MPPT Sizing

[Scott J Martin]

I have 9 Yuma CIGS 200W Panels from BougeRV. I plan to serial connect them into 3 arrays of 3 panels each.
I have 3 Victron MPPT 150/70 controllers.
I have 2 LiTime 12V - 560Ah batteries connected in Series

Volts Volts with 20%
Voltage - Open Circuit - Voc 30.4Volts 36.48Volts with 20% buffer.
3 Three Panels at 36.48 = 109.44V. Each MPPT Controller can handle 150Volts

Maximum power from PV Arrays 200 Watts per Panel, Three Panels = 600 Watts per Array

Output Current (600W divided by 14.4 Volts)
600 Watts / 14.4Volts = 41.7 Amps time 1.2 for the buffer = 50.0Amps. Each MPPT Controller can handle 70Amps

The Batteries' Specs say :
- "Recommended Charge Current - 112A (0.2C)
and
- "Max Continuous Charge Current - 250A

Am I going to exceed the "Recommended Charge Current"?

 

[MisterSandals]

Did you abandon your other thread?

 

[Q-Dog]

Each of those 150/70 charge controllers can handle up to 1000 watts in a 12 volt system, so you have way more charge controller than you need. You can limit the output if you need to, but you are wasting money on controllers you don't need.

 

[mikefitz]

Am I going to exceed the "Recommended Charge Current"?

Maybe, on a cold day with ideal solar conditions. The nine 200 watt panels will in theory under ideal conditions convert to around 130 amps at a typical charge voltage in a 12v system. In practice you are unlikely to exceed 100 amps.
A string of 3 panels , each 200 watts, will need a 150/45 controller.

2 LiTime 12V - 560Ah batteries connected in Series

It's probable using two 12v batteries in series will cause issues as they get out of balance with each other. Using a battery balancer/equiliser may help. It's far better to use a 24 volt battery in a 24 volt system.

time 1.2 for the buffer

What is this 'buffer'?

 

[Scott J Martin]

Maybe, on a cold day with ideal solar conditions. The nine 200 watt panels will in theory under ideal conditions convert to around 130 amps at a typical charge voltage in a 12v system. In practice you are unlikely to exceed 100 amps.
A string of 3 panels , each 200 watts, will need a 150/45 controller.


It's probable using two 12v batteries in series will cause issues as they get out of balance with each other. Using a battery balancer/equiliser may help. It's far better to use a 24 volt battery in a 24 volt system.


What is this 'buffer'?

I just added some extra into the equation to be cautious

 

[Scott J Martin]

I just added some extra into the equation to be cautious

Is there a way to check and see if the batteries are becoming unbalanced?

 

[Scott J Martin]

Each of those 150/70 charge controllers can handle up to 1000 watts in a 12 volt system, so you have way more charge controller than you need. You can limit the output if you need to, but you are wasting money on controllers you don't need.

Where did I go so wrong with my math?

 

[Scott J Martin]

Did you abandon your other thread?

yes

 

[1234enough]

With a 24v battery & panels set up as described a 150/35 would easily suffice, with plentiful amount of headroom left for any future panel additions

 

[Q-Dog]

Where did I go so wrong with my math?

The easy way to start is to just add up the panel VOC (the actual number on the label). You want that total to be about 80% less than your charger's VOC limit. After that, you can do math or use the Victron MPPT Calculator to fine tune and make sure you won't overvolt the controller during cold weather.

There are so many ways to do this. The 150/35 would work fine for a single string. The 150/70 and 150/85 could hande 2 strings. And you could put all 3 strings into a 150/100. That would require a combiner and fuses/breakers, but it would work fine.

I lean towards having at least 2 controllers to have some redundancy. I have 2 Victron 150/60 with 3600 watts of panels.

 

[740GLE]

Do you already own three 150/70 units?

150/70 on a 24v system can handle a lot of PV

70a*27v = 1900w

Knowing that panels hardly ever reach nameplate for actual real world production as long as the PV strings are under 150v VOC and ISC you can over panel quite a bit to deal with low cloudy production days.

If you want snag more PV, maybe some big boy 400w panels and use those other 150/70 units run 3s2p and bam you got 2400w per 150/70.

 

[Scott J Martin]

The easy way to start is to just add up the panel VOC (the actual number on the label). You want that total to be about 80% less than your charger's VOC limit. After that, you can do math or use the Victron MPPT Calculator to fine tune and make sure you won't overvolt the controller during cold weather.

There are so many ways to do this. The 150/35 would work fine for a single string. The 150/70 and 150/85 could hande 2 strings. And you could put all 3 strings into a 150/100. That would require a combiner and fuses/breakers, but it would work fine.

I lean towards having at least 2 controllers to have some redundancy. I have 2 Victron 150/60 with 3600 watts of panels.

200W CIGS Voc 30.4 Voltage - Open Circuit
3 Number of Panels in the Array
3 x 30.4 = 91.2V

Charger's Voc Limit 150
150 times .8 = 120

PV Array is within MPPT Controller's limits

I bought the Victon Controllers because they "Network" and are aware of each other.

