Simple and inexpensive battery heating and cooling in a harsh environment? - Page 1
Forum section: electronics / beginners

author: SlowBro
author_rank: Regular Contributor
timestamp: September 04, 2017, 12:53:58 pm
content: What are your recommendations for methods or devices that are neither complex nor expensive to keep batteries warm and cool in a harsh (hot/cold/moist/dusty) environment, to ensure long cell life?I'm designing a small solar-powered camera product and I have my choice of battery types: lithium, lead, nickel, etc. The camera would sleep most of the time so for average hourly use I estimate around 10mA x 12V (120mW). The environment could be very dusty, humid, hot, or cold. I cannot require constant maintenance, so a fan with filter does not seem to be a good idea. I can go with a larger pack to reduce the charge/discharge rate, if that is necessary.Since this is for the outdoors and the initial sales would be in the United States, I expect ambient charging temperatures to be between -18°C/0°F in the winter and 38°C/100°F in the summer. Discharge temperatures could be as low as -34°C/-30°F in the winter and 38°C/100°F in the summer. Humidity can be as much as 100% but 87% is more typical in locations like Florida or Louisiana.Naked lead batteries seem to be a fit because they are installed in vehicles that get both extremely hot and cold. But would a sealed plastic enclosure make a difference?More info:How does my device looks? Imagine a security camera with a solar panel.What might it cost? Less than USD $100 with parts cost less than $50 would be ideal. Any more than that and I might not consider creating the product.What amount of field failure can I tolerate? A life of 5 years would be fantastic. No less than 3 years.Where is it going to be mounted, by whom? Eaves, trees, walls, by non-trained personnel e.g. homeowners, farmers.How heavy might it be? Small device, so about 1-2kg/2-4lb.Is this even a concern? On my house I havethese solar-powered security lightsthat have no heating or cooling. Just Ni-Cd batteries in a black plastic enclosure. I live in a climate with hot summers and cool winters. The devices are mounted in the sun and have been going strong for years. I see from reviews on those devices that they are installed in both very cold and very hot locations, and perform admirably. Yet thetypically-recommended charge/discharge temperatures for Ni-Cd cellsis 0°C to 45°C and -20°C to 65°C, respectively. Cells in an uninsulated black plastic box exposed to sun and snow surely must reach temperatures outside of that range, right?And there are solar-powered trail cameras that hunters use in cold and hot weather.Am I over-thinking this? Should I just drop some Ni-Cds in a black plastic enclosure and be done with it? Or are there some inexpensive temperature management solutions?

author: BrianHG
author_rank: Super Contributor
timestamp: September 11, 2017, 01:29:56 am
content: What type of Lithium would you choose. There are many types with different temperature ranges with slight voltage variations and current capacity. (I'm not talking about cell size, I'm talking about formulation.)Example Lithium chemistry chart with operating temperature range:http://www.tadiranbat.com/compare-lithium-cells.htmlOlder Lithium and NiCd/Lead acid/NiMH temperature ranges:http://batteryuniversity.com/learn/article/secondary_batteriesDo some research, but you will find there exist Lithium cells which do exceed the operating temperatures you need for your application, way beyond that of the older NiCd/Lead Acid/NiMH if you really need it.Main Lithium Chemistry tables:http://batteryuniversity.com/learn/article/bu_216_summary_table_of_lithium_based_batteries

author: David Hess
author_rank: Super Contributor
timestamp: September 11, 2017, 02:31:09 am
content: Quote from: SlowBro on September 04, 2017, 12:53:58 pmYou have already demonstrated the problem. A battery powered device does not have the energy to actively control its own temperature. A heroic effort might be made by placing the battery into a thermally insulated container but even that will not be enough.QuoteNiCd and NiMH cells are the natural solution for this because they are alkaline cells using sodium or potassium hydroxide at a concentration where the electrolyte will not easily freeze. NiCd cells are more rugged and they make special ones for high temperature and low leakage applications.You might also consider just using some big non-rechargable alkaline cells. They will have lower leakage than NiCd or NiMH and also will not easily freeze.There may be some suitable wide temperature range lithium rechargeable batteries or even supercapacitors.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 11, 2017, 03:04:10 am
content: It is your product so you can set environmental requirements as you want, but large populations in the US live in areas where charging temperatures will be at or below 0F. While solar heating may help on some days, there will frequently be wind which can totally negate this heating. This is actually more likely than your discharge temperature of -30F.You are similarly missing on the high end. Air temperatures during the day are routinely above 100F in large parts of the west, and in a somewhat smaller part of the west will exceed 110F several times annually. If you box is exposed to any direct sun you could easily rise 10-20F more.

