Charge Controllers - 101

KnowledgeSponge
KnowledgeSponge Solar Expert Posts: 173 ✭✭✭
in Solar Beginners Corner #1
I currently have a PWM 30A charge Controller. (but considering purchasing a RAMSOND SUNSHIELD PRO 60AMP 24V SOLAR CHARGE CONTROLLER REGULATOR)
Anyway, I did some searching here and at Google but couldn't find what I was looking for, at least in terms I could grasp right now.

As I understand, the Solar Charge Controller.....

1). Has inputs for connecting the solar panels which allows the INPUT of current FROM the Solar Panel TO the Charge Controller.

2). Has Outputs going To Batteries (or battery) for the purpose of Charging the battery(ies).

Where I get in trouble is the LOAD connection.
What exactly can I do with the load connection on my Charge Controller and how does it work?
Does it simply provide 12V DC to power a 12V device or 12V light?
Does it "divert" that "load" to a 12V device while Simultaneously charging the battery(ies)?

Just not sure what the LOAD connection on a charge controller is for.

Thx
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Charge Controllers - 101

    LOAD terminals are a controlled system Voltage connection. They usually have a current maximum about the same as the controller too. What's more, they will have a low Voltage disconnect point (sometimes user selectable). This is so you can run low power DC devices without draining the battery too much. The power is supplied from the battery & PV the same way it would be if it were connected to the battery directly. The exception being the LVD and in the case of some the ability to turn the load on/off with the absence/presence of light on the PV (night lighting function).
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  • Shadowcatcher
    Shadowcatcher Solar Expert Posts: 228 ✭✭✭
    #3
    Re: Charge Controllers - 101

    RAMSOND has a less than sterling reputation and we see the same "comes from China" sort of complaints about inherent quality control problems.
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  • KnowledgeSponge
    KnowledgeSponge Solar Expert Posts: 173 ✭✭✭
    #4
    Re: Charge Controllers - 101
    Shadowcatcher wrote: »
    RAMSOND has a less than sterling reputation and we see the same "comes from China" sort of complaints about inherent quality control problems.

    I think it's a PWM controller anyway. My next charge controller should be a MPPT controller I think.
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  • KnowledgeSponge
    KnowledgeSponge Solar Expert Posts: 173 ✭✭✭
    #5
    Re: Charge Controllers - 101

    there are quite a few (cheap) charge controllers on ebay. many look like this.....
    chargecontroller_zps6f3b67c6.jpg

    Are these a "Bad" idea for a low power (12v, 400 watt) setup?

    Does anyone have any actual experience using them?
    Do I need to spend more on a charge controller for a small setup like mine?

    I did buy one and so far, it seems to work as described. For how long? Dunno.
    It did seem to cut the charge rate as the battery reached full charge and the output was around 14.3 volts max

    I just don't know how long I can expect it to last or if it is likely to cause damage to my panels or battery.
    Again, according to my tests so far, it seems to be doing a good job....right now.

    As budget permits, of course I'll look into a Morning Star or other "better" charge controller.
    But for now, will these "do"?
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Charge Controllers - 101

    hmmm. that looks familiar. it looks like the same cc i saw without the cover on it with blown fets. not much to it and is junk if it is the same cc. it is much better to save for something you know is good than to waste money on something iffy or known to be bad. i hope it stays together for you long enough to save for a good one.
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  • KnowledgeSponge
    KnowledgeSponge Solar Expert Posts: 173 ✭✭✭
    #7
    Re: Charge Controllers - 101
    niel wrote: »
    hmmm. that looks familiar. it looks like the same cc i saw without the cover on it with blown fets. not much to it and is junk if it is the same cc. it is much better to save for something you know is good than to waste money on something iffy or known to be bad. i hope it stays together for you long enough to save for a good one.

    ok, Thx.
    Agreed. I'll need a better Charge Controller. You get what you pay for. Sometimes.
    What would you recommend for a 400Watt system that might eventually expand to 1000Watts ?
    It's 12v and the panels are 100Watts / 5.5A and I'm using 4 120ish Ah batteries

    btw...MorningStar has several charge controllers that look similar to the picture I posted such as this one.
    Hard to believe there could be $100 worth of better components in there.
    1609-lg-ProStar_30_Reg_6.jpg
    Not exactly, but similar. The components inside and circuit design of course being the difference Im sure.

