The Best Battery Enclosure looks like this?! (Self-Heating)
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- čas přidán 15. 05. 2024
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All the heating pads I tried: s.click.aliexpress.com/e/_DkM... s.click.aliexpress.com/e/_DDx... s.click.aliexpress.com/e/_DlV... s.click.aliexpress.com/e/_DDJ...
Temperature Controller: s.click.aliexpress.com/e/_DDo...
You can get the rest of the components in your local hardware store.
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In this project I will have to solve a winter problem for the batteries of my PV system. The problem is that those can get only charged up over 5C and in my case they are placed inside a concrete garage that will get colder than that. So I will try to build a very well thermal insulated chamber that I can heat up electrically. I want to keep it save, low power and easy to use. Let's see how it turns out ;-)
Thanks to PVCase for sponsoring this video.
0:00 My Winter Problem
1:23 Intro
2:10 How to Create Heat?
4:41 Building the Chamber
8:10 The Control Electronics
8:56 Final Tests & Verdict - Věda a technologie
Best practice is to use fire resistant materials for battery boxes, usually metal. For DIY, you can use cement fiberboard to line the inside of the box to create a safer barrier.
Good point!
Upvote this man, this needs to be seen
Yeah, im also a bit concerned about that wood box with heating and batterys. Although the heating element only reaches 50°C, it still uses 230V. A bit risky that setup
I was wondering if that whool is fireproof. But it doesn't look like it from this comment
I totally agree. I need to build a battery box for my 48 volt 300 ah lifepo4. I don't need for it to be heated though. I like the quality of build here. Maybe the internal osb can be swapped out for cement board.
I found a mirror heater (to prevent mirrors steaming up in the bathroom) is ideal for warming and drying photographic prints. It takes about 20 watts at 230v. It already has mains connections and is fully insulated so easy to use for warming projects.
Second idea - use a dead fridge or freezer if you can find one minus the compressor etc. from a recycling centre. It’s a box that’s already insulated!
Great tip!
And use compresor,evaporator and condenser to make heat pump instead of resistiv heater
@@adomijan1606 Just increase the cost and complexity of the system by 10 fold, no biggie.
yes , these are available for free all over the place, more weatherproof also.
@@treelineresearch3387 if he use the fridge just turn around inside out and instead cooling he will have heating
Please do something with those terminals. Right now if you in a moment of absent mindedness put something metal on top of the box you could short out those batteries. I'm sure you've fused it internally etc but it would be easy to put something taller than the termnals between them so a misplaced tool couldn't bridge them.
Thanks for the feedback. Should add that in the future.
6:40 when using the band saw, please keep the guard a maximum of 6mm above the work piece to keep your fingers safe
Also respirator and safety glasses are recommended.
As a seasoned woodworker, I also cringed at how high the upper guide bearings were from the workpiece. I hope Scott reads this and adjusts his practices on his new band saw.
One problem I can immediately see is that you might want to install some controllable ventilation just in case. The batteries can get warm while charging, but if the insulation is too good, they might start to overheat.
Yes those VRLA batteries will eventually vent some gas, so best to have a pipe through the case to allow it to dissipate. The easiest thing for temperature control would have been to get a cheap 12V controller and use the on board relay to do this, using the resistive heaters that are capable of running off low voltage, so use 4 12V ones in series to operate off battery stack, and then simply run the controller, with the tiny current it uses, off the 12V battery. Benefit is the display is always on, and also will monitor battery temperature in summer, where you can have an alternate output to set an alarm if the battery is getting too hot, or run a set of fans to actively cool the packs when charging, just using a second controller, and some holes in top and bottom for air flow.
@@SeanBZALiFePO4 used
@@bayenne5b Same issues with cold charge and temperature though.
@@SeanBZA the seals he used leak enough
@@SeanBZA more when it comes to charging, that's why he made it heater only, not sure how this will handle under max load in the summer though
I like your idea with the temperature controller. Its simple and fast. But please use a fuse or motor protection switch. If the heater resistance goes down, the fuse cuts the power instead of increasing the heater power and generate a fire hazard.
