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Those Cheap Blue Charge Controllers

DavidAnderman

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May 1, 2020
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There are actually two flavors of them, cheap and cheaper. The cheaper ones are smaller, and go for $10 or so.

No, they don’t have MPPT capability.

The big ones claim to have 100 amp capability for some models.

it would be nice to know the name of the manufacturer to be able to call them something other than “cheap blue”. Is there a model number?

I have purchased a few of these. One failed spectacularly; perhaps I connected it to too many panels or too high a voltage. Another simply stopped working after a few days. Those were the larger ones, the small ones seem okay, but I am testing that does not charge a battery. Even though there is no load, 5he battery voltage never goes up, it just goes down, slowly.

why do I buy these cheap controllers? Sometimes I will set up a panel and battery in the field, maybe to pump some water or run a fan, and I need a cheap, low capacity 12v controller.
 

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Mine, black & green 30amp type, were putting out so much heat I zipped tied a old server cpu cooler to the back. Barely feel any heat now.
Reading comments from solar forums it's the voltage that destroys the charge controllers quickest so I make sure the Voc is well under the limit.
 
Mine, black & green 30amp type, were putting out so much heat I zipped tied a old server cpu cooler to the back. Barely feel any heat now.
Reading comments from solar forums it's the voltage that destroys the charge controllers quickest so I make sure the Voc is well under the limit.

What is a safe voltage for these controllers?
 
What is a safe voltage for these controllers?
It should say on the controller itself. I have a few and some are 25v, some are 50v. When determining your input voltage, use VoC and note that this voltage is rated at 25 deg C and will increase as the temperature decreases. ( ~.4v per deg C ? ... varies per panel).
 
Most importantly from reading the various distributors/Amazon reviews is always have a battery with some charge left in them hooked up before even thinking about taking the PV panels out of the closet. Failure to do so kills some circuits in these. If just PV is hooked up alone they will melt-same thing happens if your battery dies. If battery is hooked up later after killing the logic circuit they will boil the battery as the high voltage disconnect feature was previously destroyed.

From my experience from being stupid, impatient, and having received one with a 80W Foldable some time ago (same manufacture but different colored plastic on outside case by the size/features/LCD display) there is no reverse polarity protection. Killed mine even before first use when I just ever so briefly hooked the battery up backwards -it killed the ability of the thing to do high voltage disconnect. They have high initial failure rate so definitely not plug and play as you have to do the QC check on these yourselves prior to use. These things die to easily but none the less they are so cheap I did buy another as an last resort spare controller. Beware that the one with the photo right on the original post is often time sold on Chinese sights and Amazon as "MPPT" and apparently they are not according to several angry youtube videos.

If you are smarter than the controller they do have a place as as cheap consumable in a cheap consumable system, just like batteries in a flashlight of yesteryear, that you replace over time-especially good for the Newbie-tinkerer that does not know what to buy and use-for most the first time buyers you have your first system for less than a year before you know what you want/need and replace that first system. No sense throwing good money for high quality if it rarely gets used or the total system life is not long.

Unfortunately ........ my first one of these things was smarter than I. It was a learning reminder for good electrical safe practices.

They really should redesign these suckers to put more safety circuits in them as it would not cost much in the long run considering how many of these suckers they churn out in the mass production circuit board facilities.

On the smaller one mentioned above, I do not think it has as many features like showing PV amps in-at least that's what I see on the user uploaded photos and scan of the instructions, ..........so I spent $10 more and bought the larger one for $20 for my throw away spare on the portable set.
 
it would be nice to know the name of the manufacturer to be able to call them something other than “cheap blue”. Is there a model number?

There's nothing particularly identifiable on the board, usually just a date code and revision. CY seems to appear in several places, 'CY V1.4', 'CY1220' (12v 20amp) but as to who makes it no indication. They probably don't want their name permanently tarnished by being associated with them. ;)

The ones I have here are stripped down minimalist circuits in some ways yet in other ways there are components there that just don't make any sense. There's no current shunt, instead they use the drop across the FETs to determine current, smart thinking there. It's clear, in my mind at least, that who ever actually did design the things really didn't have much of a clue and was just leggo-ing together bits of circuits and concepts from where ever. ie, 'full Chinesed' it.
 
I have 2 strings of PV arrays to feed one bank of 12v batteries, with the 2 arrays facing in different directions. That means I need 2 charge controllers. So, for the 2nd array (3 250w 36V panels), I bought a blue controller that claims 100 amp capability. I will run the 3 panels in parallel, which will give me 750w, cannot remember if the amps will be multiplied by 3 or not, but it won’t be anywhere near 100 amps, and the voltage will stay at 36V, plenty low for this controller.
 

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PWM controllers work by pulling the array voltage down to near battery voltage. The further away from battery your array Vmp is, the worse your power losses become. If 36V is your panels' Vmp, thats about 6.94 amps (36V x 6.94A = ~250W per panel). Pull that down to near 12V battery, let's say 14V, and that becomes 14V x 6.94A = ~97W per panel.
 
PWM controllers work by pulling the array voltage down to near battery voltage. The further away from battery your array Vmp is, the worse your power losses become. If 36V is your panels' Vmp, thats about 6.94 amps (36V x 6.94A = ~250W per panel). Pull that down to near 12V battery, let's say 14V, and that becomes 14V x 6.94A = ~97W per panel.

so, using an array of nominal 12v panels would be optimal for this controller?
 
Yep, if your total battery voltage (say series connected) is 12v, you should aim for 12v class panels. If battery is 24v, then 24v class (paying atention to Vmp as many 24v panels have Vmp of 36 or higher which isn't optimal for PWM)
 
What is a safe voltage for these controllers?

The manual says for 12v the max is 23v (24v/46v)
I have 47.5voc panels split in half & have used the bypass diodes as blocking diodes so it doesn't matter what orientation the panels are to each other as long as only 2 are directly facing the sun at the same time.
 
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