Pond Boss Forums AERATION Systems questions DIY solar aerator - help needed

Hi everyone! I�m totally new to solar power but I went ahead and tried to build myself a solar powered aerator for my pond. It works but not as well as I would have liked. I�m on a pretty tight budget so I thought I could run it without a battery, but that did not work for some reason. I got a cheap 100 watt solar panel kit from harbor freight that came with its own charge controller. Then I added a Blue Diamond ETA 80 pump and an inverter. The charge controller would not work without the battery, but even with one, the pump only ran for a few hours and then would have to charge again. Do I need more solar panels? Or should I have a smaller pump? Or is there a way to have the solar panels power the pump instead of just charging the battery? My pond is about a half acre and around 8 ft deep in the center. Any help would be greatly appreciated! Thanks!

I am not very knowledgeable about solar systems. I am also looking to setting up a solar aerator. You pump is probably adequate. I suspect your battery is too small or too few of them. What type of deep cycle battery do you have and how "big" (capacity) is it?

What type of diffuser are you using and what is the cfm of the compressor? Both will let those knowledgeable help with more info.

I used a 12v 275 amp lawn mower battery. The pump is 2.6 cfm. I just made homemade diffusers by making a circle with the air hose and drilling 1/16 holes in it. I originally had two set up but then I then I switched it back to one because it seemed like it might not have had enough power for both. Not sure which is best though?

There a guy on YouTube who builds/sells solar powered systems on the cheap. There is something that you may need to override due to the low output during cloudy days and low light.
It is an official sounding channel...there it is! Missouri Wind and solar. You may learn some good info. I did!
Most DIY systems, he admits to, are limited by water depth. Septic pumps cannot pump air below about 8ft.
He has a lot of videos. It sounds like he would be willing to talk to you if you have specific questions.
Good luck! Please update this post or another with your progress

So what you are saying is you are running an AC pump with the inverter.
Your Pump motor is an 80w unit. At peak Pv your panel will provide about 90% conversion in direct sunlight. Charge controller uses some power, inverter uses some power, etc.. you are quite a ways below supply power needed to run an 80w pump and keep battery charged.
I run 2 80w panels and 4 300ah batts in series-parallel to run a 60w (DC) motor. For daytime aerator operation it's best to run a 24v DC pump on a 18v panel and wire direct from panel to pump.

What Snipe said! You need way more panel.

Plus the fastest way to destroy your battery, or any battery for that matter, is to run it down to dead a few times. Each time you do that it damages the battery. Try to work it to where WORST CASE you pull the battery down to 50-60% charge at the lowest. I try not to pull mine down below 80%.

Thanks! I did watch a couple of his videos already. However, it didn�t seem like he went into too much detail about the components needed without buying one of his kits (I certainly don�t blame him for that). I actually went to their website before I got anything but it was a little more than I wanted to spend for the whole kit. I guess I could ask him about individual parts though

That�s what I was afraid of! Do you think I can get away with a smaller or more efficient pump for my size pond? Or is getting more panels the way to go? I assume there is just some sort of adapter I could get to connect them all to the same controller right?

I believe my charge controller doesn�t allow the battery to drop below 10.8 v, so hopefully that�s not too low to damage it. But yeah I guess I have to get more panels. Would another 100 watt panel be sufficient?

There are all kinds of formulas for figuring that out, but I don't know them off the top of my head. Just know that a 100 watt panel is rated 100 watts in a lab, not the real world. So a 100 watt panel at sea level is more like an 85 watt panel. Then controller losses, etc. I prefer to over panel if possible. See how much panel your controller can handle and go with that - is my style. Then you could always add a second battery in parallel to double your capacity, but enough panel will be even more important.

It's a long learning process. I am just now feeling like I have improved from totally clueless to know enough to be dangerous.

If you will list specs of your controller, such as is it 12/24v, 20 amp, MPPT or just PWM type. If you'll list specs I think I can help, but to start with, a single panel rated 100w is not enough for an 80w pump unless you are wiring it direct to pump (DC) but your pump is AC so you can't do that.
If your setup is 12v you have to be very careful about wire size, 24v-not so much.
It's not too bad figuring all of this out, we just need some info on your controller.

E26,
At the risk of starting something...

First thing to consider is what you want to accomplish. Then set the requirements. Then see if you can afford to do it.

