Question about Solar charge controller overheating

[Dacflyer]

Hi, I have another question of my charge controller.. https://www.ebay.com/itm/363022568161
The unit is good for 150VDC max. input and I am on 24VDC system. I know this is a lot of conversion power.
My input voltage is about 120VDC 855W The unit gets quite hot,, enough that i needed to add in a cooling fan.
I am still below the maximum input. I want to add in more solar.
I wish to add 295W extra.. ( so i will have a total of 1,180W ) The controller says it can take 1300w max.
I will plan to change input voltage to about 80vdc, 2s2p configuration. this will give me about 80V input
So will this change decrease the heat ? is it safe?
I still plan to still use the fan for cooling the heatsink.
Any advice on this ? I think i am within my limits. This will be charging 200Ah AGM 24V
Inverter is a hacked UPS APC1400 ( 950W max ) but i'm not maxing it out. Average about less than 200W, but if i work in my shop, i might get to about 300 or 400 watts for like a few hrs. This is just running lights only. for now, til i get my big system up and running..
Still waiting for china deliveries..

 

[HRTKD]

If you think you're already overheating the charge controller, why would you add more panels? With your new panel configuration you're going to reduce the input volts, but the watts will increase.

It seems like you bought a cheap solar charge controller and you need to live well within it's real world limitations.

 

[Dacflyer]

I think I can keep things under control with a fan.. it cools the unit well.
It has a year warranty.. so if it fails, i'll deal with that..
But if i keep it cool.. would there be anything to be concerned about ?
as far as my voltage reduction,, 80v should still be fine for 24v system,, there won't be such a wide voltage span,, less conversion..
so maybe less heat?

 

[schmism]

voltage doesnt create heat. Current does. Pushing more current (more panel watts) will only increase the amount of heat that is generated.

You have a photo of your unit? You have the 50a version? The unit should be mounted on a wall with the fins on the back also mounted vertically.

The reason the entire rear of the unit is cooling fins is because they make a bunch of heat.

 

[Dacflyer]

Yes, it is vertical mounted...yes i have the 50A version.
ya, it is a large heatsink.. but not sufficient. without fan, i can't keep fingers on it for very long..
with the fan. it's barely warm.. it seems to do the work
the reason I'm changing the voltage is.. It's they only way i can add another panel without maxing out the controller. 4 panels in series will be overvoltage, 2s2p I will be within limits

 

[BiduleOhm]

ya, it is a large heatsink.. but not sufficient. without fan, i can't keep fingers on it for very long..

It's not because a heatsink is above human skin burning temp that it is too hot. Heatsinks are bulky and expensive so it makes sense to use one as small as possible while still doing the job, which means it'll run somewhat hot.

Plus, for example, in 30 °C ambient you only have 20-25 °C of dT until you reach burning skin temps and that's not a lot of delta for a passive heatsink.

So as long as you stay within the SCC limits and as long as it's correctly mounted then it'll be fine.

Now even a small breeze will divide the heatsink Rth by 2 or 3 in comparison to passive only so if you're ok with adding a fan (noise, power consumption, ...) then you can have one, it can do only good

 

[Dacflyer]

I was always taught that if you can't keep your fingers on it, then it's too hot..
Going with a smaller heatsink to save money on a product is just being too cheap,
a larger heatsink wouldn't be that much more.
If you build and design a product, and you want fame of a good product, you make the necessary changes to make it a top product.
Nothing beats good R&D

 

[Forbisher]

I was always taught that if you can't keep your fingers on it, then it's too hot..
Going with a smaller heatsink to save money on a product is just being too cheap,
a larger heatsink wouldn't be that much more.
If you build and design a product, and you want fame of a good product, you make the necessary changes to make it a top product.
Nothing beats good R&D

When you buy cheap junk like this what did you expect?

 

[Dacflyer]

It does well otherwise, I can't complain about it except for that it needs a fan..
Keeping the display light on would be a bonus. It times out too quickly.
And for my small project, I didn't need anything top of the line..
I mainly was just wanting to know if what i was reconfiguring would be ok.
I'm sure I'm within limits..

