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Cheap 4-life

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Hey wolf. Things are looking good.
For heating batteries I am using seed germination pads. I use a small 3”x 20”. It’s keeping the batteries at 50f. It doesn’t get below 20f where I live, so the small pad is working well. For you Id recommend a few of the bigger pads. Here’s a link
 

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Wolf

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Yes according to Batrium the "Mons" have a typical error window of ±2°C and a min and max of ±5°C. That's pretty considerable given the fact that we really can't charge Li-Ion at 0°C else we damage the cells. In my case the batteries are placed in a shed outside and I was very worried about charging the batteries at a temp below 0°C. Right now my Watchmon tool kit is showing a 3° difference between cells 1°C to 4°C.
My battery box sensors indicate 5.51°C and 4.88°C. The BM680 sensor has an accuracy of ±1°C and the DS18B20 between -10°C and +85°C a ±0.5°C window. So I am inclined to believe them a little more than the Batrium.
Wolf
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Wolf

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Hey wolf. Things are looking good.
For heating batteries I am using seed germination pads. I use a small 3”x 20”. It doesn’t get below 20f here so it’s working well. For you Id recommend a few of the bigger pads.
Thanks Cheap.
I will put it in my links for future reference. In my search for keeping my batteries warm I have thought about this solution and may have to resort to something like this if my heaters can't keep up. As these are from the "Grid" 110V powered I have not put them in my plan yet. At this time all my heating is done through my massive 12V AGM Telecom 560Ah battery charged by Solar. Well 😇on occasion I have to use some grid to supplement but the majority is Solar.🙄
Wolf
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OffGridInTheCity

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In the trailer, for battery heating, I used these "RV Water Holding Tank Heater Pads" - https://www.amazon.com/gp/product/B07GW8ZX7X/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 - underneath the packs. I have 3 of them (180watts total), 1 for each cabinet / 5 packs.
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They work OK to keep the 30gal water tanks from freezing and once I add the trim to enclose the batteries on top of the cabinets in pic above, they should keep batteries warm. Just put them in place and haven't tested yet - but can test and monitor via longmon temps :)
 
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Cheap 4-life

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Wolf, they are 110v but the GTIL2s use batteries which get charged by solar, which supplies the power the heater pads need.. The pad heater would still be getting it’s power from solar.
 

Wolf

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Wolf, they are 110v but the GTIL2s use batteries which get charged by solar, which supplies the power the heater pads need.. The pad heater would still be getting it’s power from solar.
True but right now my solar production is limited due to snow and the azimuth of the sun. Also the cold happens at night mostly. At this time I get maybe around 4 to 5 hrs of 100% off grid for the house. So that's why I have the shed array supplying my 12V shed battery. Also to supplement my heaters with fans I do have a 110V charger to keep the 12V AGMs happy which in turn (the charger) is supplied by solar with the GTIL during that precious 4-5 hrs of solar power generation. So we are doing the same thing just a little differently.
 

Oleksii

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...


Great results this AM, 207.42Ah which gives me an average of 2593mAh per cell that's 99.73% of SOH with a discharge to 3.0V.

View attachment 15035


Wolf

What resistor did you use in this case for Extra discharge?
Am I correct that it should be optimal one,to make a maximal voltage drop for iCharger itself and produce most of heat to resistor, but not iChanger?
 

Wolf

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4.2 Volts 30A requires 0.14Ω
So I pretty much home built a 0.14Ω resistor using 7 1Ω 100W resistors which calculated to 0.1428Ω.
Actual is 0.153 so 27.5A. Close enough.
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Wolf
 

Korishan

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Close enough for gov't work :LOL:
 

ajw22

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Nov 16, 2018
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Always thought about building something like this! But always too lazy to do it ;-)
Any chance of running the fan on the same battery power source? Perhaps with a small boost converter?

Can't wrap my head around how the leads are connected... is this picture from the pre-assembly stage?
And you should attach the 2nd lead to the opposite end of the busbar, so that the resistors are loaded more evenly.
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Wolf

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Any chance of running the fan on the same battery power source? Perhaps with a small boost converter?

Can't wrap my head around how the leads are connected... is this picture from the pre-assembly stage?
And you should attach the 2nd lead to the opposite end of the busbar, so that the resistors are loaded more evenly.
I suppose you could run a fan off of the source load. In my case It was 4.2V to 3V. 3V to 12V boost do exist so yea I guess I could have done that. The only problem is that I would be tied to the limited input V range of the boost so I decided that 12V separate input would be the way to go. If I wanted to do a capacity test on a 48V battery I don't thing the boost would like that. I'm sure there are ways around all that but for sake of simplicity..................

