Proposed System....what do you think?

[pda1]

Mr. Prowse has provided such an excellent resource that in my copying his working I hope I assemble and select everything correctly. It'll be a 24v system.

So, here's my proposal for design which is the same one as Will provides; https://www.mobile-solarpower.com/4000-watt-24v-solar-system.html

- PV panels are Trina Solar SS250P-60 (here are the spec's found from the Ebay listing;

Rated Power of each panel: 250W

• Open circuit voltage (VOC): 37.6 V
• Max power voltage (VMP): 30.3 V
• Short circuit current (ISC): 8.85 A
• Max power current: 8.27 A
• Power Tolerance 0/+3%
• Maximum system voltage: 600V (UL)
• Fuse Rating: 15 A
• Frame: Anodized aluminum alloy
• Weight: 41 lbs
• Dimensions: 64.95" × 39.05" × 1.37" inches

Layout- because of space and placement of the panels, I'll have 5 panels facing South located on our yard, another 5 panels will be on a West facing roof (45° angle)

The idea is to let the Sun charge early in the day with the 5 South facing panels and then later in the day with the 5 West facing panels.
Each string of 5 panels will be connected in series.

The 2 MPPT controllers- 5 panels will be connected to each controller. I'm somewhat concerned that the input voltage to each controller will be exceeded and thus destroy the controllers. I'm new to this stuff....and cautious. What are your thoughts about this?

Batteries- I'll be using a LiFePo 24v 100Ah which I intend to purchase 8- 3.2v cells on Ebay, probably, making it a 24v battery. Why 100Ah? Because that seems to be a common Amp hour for most systems. Later, if need be, I assume I can increase the Amp hours by putting adding another 24v 100Ah battery in parallel. Let me know if this is wrong.

Battery Balancer- don't remember if one is needed.

BMS- will buy 2 OverKill BMS or perhaps Victron?

No Automatic Transfer Switch- at the moment I don't need one.

Inverter- pure sine wave just like Will's design mentioned above. However, I would like to add a separate 120v breaker system to the inverter for several 15a circuits.

The remainder of the system will be as pictured in Will's 24v system (mentioned above).

Lastly, I'm concerned about Bluetooth capable equipment for several reasons;
1- Not open source
2- Don't want the equipment to be hacked, modified or disabled by a malicious actor (as they say).
3- Perhaps I can use an old cell phone with Bluetooth capability?
4- I don't want anyone else looking at the power figures generated by my system.

Conclusion- what are your ideas? Any improvements you'd suggest? I certainly want to do this setup correctly the first time.

Thank you,

Peter

 

[crossy]

Rule-1 would be never, ever, exceed the maximum open-circuit voltage of your charge controller, upset and the exit of the Magic Smoke will ensue.

The panels come up to the O/C voltage very rapidly when it gets light even if there's no appreciable power being generated. This is the danger time for your controller.

 

[pda1]

So, how is that problem solved? It seems most MPPT controllers have an upper limit of 150v.

Guide me in the right product direction so I don't wreck the controllers. Or recommend another controller or panel arrangement, there's got to be a simple solution.

Thanks,

Peter

 

[crossy]

Your panels are OC voltage of 37.6V. If your controller is max 150V (do verify) then you can have up to 150/37.5 panels in series (4).

Have you got room for 6 panels on each array which you can arrange as two groups of 3 panels in series then put the groups on each roof in parallel?

 

[pda1]

No, I only have 10 panels total.

 

[crossy]

That makes life awkward

You could try to find an MPPT that will handle 200V.

EDIT A quick look on AliExpress netted this https://www.aliexpress.com/item/4000021535485.html good for 190V.
5 x 37.6 is 188V close.

EDIT 2 Here's a 200V one https://www.aliexpress.com/item/32931597292.html

Another Edit Or you could put 4 panels in series on one roof and 2x3 in series on the other.