 

[BiduleOhm]

I was always taught that if you can't keep your fingers on it, then it's too hot..
Going with a smaller heatsink to save money on a product is just being too cheap,
a larger heatsink wouldn't be that much more.
If you build and design a product, and you want fame of a good product, you make the necessary changes to make it a top product.
Nothing beats good R&D

I agree on good R&D but the heatsink is here to cool components properly, not to not burn your fingers. If running the heatsink at 60 or 70 °C for example is plenty fine to cool the components with some margin (and it usually is given most components can handle much higher temps than that) then it's good design and there's basically only inconvenients (well, besides not burning your fingers) to putting a bigger heatsink.

Also it's usually not a linear rule so to divide the temp by two for example you'll need to increase the size by more than twice, so you hit the diminishing returns point very very quickly.

And if we're talking 40-45 °C ambient as you have each summer in some countries you'll not even be able to run the heatsink at lower than burning temps at all.

 

[BiduleOhm]

I know only a little about electronics but one thing I know for sure is that all electronics hate heat. I have pulled many inverters apart to salvage components and the main things that hate heat are capacitors and Mosfet/ IGBT's and inverters are full of them. Keeping them cool is a no brainer.

Yes and no. Electrolytic capacitors hate heat, that's for sure. Other cap types are pretty ok. Mosfets don't really mind high temps as long as you don't go over their maximum Tj. You can see page 279 of this pdf that there's a big difference in failure rate between 25 and 55 °C but not much between 55 and 85 °C or 85 and 125 °C. Voltage is also a far bigger factor in longevity as you can see here; a 4 V increase makes a bigger difference than going from a Tj of 50 to 150 °C...

Also mosfets are super reliable if you don't go past their maximum ratings, a 10 or 20 °C increase on the Tj will not make any practical difference (unless you plan to live for hundreds of years), especially as other components are far more likely to fail before the mosfets.

I also know from several other interests that there is no comparison between passive cooling and forced air cooling. A fan shoots the rating of a heat sink through the roof.

Yes, that's what I said, even little air flow decreases the heatsink temp by a lot. And the reliability and longevity of your system goes to the drain because you now have a mechanical part who will wear and fails in years if used 24/365. Adding a fan to an already existing passive design is ok as when it fails the system will still able to dissipate the power needed passively, but doing an active cooling design from the start is a worse design than doing a passive one (even if it runs at fingers burning temp) IMHO.

My setups with the old panels are perfect. When there is no/low sun the things don't or barely run. The more sun, the harder the inverter is working the faster the fan blows. It's the perfect fully automated, stepless control cooling system. I have had a similar setup in my shed window for about 8 years now. Some broken house panels on the roof wired to a double radiator fan in the shed window. Sits there all day every day and has done for years blowing a gale in the summer and still going. The fans were off a 12 YO car when I got them and they still haven't work out unlike a lot of internet hype and paranoia would suggest. I use them on my stationary engine generators and people talk about them failing. 8 years of daylight hours use, that's dependable enough for me!

I would say you are on the right track with the fan. If the thing is getting hot, Put on more or a bigger fan.
I'm not sure about the Voltage/ current heat creation equation. Higher voltage on the input means higher amps on the conversion so I'm not sure if lowering input current will make any difference.

Of course if fans and power to run them are free or near free and noise isn't a concern then do it

 

[Dacflyer]

Update on this charge controller, it's doing quite well with the fan mod.. I'm getting great charges per day, over 3,000wh a day, it keeps my 200ah bank charged up just fine. Might add in another more batteries, just to give me more reserve. 3,175wh is my highest charge to date..
The only disappointment is customer service.. Yes I know you get what you pay for... But someone's gotta test it.. And i like this unit can handle up to 50A
EPEVER only goes up to 40A..and cost easy more.

 

[Hedges]

Try adding a chimney over the fins. That may provide higher airflow passively.
Works pretty well for oil lamps.

I wired a spare PV panel to some brushless DC fans that didn't mind gradual power-up.

 

[Dacflyer]

I made a small flat fan box with a 4" PC fan, it blows air down all the fins.. and i made the fan proportional speed controlled.
The speed varies according to how hot it is. The fan never goes full speed. so it's doing a good job of keeping things cooler.
I'm satisfied with it.