520w 24v solar system voltage drop

mnsdall · July 2013

Hi guyes ,
I hope you doing very well.
I recently install 4 130w (12v) solar panels connected in 2,2 in parallel so it's as a 24v system (panel specification in Image sorry its not very clear
http://www.diynot.com/network/mnsdall/albums )
And I'm using 30A PWM charge controller.
The problem is when I connect my battery bank(600ah Gel amg batteries)
And in full sunshine 45C' it's voltage drop and only I get 25.8 v max.
But open circuit v is fine approx 35v
I'm using 16mm2 single core cable.
Can any one help me to solving this problem.
Thanks a lot.

solar_dave · July 2013

Re: 520w 24v solar system voltage drop

From here:
http://pvsilicontech.com/pvs/uploads/130W-RY.pdf

Product Specifications
No. of cells and connections 36 in series (4x9)
Dimensions (mm) 1470 x 675
Weight (Kg) 13
Electrical Characteristics
Open Circuit Voltage (Voc) 21.6
Optimum Operating Voltage (Vmp)17.4
Short Circuit Current (Isc) 8.38
Optimum Operating Current (Imp) 7.43
Maximum Power at STC* (Pmax ) 130
Maximum System Voltage 1000

Temperature Coefficients
Temperature Coefficient of Isc +0.05%/C
Temperature Coefficient of Voc - 0.34%/C
Temperature Coefficient of Pm - 0.5%/C
Power Output Tolerance ±3%

What are the specs on the charge controller?

vtmaps · July 2013

Re: 520w 24v solar system voltage drop

mnsdall wrote: »

And in full sunshine 45C' it's voltage drop and only I get 25.8 v max.
But open circuit v is fine approx 35v

Temperature Coefficient of Voc - 0.34%/C
Open Circuit Voltage (Voc) 21.6

Temperature Coefficient of Pm - 0.5%/C
Optimum Operating Voltage (Vmp)17.4

Welcome to the forum
When panels heat up, their voltage goes down.
At standard temp your panels (two in series) should be 43.2 (open circuit) and you are seeing 35 volts because of elevated temperature.

The Vmp drops faster than the Voc with increasing temperature, so its not surprising to see a drop from 34.8 volts to 25.8 volts, and that assumes your batteries are at the absorb stage of charging. If the batteries are too discharged they will pull the voltage down.

Also, if your batteries are hot and the charge controller has temp compensation, the voltage will be lower.

What charge controller do you have?

--vtMaps

Cariboocoot · July 2013

Re: 520w 24v solar system voltage drop

Welcome to the forum.

Two questions:

1). What is the distance between the array and the charge controller?
2). What is the battery Voltage without the array connected?

It is quite normal for array Voltage to be "pulled down" to battery Voltage. If the battery is low, the Voltage will be low. As the battery charges it comes up. If it never rises above 25.8 you have a problem or problems.

At least one of these is that you've only got about 14 Amps of charge current available to a 600 Amp hour battery bank. That's a 2.5% rate, and will take a long time to charge those batteries.

mnsdall · July 2013

Re: 520w 24v solar system voltage drop

10m only space is between chargecontroller and array

mnsdall · July 2013

Re: 520w 24v solar system voltage drop

vtmaps wrote: »

Welcome to the forum
When panels heat up, their voltage goes down.
At standard temp your panels (two in series) should be 43.2 (open circuit) and you are seeing 35 volts because of elevated temperature.

The Vmp drops faster than the Voc with increasing temperature, so its not surprising to see a drop from 34.8 volts to 25.8 volts, and that assumes your batteries are at the absorb stage of charging. If the batteries are too discharged they will pull the voltage down.

Also, if your batteries are hot and the charge controller has temp compensation, the voltage will be lower.

What charge controller do you have?

--vtMaps

Chargecontroller
PWM view star VS3024N
So how can I solve I can't decrease temp😰

mnsdall · July 2013

Re: 520w 24v solar system voltage drop

Cariboocoot wrote: »

Welcome to the forum.

Two questions:

1). What is the distance between the array and the charge controller?
2). What is the battery Voltage without the array connected?

