Hello All,
Just wanted to know if anyone has tried to power a Moteino and Radio with lifepo4 3.2v cells. The ones I am looking at are 3.6v when full to 2.0v when discharged. the reason I am looking at them is that they have great Temperature tolerance (-30°C to +60°C). Also they are supposed to be designed for a 5 years service life and over 1600 cycles. some other sites list getting over 4000 cycles before they hit 80% of capacity.
https://www1.elfa.se/data1/wwwroot/assets/datasheets/APR18650M1_Datasheet_APRIL2008_eng.pdf (https://www1.elfa.se/data1/wwwroot/assets/datasheets/APR18650M1_Datasheet_APRIL2008_eng.pdf)
I know Felix bypassed the VIN for his long term coin cell test but I am thinking that for this I should put a booster in front of it before connecting it to the Moteino.
Thoughts?
Quote from: jarrods on May 15, 2015, 09:28:06 PM
Hello All,
Just wanted to know if anyone has tried to power a Moteino and Radio with lifepo4 3.2v cells. The ones I am looking at are 3.6v when full to 2.0v when discharged. the reason I am looking at them is that they have great Temperature tolerance (-30°C to +60°C). Also they are supposed to be designed for a 5 years service life and over 1600 cycles. some other sites list getting over 4000 cycles before they hit 80% of capacity.
https://www1.elfa.se/data1/wwwroot/assets/datasheets/APR18650M1_Datasheet_APRIL2008_eng.pdf (https://www1.elfa.se/data1/wwwroot/assets/datasheets/APR18650M1_Datasheet_APRIL2008_eng.pdf)
I know Felix bypassed the VIN for his long term coin cell test but I am thinking that for this I should put a booster in front of it before connecting it to the Moteino.
Thoughts?
I looked at that datasheet and have three thoughts:
1. it has absolutely NO data related to the power domain you'll be running ( just a few mA on average).
2. the datasheet is 7 years old. There has been a lot of battery development and LiPo experience since then - like do not ever discharge a LiPo to 2.0V!
3. These batteries come with no protection circuit, either overcharge or over discharge making them a time bomb - literally.
Do you need to operate at -30C? And, if you do, why don't you use a Lithium Primary cell, like Eveready L91, which will operate down to -40C?
Tom
This is an outdoor mutli-year deployment and will be Solar. In some areas where this will be deployed it gets quite cold -5. So I want to make sure what ever I put in will have some room in cause it gets colder then typical. Cold is not the only issue, in the summer these area will typical get up to 40 - 45c (103 to 110). this is outside the operating range of most rechargeable cells. that is why I was looking at batteries using in EV applications. The battery listed in that datasheet is apparently one of the most popular and has a very long life. Granted that is for high current application.
I am also looking at another cell that is is good from -20c to 60c that should be good enough for outdoor use and is rechargeable.
@jarrods: Which battery did you end up picking? The LiFePO4 look as though they may be worth a shot. The higher temperature operating range is definitely attractive. I think most people tend to forget that regular lithium batteries get rapidly degraded at anything much above moderate temperature.
Unfortunately, few of the inexpensive off-the-shelf charger circuits seem geared toward LiFePO4. I'd be tempted to use the moteino to measure the voltage periodically so as to manage the charge termination. Given Murphy's Law, I'd feel better, though, if there were an additional failsafe in addition to only that. I imagine a regular CV CI charge circuit would do the job. As an extra protection, one could add temperature monitoring, though maybe (?) that's overkill.
Quote from: WhiteHare on December 11, 2015, 03:20:41 PM
I think most people tend to forget that regular lithium batteries get rapidly degraded at anything much above moderate temperature.
There's probably a reason 'people tend to forget' this...
I suppose it depends on what you call 'moderate temperature' or whatever a 'regular' lithium battery might be.
Source: Energizer L91 Product Datasheet.
Well, good to know, but I meant to refer to rechargeable batteries, like Lithium Cobalt. Sorry for not being more exact with my language.
The use-case I'm thinking of is where there's potentially more energy being expended, like opening/closing some blinds, or maybe a proper solar powered garden LED light, possibly remote controlled as to when it comes on and goes off. I have doubts that primary lithium cells, like the energizer, would be the right pick for those applications. Well, maybe an argument could be made for the blinds, but definitely not for the garden light.
Quote from: WhiteHare on December 11, 2015, 04:52:49 PM
Well, good to know, but I meant to refer to rechargeable batteries, like Lithium Cobalt. Sorry for not being more exact with my language.
My only point is that if you're going to make pronouncements, be clear about what you're referring to. A general statement like 'regular lithium' is bound to be misunderstood.
Tom
Hi Guys,
I feel off the map for the last few weeks, it's been super busy and the family got sick.
I ended up going with a 18650 http://www.batteryspace.com/prod-specs/18500%201400mAh%20SCD-04-390.pdf (http://www.batteryspace.com/prod-specs/18500%201400mAh%20SCD-04-390.pdf) Li-ion cell. It had decent temp specs. It is a 1400maH battery that will hold 80% after 300 cycles. since i don't plan on deep discharging that amount each day ifigure i should be able to last a LONG time on these without sun to recharge or degraded solar panels (dust, dirt, etc) and it should last couple years. long enough for me to figure out a better solution
I will start testing them this month, so i dont have any data yet as to how well they perform.