Just a suggestion. You can cover the two poles with caps in order to electrical-isolate the poles, so that it won't cause short circuit if something touches both of the power poles accidentally.
For example: put a random metal ruler on the box.
Oh boy.... That would be exciting 😂
I'd be putting a large block between them to reduce the chances of a metal object touching both... Spanners, rulers, poles, etc are mostly straight, so if there's a physical barrier taller than the terminals placed between or around them, you've reduced the chances quite low.
Personally, I'd have put the terminals inside where visitors can't touch.
The BMS has short circuit detection. And all 4 BMS's would have to fail for it to not work since they're all in series. The detection and shutdown time is something like 0.03 seconds. You'll get a quick little spark but that's about it. More importantly you risk damaging the Victron charger, and those aren't cheap.
But yes, it's still a better idea to cover them up. 50V is getting close to the danger zone for skin conductivity anyway. I think ~70V is the "high voltage" zone.
@@andrewt9204 All of 4 BMS might actually fail. Typically BMS has to disconnect abattery and it's output voltage will drop to 0V, but here it might drop from 13V to -39V (all outher BMS'es haven't disconnected yet and load is short circuit, voltage 3.25V per cell).
Output transistors for that BMS then fail short (Vgs overvoltage with Vds overvoltage do destroy isolation barrier - creates above mentioned failture) and the same situation repeats 3 more times.
Thanks for expressing my first thought on seeing that. A quick wood box seems like it would be easy enough and I wonder if he added something later.
4:45 Love the old fashioned folding rule. Haven’t seen one in decades. Instead of the mat and soldering mains wires, I might have considered a 40 Watt incandescent bulb and off the shelf socket. Great video.
That's a great idea!
Yeah, but the bulb presents 2 problems. 1) It is wasting energy in the form of light 2) It is not as compact as the heating pads and would not easily fit in that space
@@nimoy007in an enclosed space the light will turn into heat anyways, so it's no big deal, and underrunning a higher wattage bulb will also put out even more IR compared to visible light.
@@foorje one of those funny cases where we _want_ to lower the efficiency to even worse than it already is
@@Kalvinjj yeah, though it also has the extra positive consequence of increasing the lifetime of a lightbulb too
I was actually expecting a small chamber for yourself🤣 It would honestly be a pretty cool project as an emergency micro shelter or something, with proper ventilation and filtering, etc.
Haha maybe next time. But I thought it would make for a pretty intriguing opening joke ;-)
A camouflaged safe room that look like a packing crate. 🤣 2x👍
There was a movement for a while to make super-insulated tiny "capsules" for the homeless. Of course the various governments went "Oh HELL no, building codes say no-no-no!".
where i live people do something like this for their bed to not die from the cold during the night....
@@faustinpippin9208Northern Europe these past two years?
Ein paar Kritikpunkte:
Die Kabine ist nicht gerade Feuerfest, was ich für ein Batterielager anraten würde. Eine Auskleidung mit einem feuerfesten Material hätte ich besser gefunden. Eine einzige Fermacellplatte hätte wahrscheinlich schon gereicht und ist billig.
Die (anscheinend blanken) Anschlüsse durch das Holz und die Mineralwolle finde ich auch nicht gerade sicher. Kommt da mal Wasser drauf, startest du ne Elektrolyse. Ich glaube zwar nicht das es direkt zu einem Brand kommt, aber zumindest ruinierst du dir die Anschlüsse und evtl. sogar die Batterie. Und die blanke Anschlüsse oben drauf laden gerade dazu ein mal ne Blechkiste drauf zu stellen🤣
Sorry für soviel Kritik, aber die Menge an Energie in der Kiste ist nicht zu unterschätzen und du möchtest dein Haus und deine Familie sicherlich behalten....
Be interesting to find out if the batteries give off enough heat once put online to maintain temp in the box. Please keep us updated.
GreatScott has invented the Lithium battery oven / cooker. GOOD JOB!
Keep warm Scott! 👍👍
I will try :-)
Really good idea. Personally i would have put the terminals and the control unit on the side. So the top can be used as a work surface / bench-top. Can never have too many work surfaces !.