    I think I want to invest in a MPPT Charge Conroller although I read that it is only beneficial ABOVE 600 Watts.

    I guess I may have to dig in the Heels and go with an Outback MX60 or FlexMax.
    But I read on here somewhere that those can fail as well.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #8
    Re: Charge Controllers - 101
    KnowledgeSponge wrote: »
    I think I want to invest in a MPPT Charge Conroller although I read that it is only beneficial ABOVE 600 Watts.

    It is beneficial at almost all wattages.

    The question is: Is it worth hundreds of dollars to improve the efficiency of a 100 watt system (perhaps an extra 25 watts) versus hundreds of dollars to improve the efficiency of a 2000 watt system (perhaps an extra 500 watts).

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #9
    Re: Charge Controllers - 101
    KnowledgeSponge wrote: »
    I think I want to invest in a MPPT Charge Conroller although I read that it is only beneficial ABOVE 600 Watts.


    In addition to what VT noted, if you are using Grid-Tie panels, you'll need a MPPT controller to utilize the full potential of the panels.
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  • KnowledgeSponge
    KnowledgeSponge Solar Expert Posts: 173 ✭✭✭
    #10
    Re: Charge Controllers - 101
    Rybren wrote: »
    In addition to what VT noted, if you are using Grid-Tie panels, you'll need a MPPT controller to utilize the full potential of the panels.

    I can't really think of a good reason to use a GT inverter for my purposes. Maybe I need to "absorb" more.
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  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    #11
    Re: Charge Controllers - 101

    Not a grid-tie inverter; grid-tie panels. ie. Panels that aren't designed to a 12V or 24V system.

    The GT panels are often significantly cheaper.
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #12
    Re: Charge Controllers - 101

    depending on your battery banks specifics, a LONGER absorb may be needed not just beneficial to allowing/finishing a charge daily. Read NorthGuy's threads on the troubles with charging his batt. bank...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    #13
    Re: Charge Controllers - 101
    KnowledgeSponge wrote: »
    ok, Thx.
    Agreed. I'll need a better Charge Controller. You get what you pay for.

    Hard to believe there could be $100 worth of better components in there.
    1609-lg-ProStar_30_Reg_6.jpg
    Not exactly, but similar. The components inside and circuit design of course being the difference Im sure.

    I purchased Morningstar mttp 15 amp & the 300w suresine , the suresine 300 lasted 15 minutes , Buzzed , fluffed (let the smoke out) and then there's that smell (just think confide elevator / lift) ..

    Called Morningstar , handled over the phone , new SS300 sent a week later , & heard news of a larger full sine wave inverter (WHERE IS IT ?? After a year) . Great company , and you get to use a computer & program to download from the CC or the inverter to see & understand so comprehension makes sense on your scale.

    I have a few Asian units , for playing and stuff , for real , buy quality ..
    My chicken coop gets lower quality testing , my real costing areas get quality items ...
    It will cost you , somewhere .

    VT


    Ps nice pup!
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  • KnowledgeSponge
    KnowledgeSponge Solar Expert Posts: 173 ✭✭✭
    #14
    Re: Charge Controllers - 101
    CDN_VT wrote: »
    I purchased Morningstar mttp 15 amp & the 300w suresine , the suresine 300 lasted 15 minutes , Buzzed , fluffed (let the smoke out) and then there's that smell (just think confide elevator / lift) ..

    Called Morningstar , handled over the phone , new SS300 sent a week later , & heard news of a larger full sine wave inverter (WHERE IS IT ?? After a year) . Great company , and you get to use a computer & program to download from the CC or the inverter to see & understand so comprehension makes sense on your scale.

