New solar system installed

[dapago]

Hi there,

I am installing a new solar system and would love your inputs on the solutions and materials I have bought so far and the one I have recuperated from an old installation.

- 2 CC Tristar mppt 60a (new)
- magnum pure sine wave inverter 24V (4 years old)
- 12 x 210ah Trojan T605 batts (new)
- 6 X 215W panels wired 3s2p to one Tristar mppt (5 years old)
- 4 x 250 W panels wired 2s2p to the second Tristar mppt (5 years old)
â€"â€"â€"â€"â€"â€"â€"â€"â€"â€"-
- 1 Tristar PWM 60a (4 years old)
- 2x430ah Trojan L16 (2 years old)
- 2x250W wired 2s1p (5 years old)

Material still to be bought (inputs needed here)
- a 12V inverter for the smaller install
- connecting box for the bigger installation (the one with the 2 mppt). MIDNITE MNDC125 MAYBE?
- 1 hub with 1 remote display for the CC’s (i don’t want to buy a display for each CC if I can easily switch off 1 remote display from a hub and connect it to the other CC)

Any inputs will be greatly appreciated.
Thanks a lot.

[ClassicCrazy]

The Midnite Mini DC boxes are great - I have used them for all my installations so far.
There is room in them for 5 din rail breakers though the max on those is 60 amps each. So if you need above that you need the breakers with the studs on them and then the Mini DC box only has space for three. 
So depending on your system you could make two charge controllers fit - and use two of the breaker spots for PV input - and two for the charge controller to battery outputs - this is if you can get by with the 60 amp breakers.

The Mini DC box you are talking about with 125 amp breaker for the inverter is going to depend on which 12v inverter you end up choosing to use. Samlex makes some good sine wave inverters that are lower cost because they don't have a battery charger in them.

Larry 

[dapago]

The Midnite Mini DC boxes are great - I have used them for all my installations so far.
There is room in them for 5 din rail breakers though the max on those is 60 amps each. So if you need above that you need the breakers with the studs on them and then the Mini DC box only has space for three. 
So depending on your system you could make two charge controllers fit - and use two of the breaker spots for PV input - and two for the charge controller to battery outputs - this is if you can get by with the 60 amp breakers.

The Mini DC box you are talking about with 125 amp breaker for the inverter is going to depend on which 12v inverter you end up choosing to use. Samlex makes some good sine wave inverters that are lower cost because they don't have a battery charger in them.

Larry

Thank you. The 12V inverter will only be used to power a 1hp pump 30 minutes/day and a freezer (1200w/24h). A 1500W modified sine wave inverter should be ok unless someone here has a better idea.

Regarding the MNDC box, I don’t know witch one to order. I will have 3 CC, 2 inverters and the paneles wired 3s2p, 2s2p and 2s. Same for the DC breakers. I don’t know how many to order and capacity for each ones. Maybe someone can help here?
I have attached the panels spec.

[dgd]

- 2 CC Tristar mppt 60a (new)
- magnum pure sine wave inverter 24V (4 years old)
- 12 x 210ah Trojan T605 batts (new)
- 6 X 215W panels wired 3s2p to one Tristar mppt (5 years old)
- 4 x 250 W panels wired 2s2p to the second Tristar mppt (5 years old)

With that 2300 watts of PV into a 24v battery bank you could have easily used a Midnite Classic 150 controller. The Classic with WBjr and Deltec shunt would probably have cost less than a pair of Tristar 60A controllers and with available free software you could monitor the Classic using a computer or tablet device.
Maybe use the six 215 as 3s2p and just use three of the 250w as 3s1p would still get you just over 2kw of pv.
Twelve small FLA batteries doesn't look the best idea either, a single string of something like L16s would have been a better way to go. Keeping your three strings of T605s balanced will be interesting and likely their life will be shorter compared to a single string of four L16.

dgd

[dapago]

- 2 CC Tristar mppt 60a (new)
- magnum pure sine wave inverter 24V (4 years old)
- 12 x 210ah Trojan T605 batts (new)
- 6 X 215W panels wired 3s2p to one Tristar mppt (5 years old)
- 4 x 250 W panels wired 2s2p to the second Tristar mppt (5 years old)

With that 2300 watts of PV into a 24v battery bank you could have easily used a Midnite Classic 150 controller. The Classic with WBjr and Deltec shunt would probably have cost less than a pair of Tristar 60A controllers and with available free software you could monitor the Classic using a computer or tablet device.
Maybe use the six 215 as 3s2p and just use three of the 250w as 3s1p would still get you just over 2kw of pv.
Twelve small FLA batteries doesn't look the best idea either, a single string of something like L16s would have been a better way to go. Keeping your three strings of T605s balanced will be interesting and likely their life will be shorter compared to a single string of four L16.

dgd

Regarding the batts and the Classic 150 yes you are right BUT I had to wait +2 months to get them ordered and shipped. Because the old system collapsed (very bad installation from the past owner) I had to do with what I had and what was availabl ASAP. I had access to 12x210ah new batts and yes it will be harder to get them balanceD.