I recently did something similar but for cold with an old refrigerator. I used an STC-1000 that I bought on Amazon as a thermostat. This device has two relays, one for cold and one for heat... that is, one that is activated when the temperature drops below a limit and another when it rises above another limit. In addition, it has programmable temperature alarms in both cases and comes prepared to fit in a rectangular hole... it can fit very well and cleaner in your box.
You could also use an old refrigerator for the box. I don''t know whether your batteries degrade when they get hot, but you may be able to make use of cooling sometimes. It's gotten up to 46° C (115° F) where I live. Probably just run the cooling off mains for those rare situations. It may be sufficient to simply open the door at night to let things cool, then close in the morning. I know it's not in the spirit of automation, but it works.
Sehr gute arbeit. Perfekt ausgeführt. 👍
Something to maybe keep in mind would be something like a air quality meter inside the chamber if for some reason something goes wrong with the batteries. Otherwise great project idea.
Awesome feedback. Would be interesting to find out how air quality changes when such a battery becomes faulty. Will look into that.
@@greatscottlab Generally they emit vapours of sulphuric acid. Simplest test is a water monitor placed low down, where the condensing acid will trigger it, though long term it will corrode the electrodes away.
Batteries emit hydrogen. Seems like this could build up an unsafe amount and explode
Lead acid batteries emit hydrogen as the electrolyte evaps away. The sulfuric acid doesn't go anywhere, it just gets more concentrated as electricity separates the distilled H²O in the solution.
Lithium Ion doesn't have this problem to my knowledge, but has its own problems if the lithium is allowed to oxidize (runaway exothermic reaction = ka-boom). I'd line both in kaowool personally, and if using lead acid just attack the top with a 3in hole saw one time and leave the hole, Hydrogen will escape thru the kaowool, since y'know, it moves thru everything. Figuring out how to hold hydrogen inside a cavity was/is still an engineering feat.
Those batteries are completely sealed, if something happens where a cell has an internal short or something, it will release a lot of gasses. The battery box will explode as they do not have a pressure relief. Unless part of the case has a thin section or scored circle that the case will burst in that one spot safely. At that point the BMS will shut down on a low cell voltage and since his 4 batteries are in series, the system will shut down.
LFP is pretty stable though, if it hasn't failed in several cycles, it likely never will under the same conditions.
I appreciate your job Sir! Ur brilliant
Nice box! I'm fairly confident that the heat generated from normal use will maintain a Cosy temperature. You may, in the summer, even have to add fresh air ventilation to keep them cool!
Would love to see a long term follow-up video!
I discovered it's actually very easy to make your own heated clothing by weaving some carbon fibre tow into pads, and directly applying 5V from a battery bank, then sewing the pads into your clothing. You want to make sure the strands are long enough to not get too hot of course, I did some testing a bit back and as far as I can tell, if you damage part of the tow, it actually makes it cooler rather than that part getting hotter than the rest. You should definitely look into that as a project
Thanks for the feedback. Sounds interesting. Will do :-)
I'm fairly sure that's all they do with the heated gillets you can buy actually. I had one on which the power button broke so I took it apart. There was no circuitry as far as I could find except for the button having 3 modes limiting the current for different heat levels. The pads that heated up did indeed have something woven through them, although I don't think it was carbon fibre tow. I was able to reproduce a nice 40C with some long enough attached directly to a lithium battery (so no BMS from a battery bank, I was just testing after all). I'd forgotten all about that, life got in the way and I never did much else. But I did check if damaging a part of the length of tow caused a hot spot, and it didn't. I'm not sure why, but I found that very interesting. It's basically it's own safety measure if my tests were correct
I think that red silicone wire stuff that Scott tried is carbon fiber based, apparently designed for underfloor heating, but can be cut down to shorter lengths for lower voltages, I have similar stuff and it works great!
Is carbon fiber safe to have flaking off into your clothing?
