Help needed pls

lee1

Hi new here and need so help 
So I have a 250w solar panel on my out building ,I have a 110ah battery to run some lights, and a pwm 20a charge controller 
So I have measured volts from solar panel and am getting around 50v 
The charge controller shows only 1-2 amps of charge to battery and battery is not charging 
What is going wrong plse 
Should it charge at more amps 

New_Mexico_Will

Is the battery full?  The charge controller will taper back to a lower amperage as the battery becomes full.   

Photowhit

lee1 said:

Hi new here and need so help 
So I have a 250w solar panel on my out building ,I have a 110ah battery to run some lights, and a pwm 20a charge controller 
So I have measured volts from solar panel and am getting around 50v 
The charge controller shows only 1-2 amps of charge to battery and battery is not charging 
What is going wrong plse 
Should it charge at more amps 

You have the wrong type of charge controller for that solar panel.

Did you read the specs on the charge controller? It likely wants 7-20volts input.

Your measured 50 volts is likely a bit low VOC for a 72 cell panel, though it could be a 60 cell panel. So the voltage is too high for most PWM to deal with, it has to do something with the extra voltage and doing it's best if it has output. PWM can only pass through the amperage, so at 50 volts a 250 watt panel would have 5 amps output max (amps x volts = watts).

To get the most out of your solar panel you will need a MPPT type charge controller.

lee1

Hi 
No the battery is at 10.8 v charges a small bit maybe up to 11.8 volts the battery has never been fully charged 
Thanks for your help

lee1

The own says it takes up to 50v 
But may be wrong 
So mppt is the answer ??

lee1

Pwm*

BB.

OK... Slow down a bit.

What is the brand/model of charge controller (link to product page is OK)?

What is the Vmp/Imp rating of the panel?

Using a volt meter, what is the Vpanel input voltage at the charge controller input? What is the Vbatt voltage at the output? (right at the terminals--Looking for good electrical connections)

How are you measuring the charging current (the charge controller's screen)?

Is the panel in full sun (no shading from trees, pipes, chimney)? Any shading on solar panel kills it charging current/output voltage

What AWG (diameter) of wire and length of wire from charge controller to battery?

Just to confirm, 12 volt @ 110 AH Flooded Cell lead acid battery?

When connecting the charge controller... You always connect the controller to the battery bank first, then to the solar array. When disconnecting, disconnect solar array first, and battery bank second. Connecting to the solar array first can "confuse" the charge controller and possibly even damage it. Also, connecting the solar panel first, the charge controller can "boot" and configure its output voltage incorrectly.

-Bill

lee1

Ok this is what I know how to do , told you I was new I have checked the voltage from solar panel with multi metre
Guage of wire not sure it's about 3mm in diameter  And they are about 2 feet apart
And yes I know the bit about connecting battery first that I do no lol
Yes on the battery lead acid
And yes in full sumn it was showing 2 amps on a separate meter this the controller 

https://www.amazon.co.uk/Controller-Topcloud-Parameter-Adjustable-Regulator/dp/B08FCQMPV3/ref=asc_df_B08FCQMPV3/?tag=googshopuk-21&linkCode=df0&hvadid=463098914393&hvpos=&hvnetw=g&hvrand=960586661700970134&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=1006886&hvtargid=pla-947429852321&psc=1#

BB.

We are not on site with you... So you need to be very clear/accurate/detailed in what you tell us... What is the Voltage on the Vpanel input and Vbatt output on the charge controller's terminals, etc...

The confounding issue is that the charge controller behaves differently based on output voltage, time, etc... And the controller may be behaving as designed, or not (bad). Going through step by step debugging helps us help you.

3mm is a bit smaller than 12 AWG (3.31mm diameter). That is OK for upwards of 25-30 amps--However for charge controller to battery bank, you want around 0.05 to 0.10 volt maximum drop for the charge controller to accurately measure battery voltage/state of charge. For 2 feet of 13 AWG @ 15 amps on a 12 volt battery, your voltage drop would be roughly:

https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=6.571&voltage=12&phase=dc&noofconductor=1&distance=2&distanceunit=feet&amperes=15&x=0&y=0

Result

Voltage drop: 0.12
Voltage drop percentage: 1.00%
Voltage at the end: 11.88

Which at 2 amps, is not an issue right now.

For a 250 Watt panel, they are typically Vmp~35 volts or Vmp~30 Volts... The charging current you would expect from such a panel (in full time noon-time sun) on a PWM charge controller would be:

• 250 Watts / 35 volts Vmp = 7.1 amps Imp (Vmp 35 volts)
• 250 Watts / 30 volts Vmp = 8.3 amps Imp (Vmp 30 volts)

So--Full noon time sun, somewhere around a maximum of 7 to 8 amps into the well discharged battery. And if there is any haze in the air--You might get 1/2 that current.

If the PWM controller is working correctly, you will see Vbatt terminal with ~11.8 volts, and Vpanel with ~11.8 to 13.x volts.

PWM controllers are a "computer controlled" switch. The switch is either on or off... (full charging current, or zero charging current) is 100% and 0% charging. Or when the battery is around 14.4 volts, the charge controller will be on for part of the time and off for part of the time (switching hundreds of times a second)... I.e., 50% charging current would be 50% on and 50% off.