 

[pda1]

Your panels are OC voltage of 37.6V. If your controller is max 150V (do verify) then you can have up to 150/37.5 panels in series (4).

Have you got room for 6 panels on each array which you can arrange as two groups of 3 panels in series then put the groups on each roof in parallel?

Maybe that would be better? Hoping I understand this correctly I made some modifications;

Array 1 (has 6 panels)- 2 groups of 3 panels in series (Oc output would be 112.8v of each group)
Combine these 2 groups into parallel and feed MPPT number 1 with 112.8v

Array 2- (has 4 panels)- 2 groups of 2 panels in series (Oc output would be 75.2v of each group)
Combine these 2 groups into parallel and feed MPPT number 2 with 75.2v

Does that sound correct?

Any idea what gage wire would be used on a run of about 100 feet?

Again, thank you...

Peter

 

[pda1]

200v MPPT's are very expensive.....ugh

 

[wattmatters]

No, I only have 10 panels total.

If you can't add two panels, then either:
- change the array set up to have 6 facing in one direction and 4 in the other. Then run 3S2P into one MPPT and 2S2P into the other MPPT.
- remove a panel from each array and run 2S2P into both MPPTs

Always allow headroom to not exceed the MPPT's Voc limit.

The colder your area gets, the more voltage headroom you need to leave. Reason for this is the panel's Voc goes up as panel temperature falls (conversely it declines as panel temperature rises). If you get down to freezing then allow about 10% minimum. If you go well below freezing then you'll probably want at least 20% headroom.

e..g the Voc of your panels is 37.6V
At freezing that will be closer to 41V.
150 / 37.6 = 3.98 panels
150 / 41 = 3.65 panels

So while you might just scrape in under the Voc limit with 4 panels most of the time (as the working voltage at normal temps will be less the Voc), on a cold morning you can do some damage.

A max of 3 of those panels in series for a charge controller with an input limit of 150V.

You get around the voltage limit by putting small series of panels in parallel.

3 panels in each series with 2 series in parallel - 3S2P. This keeps the voltage down but doubles the current the wires need to carry, so cabling needs to be chosen to carry the higher current.

 

[pda1]

That makes life awkward

You could try to find an MPPT that will handle 200V.

EDIT A quick look on AliExpress netted this https://www.aliexpress.com/item/4000021535485.html good for 190V.
5 x 37.6 is 188V close.

EDIT 2 Here's a 200V one https://www.aliexpress.com/item/32931597292.html

Another Edit Or you could put 4 panels in series on one roof and 2x3 in series on the other.

Thanks

 

[pda1]

Good ideas which I hope I understand.

Is the following correct?

Array 1 (has 6 panels)- 2 groups of 3 panels in series (Oc output would be 112.8v of each group)
Combine these 2 groups into parallel and feed MPPT number 1 with 112.8v

Array 2- (has 4 panels)- 2 groups of 2 panels in series (Oc output would be 75.2v of each group)
Combine these 2 groups into parallel and feed MPPT number 2 with 75.2v

 

[HRTKD]

Victron does not sell a BMS for DIY batteries. The BMS they sell is specific to their battery.

As I recall, with my Victron components, I can change the Bluetooth password. Granted, it's a six digit key, so someone with enough time and access could figure it out. I suppose you could unplug the Bluetooth module of the BMS. The Victron solar charge controllers and the BMV-712 do not have a Bluetooth dongle, so no unplugging that.

 

[wattmatters]

Is the following correct?

Yes

 

[anadiner]

HE

Mr. Prowse has provided such an excellent resource that in my copying his working I hope I assemble and select everything correctly. It'll be a 24v system.

