How much power are you solar panels generating?

[Hevs]

Hi all. 

 

I am new to boating and just installed solar panels on my roof. I have two 400w panels and don't seem to be generating alot of electricity. 

 

Today it has been glorious sunshine, almost no clouds in the Midlands area and I generated 410wh. This is less than yesterday - which was very, very grey. 

 

About 2 weeks ago, on a day less lovely than today I generated 2.17kwh. Which is significantly more.

 

There is nothing shading my panels, they are a tad mucky in the corners though. 

 

Should they be generating more? What are you guys generating with similar set ups?

 

Thanks for all of your help in advance. 

 

Heather.

[Tony Brooks]

How well charged are your batteries? Is any of the panels shaded? I suspect the power produced figure is what is sent to the batteries and as Watts = amps x volts with well charged batteries the amps will be low so the Wh will also be low.

[rusty69]

500 W Limited to 30A charger. More solar harvest when it is cooler, so will depend on the kind of panels you have,and how they are mounted.

[Alan de Enfield]

13 minutes ago, Hevs said:

Hi all. 

 

I am new to boating and just installed solar panels on my roof. I have two 400w panels and don't seem to be generating alot of electricity. 

 

Today it has been glorious sunshine, almost no clouds in the Midlands area and I generated 410wh. This is less than yesterday - which was very, very grey. 

 

About 2 weeks ago, on a day less lovely than today I generated 2.17kwh. Which is significantly more.

 

There is nothing shading my panels, they are a tad mucky in the corners though. 

 

Should they be generating more? What are you guys generating with similar set ups?

 

Thanks for all of your help in advance. 

 

Heather.

 

You need to understand that the batteries control how much they will accept, fully charged batteries will accept virtually nothing even in the strongest sunshine, whilst partly charged batteries will take all the solar can put out (even in cloudy conditions)

[rusty69]

Worth checking your connections are good and tight.

[Tony Brooks]

Just now, Alan de Enfield said:

 

You need to understand that the batteries control how much they will accept, fully charged batteries will accept virtually nothing even in the strongest sunshine, whilst partly charged batteries will take all the solar can put out (even in cloudy conditions)

 

That is unless you have lithium batteries, but to use those properly it is expensive, very expensive, and they need the owner properly understanding them.

[robtheplod]

6 minutes ago, Alan de Enfield said:

 

You need to understand that the batteries control how much they will accept, fully charged batteries will accept virtually nothing even in the strongest sunshine, whilst partly charged batteries will take all the solar can put out (even in cloudy conditions)

that occurs on our boat..... in the morning solar goes nuts at about 7am then reduces throughout the day regardless of sun (or so it seems!)....

[Tony Brooks]

This is not an answer to your question, but something you need to get a grip of. How are you monitoring the state of charge of your batteries. If you say the solar controller then they tend to tell lies, along with most, but not all, battery meters that give % charged figures. I fear that you may be at the bottom of a very steep leading curve re looking after batteries. If you do not get to grips with it before winter, then expect frequent payments for new batteries.

 

Look at the Battery Primer topic that is pinned at the top of the maintenance forum. Then ask about anything you do not understand.

[GUMPY]

I suspect your batteries are fully charged and have been since about midday. Hence not much output.

[Hevs]

29 minutes ago, Tony Brooks said:

How well charged are your batteries? Is any of the panels shaded? I suspect the power produced figure is what is sent to the batteries and as Watts = amps x volts with well charged batteries the amps will be low so the Wh will also be low.

No panels are shaded and the battery is measuring 13.2 volts throught the victron app and inverter. 

[Hevs]

25 minutes ago, Alan de Enfield said:

 

You need to understand that the batteries control how much they will accept, fully charged batteries will accept virtually nothing even in the strongest sunshine, whilst partly charged batteries will take all the solar can put out (even in cloudy conditions)

This makes alot of sense! 