The Vpanel input voltage from the solar panels with a typical volt meter will vary from near Vbatt (100% on) to Voc (around 40 volts) when the controller is at 0% output (switch open).

Telling us all these voltages will help us diagnose the system.

The 250 Watt panel, depending on Vmp of the solar panel will affect the "efficiency" of the charging system. For example, three common Vmp panels:

• 250 Watt / 17.5 Volts Vmp = 14.3 Amps Imp ("optimum" for charging 12 volt battery)
  
• 250 Watt / 30.0 Volts Vmp = 8.3 Amps Imp (common Grid Tied solar panel)
  
• 250 Watt / 35.0 Volts Vmp = 7.1 Amps Imp (common GT Solar, also used for 24 volt battery systems with PWM controller)
  

And you see how much power (Watts) is going to charge your 12 volt battery (remember that Vbatt bus runs from 10.5 volts (dead) to 14.5-14.8 volts charging set voltage, to 15-16 volts Equalize Charging.

• 14.3 Amps * 11.8 volts charging = 169 Watts
  
• 8.3 Amps * 11.8 volts charging = 98 Watts
  
• 7.1 Amps * 11.8 volts charging = 83 Watts

This is just what a PWM type charge controller does... It cannot efficiently take a "higher" voltage solar panel and charge a lower voltage battery bank.

If you had an MPPT (maximum power point tracking) solar charger, roughly the best output you could see (cool/clear/near solar noon, with discharged battery), you would see:

• 250 Watts * 0.77 panel+controller derating * 1/11.8 volts charging = 16.3 Amps MPPT controller charging 11.8 volt battery in optimum solar conditions.
  

You have asked a lot of questions and provided some information... However, without "details"--I can only give you examples of what you might see, and answer why PWM vs MPPT controller with 3 types of solar panels. Depending on the answers to the questions above--You could be seeing 1/2 of the available panel Wattage by using an PWM controller vs an MPPT controller.... But I need the solar panel specs to be certain.

I am guessing you are in the UK (London/Liverpool area)? If you have less than sunny/clear weather with the array pointing at the sun and an > 30 Vmp panel--Seeing 1/2 of the expected current from the panel (i.e., 1/2 of 7.1 amps = 3.5 amps) is not not unexpected.

Knowing your location, we can roughly predict your harvest:

http://www.solarelectricityhandbook.com/solar-irradiance.html

Liverpool
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 37° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
1.19	2.04	2.81	3.78	4.48	4.30
Jul	Aug	Sep	Oct	Nov	Dec
4.29	3.93	3.22	2.22	1.35	0.95

So--Not a lot of sun during winter...

And the charging current for a 110 AH lead acid battery would suggest around 5% for weekend/backup use. And 10% to 13% rate of charge for daily use:

• 110 AH * 0.05 rate of charge = 5.5 Amps minimum
• 110 AH * 0.10 rate of charge = 11 amps nominal
• 110 AH * 0.13 rate of charge = 14.3 amps "typical" cost effective maximum

If you had a solar array matched with the proper type of charge controller, the above maps to:

• 110 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 104 Watt array minimum
  
• 110 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 207 Watt array nominal
  
• 110 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 269 Watt array "typical" cost effective maximum

Your present setup is, probably, less than optimum (depends on actual Vmp specification for your panel). An MPPT type charge controller can probably increase your charging current by roughly 2x over your present setup (assuming Vmp-panel >=30 volts).

Anyway--Lots to think about--And why we ask for detailed answers to our questions... At this point, your system could be working as expected to "broken", to needs improvement (depending on your power needs and present system configuration/parts used).

-Bill

lee1

Wow lots to take in there 
So knowledgeable thank you so much 
I think I need to read a bit more 
To be fair I'm not sure of some of those things to measure and how to start but I will find out 
Looks like some solar homework 
Many thanks again 
Lee

BB.

That is why I really like to do things step by step. It is a lot to jump into the middle of a system design while trying to debug what you have.

Anyway, the beginning stuff.. A simple DMM (digital volt meter... What that will give you at least two-three decimal points (12.12 to 12.123) for accurate/repeatable measurements. Some that reads 12.1 volts--Not really accurate enough (especially when you get to higher battery bank voltages).

If you want to get into the details of how a solar system (or really any electrical power system) operates, an AC+DC Current Clamp DMM is really nice. When measuring current, you just "clamp" the wire with the meter and read the current. There are AC+DC CC DMMs (which we want) and AC current (AC/DC voltmeter) DMMs too (good meters, but only measure AC current--Not good for DC current). Here are a couple examples of current clamp meters:

https://www.amazon.co.uk/UNI-T-Current-Capacitance-Resistance-Measurement/dp/B07CNGJXFJ (lower cost meter--Good enough for smaller systems)
https://www.amazon.co.uk/Digital-Auto-Ranging-Measures-Resistance-CL800/dp/B019CY4FB4 (mid-price better meter).

The above are just suggestions--The prices are higher in the UK vs the UK, so make your picks.

-Bill