Thanks for ur reply
Ans.1 :10m
2.after 5,6 hour charging its show 25.4,5
But if I put load 200,300w it's discharge in 2,3 hr
3.array voltage always same even I connect 300ah battery bank

vtmaps · July 2013

Re: 520w 24v solar system voltage drop

mnsdall wrote: »

So how can I solve I can't decrease temp

How to solve the low voltage problem depends on exactly what the cause of the problem is. Look again at Cariboocoot's response... you may not have enough panels to charge your batteries. Can you get hold of a battery charger and try charging them?

--vtMaps

mnsdall · July 2013

Re: 520w 24v solar system voltage drop

Cariboocoot wrote: »

Welcome to the forum.

Two questions:

1). What is the distance between the array and the charge controller?
2). What is the battery Voltage without the array connected?

It is quite normal for array Voltage to be "pulled down" to battery Voltage. If the battery is low, the Voltage will be low. As the battery charges it comes up. If it never rises above 25.8 you have a problem or problems.

At least one of these is that you've only got about 14 Amps of charge current available to a 600 Amp hour battery bank. That's a 2.5% rate, and will take a long time to charge those batteries.

So how much current required for 600ah battery bank?
Is my battery bank larg as compare array?
I have sun light around 10houre per day. Is it's not enough?
Pls give me reply thanks

vtmaps · July 2013

Re: 520w 24v solar system voltage drop

mnsdall wrote: »

So how much current required for 600ah battery bank?

You need to be able to push at least 30 amps into those batteries. Even if your charge controller could produce 30 amps, all of it may not be going into the batteries... if there are any loads they will take some of the 30 amps and leave less for the batteries.

Of course, depending on how much current you draw at night, you may need much more than 30 amps during the day to catch up with your discharge at night.

When the battery voltage increases to the absorb voltage, the batteries will then accept less and less current.

If you can't get a battery charger to use on your batteries, disconnect one string of the batteries and let your panels charge the other string. If the batteries are severely discharged it may take a few days to get them fully charged. Make sure you have no loads (day or night) while you are doing this.

By the way, how hot are your batteries and do you have temperature compensation on your charge controller?

--vtMaps

Photowhit · July 2013

Re: 520w 24v solar system voltage drop

Lots of things here, Most Gel AGM batteries only take about 5% charge rate(from my faulty memory).

You have 600Ah 24V battery? so 2 - 600Ah 12 volt batteries? or 12 - 600Ah 2 volt cells? That's a big battery bank! I use 4000Kw array to charge my 800Ah battery.

What stage is your charge controller when your measuring the voltage? Are you disconnecting to measure the VOC? or is it just from you Charge controller with batteries disconnected, or measured at your Charge controller with batteries disconnected, but the still wired to the CC?

A measured Voc at the charge controller of 35V is pretty low. The VMP is usually 75-80% of VOC so I think your looking at the right issues. a 6 gauge wire(16mm2 converted) is pretty reasonable for 30 meter wire run(you haven't bough 20 meters and left the wire coiled on the floor?), heavier wire would reduce you voltage drop.

If you can, I'd measure the VOC at the panels when your checking connections, this would give you a good idea of what your loosing across the wiring.

Do you have alternate means of charging the battery?

mnsdall · July 2013

Re: 520w 24v solar system voltage drop

Photowhit wrote: »

Lots of things here, Most Gel AGM batteries only take about 5% charge rate(from my faulty memory).

You have 600Ah 24V battery? so 2 - 600Ah 12 volt batteries? or 12 - 600Ah 2 volt cells? That's a big battery bank! I use 4000Kw array to charge my 800Ah battery.

What stage is your charge controller when your measuring the voltage? Are you disconnecting to measure the VOC? or is it just from you Charge controller with batteries disconnected, or measured at your Charge controller with batteries disconnected, but the still wired to the CC

Thanks for replying
1.I have 12v,150ah *4 battery

2.connected with cc but battery disconnect
3.i don't connect extra wire
4.no I don't have alternative for charging

mnsdall · July 2013

Re: 520w 24v solar system voltage drop

By the way, how hot are your batteries and do you have temperature compensation on your charge controller?