    I have a few Asian units , for playing and stuff , for real , buy quality ..
    My chicken coop gets lower quality testing , my real costing areas get quality items ...
    It will cost you , somewhere .

    VT
    Ps nice pup!

    You kinda sorta made the case FOR the cheap charge controllers :cool:
    I have only used it once, but so far....the ebay cheapie is doing exactly what it's supposed to.
    I'll keep a close eye on it until I upgrade.

    Hopefully, since the Solar Panels are isolated from the charge controller by fuses, if anything goes
    wrong with the charge controller, the fuses will protect the Solar Panels. I also want to put heavy duty Diodes
    in the line going from the combiner box to the solar panels so that current can only flow ONE direction and not
    back TO the panels in case of a problem. Radio Shack has some heavy duty Diodes for this.

    I know the charge controller "should" have blocking diodes in it, but I would feel safer with known quality external Diodes....JIC

    Man, this "hobby" costs! :grr
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #15
    Re: Charge Controllers - 101

    Charge controllers do not have nor need "blocking diodes" per se: they are solid state devices themselves. As such they perform the same function as the diode would. Adding external diodes only drops Voltage available; it is not necessary. If something is going to fail it's going to fail. There is a limit to how much protection you can put in place and if that "extra insurance" becomes detrimental to function then you've gained nothing.
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  • KnowledgeSponge
    KnowledgeSponge Solar Expert Posts: 173 ✭✭✭
    #16
    Re: Charge Controllers - 101
    Cariboocoot wrote: »
    Charge controllers do not have nor need "blocking diodes" per se: they are solid state devices themselves. As such they perform the same function as the diode would. Adding external diodes only drops Voltage available; it is not necessary. If something is going to fail it's going to fail. There is a limit to how much protection you can put in place and if that "extra insurance" becomes detrimental to function then you've gained nothing.

    How "detrimental" ?
    In my mind, a "small" sacrifice in order to protect a big expense might be worth it. SMALL being the key word.
    Since I currently only have a cheap charge controller, the extra insurance might be worth the small hit in efficiency? If it's small.
    Wouldn't it depend on the size of that "hit"?

    I'll have to look into the specs for the diode I planned to use and see if I can determine how much voltage drop I might suffer.

    Since you have an Outback MX60, I can understand how this would not be a concern for you.

    Eventually, I'll spring for one myself. Right now....no can do.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #17
    Re: Charge Controllers - 101

    One diode will knock out at least half a Volt. Doesn't sound like much, but on a low Voltage system (12 V with PWM) it adds to the drop in the wiring. Depending on how everything else is configured, on a hot day you may not get full charging Voltage.

    You can also go overboard: that blocking diode could fail just as easily as the controller. So you add another and now you're down 1 Volt at least. That diode could fail. Add another. How many are you going to trust? How paranoid do you want to be? True, redundancy decreases the chance of component failure, but that chance is extremely small to begin with even on a cheap controller.

    The controller, if no good, may itself bleed Voltage from the batteries. A diode on the PV line won't stop that.

    If you can't trust the controller in the first place, get a different controller.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #18
    Re: Charge Controllers - 101

    Diodes have between 0.2 and 1.0 (or a bit more) volt drop... Charging a 12 volt battery with a 1 volt drop:

    1 volt drop / 14.5 volts charging = ~ 0.07= 7% drop in energy collected

    The big problems with diodes is they get hot (P=I*V=10amps*1volt-drop=10 Watts per diode)... So you should have a heat sink. Big metal diodes have metal bodies which may connect to your heat sink... Now you need good ventilation and yet need to make sure that nothing shorts against the diodes/heat sinks.

    They really do not by you any reliability or safety. "Blocking Diodes/Circuits" are not needed for 12 volt battery banks, and are about break even on a 24 volt battery bank. Over 24 volts, yes you should have something to block reverse current flow (if you don't trust your charge controller).