I use poly or mono crystal panels and MPPT controllers. I "expect" 60% production at best. Currently I have been able to generate more, but I have a lot of experience.

About batteries, I use good deep cycle batteries. I use 6 volt batteries and set then up in series. I started out with a 12 volt system, but eventually I have upgraded to a 48 volt system. In 12 volts, you will be limited. At 24 volts, you have more options. When you get to 48 volts, you will have a lot of options.

If you are going to do this on a budget, consider getting the right panels for a PWM controller like the Brat and go 24 volts. If you don't use MPPT, you panel selection is paramount. If you use "12" volt panels, you will be waisting 40% of your power just to start with. I currently use the Kid MPPT charge controller and panels that allow for the Vmp to be used while tracking.

If all of this is greek to you, you can still do this but you will not have a best value system. Also, if you are using a step sign-wave inverter, your pump will wear out a lot sooner.

SO simply put, let us know the requirement and the budget and we will see what we can do.

My barn is powered by solar; currently have three 200w Hightec panels wired in series, going to a Renogy Rover 40A MPPT controller, charging four Duracell 6V GC2 golf cart batteries in series, powering a 24V AIMS 2000W inverter/charger. Usable power from full batteries @ 25.6V to 50% depth of discharge is 2500W.

I have three more panels to install for two parallel 600W strings, 1200W total PV. My panels are oriented west-southwest, so not ideal, and I've never generated more than 450W/75% from my current three-panel string.

I'm about to pull the trigger on an aeration system, which will be powered by my barn solar and therefore the solar is a significant limiting factor. I'm torn between getting a larger diaphragm pump that will be near maxed out on my 0.4A, 12' deep pond (I think a single 9" or 12" diffuser would be fine, two 9" might be pushing it with diffusers at 10' depth) because it is so much more energy efficient, or going with a 1/4hp rocking piston pump that uses twice the energy but more CFMs at higher PSI, allowing for faster turnover and shorter run time.

At a MINIMUM I would go with 200w of PV into a MPPT controller, and two 6V GC2 batteries in series. Yes there's a bit more upfront investment, but it'll help alleviate headaches from compromised equipment down the road.

It is 12v, 10A. I don�t know if it is MPPT or PWM... I didn�t see that anywhere. It came in a kit... thunderbolt magnum from harbor freight. The wires in the kit look like 14 or 16 gage braided wire... I was wondering if that�s enough. I was actually considering trying to return the pump I have and getting a DC pump that�s about 60w. I think that may be powerful enough for my pond and then I won�t have to get more panels. Would that be wise or are more panels the way to go?

Harbor Freight is all cheap PWM controllers.

I understand you want to do this on a budget so I'm going to tell you my thoughts based on what you have.
If using 12v only, with a single panel yer already in trouble-trying to do what you are..
I also understand where the guys above me are going with high-end systems.
With that said, I know you don't have enough power to run your pump without charging a battery, so let's back up.
To get the inverter to work properly, you need 2 panels in parallel to get the amps up. You probably need a minimum of 2 100w panels to make this work.
Not knowing what type controller you have, this can be an issue in efficiency-this is not the place to cut corners.
You really need an MPPT controller, #1. Poly panels would be best but mono will work, #2. You need an inverter that can handle the input safely and this is where you need to do some research on making sure it can optimize your input (That is maximized by your MPPT controller) to properly cycle the battery and I believe you need (at the least) 2 batteries of decent quality. Series or parallel will depend on panel type and output (usually 24v is more efficient) so series wiring is in order.
Whether you can run this at night or in the day is dependent on how far you want to go money-wise. If running day time only, then forget the battery, The controller will only provide power to the inverter when it reaches a minimum value required and the pump will kick on.
For night-time operation, things get more complex and more expensive and there really isn't any way to get around that part.
Bottom line is what are you trying to do with this kit?
The guys above have touched on the important bullets for an optimum system.

E26,

There are a few things here being said that are not your best options, so I'll lay it out.

Panels, you need two 100 watt "12 volt" panels minimum. Expect $100 per panel plus shipping unless you can find them locally.

Charge controller, Use the Brat if you want to go PWM. Quick search, $100 delivered.

Batteries, use two 6 volt Golf cart batteries. 200AH minimum. Expect $150 each.

