How do I decide on the best C.C for my configuration ? Tristar mppt. outback or midnite?

nobody928

I am planning on upgrading to an mppt charge controller and trying to decide whats best for my needs. I have a xantrex c40 right now, but this controller only alows up to 480 watts of panel power at 12 volts. I would like to have 600 watts of total panel to feed my battery bank.

I am using a 12 volt system. I use an axess 12volt led tv and 12volt fans pretty often. I also have an edgestar mini refrigerator/freezer. I currently dont use my refrigerator much do to the power consumption. I would like to be able to power it as well as all my other needs wich is why i am upgrading. The fridge takes 75 watts to get the compresor going but only about 30 watts after that to run as needed.

I think if I add two more panels and a MPPT charge controller my system will be enough to get by on. The only problem is im not sure what charge controller to buy.

I live in a heavily treed area and get snow now and then.

3x140 watt panels/but expanding, 5x 105 amp hour agm batteries, C-40 charge controller/upgrading to mppt. Champion 1500 watt generator, diehard smart charger for now.

Cariboocoot

Re: How do I decide on the best C.C for my configuration ? Tristar mppt. outback or midn

The key here is the batteries. Off-grid systems are based on that. They need to be sufficient to handle the load requirements; panels are to recharge the batteries. Do not try to rely on panels to run things. You will be disappointed if you do. It's nice to be able to make use of any excess power they may provide, but you don't want to depend on it being there.

So five 105 Amp hour 12 Volt batteries. Shall I repeat the lecture about multiple parallel batteries? Especially on a low Voltage system.

420 Amps hours @ 12 Volts would normally have (42 Amps * 12 Volts / 0.77) 654-ish Watts on it so you are right in wanting to expand. You'd need a controller capable of handling that 42 Amps, which means you are looking at one of the higher-end controllers. The minimum controller here is the Morningstar Tristar 45 Amp MPPT. You may not be happy with that choice when you decide to expand again. At the top is the MidNite Classic 150. In between would be the Outback FM60. Xantrex also makes a 60 Amp MPPT, but personally I don't like the way it functions.

Now about those panels. Can you get more of the exact same ones? If not you may want to consider selling them and replacing the lot with "GT" type panels which tend to be cheaper per Watt. Mixing panels that don't match can be difficult at best and a waste of power potential at worst.

With 140 Watts you don't have a 650 Watt array choice; you should go up to 700 Watts (five panels) which would produce about 45 Amps.

BB.

Re: How do I decide on the best C.C for my configuration ? Tristar mppt. outback or midn

A nice "mid range" charge controller is the 12/24/48 volt 30 amp MPPT controller from Rogue. Comes with all the basic parts (LCD display, Remote Battery Temperature Sensor)--Which can cost an arm and a leg as options from other vendors. This is a new model, the previous two models have always had very good reviews and great support from Marc.

For a "modern" MPPT type charge controller, they control their output current to prevent it from exceeding their rated limit (i.e., even with extra panels/sun controller will not output more than 30 amps, safely and reliably).

So, that does let us do some over paneling as panels in normal to warm conditions usually output less than rated power:

30 amps * 14.5 volts charging * 1/0.77 panel+controller deratings = 565 Watts "maximum cost effective" solar array

The next MPPT controllers are generally 45/60/80+ amp rated output (and more expensive).

So--Before going down the selecting the hardware, make sure you have the basic system requirements (solar array, battery bank capacity, loads, amount of sun) issues all calculated out first... That will limit your selection choices a lot and reduce confusion.

You might also want to look at Battery Monitors (Trimetric is a good start) (Victron is another good brand) too... AGM batteries can be difficult to manage (no method to measure specific gravity). Will also give you a better handle on your loads.

Lastly--Trees--Shade is a killer for any solar array--Panels only work if they have full sun. Any shade pretty much kills the panel/array output. And trees grow--OK now, deep shade a few years ago.

If you have an open clearing that is a few hundred feet away--You can get a higher input voltage MPPT controller and put your panels in series to (typically around 100 Volts Vmp maximum for a typical MPPT controller with 140-150 vdc max input). That will allow you to run lighter gauge copper wire from the array to the home to power your 12 volt battery bank.

-Bill

NorthGuy

Re: How do I decide on the best C.C for my configuration ? Tristar mppt. outback or midn

600W at 12V is 50A, so you will need a 50A MPPT charger. If you had a 24V system, you would only need 25A charger. Perhaps switching to 24V and using 24-to-12V DC-DC converter could be a way to go. The DC-DC converter will also provide cleaner power.