@@PBnFlash I would argue yes, the type I'm referring to anyway, and the way in which it would be applied in a clothing situation. You can safely eat the stuff probably (not that I'd recommend that), but if it's within clothing fibres etc, the likelihood of inhaling any micro particulate matter is negligible, and it's machine washable. Or hand wash. My point being I don't see even the largest amount of carbon particles you could potentially inhale from it, being worse than latent pollution. Again I may be wrong, it's why I really wanted him to give it a look.
EDIT: And of course you can encase the carbon tow in something if that is a concern. As I said, I only briefly looked at it and not at all from a research standpoint, I just realised carbon tow was weavable, and it is used in clothing unheated so I assume it's generally safe.
Not only is this a great insulation chamber, it also looks like an excellent energetic and unstoppable house igniter!
Trophy Batteries are self-heating and rack mountable. Thanks for your great content.
Great project from Great Scott!
Glad you liked it!
This reminded me to build something similar for my resin printer for this winter!
Congrats on 444 video Great Scott!🥳
Awesome project!
There are special mounting claps to attach cables to the heating mat. And insulation too. No soldering is needed. It would be great to add some hardware-based temperature and overcurrent fuses.
You could have used your Cerbo GX on the wall behind the battery box to do the switch on/off of the heating element with its relay output and Temperature sensor. This would also allow you to monitor the internal temp on the VRM Portal.
Maybe another video on how to set this up!
Wow thank you for the in depth video. Please using your knowledge of electronics please make a video on how to salvage camera modules from old or broken phones.
Great job as always. Btw, are you considering adding temperature monitoring to check if it will work as expected over time?
Yesterday I did similar project for my 8xEVE 280Ah, and thermal pad was an issue. Thank you for ideas!
Nice job. Some tips for your next video.
1.
Put the heater on the bottom. Warm air rises.
2.
Put the sensor at the lowest battery.
3.
Use isolation with reflective material. Heat will leak out of the box via conduction, convection and radiation. You covered the first 2.
Hope this helps. In winter time you can use every Watt you save.
I would add an inline temperature switch for the heater cable in case the relay fails short.
20or 30°C bimetallic switch should do the job, just keep in mind they aren't very accurate and can have a large hysteresis.
Also would have an over temperature alarm for it
Great scott!!! You are brilliant!!
Haha thank you very much. I try my best with my projects ;-)
❤❤❤ lovely sunday with great scott
Awesome :-)
Brilliant work, dude! Really well done! 😃
I don't know why, but I kept remembering about the mini freezer project! 😂
Anyway, stay safe there with your family! 🖖😊
Brilliant content, keep it up, Scott, I love your videos.❤
Thank you! Will do!
I am extremely interested in how it turns out over time. Currently we are off grid and our generator shed that I made is insulated very well in a very similar fashion but is also very well ventilated because we use flooded lead acid batteries. We are looking to change those out for those new batteries like you have but that's going to be next year. So I am interested to find out if closing up the ventilation and possibly adding active heating is a worthwhile for our little system.
Really good project! If done in larger scale I would maybe try to heat it with water. Since the water could be at 20 Celsius and circulate in copper tubes that would conduct the heat to the batteries. Also it could be used as a coolant during the summer. This would make it possible to have it everything outside as a compartment. Like a small toolshed just for batteries.
I'm cold. ❄️
Thank you! I appreciate it.
Any time! ;-)
Not sure why but this is one of my favorite projects of yours. Nice!
Wow, thanks!
Very nice, thank you for making the video!
If I may suggest a tiny improvement, would you perhaps want to add some nonconducting stop between the poles, so that you can't accidentaly place a conducting element, such as a screwdriver that can short the battery contacts?
Lovely engineering! You should compare this box to the food delivery boxes with reflective insulation to test which is better.
Tungsten light bulbs are also good heaters for enclosed spaces.
Looks great, one thing I would do different is the placement of the heater I think putting it and the temp sensor close to the bottom would give you better efficiency because of convection.
Putting it on the side allows the air to build up speed as it heats up, whereas on the bottom it would heat the air uniformly and rise more slowly. Generally higher air velocities are preferred for heating a space, as the differences in air temp will equalize naturally, more quickly, at higher velocities.
