explosion hazard or rot the metals in the box like terminals, cable, etc.

Just from here.

Tom

[ClassicCrazy]

Check - insulated box will be the next project - getting some amps going into them was the first project  -  ha ha .

[Volvo Farmer]

I put my first set of batteries in an insulated box. They stayed warm enough all winter that I could keep distilled water in the battery box without freezing. They got quite warm in that box if I tried to equalize them in the summer though.  When I replaced them, I decided to ditch the box. It has been ten below zero here for a week with highs in the twenties. Voltage is a little lower in the mornings, but since we're only 125Ahr out of a 800Ahr bank overnight, I don't need the extra capacity and I'm hoping to gain longevity by letting them run cold.

[Halfcrazy]

It is definitely a double edged sword. If you insulate them well they are happy in the winter but unhappy in the summer. While cold just reduces there available capacity at the moment, heat will do permanent damage. I tend to insulate mine and then uncover them in the summer. Mine live in the shop that is heated to 45F during the winter, but can get into the 80's in the summer. I probably worry to much about keeping them warm but they stay 60-70F this time of year just from there own heat.


PS pay no attention to the cables they are temporary as the new Trojans have the terminals turned 90 degrees and I had not made new cables as of that picture.
Ryan

[Vic]

Zero F wasn't one of those some values, more like mid 60s to mid 70s.

But I could be wrong, but my rule of thumb is that batteries like what we
like, temp wise. Where we do the best work, is where they do the best work.

Batteries are just fine down to @-15f (@-25c) but they loose 1/2 of their capacity. My batteries live outside in Missouri and have been fine down to the annual -10-15 max low, but I don't use them much in winter being the summer battery hog. If your in a substained -15 or so you want to watch how far you draw down the battery, since it has less capacity it looses capacity quicker and SG and then you can run into issues.

Well battery life is halved for every 10 degree C increase in temps above 25C,  and believe doubled for every 10 C below 25 C.  My reference had nothing to do with capacity or freezing,  but really health.   Beyond  freezing the battery for its given SOC,  I do wonder about other effects,  as mentioned -- stratification/electrolyte mobility + the accuracy of the temp compensation during charge.  There are limits beyond freeze or capacity  concerns.

But  am not worried down to about 32 F for the banks here,  as they have more capacity than normally needed.  Opinions,  Vic

[Vern Faulkner]

Ryan: looks to me like you have a series-parallel setup. The longtimers at Solarpanel talk all advocate avoiding parallel, entirely, based on the logic that the resistance in one leg will be different from another, leading to unbalanced workloads/charging.

What's your thoughts on that point of view?

[Halfcrazy]

Well I have always gone with the theory 1 string is optimum, 2 is just fine and 3 is acceptable. Unfortunately there is not always a perfect solution for a particular need in Amp Hours. 2 volt cells make sense and have some merit as if one or two fail you can still operate.

Ryan

[boB]

Of course a proper battery balancer will make it OK to parallel almost as many strings as you need.

boB

[Vern Faulkner]

Of course a proper battery balancer will make it OK to parallel almost as many strings as you need.

boB

Never heard of such a thing. 'Splain?

My issue here is that I've done the power consumption analysis/forecast for our future home and have deemed a daily use of just less than 1,200 watt/hours per day.  Assuming a five-day sunless period, I'd need a battery bank of 1000 AH at 12v, 500 AH at 24v.

My current plan, then, would be to run a 24-volt pack (since the 12v, 1000 amp/hour pack would require a charge current greater than a single controller could produce). The only reasonable way to make 24v at 500 a/h, as I see it, is to slide six 2v-500 AH rolls-surrette batteries in line.

But it would be less expensive to series-parallel 2 x 4 trojan 6v 370 AH batteries, and that would also allow a greater reserve.

[vtmaps]

Vents are essential to let the outgassing escape so it does not create an explosion hazard or rot the metals in the box like terminals, cable, etc.

Hi Tom, I've got a little nit to pick on that advice.  The gasses are not corrosive.  What is corrosive is the sulfuric acid mist that escapes from the cells while they are gassing.  As the gas bubbles break the surface of the electrolyte they suspend tiny droplets of electrolyte in the air.  Some of this mist escapes through the battery vent.

Some folks aim the vents on their battery caps away from the terminal lugs to help prevent corrosion.  A better solution is to buy Water Miser vent caps.  These are NOT the type of cap that has a catalyst to recombine H2 and O2.  These caps have a column of plastic beads on which the mist condenses and drips back into the battery.

Most venders sell only one size, but if you order from the manufacturer you can order one of three sizes.  The taller the size, the better they work.

--vtMaps

[TomW]

vtmaps;

Not to be argumentative but..

Just 2 comments;

OK "when / if the gasses recombine they create a corrosive environment". Venting helps prevent this.

I have had terrible luck with those watersavers being more messy than the stock caps and did not see any real water savings and did see a lot more wet cell tops. Used them on 2 different banks with same issues.

Just my experience.

Tom

[ClassicCrazy]

New and improved - now with  15 minute insulated battery box.

[Photowhit]

Looks dang pretty compared to my scraps of styrofoam, insulating!