panels to battery 40m

[greenhouseparos]

hi
i am installing 20 suntech 190+ad panels in a stand alone system. the panels have to be mounted 40m away from the batteries which is causing me some problems with cable sizing. my current idea is to use 2 morning star 60a mppt chargers with 2 10 panel strings wired for 72v (2 panels series) 5 parrele pairs. this will need 16mm cable for a 3-4% volt drop.
chargers + cable will cost about 1500euro.
if i fitted a inverter directly under the panels and run 220v to the batteries how would i charge the batteries? could i conect to the main inverter stecca 3500xtm  (which has a battery charger) or would i need a seperate charger.

[Justme]

I would look at raising the array voltage by about double to quarter the cable size needed for the same losses. So look at other charge controllers / inverters that can take the higher voltages.

[billi]

stecca   is same as studer-innotec i think   and they have perhaps better information  about "AC-coupling"  and as far as i know you can have a Grid tie inverter connected  , but i think your PV Panel size will exceed the  inbuilt charger capacity (of your stecca 3500xtm )

If you would have a 48 volt system you only need one  MPPT chargecontroller
Billi

[billi]

Ah  ....  Perhaps a mixed idea would be elegant  

a small Grid tie inverter ( not at the panels  better close to off grid inverter ) and run the high DC Voltage  cables  to him  

this inverter adds then power to your off grid one during the day  and the rest of the panels connected to one MPPT controller to charge batteries directly  

I had a look at your Stecca inverter and they say it can handle 90 A   of AC charge  so about 2300 watt

Perhaps not much more expensive  

have a read here and click on "Partial AC-coupling in Minigrids"


 http://www.studer-innotec.com/?cat=whitepapers  

[greenhouseparos]

I would look at raising the array voltage by about double to quarter the cable size needed for the same losses. So look at other charge controllers / inverters that can take the higher voltages.

using the morningstar 60a i could get the voltage up to 109v 3 strings of 3 but this uses only a total of 18 panels which would mean another controller. do you know any charger makes that can handle larger voltages?

[greenhouseparos]

If you would have a 48 volt system you only need one  MPPT chargecontroller
 
saddly costs prevented a 48v system as the batteries would have doubled.

[Justme]

using the morningstar 60a i could get the voltage up to 109v 3 strings of 3 but this uses only a total of 18 panels which would mean another controller. do you know any charger makes that can handle larger voltages?

Outback FM60 or 80 both do 145v. You can over size the array to controller. The extra amps just dont get captured. I have a theoretical 100amps from my array but have used an 80amp controller.

 
saddly costs prevented a 48v system as the batteries would have doubled.

Not quite true.

You still need the same total stored energy even though its a 48v bank. So the AH capacity can be 1/4 of the 12v banks.


If you use 3kWh per day & want 3 days autonomy then you need 3 kWh x 3 days x 2 (so you never go below 50%) = 18kWh

18kWh @ 12v = 1500ah or 15 x 100ah 12v bats (not that you should ever use a bank of that many bats)
18 kWh @ 48v = 375ah or 16 x 100ah 12v bats

The only way it can cost more is if you have a total need of less than 2.4kWh (so a 4.8kWh bank) so thats a usage of less than 800wh per day.


edit to add


why not have the bats near the array & have the inverted power travelling the distance?

[camillitech]

In the grand scale of your considerable investment is 40m of 16mm square really that expensive  http://www.tlc-direct.co.uk/Main_Index/Cable_Index/Armoured_SWA/index.html 178GBP for 16mm as opposed to 65GBP for 4mm    or am I missing something. My wind turbine's 160m from my battery bank and my hydro turbine 470m, the one I'm currently installing is 1000m away  Think yourself lucky 

Good luck, Paul

[Justme]

You could also do a cost benefit analysis to see if the net gain from the bigger cable is worth the cost.

[greenhouseparos]

In the grand scale of your considerable investment is 40m of 16mm square really that expensive  http://www.tlc-direct.co.uk/Main_Index/Cable_Index/Armoured_SWA/index.html 178GBP for 16mm as opposed to 65GBP for 4mm    or am I missing something. My wind turbine's 160m from my battery bank and my hydro turbine 470m, the one I'm currently installing is 1000m away  Think yourself lucky 

Good luck, Paul

no considering the overall costs 200euro more on a 16000euro system is not much. Just exploring options. my wind turbine will also be over 100m from the batteries.