Yea the 2nd lead should be at the other end and that is in the next revision as I need to lengthen the leads anyway and mount it on proper board.
Work in progress but hey it works and did the job for 28 packs so far.
Wolf
 

Wolf

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Small little update on the battery box heaters.
Last night was the coldest so far with a shed temp of -6.80°C.
The heaters are working good so far, cycling on and off and keeping the box at ≈6°C in the center and with the right side at 1°C. The sensor is mounted on the wall facing outside. I may change that to get a more accurate air temp reading rather than a surface.
Batrium is showing 3.0°C average cell temp. I really got to get the 3 other sensors installed but at this temperature....... not.
Wolf
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Wolf

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Another update.
So call me stupid, but I have a defence, I am not an HVAC engineer. Turns out you can heat the bottom of a box all you want but the heat will not be evenly distributed within the box especially if you have shelves (even with generous holes for air circulation) like in my battery box. The heat will travel to the top but on its own schedule and that is not very fast.
Initially my answer was pump more watts (as in heat) into the box but that didn't seem to change much other than draw more power. Top of the box in the middle was getting relatively warm but the sides where just cold.
My theory was very flawed. Heat the enclosed box from the bottom heat rises to the top and warms everything in between. Right? Wrong!
Flaw.png
Turns out that even with modest fans blowing upwards the heat gets trapped in the layers of shelves and really never completely gets to the top.
Odd.
Then I had an epiphany /eureka facepalm/plant moment in the middle of the night. Woke me right out of a deep sleep.
Of course the heat won't circulate it has nowhere to go we need to have a form of forced convection.
So with -12°C in the AM and a gorgeous sunny day ahead I switched to the Pb battery bank for solar charging as my cells where at a dangerously close temp of 0°C. No taking chances here.
Pre.png
All suited up with Everest gloves, parka, scarf, and flannel lined jeans I proceeded to split the box into 2 zones a warm zone and a cool zone.
Proper.png
I will take pictures of the final look of the box when it is totally finished.
I raised the esp32 temp to 8°C to also compensate for the added air flow and wella it works just great. Batrium is no longer complaining about low cell temp and the box temp has stabilised considerably.
Batrium repoerting.png
With the constant circulation fan in place the air is always moving and sensor reaction is very fast. The heat runs for about 4 to 6 min at a time, compared to the 5 to 6 hours before, with a 10 to 15 min rest. which makes it a lot easier on the 12V AGMs.
The Box temperature is also far more consistent now.
Wolf
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OffGridInTheCity

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Fantastic work - really cool! Its amazing how simple ideas (heat in a box in this case) often take additional levels of 'nuance thought/experiment' to work properly, and in this case, a bonus of more efficiency as icing on the cake.

>Then I had an epiphany /eureka facepalm/plant moment in the middle of the night.
I never have good ideas which is why I lurk on the site :)
 

Cheap 4-life

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Looks in the pic like your little heaters have built in fans? Couldn’t you mount them on the middle wall where the circulator fan is?
 

Wolf

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Looks in the pic like your little heaters have built in fans? Couldn’t you mount them on the middle wall where the circulator fan is?
Could, but at -12°C I was not about to. I wanted the solution to happen as quick as possible lest my digits fall off due to frostbite.
The current system is by no means the final solution as the separators are made from quick cut outs of 1" Foam Board Insulation.
If this heating system works well into the -30°C ( -22°F) It does get that cold on occasion here in Maine, and of course it will be a beautiful sunny solar day. So I would want to be able to charge my batteries. Then the system will be refined to utilize the least amount of moving parts necessary.
I do appreciate your idea though.
One small problem with using the little heater fans is that after they shut off the fans also shut down. Again not a showstopper I would just rewire the fans onto a seperate relay to run continuously after a certain temp drop Say anything below 10°C fans would run continually and the heating matrices would cycle on and of at 8°C.
The way it is set up now the circulation fan runs all the time heaters on or off.

Wolf
 

Cheap 4-life

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Might not hurt to let the fans shutoff when heaters aren’t on. Might actually help.

In bed when your brain can relax and think about one thing without distractions can allow some of the best ideas to be thought of
 
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Wolf

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Might not hurt to let the fans shutoff when heaters aren’t on. Might actually help.
So I tried turning off the circulation fans (correction should be just "fan") for 2hrs 10:45am to 12:45pm and this was the result.
I think I am keeping the circulation fan on.
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Wolf
 
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Cheap 4-life

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I was saying shutting off the circulator fan when the heaters are not running due to the box being at a high enough temp.
 

Wolf

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Might not hurt to let the fans shutoff when heaters aren’t on. Might actually help.
I was saying shutting off the circulator fan when the heaters are not running due to the box being at a high enough temp.
OK you now have me confused. 🙄 Easy to do.
The small heaters (4) have fans that are attached to them. Those fans (4) turn on and off with the heaters.
The circulation fan (1) (no heater attached) was always on. That is what I turned off for 2 hours.
Wolf
 
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