You have an inverter and the pump. Use them until they quit and then look for a better matched pump.

Using this setup, I would expect 1.2 KWH of power nominal. If it is cloudy in your area often, then cut that in half.

"There are a few things here being said that are not your best options, so I'll lay it out."

Was there something I suggested that was incorrect??

Thanks guys! That was all very helpful. I do understand the perks of putting in a better system right away, but it�s just not an option right now, so I appreciate the input on how I can do this as cost effective as possible. I thought taking some action now and improving it as I can would be better than waiting until I can afford a better one. 3 years ago my pond was at least 75% covered in lily pads. I used an herbicide to remove the majority of them and only left 3 smaller patches. At the time the water was crystal clear, but gradually I have been seeing it get worse each year. This summer the pond really got mucky and has a lot of algae and seaweed growing up. So I was hoping an aerator would help.

So back to my aerator... My original plan was to run it just in the daytime without the batteries, so I think that may be the area where I can save some costs. I will get another 100w panel, and then that should run the pump without the battery, right? Or do I need something else to make that happen? If I get poly panels, will that be ok with the ones I have? I will also look into a new charge controller and inverter (I got a cheapo inverter too). Any suggestions for quality affordable ones would be appreciated. I may try it with what I have too just to see how it works. Does this sound like a reasonable plan? Thanks again

E26,

Your panels are amorphous film solar panels. They will not work well with poly or mono crystals as their production voltage is different. There will be other incompatibilities as well.

Your panels need to be the same type and have the same specs. ( A matched pair is obviously best).

For an inverter, you need to think of the startup current pulled for any pump you have or are considering. If your inverter is too small, it won't work. Pure sine wave inverters are much better for anything sensitive.

If you are going to try to get a DC pump and run it straight off the panels, you must learn about Linear Current Boosters or you risk damaging your pump. Yes there are other ways to connect them, but that is even more advanced than using an LCB.

I cannot talk to wether or not your current setup will help or hurt your pond. But I do know you are eventually going to have to decide which way you want to go. Yes you can use what you have, or you can upgrade when you can afford to do so. Either way, learn about balancing your system so you do not damage your batteries, panels, or pump.

If you upgrade one piece at a time, buy the batteries last as they have a "shelf life" if not used and charged regularly.

Highflyer has a very good working knowledge of this as I learned on the phone with him today. Great to have that knowledge here to tap into and I look forward to speaking with him again.
Thanks for the info highflyer! And yes, I still have a couple of questions but we're on the right track.

Thanks again guys! I ordered a 500w pure sine wave inverter, and on Friday I�m picking up another 100w of the same panels that I have. I�m going to try it without the batteries and with the controller I currently have (unless you think that is a risk for messing something else up?). I�ll update you when get it running!

Loss of the majority or your water lilies contributed to your cloudy water. Higher types of plant life in the pond competes for nutrients and in other ways tends to create more toward clear water and vice versa.

Yeah I figured that out a little too late lol. Either way I needed to get rid of some of those lilies... the pond was pretty much unfishable. But yeah I fixed one problem and caused another. Hopefully the aerator helps!

E26,
With the type of controller you have, you will damage your inverter and pump if you don't have a battery in your system. If you are going to run daylight hours only, almost any battery will work. It is there to stabilize the voltage. Without it, the voltage will spike and sag with the solar output and inverter load. If you are going to run at night, I would go with the golf cart style 6 volt batteries as needed for the load you anticipate (two batteries minimum obviously).

Let us know how it goes after Friday's upgrades!

Thanks for the warning highflyer! I�ll keep my current battery (12v 275A) for now and just plan to run it daytime. Is it ok to leave it on 24/7 with that set up or will that be too much drop in voltage at night to cause damage?

E26,
Do you know the wattage of your pump? Or amperage?

I would doubt that one battery would be able to hold enough charge to last the night. Further, you would need to have enough panels to run the pump and recharge the battery every day. That would be a tall order for those panels. Once we know the runtime you can reasonably expect, I believe other experts would have you consider starting your pump some amount of time before sunrise so to get the cooling benefit and allow the batteries to start getting refilled with the sunrise.

The pump is 80 watts. Amperage capacity is 1.6. I don�t know how important it is to run the pump continuously, but I would think even if it shuts off for a few hours it would still be helpful for the pond quality. If the battery dies overnight, would it just recharge in the morning and then after it is charged the pump will run? Or are you saying it will try to charge the battery and run the pump at the same time and that won�t work?