I am planning to connect all 3 Controllers to Positive and Negative Terminal Blocks and attach the battery to the same blocks

 

[Brucey]

I am planning to connect all 3 Controllers to Positive and Negative Terminal Blocks and attach the battery to the same blocks

Sounds like a job for a Lynx Power in (can be converted to hold megafuses like a Distributor with a couple bucks of nuts and bolts)

Victron Lynx Power In - Power Distribution System (M10)

Optimize your power distribution with the Lynx Power In - part of the Lynx Power Distribution System. Compatible with LiFePO4 battery banks.

www.currentconnected.com

 

[Chispas]

Sounds like a job for a Lynx Power in (can be converted to hold megafuses like a Distributor with a couple bucks of nuts and bolts)

Victron Lynx Power In - Power Distribution System (M10)

Optimize your power distribution with the Lynx Power In - part of the Lynx Power Distribution System. Compatible with LiFePO4 battery banks.

www.currentconnected.com

Fancy looking bus bar but could actually work out cheaper than individual components ?

 

[Brucey]

Fancy looking bus bar but could actually work out cheaper than individual components ?

Generally ends up being cheaper than two separate bus bars rated for 1000A.

Note there is some question on if the bus bars can actually carry 1000A long term but anything under 800A or so you should be good to go.

Our own Adam De Lay:

 

[740GLE]

Fancy looking bus bar but could actually work out cheaper than individual components ?

All depends on how you plan to implement over current protection.

With x3 70a SCC, cheap mega fuses in one enclosure is pretty handy.

 

[Brucey]

All depends on how you plan to implement over current protection.

With x3 70a SCC, cheap mega fuses in one enclosure is pretty handy.

The beauty is if you leave enough space initially you can hot add additional units to each end (assuming shunt in middle and loads on one side).

 

[Brucey]

All depends on how you plan to implement over current protection.

With x3 70a SCC, cheap mega fuses in one enclosure is pretty handy.

Especially now they have cheaper 5 packs:

Victron MEGA-Fuse 32V/48V/80V

MEGA-Fuse by Victron Energy are designed for heavy-duty applications, providing superior protection for battery and alternator systems. Ideal for high current and heavy-gauge applications.

bluemarine.com

 

[Chispas]

Generally ends up being cheaper than two separate bus bars rated for 1000A.

Note there is some question on if the bus bars can actually carry 1000A long term but anything under 800A or so you should be good to go.

Our own Adam De Lay:

im looking at 2 x 150/35 & 2s 600W 54 VOC on each & then 24 V lfp, not sure if it will be 2 x 100AH or 1 single 200AH ? im going to have to take a look at the datasheet to see if its doable.

 

[Brucey]

im looking at 2 x 150/35 & 2s 600W 54 VOC on each & then 24 V lfp, not sure if it will be 2 x 100AH or 1 single 200AH ? im going to have to take a look at the datasheet to see if its doable.

Oh that's not a problem at all.

I have the following on two distributors (power ins with fuses and circuit board for fuse detection)
Midnite Rosie (7kW)
450/100
250/100
150/35
150/35
Pheonix 48/1200

Pushing about 12-13kW thru during full sun and no problems at all, max of about 250A.

 

[Chispas]

no, no probs with the Amps or Volts, I just need to see if theres enough terminals & how the in & out works. Ive got the manual downloaded & Ill take a look later, off back to work now.

 

[Q-Dog]

200W CIGS Voc 30.4 Voltage - Open Circuit
3 Number of Panels in the Array
3 x 30.4 = 91.2V

Charger's Voc Limit 150
150 times .8 = 120

PV Array is within MPPT Controller's limits

I bought the Victon Controllers because they "Network" and are aware of each other.

I am planning to connect all 3 Controllers to Positive and Negative Terminal Blocks and attach the battery to the same blocks

On the 150volt controller you can probably get away with 4 of those panels in series.

 

[740GLE]

no, no probs with the Amps or Volts, I just need to see if theres enough terminals & how the in & out works. Ive got the manual downloaded & I’ll take a look later, off back to work now.

4 official m8 (or m10) terminals, but you can “hack it” to get 6 by using the expansion terminals on the ends

 

[Scott J Martin]

Sounds like a job for a Lynx Power in (can be converted to hold megafuses like a Distributor with a couple bucks of nuts and bolts)

Victron Lynx Power In - Power Distribution System (M10)

Optimize your power distribution with the Lynx Power In - part of the Lynx Power Distribution System. Compatible with LiFePO4 battery banks.

www.currentconnected.com

I was worried about where to put all the fuses. Good video ... thanks

 

[Brucey]

4 official m8 (or m10) terminals, but you can “hack it” to get 6 by using the expansion terminals on the ends

All the power ins and distributors have m8 bolts for the four main pairs of terminals.

The m8 and m10 models differ in the sizing for the expansion terminals. So you would still use m8 for your four main connections.