    Of course, if you don't trust your charge controller to "protect" your solar array... How about your expensive battery bank. If the controller fails, the batteries are very much at risk (vs the theoretical risk for the solar array).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • KnowledgeSponge
    KnowledgeSponge Solar Expert Posts: 173 ✭✭✭
    #19
    Re: Charge Controllers - 101

    Read your posts thoroughly. Thx for taking the time to reply.

    There's something else about Charge controllers I don't yet grasp......

    If I have 10, 12v 100watt panels and they each are capable of 6A, would I need a single 60A charge controller or should I go a certain percentage over?

    Also, Is it common to have more than ONE charge controller in a solar PV system?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #20
    Re: Charge Controllers - 101

    If you have ten panels capable of 6 Amps each then the total maximum current is going to be 60 Amps (in theory) and a 60 Amps charge controller would handle it.

    Ready for the "however"s?

    NEC regs require derating to 80%, so to meet those requirements a 60 Amp controller is only capable of 48 Amps "continuous" (one of the regs I have issue with).

    Not all controllers require this derating; some will state this.

    In the even of certain conditions the current may exceed the panels' output specs. Most MPPT controllers will 'clip' this. Some PWM controllers will, some won't.

    Margins for error are good thing. :D

    It is not common for systems to have multiple controllers, but it also is not unusual. The worst case is trying to get an inexpensive PWM to work in harmony with an MPPT. The best case is all controllers the same, and preferably communicating with each other. Top-of-the-line: MidNite Classic's "follow me" protocol where one acts as master controller and the others do what they're told.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #21
    Re: Charge Controllers - 101

    It is the old "it depends" answer...

    If we assume that those panels are all Imp~6amps and Vmp~17.5-18.6 volts and this is a 12 volt battery bank (maximum charging voltage around 14.5 to 15.5 volts) and you are using a MPPT type charge controller--Then yes, you will see ~10*6amps=60 amps maximum.

    The NEC requires the system to be rated (or derated) by 1/1.56 (1.25 NEC derating and 1.25 J. Wiles derating for charge controller).

    If this was an inexpensive charge controller, then, yes you should not load the controller more than 60/1.25 to 60/1.56 or ~48 amps to 38.4 amps...

    However, if you read the charge controller specifications (for a name brand like MorningStar) they will tell you that the controller is rated for 60 amps use and you do not need to derate by the NEC requirements (we don't derate our computer power supplies because somebody at the NEC things computer supplies are dangerous if operated at rated/design loads).

    Always read the manual--But PWM controllers do not have the abilty to "modulate" output current (i.e., run a 100 amp array into a 30 amp charge controller). And while some controllers will have over current/over temperature shutdown--That should not be a normal operation.

    MPPT charge controllers are truly digital switch mode power supplies--And they do have the ability to modulate/limit their output current (a 100 amp array and 60 amp output--the MPPT controller will output 60 amps all day long just fine).

    There are some details in how solar panels and charge controllers work...

    For example, people say frozen panels will output more power (watts)--And that is true... However, it only outputs higher output voltage (instead of 17.5 volts Vmp standard it may output 21 volts at Imp instead). For a PWM controller, this is a "don't care" situation. Imp actually reduces a tiny amount in very cold conditions--So a PWM controller will not "output more power" when the array is cold.

    An MPPT controller works by the equation Power=Voltage*Current.... Or Vpm*Imp=Vbatt*Ibat (ignoring ~5% losses at the moment).

    So--You can see that an increase in Vmp-cold or decrease in Vbatt (discharged battery operating at lower voltages), you will get an increase in available output current (up to the maximum rated output for the MPPT charge controller).

    More or less, a MPPT charge controller is sort of like a digitally controlled Variac (variable AC transformer)... It "matches" the IV curve for the solar array to the IV curve of the battery bank--Or sort of like the automatic transmission matches the engine power curve to the present road conditions/throttle position.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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