[greenhouseparos]

using the morningstar 60a i could get the voltage up to 109v 3 strings of 3 but this uses only a total of 18 panels which would mean another controller. do you know any charger makes that can handle larger voltages?

Outback FM60 or 80 both do 145v. You can over size the array to controller. The extra amps just dont get captured. I have a theoretical 100amps from my array but have used an 80amp controller.

 
saddly costs prevented a 48v system as the batteries would have doubled.

Not quite true.

You still need the same total stored energy even though its a 48v bank. So the AH capacity can be 1/4 of the 12v banks.


If you use 3kWh per day & want 3 days autonomy then you need 3 kWh x 3 days x 2 (so you never go below 50%) = 18kWh

18kWh @ 12v = 1500ah or 15 x 100ah 12v bats (not that you should ever use a bank of that many bats)
18 kWh @ 48v = 375ah or 16 x 100ah 12v bats

The only way it can cost more is if you have a total need of less than 2.4kWh (so a 4.8kWh bank) so thats a usage of less than 800wh per day.


edit to add


why not have the bats near the array & have the inverted power travelling the distance?

i have 12 2v opz 1100ah batteries couldnt afford more. siting the batteries and inverternext next to the panels would require building some kind of weather proof construction which would eat up valuable euros.
thanks for the info   

[Justme]

i have 12 2v opz 1100ah batteries couldnt afford more. siting the batteries and inverternext next to the panels would require building some kind of weather proof construction which would eat up valuable euros.
thanks for the info   

But thats the point. With a 48v system you would have only needed cells of about 550ah (I assume you are set up as 24v) . As they would be cheaper each you then have the funds for the extra cells. One way or the other you are going to have to spend extra money compared to an ideal system thats located all in the same spot. Could be on wire, a shed or even in the losses in the system due to bad planning / implementation. A large battery bank will be perfectly ok on a pallet with a cheap tarp / tin roof. Dep on the temps you get you might need some sort of insulation. Mine is outside & uninsulated. Even when its -18c the bank still works within what we need even if its not working at full capacity.

Now that its too late to change the bank V you have to live with it.

As there are not many solutions & all of them cost its now down to which cost / level of performance balance you are happy with.

In your first post you said you were going to install 20x190w panels & use 2 x 60 amp controllers.

Are you sure thats right?

I make 20 x 190w = 3800watts or 158 amps at 24v. That will need 3 x 60 amp controllers not the 2 you are planning on. It will work but you are loosing quite a bit of power / energy. 30 amps at 24v is the same as removing 720 watts of array during peak times. 2 x 80amp FM 80's would be much better & you get the 145v input too so helping on two fronts.

[billi]

Just exploring options. my wind turbine will also be over 100m from the batteries.

  not the easiest  to  combine wind and PV  and maintain an expensive battery
What  is your plan, how  to  connect the windturbine ?

The suggested Outback MPPT PV controller  might be helpful  with a windturbine idea

Billi

[stephendv]

The midnite solar classic charge controllers can handle up to 250V: http://www.midnitesolar.com/productPhoto.php?product_ID=258&productCatName=Charge%20Controllers&productCat_ID=21

But you'd have to import it from the US, no European distributor is selling them yet, AFAIK.

[greenhouseparos]

The midnite solar classic charge controllers can handle up to 250V: http://www.midnitesolar.com/productPhoto.php?product_ID=258&productCatName=Charge%20Controllers&productCat_ID=21

But you'd have to import it from the US, no European distributor is selling them yet, AFAIK.

just read your ac coupling article on your link. very interseting.
my problem has arisen for strange reasons. the initial system i planned used 18 suntech 190 pannels. i ordered 22 becuase i need 4 for a bore hole pump. when they arrived at the dealer he had 26 because he had to order a pallet. he offered the extra 4 pannels at cost price (an offer i couldn't refuse). now i am trying to fit the extra 4 into the system with out the costs rising sharply. the original 18 on 2 x 60amp morningstars worked. 18 pannels 2 sets of 9 3 parallel 3 series on the 2 chargers 109v at 15 amps over 40 m = 6 or 10 mm cable. i will use 2 of the extra pannels for water pumping and have 2 left. trying to fit them into the house array seems expensive and not cost efficient. will definatly have a use for them but not for the house array it seems.