MPPT Question

Kyfarmgirl

New Member
I am trying to get some air conditioning going in an off grid cabin my son is living in on my farm. I had some 250 watt panels not being used. He has a DC only mini split purchased from China (haven’t cracked it open yet).

I THINK my plan is to use 9 panels in a 3s3p array. According to Midnite Solars calculator the
array power=2250 watts
Array current is 25 amps
VMP is 90.6 v
VOC is 112.2 v

however, my math noted 39 amps with a VOC of 130v.

my panels are rated at
VOC of 37.4v
VMP of 30.2v
ISC of 9 a
Max power current of 8.43

based on my calculations I was looking to buy the below MPPT controller. At this time this will be a totally DC system. His battery bank will have to grow over time.


Tracer 5415AN MPPT Charge Controller 50 amp​

12V / 24V / 36V/ 48V DC Auto

Rated charge current: 50 amp

Max Input Power: 625W-2500W ( 625W/12V battery 1250W/ 24V battery 1875W/ 36V battery 2500W/ 48V battery)

Max.PV open circuit voltage: 150VDC (138V at 25℃ temperature)

Battery type selection: Lithium, lead-acid ( Gel, Sealed ) Flooded batteries and User

Common-Negatived Ground Controller

Battery Input:8V~68V

User programmable for battery types, load control etc.

Termina: 6AWG/16mm2

Recommended cable: 6AWG/16mm2
 

OffGridInTheCity

Solar Addict
>however, my math noted 39 amps with a VOC of 130v.
Don't understand this comment.
>Array current is 25 amps
This looks more accurate. The MPPT will bring down the voltage - to maybe 90v - and with 3s3p you'll have 90v @ 25a = 2250w max.

Looks to me you're on the right track - note that you need to go 48v battery to take advantage of 2500w capabilities of the controller. You don't say mini-split BTU or sq feet of cabin - this would help narrow the discussion :)

I have 1,200w solar panels flat on top of my cargo trailer and they produce 3kwh/day over a summer (longer) day. The trailer has a 9,000BTU (120v) mini-split and it operates between 1kwh - 5kwh / day depending on temperature extremes to cool/heat 100sq ft well insulated.

I would think 2250kw PV array would create at least 6kwh/day on a sunny, summer day - enough to cool a couple of hundred sq ft to some degree... :)
 
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Kyfarmgirl

New Member
Looks to me you're on the right track - note that you need to go 48v battery to take advantage of 2500w capabilities of the controller. You don't say how mini-split BTU or sq feet of cabin.

I have 1,200w solar panels flat on top of my cargo trailer and they produce 3kwh/day over a summer (longer) day. The trailer has a 9,000BTU (120v) mini-split and it operates between 1kwh - 5kwh / day depending on temperature extremes to cool/heat 100sq ft well insulated.

I would think 2250kw PV array would create at least 6kwh/day on a sunny, summer day - enough to cool a couple of hundred sq ft to some degree... :)
I appreciate your info!!! I thought I would need a 48 v battery system with that MPPT charge controller. Solar is more complicated than I thought!!!! I am trying not to make a costly mistake.

The cabin is a well insulated 480 square feet. His small 9000btu air conditioner does well but he is running it off a generator which is not practical in the summer!!!! Not to mention loud and uses gas/propane! Luckily my neighbors are far away!!!!

FYI, I LOVE southern Oregon and have been out there traveling many times the past few years! Such an awesome area!
 
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