E26,
Going back and checking your battery, I now see it is a lawnmower battery. It does not have a lot of amp-hour capacity. I would guesstimate 10AH. This means it is only going to give you one hour of runtime before damage starts to happen. I would set it up to run around 9AM and have it turn off around 3PM max after you are sure it can produce enough power for this timeframe. This may be too much for the battery if it is cloudy.

I would expect you could get as little as 10 watts per "100 watt" panel if it is cloudy during the day. This means you really need to pay attention to your voltage to see how the battery is doing periodically.

So here is my recommendation:

Get your second 100W "panel"
Run for three hours a day and see how the battery does
Up the run time as your setup allows
Get a better charge controller
Get better batteries
Run your system as long as possible for the power you are producing less 15%
Reassess

Ok thanks. Another thing I was wondering is if I should connect my inverter directly to the battery or to the load output on the charge controller? My understanding is that connecting it to the controller probably won�t produce enough power, but connecting it right to the battery is what can cause the battery voltage to drop too low. Is that right? If so, what�s best for my set up?

Two things to add first, that lawnmower battery can only handle about 3 amps max charge rate without damage. It's just too small to do much. It is a starting battery and that is just about it. That said, if you want to run during the day it will work. I would connect the inverter directly to a fuse or CB that ties into the battery. If you are not protected, you are asking for trouble. Second thing, get yourself a cheep DC timer from any online retailer ($10-20). Us it and a higher power relay and use that to power the inverter for the hours of runtime you believe you can support.

That inverter will smoke that cheep PWM controller if it pulls too much power. DO NOT connect an inverter to the load side of that tiny controller. You will release the mythical blue smoke, and it never goes back in.

There is excellent, experienced, very wise, valuable and free advice provided in this thread for those with solar aeration inklings and thoughts of building one. Believe it and appreciate the advice. A big thank you to those gracious members who are contributing.

Absolutely! I am very grateful for those taking the time to give me some great advice! Thank you all!

Thanks Highflyer! Here�s an update of where I�m at and what I hope to do in the future based on your advice. You are right that the battery is way too small to do much. Right now, I don�t want the unit running 24/7 because I heard that could lead to fish kill if you aerate too much too soon, so I�m ok with it for now. I do want to upgrade in the future (hopefully before winter to prevent freeze), and I�ll probably get two 6v deep cycle batteries. Currently the pump runs fine from about 9:00-7:00 which is great for now, but it will run the battery too low. I believe the inverter shuts down and alarm goes off at 10.4v. I also believe the inverter has a built in fuse. Do you still think I should put another one in? I really like your idea of a timer that would be a good cheap solution for now. I was also actually looking into a low voltage shutdown that I think would be ideal for me especially if I end up spending more on batteries. From what I understand draining the battery to 10.4 will damage it eventually, plus with this device I wouldn�t have to worry about draining the batteries on cloudy days (which could still happen with the timer). Here is a link to it. https://mwands.com/shop/product/battery-protection-switch#

E26,
The battery is too small and the wrong type. It is a starting battery not a deep cycle battery.

The internal inverter fuse is a last chance fuse. I would still use an inline fuse.

In your area, the batteries will need to be protected from the cold in winter, especially as hard as you are going to run them.

See if your charge controller has a low battery disconnect. If it does, you can use the load outputs with the low voltage cutout to power the relay which runs the inverter. This way, when the charge controller sees the battery voltage sagging, the controller can kill the relay and thus the inverter until the battery recovers.

If your charge controller has a low voltage cutout for the load, that will be all you need to use. I have no dealings with MWandS. I would look for a cheeper solution from a reputable retailer if the charge controller does not have this protection. I do know the Brat charge controller does have a selectable low voltage cutout.

Bill,
I am humbled to receive such an endorsement from one I hold in such high esteem. Thank you for the complement. I will continue to help where I can.

What I am thinking about is to "build" virtual solar systems for 12, 24, and 48 volts. These systems would use off the shelf parts I know about and I would be able to give estimates of the daily power available. Some of the issues would be battery sizing, panel selection, controllers, and inverters (if AC power is wanted/needed).

