Looking for tips to improve out setup for cold weather

[spwath]

Hello,
I work for an acoustics consultant firm, specializing in environmental (outdoor) noise. We are based in Wisconsin so it can get cold. Our current setups consist of a RIGID plastic toolbox with an AGM battery to power our equipment (sound level meter, sound recorder, ultrasonic anemometer and cellular router). We have a 50w flexible solar panel mounted on a board mounted on top. We leave these units out in the field for a few months. Sometimes they die, particularly in colder weather. We are looking to improve that.

My current plan was:
Upgrade to lithium batteries with built in heater (such as the renolgy option)
Put insulation around the inside of our boxes
Upgrade solar panels to 100w

Any thoughts on my plan or potential improvements?

Here are some pics of the setup

 

[MisterSandals]

Any thoughts on my plan or potential improvements?

Get bigger/more rigid panels? Point them towards the sun (better for winter). Keep snow off of panel.

How many Wh do your electronics use each day?

 

[spwath]

Get bigger/more rigid panels? Point them towards the sun (better for winter). Keep snow off of panel.

How many Wh do your electronics use each day?

Not entirely sure - never measured it. But doing an indoor test the equipment seemed to last for around 1.5 weeks with no solar panel attached, with a fully charged 100 ah battery.

Yeah, was thinking we could get some 100 W rigid panels. I dont think they would be a ton bigger which is good for transporting them. Pointing towards the sun is something we have not considered too much, but I guess we should. Keeping snow off could be difficult, as they are often remote and we only check on them every few weeks. Most of our work isnt in the middle of winter though.

 

[MisterSandals]

Not entirely sure - never measured it.

So you are looking to size a system without knowing the requirements?

100Ah x 12V = 1200Wh (lead acid 50% usable so 600Wh)

1.5 weeks = 10.5 days x 24 h/d = 252h

600Wh / 252h = 2.38W draw

Keeping snow off could be difficult,

In the winter, mounting the vertical is not a terrible solution. It may actually be better oriented than flat.

Where in Wisconsin? I am heading there Wednesday for 40th college reunion (Ripon) and family reunion (Neenah).

 

[spwath]

@MisterSandals said something (I forgot to quote)

Fair point, perhaps we should measure them with a multimeter to get a more exact current figure.
These systems were already made when I joined the company, but I helped improve them by adding the cellular routers and cleaning up some of the wiring. Some of our equipment varies, as dose the power draw.
We may not want to mount the panels vertical, as there is an additional consideration with our setups - noise. Having the solar panel vertical could create extra wind noise, which we want to try to avoid as much as possible to not contaminate our results.
We are in Madison Wi (although have projects all across the US)

 

[SamDeleted]

Upgrade to lithium batteries with built in heater (such as the renolgy option)

Heated lititum might be a good option ... but LiFePo4 batteries are notoriously hard to work with in the cold, AGM batteries perform much better ,

you could go with AGM battery , a small 12v heater and a 12v thermostat , links below

https://www.amazon.co.uk/Insulated-Thermostatic-Conditioner-Electric-Instrument/dp/B089YB8HGX/ref=asc_df_B089YB8HGX/?tag=googshopuk-21&linkCode=df0&hvadid=510948449176&hvpos=&hvnetw=g&hvrand=16918268358969384103&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9045262&hvtargid=pla-1224958662209&psc=1

https://www.amazon.co.uk/HALJIA-Temperature-Controller-Thermostat-Waterproof/dp/B07BFNLW5C/ref=asc_df_B07BFNLW5C/?tag=googshopuk-21&linkCode=df0&hvadid=256190982391&hvpos=&hvnetw=g&hvrand=796411499306524013&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9045262&hvtargid=pla-454962304273&psc=1

but either way if you're heating you will need more power to cover it . And better insulation , spray foam , kingspan

 

[SamDeleted]

When you're looking at insulation think about thermal transfer , you don't want any part of the battery touching the edge of the box , a thin layer everywhere is better than loads of insulation in one place and none in the other

 

[MisterSandals]

additional consideration with our setups - noise.

Wind noise?
It wouldn't take much to pole mount one vertically "some distance" away.