I've been with you for literal years at this point, and I know I said it when you first changed the introduction animation, but bloody hell your quality of production has just completely shot through the roof. The workshop(s) are looking superb and you've somehow managed to make design and construction of a 'reverse battery fridge' interesting. Bravo, Scott. I really do think you're doing a fantastic job, and I'm so pleased to be along for the ride.
One change I would have made, I would have added mylar or some sort of reflective material behind the heating elements. Without doing that, you’re basically just heating the wood behind it. Adding reflective material will also help use less energy also.
Good idea. Can still do that :-)
Thats a Great Idea
I use 3x Victron Battery Balancers on my Lead Acid Batteries to allow equal Charge across whole bank. I Recommend it. Electrician by Trade and Been in the Solar Business for 7 Years@@greatscottlab
@@greatscottlabemergency blankets :) I've used them in summer over windows that get direct sun to avoid overheating. They work well both ways !
I Gun Safe dryer works by creating a little heat to keep the inside of the safe warmer than outside. Also, maybe heat exchangers for your garage vents so it doesn't get so cold in there.
Highly recommend MRBF terminal fuses for you. Very cheap, very easy, and will protect the entire cable length since they allow an installation that has essentially zero un-fused length.
This is the kind of job that incandescent bulbs were often good for. There's also goldenrod heaters that I've never used but often heard about. Though with good insulation, the waste heat from the operation of the electronics should be more than adequate.
i have 10 of those batteries in an old fridge. i added a reversing valve and an inkbird thermostat to it. so it heats during the winter and cools during the summer. i gets in the negative temps here regularly during the winter and up to 110°f+ during the summer
Have you considered how hot the batteries charging or discharging could make the chamber?
Hello, mr. Great Scott! Here’s a golden tip: if you want a faster and a uniform heating just add some(s) Fan inside there, to the heated air get some motion.
Also you should add fans to push air out of the box when the temp goes too high.
Greetings from Brazil 🇧🇷
Next time a mirror heating sticker might work. Those are made for 230v AC and only emit around 5W in a 30*30cm sticker.
Good idea. Never thought of that.
I do know that the chemistry of led acid batteries that you are using is far less volatile than lithium-ion or lithium-iron phosphate but still, is keeping them in an isolated wooden box (while charging some hydrogen may still be venting) together with an electric heater such a “hot” idea when we are taking fireproofing under the consideration? 😊
Bigg fan of great scott. I want a power supply like your's
Your channel is amazing 😎
Thank you so much 😀
if you are using a wooden box, I would add a temperature limiter. Just in case the relay in the relay contacts get welded while switching.
i like such monitoring and control projects! will you be trying any electrochromic windows or something
I was planing a similar setup for my gel lead-acid batteries, I was using stick-on car mirror heaters with 6 watts each under one of the batteries. I never got to testing or using it though - my 'designed in germany' batteries died after less than 100 cycles .... in summer.
You should close the ventilation while you are not inside the garage. Also you should install air recuperator to preserve heat while exchanging air
You might want to wire in series to the relay a non self resetting thermal cutoff, in case the relay fail in SC mode.
A Positive Temperature Coefficient (PTC) heater might be worth looking into.
0:04 Really loving the japanese-inspired design!
Excellent as always! Please consider airtightening the box - especially the holes you drilled for the controller. Keep up the good work! To test, I can recommend a standard disco fog machine (used it lately in my bathroom to find air leaks)
Thanks for the feedback :-)
@@greatscottlab This box will accumulate deadly gasses.
toller Kühlschrank
My 48V 280Ah Battery is also in an isolated box. Isolation is 100mm. The heating is done by two (redundance) 230V 35W heater foil. They are glued to an aluminium plate, where the battery is positioned on. The heating has three (redundance) sensors. Two at the aluminium plate next to the heaters and one at the top above the battery. Additional the balancer is also in the box, which also makes some heat. The sensors are Dallas 18B20 and are connected to an ESP8266. The ESP is connected to an SSR, which is triggert with some kind of slow puls-width-modulation of 4 sec.