One of the biggest issues is that most people that start using solar always want more power. So upgradability is key to best value solutions.

Thoughts?

Ok thanks. I just order an in-line fuse and a $40 Victron low voltage disconnect because my charge controller doesn�t have that capability. I will definitely upgrade the battery as soon as I can. Thanks for pointing out my batteries will need protection in the winter... I hadn�t even thought of that! Can I just put them in a well insulated box? Does it need any ventilation? I�m not sure how else I could keep them warmer out there?

I hope this thread is archived for future reference.
Highflyer has also helped me a considerable amount on getting my DC system optimized. This is priceless here, especially when the folks selling an "aeration system" can't give advice at the level we are receiving right here.
EDIT: Highflyer, I would think a Virtual system would be of incredible value here. I can add weight to that by saying by our phone conversations, you are very obviously not new to this. Your experience level here is more than one could ever ask for. I for one would like to see your ideas to straighten a lot of the misunderstandings of solar usage out.
Thank you.

E26,
An old cooler would be a good start. Yes you do need "any" ventilation. The smallest of outlets for escaping gasses is all I use for small systems. Tip of the day for ventilation holes, point then down so the rain does not fill your battery box.

More about winter ops, do not under any circumstance let your batteries go flat in winter, if they freeze, they are for all purposes dead. Yes they can be revived, but that is a higher level of understanding and takes a long time to accomplish if the battery does not rupture. Ask me how I know....

I'll see if Bob would like a new thread about solar systems, or if he would like it here. Either way I think I can have something easy to understand in short order.

I understand that cost is a big factor for most, but if you can't fulfill the requirement, the system is of little use. So in my mind, it is "know the requirement first," them see if solar is right for you. Then add 10% just because "it" happens.

A few things to know right up front:

12 volt systems are very limited. 10 amps is only 120 watts nominal
even at 30 amps, you are only at 360 watts nominal. Multiply that by the hours of sunlight you receive and subtract for clouds and you will have a rough idea of the power you can use daily.

24 volt systems are twice as powerful for the same amps. So now you can "make" something close to 700 watts at 30 amps. But with this power, you can't run high loads for very long.

So if you want to use a lot of power, 48 volt systems are where you are going to end up.

My current big system uses Eight 6V 428AH batteries and the same six 230 watt panels wired two strings of three in series for a total of 1380 watts potentially. I have seen 1250 watts during noon time sun and a spike wattage of 1365. I use a Midnite solar Kid controller and all of my wire is high grade. The cables from battery to battery is 1/0 high strand count welding cable. I "build" my cables custom. My current inverter is adequate. I am waiting for a new offering from Midnite before I upgrade my AC inverter. I have made 8KWH of power in one day testing this setup. I also have my panels on a solar tracker I built. It allows for southeast to northwest tracking. If I did not have the tracker, I would expect to loose 2KWHs minimum on this system daily. I can also set up another identical set of panels and use the same battery bank for twice the power available daily. It has the capability to accept that much charge without damage. Again, I sized the parts correctly for the potential upgrade.

In short, there is a lot to learn/know about when setting up a solar system. If you don't know, you can spend a lot of money on things that are not going to give you your best value.

The biggest thing I can say is that I had a lot of help from those who are way smarter on this than me. All I can do is share what I have learned. And I am glad to do so.

I have been collecting a few pieces of information about solar aeration. I will put this thread with some other info in the Archives of Common Pond Q&A.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=511063#Post511063

Hi everyone, bumping my old thread because I finally got the chance to invest in two 6v golf cart batteries for my solar aerator. The only other part of my system I still need to upgrade is the charge controller. I am thinking of getting an affordable MPPT controller. Not sure how many amps I would need it to be, or what brand is best. Anyone have any recommendations that would suit my needs? Thanks in advance!

Midnite Kid hands down. It is a great little charge controller!! It's not "cheap", but you get what you pay for. It would also give you some room to grow.

Eagle,

How much energy do you need? What size solar panels are you using? How many panels are you using. Do you want to be able to upgrade your production in the future?

With this information, I will tell you to buy the Kid. It is the best and it is manufactured in the USA.

Eagle26, Highflyer is the "Man" when it comes to solar.. Give him what you are expecting and he'll tell ya how to make it work.