author: SlowBro
author_rank: Regular Contributor
timestamp: September 19, 2017, 06:33:56 pm
content: Apologies for the delay in response. Had to flee a hurricane then was busy afterward. TERRIFIC responses everyone. I'm thinking I will go NiCd as I've seen it recommended in several places (including here) and also these are typically used with the little solar garden lights. There are some high temp NiCds (these look interesting) which only leaves me less protected at the low end. If the enclosure is dark colored, and given that charging usually only occurs through the noon hours (hottest parts of the day), cold weather shouldn't be a severe problem. The box should get warm, and ambient temperatures would be warm, so it should not have much trouble reaching the 0°C/32°F minimum charging temperature listed in those cell's datasheet.Discharge temps are -20°C/-4°F which presents more of a problem if there is an overnight visitor on a cold night. Not sure what to do about that.Thanks everyone!

author: SlowBro
author_rank: Regular Contributor
timestamp: September 19, 2017, 09:05:39 pm
content: Also looking atthese lead acids.When estimating battery life do I use the average year-round temperature of the expected environment, or the maximum expected temperature?In the United States thehighest average temperatureis a mere 21.5°C/70.7°F (Florida) which is a very cozy temperature for batteries. Add 20°F for case temperatures and the maximum average would be 32.6°C/90.7°F, which according tothe datasheetstill gives a five year service life, at worst. The mean average is much lower. (10.9°C/51.7°F; Indiana)If however I must take the maximum expected temperature (around 43°C/110°F) that greatly limits the expected life.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 19, 2017, 10:12:13 pm
content: Quote from: SlowBro on September 19, 2017, 09:05:39 pmYou basically have to integrate the times and temperatures. Also state averages are too course to tell you what you want to know. Just a quick check shows Phoenix, AZ has an average annual temperature of 75.1 degrees. The state average is lower because of the mountainous north. You need to figure out where your box is going to sell and use those environments. Obviously a swimming pool monitor can avoid low temps, and something to monitor freezing in the well house can avoid high temps, but something like a game camera will get the absolute worst environments around.You also have to play a consistent game. If you are going to count on solar heating for your box in the winter you have to accept solar heating in the summer. Or repaint it twice annually. Or sell different colors to different markets, accepting that there are places in the high deserts of the west that are extreme on both ends of the temperature scale. Same thing for pointing out that charging peak charging occurs during the warmest part of the day. Charging heats the cells, adding to whatever the ambient temperature in your box is.As a quick reference point, when I lived in Southern AZ the NiCd cells in garden lights lasted about 3 years. That applied to the original cells and to intermediate quality cells I used to replace the originals. Standard deviation on this value was large, well over 1 year. All batteries in the lower parts of the desert southwest live short, nasty lives - whether they are PbO batteries in automobiles, NiCds in various devices or the newer technologies.

author: SlowBro
author_rank: Regular Contributor
timestamp: September 20, 2017, 12:48:46 am
content: Quote from: CatalinaWOW on September 19, 2017, 10:12:13 pmThat's more in line with my expectations, thanks.

author: GigaJoe
author_rank: Frequent Contributor
timestamp: September 20, 2017, 02:27:28 am
content: I have a solar feeding sign with 2 NiCD batteries inside , my infra Term shows +57 Celsius in some days, due to black case and a direct sunlight, battery live 2 years dropping capacity on 3-th year around 50%. Then I install nimh - capacity are much larger but degradation speed around the same ..

author: SlowBro
author_rank: Regular Contributor
timestamp: September 20, 2017, 09:11:40 am
content: Good feedback GigaJoe. Maybe I should sell it with removable cells like Eneloops and just count on the user to replace them periodically?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 20, 2017, 05:34:31 pm
content: The right approach will depend on your market and the life of the batteries. If you have a relatively high current application such that even the best non-rechargeable batteries only last a few days or weeks then a rechargeable with two year life will be very appealing. If the current drain is small and capacity life approaches the storage life of rechargeable batteries the non-rechargeable battery looks appealing. Look into the long life Lithium batteries from Tadiran. If your current draw is small enough you might get years of use.All of these answers get modified by how difficult it is to change batteries in your application. Something in a remote or difficult site might even justify putting a lot of excess capacity in along with circuitry to switch out dying cells.All of this thought that you are going through is the meat of the early design stages. Figure out what the really important factors for your design. Figure out the real environments. Figure out what would be nice and what is necessary. Write it all down so you don't forget as you go through the design. Be prepared to come back and make some hard decisions when you find that you just can't get there from here.