MPPT size help

[littleharbor]

I have one of the EP 3215 model, (30 amp 150 Voc), with the optional meter. Voltage setpoints are adjustable with the external meter. It has done its job without any issues.

When you are thinking about adding additional panels remember you can double the input wattage when switching to 24 volt. Be sure to series wire your panels for higher than system voltage if switching to 24 volts and always connect your battery bank first , which allows the controller to sense whether 12 or 24 volt system .

[LETitROLL]

+1, Love my victron, just got the cable recently for the full adjustability now, very nice. I have had some renogy products in the past, i feel they are okay, kind of the better end of the cheap stuff. Didnt pay too much more for my victron though and no comparison.

[Brian53713]

Renogy 100w get free delivery, 1.30 perwatt. Bigger panels no free delivery. Also easier to deal with. Sturdier. Victron Blue solar mppt, excellent European company. 5 year warranty. Website will build confidence.

[idiggplants]

Wait for what? A Renogy/Episolr 40 amp controller maximum input is:

520 watts with 12 volt battery
1040 watts with 24 volt battery.

Do the math

520 watts / 13 volts = 40 amps
1040 watts / 26 volts = 40 amps

Rad the manual page 10

not looking for specifications at this point. looking for folks with good or bad experiences with, or opinions on, the controller.

[extrafu]

Wait for what? A Renogy/Episolr 40 amp controller maximum input is:

Rad the manual page 10

We are all reading files from your HDD Sorry buddy, couldn't resist!

[Sunking]

ok thanks guys. i think im leaning towards the 40a version. that will allow us the most flexibility. i dont think a step down converter will work for us. too much loss.

hopefully i can get a couple more people chiming in on experience with the renogy aka epsolar mppt controllers.

Wait for what? A Renogy/Episolr 40 amp controller maximum input is:

520 watts with 12 volt battery
1040 watts with 24 volt battery.

Do the math

520 watts / 13 volts = 40 amps
1040 watts / 26 volts = 40 amps

Rad the manual page 10

[idiggplants]

ok thanks guys. i think im leaning towards the 40a version. that will allow us the most flexibility. i dont think a step down converter will work for us. too much loss.

hopefully i can get a couple more people chiming in on experience with the renogy aka epsolar mppt controllers.

[Sunking]

MPPT Size

Amps = Panel Wattage / Battery Voltage.

[cabindave]

It's definitely efficient enough to operate when you are actually using equipment. We have a shut off switch to shut it down when not at our cabin. That way it is not slowly draining the battery while running nothing at all. It is not perfectly efficient, but the way I look at it is that we gained by charging at 24v we lose some of that in the conversion process. Also you pretty much have to go higher than a 12v battery bank at a certain system size. Specs on the unit say it is 85% efficient, and has a 0.2 (2/10ths) of an amp for a no-load current draw. The no-load draw is why we installed a properly rated shut off switch between the battery bank and the 24v to 12v converter.

As to the other question, the small charge controller would only handle your 300 watts at 24v. And yes you could run three 100 watt panels in series, I believe the max voltage to the charge controller will handle up to four 100 watt panels in series. (check the max input voltage in the manual to be sure).

If I were in your situation, I would probably get the 40amp charge controller, and an extra panel if you want, and wire them in series. Then just keep everything 12v until you want to replace the current 12v battery. At that point you could go to 24v. The larger charge controller would give you the flexibility to do whatever you find works best. Starting with that would give you time to learn your needs, and avoid purchasing another battery until you actually need it.

[SunEagle]

thats interesting. i didnt think a step down thing like that would be so cheap. is it efficient? i guess if we go 400w, we would also go with a second battery anyways, so we could put them in series.

what if we put our limit at 3x 100w panels? the 20a could handle that... but could we run 3 in series? cause otherwise they would have to be in parallel if im not mistaken?

