Understanding the Charge Controller

lazza
lazza Solar Expert Posts: 336 ✭✭✭
in Off Grid Solar & Battery Systems #1
Hi

I was just measuring a Mino (ATERSA http://www.atersa.com/datosproductos.asp?param=14) charge controller. The battery output at the end of a sunny day was reading 14V (12V 250Ah battery with 85W panel)... but when I measure the PV input the voltage was going up and down, fluctuating from 14V to 17V. :confused:.. would this be something to do with PWM?

Explanations much appreciated

Larry
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Understanding the Charge Controller

    Yes. The output has the electrical mass of the battery on it; capable of maintaining a fairly steady Voltage under varying loads. The input has the varying output of the panels which will change according to the sunlight on them, the temperature, and the load (in this case that includes the battery). PWM connects panels to battery, current flows and panel Voltage pulls down; it disconnects and the reverse happens.

    You should see fairly steady panel Voltage/current during the initial Bulk charging stage. The closer the battery Voltage gets to the Absorb set point, the more fluctuation on the panel side.
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  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    #3
    Re: Understanding the Charge Controller

    Ok great, I presume the current mirrors this pattern then, on the battery side?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Understanding the Charge Controller
    lazza wrote: »
    Ok great, I presume the current mirrors this pattern then, on the battery side?

    Yes, as current is basically a function of the Voltage difference.
    Keep in mind that the pulsing of the controller is not 50/50 on/off. It can be, but it can also be just about any combination thereof divided along any time segment according to how the manufacturer programmed it.
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  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    #5
    Re: Understanding the Charge Controller

    What kind of battery is this? An 85W panel is only going to supply around 4 - 5 Amps , or 2% rate of charge to a 250AH battery.
    Cariboocoot wrote: »

    You should see fairly steady panel Voltage/current during the initial Bulk charging stage. The closer the battery Voltage gets to the Absorb set point, the more fluctuation on the panel side.
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  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    #6
    Re: Understanding the Charge Controller

    It's a monoblock (not sure what the word is in english) normal lead-acid deep cycle. Hence, yes, it was only getting 2% rate of charge. Just added a 120W Kyocera (7A Vmp) which should sort the system out just about getting the rate of charge up to 5% minimum. Also added a 7.5 A fuse in the old panel line and 10A fuse in the new panel line before connecting them in parallel. Consumption in this system is low, so not expecting any more issues from the system... all being well
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  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    #7
    Re: Understanding the Charge Controller 2

    HI Forum

    I submitted a post a couple of weeks ago querying the operation of charge controllers.

    The particular one in question, a Mino V2, was in float mode and the panel voltage side was going up and down, fluctuating between 14V and 17V, which you guys confirmed was the PWM operation.

    I was testing another charge controller, a STECA 3030 (12V system), and this one, instead of fluctuating between med and high voltage was fluctuating between low and med (8V to 14,5V). I presume this is PWM too?

    My theory is that the Mino V2 modus operandi is by switching between panels in open circuit and then closed circuit for the charging pulse, and that the STECA switches between short circuit and then closed circuit for the charging pulse. Am I correct? or is something else happening?

    thanks for any enlightenment

    Larry
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  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    #8
    Re: Understanding the Charge Controller

    I don't know the specifics of that controller, but yes there are some that are called "shunt controllers" that work by shorting the input. (Obviously with a diode or somesuch inline to the battery.) Solar panels don't care either way, and a shunt controller is the only safe way to regulate some other inputs such as wind turbines. If a turbine is open-circuited it could overspeed and self-destruct, shunting it causes the windings to act as an electromagnetic brake and slow it down. (Although that's a balancing act too - if the turbine is wound up too fast when the shunt is applied it's also possible to generate too much heat in the windings and burn them out! Turbines can be fun... ;) )
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