So, here's my proposal for design which is the same one as Will provides; https://www.mobile-solarpower.com/4000-watt-24v-solar-system.html

- PV panels are Trina Solar SS250P-60 (here are the spec's found from the Ebay listing;

Rated Power of each panel: 250W

• Open circuit voltage (VOC): 37.6 V
• Max power voltage (VMP): 30.3 V
• Short circuit current (ISC): 8.85 A
• Max power current: 8.27 A
• Power Tolerance 0/+3%
• Maximum system voltage: 600V (UL)
• Fuse Rating: 15 A
• Frame: Anodized aluminum alloy
• Weight: 41 lbs
• Dimensions: 64.95" × 39.05" × 1.37" inches

Layout- because of space and placement of the panels, I'll have 5 panels facing South located on our yard, another 5 panels will be on a West facing roof (45° angle)

The idea is to let the Sun charge early in the day with the 5 South facing panels and then later in the day with the 5 West facing panels.
Each string of 5 panels will be connected in series.

The 2 MPPT controllers- 5 panels will be connected to each controller. I'm somewhat concerned that the input voltage to each controller will be exceeded and thus destroy the controllers. I'm new to this stuff....and cautious. What are your thoughts about this?

Batteries- I'll be using a LiFePo 24v 100Ah which I intend to purchase 8- 3.2v cells on Ebay, probably, making it a 24v battery. Why 100Ah? Because that seems to be a common Amp hour for most systems. Later, if need be, I assume I can increase the Amp hours by putting adding another 24v 100Ah battery in parallel. Let me know if this is wrong.

Battery Balancer- don't remember if one is needed.

BMS- will buy 2 OverKill BMS or perhaps Victron?

No Automatic Transfer Switch- at the moment I don't need one.

Inverter- pure sine wave just like Will's design mentioned above. However, I would like to add a separate 120v breaker system to the inverter for several 15a circuits.

The remainder of the system will be as pictured in Will's 24v system (mentioned above).

Lastly, I'm concerned about Bluetooth capable equipment for several reasons;
1- Not open source
2- Don't want the equipment to be hacked, modified or disabled by a malicious actor (as they say).
3- Perhaps I can use an old cell phone with Bluetooth capability?
4- I don't want anyone else looking at the power figures generated by my system.

Conclusion- what are your ideas? Any improvements you'd suggest? I certainly want to do this setup correctly the first time.

Thank you,

Peter

Mr. Prowse has provided such an excellent resource that in my copying his working I hope I assemble and select everything correctly. It'll be a 24v system.

So, here's my proposal for design which is the same one as Will provides; https://www.mobile-solarpower.com/4000-watt-24v-solar-system.html

- PV panels are Trina Solar SS250P-60 (here are the spec's found from the Ebay listing;

Rated Power of each panel: 250W

• Open circuit voltage (VOC): 37.6 V
• Max power voltage (VMP): 30.3 V
• Short circuit current (ISC): 8.85 A
• Max power current: 8.27 A
• Power Tolerance 0/+3%
• Maximum system voltage: 600V (UL)
• Fuse Rating: 15 A
• Frame: Anodized aluminum alloy
• Weight: 41 lbs
• Dimensions: 64.95" × 39.05" × 1.37" inches

Layout- because of space and placement of the panels, I'll have 5 panels facing South located on our yard, another 5 panels will be on a West facing roof (45° angle)

The idea is to let the Sun charge early in the day with the 5 South facing panels and then later in the day with the 5 West facing panels.
Each string of 5 panels will be connected in series.

The 2 MPPT controllers- 5 panels will be connected to each controller. I'm somewhat concerned that the input voltage to each controller will be exceeded and thus destroy the controllers. I'm new to this stuff....and cautious. What are your thoughts about this?

Batteries- I'll be using a LiFePo 24v 100Ah which I intend to purchase 8- 3.2v cells on Ebay, probably, making it a 24v battery. Why 100Ah? Because that seems to be a common Amp hour for most systems. Later, if need be, I assume I can increase the Amp hours by putting adding another 24v 100Ah battery in parallel. Let me know if this is wrong.

Battery Balancer- don't remember if one is needed.

BMS- will buy 2 OverKill BMS or perhaps Victron?

No Automatic Transfer Switch- at the moment I don't need one.