--vtMaps

Yes I'm using this

http://www.sunstore.co.uk/EP-Solar-View-Star-40A-12-24v-Solar-Charge-Controller-with-LCD-Display-VS3024N.html
But I don't know temp compensation how much I need to set

Photowhit · July 2013

Re: 520w 24v solar system voltage drop

mnsdall wrote: »

Thanks for replying
1.I have 12v,150ah *4 battery

Batteries add voltage when in series, but not amperage, they add amperage but not voltage when in parallel, so you have 2 in series which gives you a 24v 150amp battery bank and 2 in parallel, which gives you a total of 24v 300Ah battery bank.

mnsdall wrote: »

2.connected with cc but battery disconnect

The CC is likely to have some resistance, so I don't think your measuring the VOC(Voltage open circuit) I would measure with the CC disconnected and suspect you will find a higher voltage.
.

mnsdall wrote: »

3.i don't connect extra wire

Good! I've been lazy and not 'cleaned up' my cabin system, since all the wire runs were short, now I'm hesitant to do the cleanup which would make it visually more appealing to potential purchasers, but less adaptable if they wanted to change the layout.

mnsdall wrote: »

4.no I don't have alternative for charging

The good news is you don't have as large a battery bank to support, and the bad is you still don't appear to be charging the batteries.

Does your CC show the current voltage?
During the day does this voltage rise as it's charging?
Does it show what stage the charging is in?
Try measuring the voltage with the CC disconnected and see if the voltage isn't higher.
A clamp meter may tell you how much current is flowing into or out of the battery.
Does the system have loads on it? or Is it in use?(sorry if this has been covered)

mnsdall · July 2013

Re: 520w 24v solar system voltage drop

Photowhit wrote: »

Batteries add voltage when in series, but not amperage, they add amperage but not voltage when in parallel, so you have 2 in series which gives you a 24v 150amp battery bank and 2 in parallel, which gives you a total of 24v 300Ah battery bank.

but for charging batteries(4 150ah, 2,2 in parallel) dnot need 7200W for full charging???

Photowhit wrote: »

Does your CC show the current voltage?
During the day does this voltage rise as it's charging?
Does it show what stage the charging is in?

yes its show I and V for load and charging
no v always same during the day
no it didnt show the stage.
can u tell me when gel agm battery full charge the how many v that show
that much i know
its 100%=12.7
90%=1.6
80%=12.5
50%=12.1
20%=11.8
10%=11.7
0%=11.6
but i'm worrying bcz my CC http://www.sunstore.co.uk/EP-Solar-V...y-VS3024N.html is have only discharging limit v minimum 11v

Photowhit wrote: »

Does the system have loads on it? or Is it in use?(sorry if this has been covered)

yes i,m usning but not much bcz sake of low v.

Photowhit · July 2013

Re: 520w 24v solar system voltage drop

mnsdall wrote: »

but for charging batteries(4 150ah, 2,2 in parallel) dnot need 7200W for full charging???

I was just trying to figure out what we're dealing with, stating you have a 24v 600Ah battery bank is NOT correct, you have a 24v 300Ah battery bank. While 520 watts of array/solar panels isn't large enough for efficient charging. You should get some charging during the day. If your getting enough voltage and current to the charge controller and the charge controller is working properly.

mnsdall wrote: »

yes its show I and V for load and charging
no v always same during the day
no it didnt show the stage.
can u tell me when gel agm battery full charge the how many v that show

Do you have a volt meter? Can you check the voltage with out the Charge controller connected?

mnsdall wrote: »

that much i know
its 100%=12.7
90%=1.6
80%=12.5
50%=12.1
20%=11.8
10%=11.7
0%=11.6

This is for batteries at rest, with no charging or discharging/loads. This is for a 12 volt system, if your setup as a 24 volt system, you should double the voltage numbers if your measuring the battery bank as a whole.
but i'm worrying bcz my CC http://www.sunstore.co.uk/EP-Solar-V...y-VS3024N.html is have only discharging limit v minimum 11v
yes i,m usning but not much bcz sake of low v.[/QUOTE]

Again the discharge limit(low voltage disconnect?) should be 11V for a 12 volt system and should be double that for a 24 volt system (22v)