The maximum DC input voltage is usually listed on the spec sheet for the CC. Usually the smaller PWM's do not have a very high DC volt input rating requiring you to wire the panels in parallel.

[idiggplants]

thats interesting. i didnt think a step down thing like that would be so cheap. is it efficient? i guess if we go 400w, we would also go with a second battery anyways, so we could put them in series.

what if we put our limit at 3x 100w panels? the 20a could handle that... but could we run 3 in series? cause otherwise they would have to be in parallel if im not mistaken?

[cabindave]

Definitely go to series with the MPPT controller. Then you can easily get away with 10awg wire and have very little loss (provided you don't have a very long run. Check wiring size calculators, etc.)

You do have the option to run that bank at 24v if your batteries can be configured that way. Look this up. Pyle PSWNV720. I believe it would run at least 360watt continuous, more peak. We use a 24 volt battery on our setup, and the only thing that is 24v native is a mini-fridge that gets occasional summer use. Everything else is run off of a fuse panel connected to that rather inexpensive 24v to 12v converter. We also run a 12v radio, pumps, and lights.

To clarify if you want up to 400 watts into the small CC, then you would have to go 24v battery bank. The larger 40amp CC of the same brand could handle 400w panel input to charge a 12v bank directly. The 24v charge is more efficient at 400 watts (again, check the docs for graphs. They are near the end of the manual).

[idiggplants]

idiggplants,
If you do want to go to 400 you could get the 40amp MPPT tracer model from Renogy. They have a good website to order direct from and are really very helpful. I have had nothing but good luck with them. With that size you could probably hit close to 800w total. I have the 40 amp controller and am very happy with it. There are comments above that say the controller of that brand cannot switch charge voltages but that is not true. They auto recognize 12 or 24 volt banks. You just hook up your battery bank before you hook up your panels. The website has a downloads tab and manuals for every product. Definitely check those out before deciding.
There are people that are anti 100watt panels for their own reasons, but for small setups they have free shipping, and can be hard to beat. Obviously in a large setup they are often not ideal.

Reply if you have any other questions. I had an almost identical setup to what you have now. I since went to 24v and use a 24v to 12v 700w down-converter by Pyle for lighting, radio, etc.

I looked again, it seems it would be possible to squeeze your 400 watts in on the 20 amp model too if you needed to save $75. It would be the absolute max for the controller. To do this you would have to run the battery bank at 24 volts. The larger 40 amp controller would do the same wattage at 12 if you really wanted to do that.

thanks for that info. good to hear something positive from someone who has the controller.

next question is wiring... with our 2 pair of 10awg wire running out to our panels, will we be better off switching them from parallel to series? up the voltage for less line loss? that would leave the second set of wires for 2 more panels should we go that route in the future.

we do not have the option to run the bank at 24v. all the stuff in our cabin is setup like it is an RV... 12v water pump, 12v car radio... 12v sockets for car chargers... etc.

[SunEagle]

hmm. might be some confusion. the kit we would be getting would be split up...

• the cc would go onto the cabin... which is at 200w with a 100ah battery... would possibly go to 400w with 200ah battery, but that is doubtful. our power usage has been minimal for 20 years. dont plan on getting more luxurious.
• the 100w panel would go to the shed with the pwm controller. it woudl be going on a "shot" 100ah battery, just cause we have one... if that battery dies, we could get away with a 30ah battery.

OK. Thanks for explaining your system a little better. It is hard to make good recommendations when we get bits and pieces from the OP.

Small systems can get away with PWM CC's. It is only when you go above 200 watts is when a PWM throws away some of the wattage based on how it works and going to an MPPT is a better solution as long you get a "real" MPPT and not those cheap knock offs you can find on eBay.

[ButchDeal]

no point in getting a 200w panel for it. none at all. and there is also no point in an mppt setup for it either.

1) 200 plus watt modules are cheaper per watt than 100w 12v version.
2) You asked about MPPT and the subject of this thread is help with MPPT