Too much Input Power for my Charge Controller?

littleharbor2 · June 2018

EP does make 150 volt controllers. If you have decided on a Midnite Solar brand you cant go wrong there.

BB. · June 2018

Other vendors have similar websites (Outback for one?).

Please feel free to ask about controllers and the various positives and negatives about them.

Midnite is a great company, very good support, and lots of features. They do, however, have loud fans (hot room, mid-day sun, etc.). You don't want to put this in your living area (i.e., office) if the daytime fan noise would bother you (just an FYI).

We want you make informed purchasing decisions.

-Bill

Photowhit · June 2018

I'm still curious about system voltage?

jmbljb1 · June 2018

Oh man, I see that the Classic 150 is 650 dollars. I can buy another EPEVER 4210 Charge controller and hook up two PV panels to one controller and two pv panels to the other controller for a lot less than the Classic 150. That's including the additional fuses and breakers and wires. I don't know. I think I might just purchase another EPEVER and setup a two charge controller system. Any thoughts or considerations that I may have forgotten?

Photowhit · June 2018

Heck, if it's a 24 volt system, you can buy cheap PWM charge controllers.

jmbljb1 · June 2018

Photowhit said:

Heck, if it's a 24 volt system, you can buy cheap PWM charge controllers.

No, I don't have anything requiring a 24 volt system. 12 volts will run everything I'm using this for. That's a good thought thou.

Photowhit · June 2018

jmbljb1 said:

Photowhit said:

Heck, if it's a 24 volt system, you can buy cheap PWM charge controllers.

No, I don't have anything requiring a 24 volt system. 12 volts will run everything I'm using this for. That's a good thought thou.

Well if you go back to the beginning, I noted that the 40 amp charge controller was considerably under sized for the solar array. If you have a 4 - 325 = 1300 watt array on a MPPT type charge controller, you should expect it to produce about 75% of it's panel rating (NOCT value) 1300 watt array should produce about 75% of it's panel rating or 975 watts. 975 watts divided by 14.5 volts roughly the charging voltage for 12 volts = 67 Amps! This would make a 40 amps CC really too small, a 60 amp might be reasonable if it can handle the over paneling, most MPPT types can...

Midnite classic 150 is about $600 through NAWS (our sponsor)
https://www.solar-electric.com/mnclassic.html

There is also a Classic SL made for solar only, it also has some other reduction of features, but would save another $50;
https://www.solar-electric.com/midnite-solar-classic-150-sl-charge-controller.html

An Outback FM 60 would handle most of the current and I think it wouldn't have a problem with over paneling, It might be yur cheapest alternative at $430. It's big brother the FM80 is $480. I think you would only have minimal settings without another piece of equipment. Neither come with a battery Temperature Sensor (BTS) which you will want.

Northern Arizona Wind and Sun typically has close to if not the least expensive prices on Midnite gear....

...but if you are still looking around over July 4th, they might have a 5% off sale, though they might wait until later in the year.

Estragon · June 2018

Using multiple controllers can work fine. There can be an issue with units not designed to network where one sees slightly different voltage than the other and might be in a different charge stage than the other at times, but that usually isn't a huge issue.

Networked controllers, such as MN classics, will all go to (eg) absorb at the same time.

An advantage to multiple controllers is when one fails you may be able to limp by with the working twin while getting the dead one repaired/replaced.

jmbljb1 · June 2018

Estragon said:

Using multiple controllers can work fine.
An advantage to multiple controllers is when one fails you may be able to limp by with the working twin while getting the dead one repaired/replaced.

And both controllers can feed power to one battery bank, right?