I have 200 watts of amorphous solar panels. I am running an 80 watt AC pump. I don’t think I would ever need more power than that for my pond. I should mention that I don’t want to “over buy” for my small operation, but I want something decent. Thanks!

Eagle26,

You will not purchase the Kid, got it. So I would tell you to do your research online from any of the big box stores and purchase a best seller, or big box recommendation.

(Side note) Do you know the Imp and Vmp of your panels? Also, those panels are won't last year after year, so be ready to replace them or end your project. Another thing to consider is the fact that those panes may not be able to fully charge your batteries. Best of luck.

I do not know the Imp and Vmp of my panels. I can add or replace panels down the road if I need to. I’ll look into some charge controllers. Do you know how many Amps I would need it to be? Also, just checking that I only need one even though I have two batteries? I can charge both batteries together because they are wired in series, right? Thanks for all your help, highflyer. I’ve learned so much from you and others on here... still have much to learn though lol

Eagle26,

I am going to break my rule and try one more time. Imp and Vmp are the amps and voltage where the maximum energy (in watts) can be produced. If you lower the voltage or amperage, you lower the total available energy. I would guess your Film panels run around 22 volts. I would guess Vmp is around 18 volts, now tie that to a PWM controller, and they can produce 12.5ish. At the nominal 18 volts, your panels will see around 5ish amps. Multiply the 5 maximum amps with the 12.5 volts being generated by the panels and you get 70 watts ish. Now look at the losses through your system. Subtract 10 to 25 percent more. Now realize your amorphous panels loos 10-30 % after 6 to 8 months and you can see that you are running on borrowed time. It you buy a cheep overseas MPPT controller, the losses will also be high, and it won't last very long.

About your batteries. If you have two 6 volt golf cart batteries, you must use them both together to have the 12 volts needed to run your inverter. If they are 12 volt batteries and you only use one at a time, be careful. The next thing you need to learn is how much power your batteries need to be suppled to be fully charged. Your battery manufacture will give you recommended and maximum charge rates and voltages for bulk, absorb, and float.

In short, Solar power is a complex undertaking. If done poorly, there are going to be problems. To do solar power correctly cost money. There are places where you can save, but if you skimp on the important bits, it will cost you forever.

I get wanting to do solar on the cheep, but it rarely works out. You must know what you are doing. I would recommend taking a solar power class at your local Community college. Those programs are setup to guide you through the initial steps to ensure you have the foundation to succeed. Again, best of luck doing it your way.

Thanks for all your help Highflyer! I obviously have a lot to learn! I’m sorry if it came off like I wasn’t willing to take your advice. I had already jumped in by buying the cheap solar kit and was hoping to find a way to make it work. Per your advice, I upgraded parts when I could most recently adding the two 6 v golf cart batteries and new controller. Looks like I’ll have to upgrade the panels in the not too distant future as well.

Eagle - you will figure it out. IMHO It is much easier to figure it out by actually doing - even if you are not doing it right (just don't kill any components). I still don't totally understand everything and I made a heap of power the last two days lol. BUT I understand all the little details a little more each year. Maybe you run what you have, learn, and upgrade to better parts as you go and can afford to.

Hey, just thought my first post would be reviving and old thread But since some of the subforums don't get much traffic, maybe this doesn't count as an old thread?

For anyone building solar where you don't don't need to use the battery in freezing weather (or can protect the battery from freezing), I strongly recommend you take a look at LiFeP04 batteries. They're lithium, but not the lithium-ion type in your laptop.

A lead acid (flooded, gel, agm, etc) will probably last you around 300-500 charge cycles if you only disharge it around 50%. A LiFePO4 battery should last over 4,000 cycles with a 100% discharge. The downside is you can't charge them below freezing without damaging them. If you can manage the freeze issue, you get a much lower total cost of ownership over the life of the battery with only a minor increase in cost for a given usable capacity.

For example, a quality 100AH lead acid battery probably costs around $100-$150, with a usable capacity of around 50AH. So it would take 2 to get 100 AH usable. A 100AH LiFePO4 runs $300-$350 on amazon. So its close to the same upfront cost for the same usable capacity and it will last thousands of cycles. Plus higher charge and discharge rates (typically 1C, which means a 100AH battery can safely sustain 100 amps charging or discharging).

Just be careful of some cheap batteries on Amazon falsely claiming to have low temp protection.