The temperatur is stable around 20°C with a precision of 0,1°C. At 10°C outside the timing is, every 3 Minutes the SSR is triggert with a PWM of 5% for 20 Sec.
240v electric bed blankets, usually about 60w, and only warm as you sleep on them.
I'm heating at 12v, theres already 12v in the batteries that i'm needing to warm...which also means if its very cold but sunny, the 12v from the mppt (which isnt charging as its too cold) can run the heaters until it is warm enough to charge, then the heaters can turn off.
Hello GreatScott. Very nice project. I like it. May I have few suggestions for you? 1. I would make holes on the plywood between the batteries and install small fan for air circulation . This will helps temperature to be uniform inside the box. 2. Install 2 thermal sensors on bottom and top and read the delta between them. So you can adjust more precisely the temperature. And then you can play with the fan running time. It is looks became more advance. Have fun. I hope you are like the idea.
Thanks for the tips!
Seems unnecessary. The heating pad is positioned so that it will heat both sections, and I don't think there is such a big area that you would see a huge difference in temp.
@@nimoy007 Also, all he's doing is keeping it above freezing. He's not really trying to precisely control the temperature.
I have to ask. What pens do you use? You draw and write out formulas very well, and the pens also seem perfect.
Nice box!, I know its a little late but you can buy 240V car battery heaters that have a built in 30C thermostats
On your battery box build you may want a fuse or circuit breaker inside in case the exterior terminals get an accidental short. I would also put insulator covers on the terminals as well to reduce the possibility.
Hmm, maybe you should add an overpressure vent? If one of the batteries fails(overcharge etc) and vents gasses, that could destroy the whole thing if it is completely sealed. I don't think keeping lead acid batteries in a completely sealed box is a safe thing to do. Or are there enough gaps for pressure to escape?
@greatscottlab The gasket around the door seems like the easiest way for heat to escape, it would be interesting to see a thermal video of the box when it's really cold in the garage.
Hello Scott,
Nice job 👍
Il just wanted to add that for some strange reason,
watching the final isolation box, I thought of repurposing an old small fridge would have some benefits too.
Oh and some thermal imaging would be helpful too I think
Interesting!
And there will be less firehazard... My idea was old Rack box which is made out of steel...
I'm a bit surprised that you didn't see the PTC heaters. Those are really the way to go. They can run directly off of AC or DC, and at almost any voltage... they just produce a bit less heat at lower voltages. They usually come with a fan (which of course needs the proper voltage to run), but you can get them bare, with fan, or in retail units that include additional safety features (usually also a fuse and a thermal switch).
The PTCs are also very compact. There are also a few different ways you can use them. Throwing in a thermostat is easy, but you can also arrange the voltage to burn fewer watts and just leave it running continuously. So for example, if you take a little 24VDC PTC that normally produces 60W you can run it at 12VDC instead to burn only 15W. And so forth. It really doesn't take much to keep a battery box warm... 5-10W is typically plenty.
I would also say that fire safety is really an issue with batteries. I would go with the rack mount solution and then build a box around it instead of putting the batteries directly in a wooden box.
I had a heated box for some electronics in the cold attic even lover than -20°C by using a 60 W lamp. It wasn’t that well insulated but it was warm on condense free. Well this was in the 90’s and was a quick fix. Yes as all quick and temporary solutions it worked for years.
Other people have mentioned what a bad idea it is to have a flammable box, but I've got to say having no redundancy in the temperature control loop is pretty bad too you should at least have a thermal fuse somewhere that will blow if the temperatures get too hot, otherwise you're just asking for trouble.
Cool! Insulation is your friend! You weren't lazy building that box and that payed off. :)
;-)
I have that exact same cheap Bosch bench drill.