Regarding your proposition 6X215W wired 3s2p and 3X250W wired 3s1p on one single CC, just 1 question:
if I use 2 different spec panels wired to 1 single CC, will the most powerful panels (250W) downgrade to the less powerful ones (215W)?
“For panels connected in parallel, current is additive while voltage is the same. If among the panels connected in parallel there is a panel with rated voltage lower than the others, it will drag down the voltage on all the remaining panels. Therefore each of the remaining panels (with higher current rating) will underperform which means that will produce lower voltage (and power) than stated on its nameplate.Mixing solar panels with different electrical characteristics is not recommended if you use an MPPT charge controller. Different wattages make impossible for the controller to find the optimal operating voltage and current, since they are different for each panel type”.

1 mppt Tristar I got it new half price so I thought it was a good buy. As well I thought that in the  environment the system is installed (lots of dust, hot ambient temp, lots of insects, etc), a CC without fans would be a better choice.

From the 12 panels available, I decided to use the max PV to the main house and dedicate 2X250 for the PWM powering the pump and freezer wired to the 2X430Ah L16 I could save (from 8 originally installed). I thought that 2300W to properly charge a 15k battery bank was a minimum, specially that those panels are not new and must have decayed.  Maybe I made a mistake here.

[dgd]

What is the MPV (Maximum Power Voltage) for the two different types of panels you have? It should be written on label on back of panel

[dapago]

What is the MPV (Maximum Power Voltage) for the two different types of panels you have? It should be written on label on back of panel

Hi there. 30.1Vmp & 33.2vmp

[dapago]

- 2 CC Tristar mppt 60a (new)
- magnum pure sine wave inverter 24V (4 years old)
- 12 x 210ah Trojan T605 batts (new)
- 6 X 215W panels wired 3s2p to one Tristar mppt (5 years old)
- 4 x 250 W panels wired 2s2p to the second Tristar mppt (5 years old)

Twelve small FLA batteries doesn't look the best idea either, a single string of something like L16s would have been a better way to go. Keeping your three strings of T605s balanced will be interesting and likely their life will be shorter compared to a single string of four L16.

dgd

Will bus bar helps for better balancing for the bank?

[ClassicCrazy]

What is the MPV (Maximum Power Voltage) for the two different types of panels you have? It should be written on label on back of panel

Hi there. 30.1Vmp & 33.2vmp

See Vic's reply about matching PV panels in parallel and in series strings
http://midniteftp.com/forum/index.php?topic=3759.msg36449#msg36449

I thought you need to use Voc for the string calculations instead of Vmp ? Am I wrong on that dgd ?

Larry

[dapago]

What is the MPV (Maximum Power Voltage) for the two different types of panels you have? It should be written on label on back of panel

Hi there. 30.1Vmp & 33.2vmp

See Vic's reply about matching PV panels in parallel and in series strings
http://midniteftp.com/forum/index.php?topic=3759.msg36449#msg36449

I thought you need to use Voc for the string calculations instead of Vmp ? Am I wrong on that dgd ?

Larry

From what I know (little) I need to use vmp but again I can be wrong. I think voc is what’s the panel produce but vmp is what the CC receive. Again I can be wrong.

[Vic]

Larry said,
    "...   I thought you need to use Voc for the string calculations instead of Vmp ? Am I wrong on that dgd ?    ...    "


Hi Larry,

Since the major concern when adding PVs in series or parallel,  is power production,  and when the system uses
MPPT CC/s,   not having  a double hump in the power curve,  or reduced power production due to an inefficient Max Power Point chosen by the CC,   have always used Vmp/Imp,  for this calculation.   This is a consistent spec for PVs when producing power for all PVs.

Just use Voc  as a check on  PV string voltage for the coldest temperature recorded/expected  ...   But,   that's just me.

Thanks Larry for of your help on this Forum,   ou are a real asset here!   
73   Have Fun!    Getting ready for the rainy season here.    Vic

[dgd]

I thought you need to use Voc for the string calculations instead of Vmp ? Am I wrong on that dgd ?

No you are not wrong, Voc is used when ensuring the controller's max voltage input is not exceeded.
what Vic says above and...
also in a multi controller setup where one controller provides sufficient power for Absorb/Float stage and other controllers are unloaded (zero current) so the input voltage will rise closer to Voc, especially on a cold but sunny day.

dgd