Your link doesn't go anywhere. Did your charge controller ever work? Did you setup the charge controller for a 24 volt system? most that work for 12 or 24 volt systems require that you move a jumper or a dip switch on the controller to set the voltage of the system you are using. It maybe that the default setting(the setting that the charge controller came with) was for a 12 volt system and your seeing the max voltage on the controller display for a 12 volt system. You also need to set a jumper for the battery type! Well I found a manual for your Charge controller, and this isn't how yours works, it appears to auto sense the battery voltage and you set the parameters for the battery type, on page 22 have you done this? Link to manual is below.

Here's a link to your Charge controllers Manual;

http://solarsystemsphilippines.com/wp-content/uploads/2012/08/VS3024Nmanual.pdf

mnsdall · July 2013

Re: 520w 24v solar system voltage drop

First of all Bundls of thanks for explaining me in deeply
thanks may God bless you.

Photowhit wrote: »

I was just trying to figure out what we're dealing with, stating you have a 24v 600Ah battery bank is NOT correct, you have a 24v 300Ah battery bank. While 520 watts of array/solar panels isn't large enough for efficient charging. You should get some charging during the day. If your getting enough voltage and current to the charge controller and the charge controller is working properly.

Q. so how can i calculate the exact array size for battery?
that much i know is Watt of array * sunshine hour= Double of battery size if we discharge half.
but idont know about how much max current exactly gel battery need for charging on different mode.

Photowhit wrote: »

This is for batteries at rest, with no charging or discharging/loads. This is for a 12 volt system, if your setup as a 24 volt system, you should double the voltage numbers if your measuring the battery bank as a whole.

http://solarsystemsphilippines.com/wp-content/uploads/2012/08/VS3024Nmanual.pdf.

Again the discharge limit(low voltage disconnect?) should be 11V for a 12 volt system and should be double that for a 24 volt system (22v)

yes sorry as you may see in manual its work auto
so its 22 V but as i told you in table battery Voc 23.4v=10%
so i have this confusion my cc have max 22v discharge limt.Is on load its right?

Now i disconnect my 2 Parallel battery after i see this reading on CC
so now my battery bank is 150ah, 12 v in series =24v,150 ah
date:10.07.13
1:pm
pv
34.5v,4.7A
battery
28.2v,4.8A
no load

7:30pm
pv
8.3v, 0A
battery
26v,0A
Load no

9pm
pv
0v,0A
battery
24.5v,9A
load 300w
24.4v,8.9A

date:11.07.13
5am
pv
22.8v, 0A
battery
25.5v,0A
no load
7:30am
pv
26.8v,3.9V
battery
26.9v,3.9A
no load

Photowhit · July 2013

Re: 520w 24v solar system voltage drop

I'm just headed out for a 1000+Km trip this morning, so little time, If this is your reading, it looks like your system is working at least somewhat.

The only time period with 'full sun, the 1 am looks about right, with incoming from array at 34.5v,4.7A, should be charging current for Gel battery, and hopefully seeing a reduced amperage, as the battery is getting close to full, Battery voltage at 28.2 is likely being held by the charge controller so I would guess your out of 'bulk' charging and at 'absorb' where the charge controller is holding the voltage at the max for a gel battery and you have 4.7 amps passing into it. I admit I don't understand what the battery 4.8 amperage is indicating, perhaps just what the battery is taking in with a small discrepancy from the incoming from array. I would expect this to be slightly less with a PWM type charge controller.

Your 9pm with a load of 300 watts is not bad at battery 24.4v,8.9A, particularly if you have reduced your battery bank to 150 amp hours, 300 watts would mean you are drawing over 12 amps at 24.4 volts, or greater than 1/20th of your battery capacity per hour, so 24.4 volts would appear, to me a nearly full battery bank.

Your 5am battery reading with nothing coming in of 25.5 volts, looks very good! I think gel cells may rest at above what flooded cells normally do, I don't have much experience with gel cells.

Time to get on the road, perhaps someone with more experience with Gel cells will chime in, can you post what your battery manufacturers recommendations are?

520w 24v solar system voltage drop

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