Some old refrigerators can run in reverse, so it can be possible to use an refrigerator and use the control unit you showed to run the compressor
practically u build an over engineered seed/grow box:
- no need for the mineral wool, just use an 1cm tick foamed polystyrene panel
- resistor approach is good, just use an higher resistance one and an anti-slip/knurled aluminum or a proper heat-sink to increase surface
- some holes for air circulation can increase temperature uniformity in the box, a couple 4-5cm in the back of middle panel and leave like 1-1.5cm between middle panel and the door one
- electronics can be simple as an arduino with thermal sensor and a 3-5v relay as u showed and it can let u give custom thresholds and reading intervals, also take a mean of last 5-10 minutes before turn on/off the heating element.
In my own grown box for habanero peppers I just used a tungsten 25w light bulb for the heating, and a couple of kds301 thermostats to keep a temperature of about 28°C and start an exhaust fan at about 30°C.
Nice job. Using an AC mains heating pad, one potential problem is that the heater won't work during a power outage. You could make the unit self-sustaining by using a DC heating pad and connecting it to the batteries directly (using fuses, of course). LFP batteries can be discharged below 0 degrees C no problem.
There are server rack batteries available in the US that come with built-in heaters (Trophy is the brand that I know of), so presumably they'll be available in Europe soon. But as you found, it's not too hard to DIY a heater from components, so it probably makes more financial sense to buy the non-heated version and build the heater to suit the install.
For mains voltage you can use some self regulating heating cables - easy, safe, expensive.
Finally a new video
Had you considered a simple 25W incandescent light bulb ? Wardrobes or linen cupboards used to have low power heaters too. Sort of thing you used to but from a hardware store.
nice, I used similar thermostat yesterday to add heater to my co2 laser so water coolant won't freez
I would use concrete board for the inside for added fire protection...
Very nice work! My comment is that I always worry about something starting on fire particularly when using Chinese components. With so much insulation the system could get really hot if the heaters got stuck on. Maybe a completely separate safety relay system that cuts power if things overheat???
My off-grid batteries are Lead Acid type and they lose capacity during cold weather, I used two old Freezers, one was a display freezer which I laid on its side. Whilst I have no heaters in them, it does help stop them getting too cold I have a automatic fire extinqisher installed and old fire blankets are ideal to cover batteries.
Not sure how much a chest freezer might cost used but I was wondering if it would be possible to use one? Seems to have some sort of similar functions with temp sensing already?
Since you are using a lithium batteries, it may make sense for you to add an additional "safety" thermostat, just in case something goes wrong with the temperature controller. It could be a cheap mechanical thermostat wired in series to the heater and set at a higher temperature than desired (e.g. 20°C).
Btw, did you calculate what were the average heating losses in watts?
A simple little klixon would do for an inline safety cut off.
I used heated seed germination mats. They come with everything built in to maintain a 90 f temp. No other electronics needed.
Permanently installed Outdoor standby Generators will sometimes have Silicone Heating pads Directly underneath the Battery. Temperature controlled and everything. Just Plug into 120v.
I've used a water heater thermostat for a cheap thermal controller before.
I just built battery heaters last week. I did a 12V system running off my 12v batteries. I used 2 x 20W heating pads taped to the inside of the metal box, an stc-1000 heat controller, and an XH-M609 low voltage disconnect. I surrounded the whole thing in 2" XPS foam. This is superior to a regular battery heater in one way: I draw power from downstream of my system's coulomb counter. A self-heating battery could discharge its entire capacity and your system would never know it.
Sounds great. Thanks for sharing.
Scott, This will be very helpful as I will need to build a hot box for testing imbedded thermocouples where I will have to heat the entire item at different temp stages to verify and find calibration deltas.
A Build It Or Buy It ideal. Isolation transformer. Buy it or build it from a microwave oven transformer by rewinding the secondary. I think this would make a great video. I cannot find a video on line for this.
I know it's just a prototype for now, but one thing I immediately noticed is that it lacks a ventilation system - you might want to do the opposite and COOL the insides of the box if the batts get TOO warm. How about placing the heater core on the walls rather than on the door, or better yet: using SEVERAL heaters around the box ?
you could use a small air conditioner to make a sort of heat pump heater, even more efficient! or even just peltier thermoelectric coolers, used in reverse, and with a fan on the cool side, will also give you over-unity heating