Estragon · June 2018

Yup. My 48v bank has 3 controllers (2 classics and a Morningstar 45a PWM) and an inverter-charger feeding it. No problems, except the Classic and Morningstar don't speak to each other so can be in different charge stages.

jmbljb1 · June 2018

Photowhit said:

Well if you go back to the beginning, I noted that the 40 amp charge controller was considerably under sized for the solar array. If you have a 4 - 325 = 1300 watt array on a MPPT type charge controller, you should expect it to produce about 75% of it's panel rating (NOCT value) 1300 watt array should produce about 75% of it's panel rating or 975 watts. 975 watts divided by 14.5 volts roughly the charging voltage for 12 volts = 67 Amps! This would make a 40 amps CC really too small, a 60 amp might be reasonable if it can handle the over paneling, most MPPT types can...

Now that I have purchased a second EPEVER 4210 charge controller (40 more amps), I have split the four panels into two sets of two.

As I was connecting the wires, I was wondering if I should go to a larger size. The 12 awg cables on the back of the panels are rated for 20 amps, so I purchased 10 awg cable extensions, but I see that they are rated for 30 amps. So should I go to 8 awg since the charge controller is rated for 40 amps? I don't want the cables to melt or anything if 40 amps is pulled through them.

littleharbor2 · June 2018

If series wired you will only have the amps of the single panel rating flowing but at higher voltage of the series pair. You will need larger wire from the CC to the battery.

Estragon · June 2018

40a is the output of the controller at charging voltage. The input current will be the combined Imp of the parallel connected panels at higher string voltage, which should will be well under the output current.

Generally, getting a wire sized for acceptible voltage drop over the distance from array to controller will need a wire big enough that ampacity isn't a problem.

jmbljb1 · June 2018

littleharbor2 said:

If series wired you will only have the amps of the single panel rating flowing but at higher voltage of the series pair. You will need larger wire from the CC to the battery.

Is there a need to put the 40 amp breaker/fuse from the panels to the charge controller since the wire is only rated at 20/30 amps? Won't the wire give out before the breaker/fuse? Should I use a breaker/fuse rated for less amps?

littleharbor2 · June 2018

That's correct. If anything you want a smaller fuse/breaker than the ampacity of the wire. Its job is to protect the wire after all. That breaker would work on the output, provided the wire was sized to handle 40 amps.

Estragon · June 2018

OCP (breakers/fuses) should be sized to protect the weakest part of the circuit. In the case of pv circuit, the panel is generally weakest, so OCP in the panel spec (often 15a) is used.

jmbljb1 · July 2018

Estragon said:

Yup. My 48v bank has 3 controllers (2 classics and a Morningstar 45a PWM) and an inverter-charger feeding it. No problems, except the Classic and Morningstar don't speak to each other so can be in different charge stages.

I have my two 40 amp EPsolar 4210 charge controllers hooked up to my 12v 300 a/h battery bank and like you said, I don't think they are communicating, but they are working to charge the bank. However, I have all the CC positives going to battery #1 (pos) and all the CC negatives going to battery #3 (neg). What I was wondering is can I now hook my AC/DC power inverter in reverse to the battery bank and have equal draw? ie hook my Inverter positive cable to battery # 3 (pos) and my Inverter negative cable to battery #1 (neg) and have it draw equally from the battery bank. (My battery terminal screws are short and I'm running out of room on the two main terminals)

Does it even matter? Thanks for your help.

Estragon · July 2018

Rather than trying to cram too many connections on a battery post, IMHO you should make or buy a pair of bussbars for +ive and -ive connections, and make a single connection to the bank.

For parallel wiring batteries and reasons to do it in a particular way, you may want to check out:
http://www.smartgauge.co.uk/batt_con.html

jmbljb1 · July 2018

Estragon said:

For parallel wiring batteries and reasons to do it in a particular way, you may want to check out:
http://www.smartgauge.co.uk/batt_con.html

I viewed the diagrams on this webpage and my battery bank is setup like the second diagram. Numbers 3 and 4 may be perfectly balancing the batteries, but incur more money in the beginning and only seem to be redirecting 2 or 3 amps towards each battery.

Perhaps once these 3 (100 a/h) batteries go down in 10 yrs or so, I'll be able to change up my setup. Thanks so much for the help.

Too much Input Power for my Charge Controller?

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