Heated lititum might be a good option

I wonder how much power this would require. It gets mighty cold there sometimes. The panel and battery sizes required would be significantly larger.
Lemme speculate a 40W heater running 50% duty...
40W x .5 x 24h = 480Wh
480Wh / 12V = 40Ah to run heater for a day. How many overcast days in a row do you need to handle?
And then how many consecutive sunny days with about 2.5h of solar to recharge?

I'm skeptical about the feasibility of this. The 2.38W equipment draw calculation above tells me using 20x the power to heat a battery is not the "best" solution when lead acid is available.

 

[SamDeleted]

Heated lititum might be a good option ... but LiFePo4 batteries are notoriously hard to work with in the cold, AGM batteries perform much better ,

you could go with AGM battery , a small 12v heater and a 12v thermostat , links below

https://www.amazon.co.uk/Insulated-Thermostatic-Conditioner-Electric-Instrument/dp/B089YB8HGX/ref=asc_df_B089YB8HGX/?tag=googshopuk-21&linkCode=df0&hvadid=510948449176&hvpos=&hvnetw=g&hvrand=16918268358969384103&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9045262&hvtargid=pla-1224958662209&psc=1

https://www.amazon.co.uk/HALJIA-Temperature-Controller-Thermostat-Waterproof/dp/B07BFNLW5C/ref=asc_df_B07BFNLW5C/?tag=googshopuk-21&linkCode=df0&hvadid=256190982391&hvpos=&hvnetw=g&hvrand=796411499306524013&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9045262&hvtargid=pla-454962304273&psc=1

but either way if you're heating you will need more power to cover it . And better insulation , spray foam , kingspan

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A couple of these dotted about , NOT touching the battery

 

[spwath]

Wind noise?
It wouldn't take much to pole mount one vertically "some distance" away.


I wonder how much power this would require. It gets mighty cold there sometimes. The panel and battery sizes required would be significantly larger.
Lemme speculate a 40W heater running 50% duty...
40W x .5 x 24h = 480Wh
480Wh / 12V = 40Ah to run heater for a day. How many overcast days in a row do you need to handle?
And then how many consecutive sunny days with about 2.5h of solar to recharge?

I'm skeptical about the feasibility of this. The 2.38W equipment draw calculation above tells me using 20x the power to heat a battery is not the "best" solution when lead acid is available.

Our studies are not typically in the middle of winter as there are acoustic reasons (and logistics reasons) we dont want to do them then. But still can get cold in late fall/early spring.
I was thinking with insulation in the battery box, and the heat the gear produces, the heater shouldnt need to be in use too much? I saw the renology battery with heater only uses current from the solar panel to heat it, as lithium batteries only need to be warm when charging (AFAIK).
It would also be nice to go with lithium for weight savings, but thats just a "nice" thing to have so I dont have to haul as much weight out into the field.
I had thought from my research that lithium batteries were potentially better in the cold.
In our last study (in NY) two of our AGM batteries failed and will no longer charge above 6V.

 

[SamDeleted]

Wind noise?
It wouldn't take much to pole mount one vertically "some distance" away.


I wonder how much power this would require. It gets mighty cold there sometimes. The panel and battery sizes required would be significantly larger.
Lemme speculate a 40W heater running 50% duty...
40W x .5 x 24h = 480Wh
480Wh / 12V = 40Ah to run heater for a day. How many overcast days in a row do you need to handle?
And then how many consecutive sunny days with about 2.5h of solar to recharge?

I'm skeptical about the feasibility of this. The 2.38W equipment draw calculation above tells me using 20x the power to heat a battery is not the "best" solution when lead acid is available.

Op said equipment lasts 10 days on a 100 ah battery , so equipment uses roughly 10 ah per day



Say three over cast days in a row

equipment uses 30 ah, leaving 70ah for heating which works out about 24amp per day

24amps ÷ 12hrs duty = 2 amps to use per hour

2a X 12v = 24w heater max


I am not confident 24w of heating is going to be enough.....

 

[MisterSandals]

Op said equipment lasts 10 days on a 100 ah battery , so equipment uses roughly 10 ah per day

100Ah lead acid is 50% usable so i used 50Ah in the calculations.
(50Ah for 1.5 weeks)

I saw the renology battery with heater only uses current from the solar panel to heat it, as lithium batteries only need to be warm when charging (AFAIK).