Inverter- pure sine wave just like Will's design mentioned above. However, I would like to add a separate 120v breaker system to the inverter for several 15a circuits.

The remainder of the system will be as pictured in Will's 24v system (mentioned above).

Lastly, I'm concerned about Bluetooth capable equipment for several reasons;
1- Not open source
2- Don't want the equipment to be hacked, modified or disabled by a malicious actor (as they say).
3- Perhaps I can use an old cell phone with Bluetooth capability?
4- I don't want anyone else looking at the power figures generated by my system.

Conclusion- what are your ideas? Any improvements you'd suggest? I certainly want to do this setup correctly the first time.

Thank you,

Peter

Hey Im throwing together a 24v so interested in what ur doing. Will get back to u later. Its 5:30am here.

Note: my preference is 2 sets of 2 12volt batteries... meaning not a 24v. Just me but dont like relying on 1 battery. If gonna do that then why not a power station?

 

[pda1]

Here's another concern- it looks like many of the MPPT controllers people have installed have been destroyed. My guess is in most cases the cause was;

1- too much input voltage from the panels and the charger design specifications being exceeded.

2- wrong wiring to or from the mppt.

 

[HRTKD]

Here's another concern- it looks like many of the MPPT controllers people have installed have been destroyed. My guess is in most cases the cause was;

1- too much input voltage from the panels and the charger design specifications being exceeded.

2- wrong wiring to or from the mppt.

While #1 can kill a solar charge controller, #2 probably wouldn't kill the solar charge controller but could start a fire.

I would hazard that most solar charge controller failures are due to:
1. Poor quality
2. Operator error

 

[pda1]

While #1 can kill a solar charge controller, #2 probably wouldn't kill the solar charge controller but could start a fire.

I would hazard that most solar charge controller failures are due to:
1. Poor quality
2. Operator error

Yes, that makes sense.

 

[pda1]

So far here's the equipment and layout;

PV Panels

Array 1 (faces South) (has 6 panels)- 2 groups of 3 panels in series (Oc output would be 112.8v of each group)
Combine these 2 groups into parallel and feed MPPT number 1 with 112.8v

MPPT for Array 1
Victron Energy SmartSolar MPPT 150V 35 amp 12/24/36/48-Volt Solar Charge Controller (Bluetooth)


Array 2- (faces West) (has 4 panels)- 2 groups of 2 panels in series (Oc output would be 75.2v of each group)
Combine these 2 groups into parallel and feed MPPT number 2 with 75.2v

MPPT for Array 2
Victron Energy SmartSolar MPPT 100V 50 Amp 12/24-Volt Solar Charge Controller (Bluetooth)


Both MPPT controllers will be connected to a single 24v LiFePo battery.

Question- What practical problems will there be by connecting both MPPT controllers to the battery? Will both controllers need to be programmed identically to match the voltage parameters of the battery?

MPPT Victron
The prices are high but you do get what you pay for so I'm reluctant to purchase MPPTs from Aliexpress- great idea for getting stuff though. Victron appears to be a rather common and widely used maker of MPPTs.

Please let me know what you think of the equipment and layout mentioned above.

Thanks,

Peter

 

[crossy]

Looks good to me

I'd be tempted to get two identical MPPT units in case you want to add a couple of panels to the smaller group later or if one of them fails you could swap to get the maximum output whilst waiting for a replacement.

Make sure your battery settings are the same on both units and they should play nicely together.

 

[anadiner]

I know Prowse is adamant on panels facing South if ur in Northern Hemisphere and he's been messing with solar longer than most; but, I guess Im going to make what is called 'common mistake'. The sun just doesnt direct itself South where I live. Its like a West rise, East set leaning northward.

Regardless my layout has several arrays also. Ground, roof mount combo. Still checking out panels..
gotta decide wattage. Cabling absolute last because I dont want length to dictate what I do. U know, like 'oh I cant put that there cuz my cable isnt long enough' mindset.

Avoiding that trap.