Cheeseheadland only gets 3h of solar in the winter at best. Thats 21h of not heating if only from solar.
0C (32F) is the temp below which LiFePO4 should not be charged (not so bad if charged slowly just below but its increasingly worse at lower temps and higher amps).

It would also be nice to go with lithium for weight savings,

Lithium us about 1/3 the weight but if you need 10x more battery to heat itself and 2-5x (?) more solar panels, you're not saving any weight.

 

[SamDeleted]

100Ah lead acid is 50% usable so i used 50Ah in the calculations.
(50Ah for 1.5 weeks)

I think when he was testing he ran them all the way down to flat

Datasheet says they are 100% discharge rated




It's the same with most deep cycle AGM batteries , the 50% rule is an old wife's tail when it comes to AGM , deep discharges don't have a huge effect on over all lifetime ah output

50% discharge on AGM batteries - old wife's tail

This guy has an interesting take on the 50% discharge rule https://tab-rv.vanillacommunity.com/discussion/9940/agm-battery-depth-of-discharge-myth-busted Quote: "I have been wondering for some time if the "don't discharge your batteries beyond 50%" rule really applies to AGM batteries...

diysolarforum.com

 

[MisterSandals]

Datasheet says they are 100% discharge rated

Wow, had never seen nor heard of 100% discharge as acceptable for AGM.
Thanks!

So,
100Ah / 10.5 days = 9.52W average draw (as you stated).

The 150-250 100% discharge cycles seems pretty bad but illustrates that full discharge is hard on a lead acid battery. Maybe this use case of 100% discharge makes sense in terms of cost per discharge cycle. I dunno, just musing.

 

[SamDeleted]

Wow, had never seen nor heard of 100% discharge as acceptable for AGM.
Thanks!

So,
100Ah / 10.5 days = 9.52W average draw (as you stated).

The 150-250 100% discharge cycles seems pretty bad but illustrates that full discharge is hard on a lead acid battery. Maybe this use case of 100% discharge makes sense in terms of cost per discharge cycle. I dunno, just musing.

According to that guy's figures in the old thread, you loose 14% of the lifetime amps discharging down to 0%soc rather than 50%.

14% extra degradation is not insignificant , but no where near as much as I always thought, I thought going to zero would be much more damaging than that.






also I think that even a 100w panel is insufficient for fully recharging the battery from 0%soc , 100w / 12 = 8.3 amps ,

Less than c0.1 , definitely too low for lead acid ,they have a minimum charge rate

that 100ah AGM wants at least 15amps

 

[SamDeleted]

@spwath that could be your issue and why they keep failing , you're charging the battery too slow . To keep those 100ah AGM batteries healthy you need at least 200w of panel (failing that , as close as possible). AGM batteries get babied to death by too lower charge current


Or get a smaller battery like 50ah that would be happy on a 100w panel

 

[Tomthumb62]

that 100ah AGM wants at least 15amps

he could get by with a much smaller battery, maybe 20-50Ah.

 

[SamDeleted]

he could get by with a much smaller battery, maybe 20-50Ah.

Half the battery size, double the panel

 

[spwath]

@spwath that could be your issue and why they keep failing , you're charging the battery too slow . To keep those 100ah AGM batteries healthy you need at least 200w of panel (failing that , as close as possible). AGM batteries get babied to death by too lower charge current


Or get a smaller battery like 50ah that would be happy on a 100w panel

he could get by with a much smaller battery, maybe 20-50Ah.

Ok interesting, we didnt consider a smaller battery could actually help us. I dont think we would want to go too small, as we want to have enough power in case of longer periods of cloudy days and such. So I guess we will look into how large of a solar panel we can go with, if we could fit a 200w.

 

[SamDeleted]

Ok interesting, we didnt consider a smaller battery could actually help us. I dont think we would want to go too small, as we want to have enough power in case of longer periods of cloudy days and such. So I guess we will look into how large of a solar panel we can go with, if we could fit a 200w.

Maybe two 100w panels for portability

A real 200w panel is going be at least 2foot by 4 foot , maybe a bit bigger

Anything smaller than that , that quotes 200w is lying . Ye cannie change the laws of physics