 

The red alarm on the inverter was going off week before last. This was due to the shoreline power cord being broken, so hadn't been charging the battery. So perhaps the the surge in power generated was recharging the batteries as they were low.

 

However, the battery volts are still below 14 and the batteries were new when I fitted the panels recently. Doesn't that mean they should still be charging better from the solar panels? They haven't yet surpassed 14v.

[Hevs]

24 minutes ago, Tony Brooks said:

This is not an answer to your question, but something you need to get a grip of. How are you monitoring the state of charge of your batteries. If you say the solar controller then they tend to tell lies, along with most, but not all, battery meters that give % charged figures. I fear that you may be at the bottom of a very steep leading curve re looking after batteries. If you do not get to grips with it before winter, then expect frequent payments for new batteries.

 

Look at the Battery Primer topic that is pinned at the top of the maintenance forum. Then ask about anything you do not understand.

I am monitoring my batteries through the victron app which links to my inverter (I think).

 

Thanks for the recommendation 😀 

[Tracy D'arth]

Rule of thumb, panels produce at best half of the rated output.

 

If there is any dirt or a rope across etc. or they are getting hot, the output drops alarmingly.

 

Batteries, lead acid, will not take the same current when they are getting towards fully charged.

 

Wash the panels.  Check when they are cold and again when they are hot, you will see the difference. Chuck a bucket of water over them in the midday sun and see the output rise.

[Tony Brooks]

5 minutes ago, Hevs said:

No panels are shaded and the battery is measuring 13.2 volts throught the victron app and inverter. 

 

I regret that any instantaneous voltage reading is only very, very loosely related to state of charge of lead acid batteries. If you ant to use voltage then you MUST go through a procedure and that is not so easy at this time of year with solar.

 

Wait until all charging has stopped and they either put on a moderate load for a few minutes or wait an hour or longer and the take a voltage reading with no electrical item drawing current. From that RESTED voltage, you can infer the rough state of charge

 

12.7 to 12.8 more or less fully charged.

12.5 CONSIDER half charged if you want long battery life, but actually about 3/4 charged.

12.2 to 12.3 consider this as fully discharged as the batteries should go for long life, stop drawing electricity and recharge ASAP.

Around 11.8 volts = fully discharged and get ready to buy new batteries.

 

These are very general values and they do alter a bit by battery manufacturer and technology employed.

 

 

[Hevs]

2 minutes ago, Tony Brooks said:

 

I regret that any instantaneous voltage reading is only very, very loosely related to state of charge of lead acid batteries. If you ant to use voltage then you MUST go through a procedure and that is not so easy at this time of year with solar.

 

Wait until all charging has stopped and they either put on a moderate load for a few minutes or wait an hour or longer and the take a voltage reading with no electrical item drawing current. From that RESTED voltage, you can infer the rough state of charge

 

12.7 to 12.8 more or less fully charged.

12.5 CONSIDER half charged if you want long battery life, but actually about 3/4 charged.

12.2 to 12.3 consider this as fully discharged as the batteries should go for long life, stop drawing electricity and recharge ASAP.

Around 11.8 volts = fully discharged and get ready to buy new batteries.

 

These are very general values and they do alter a bit by battery manufacturer and technology employed.

 

 

This was so helpful! Honestly,  thank you so much.

[Alan de Enfield]

10 minutes ago, Hevs said:

I am monitoring my batteries through the victron app which links to my inverter (I think).

 

Have you got a multimeter ?

If not then for the sake of 'a tenner' get one ASAP.. It will become your most used 'tool' on the boat and now you need to measure the actual voltage at the battery terminals to get the true voltage.

[DShK]

 Have a read of this thread if you haven't already  It's a very useful read. Tony's website http://www.tb-training.co.uk is a great resource too.

 

1 minute ago, Alan de Enfield said:

 

Have you got a multimeter ?

If not then for the sake of 'a tenner' get one ASAP.. It will become your most used 'tool' on the boat and now you need to measure the actual voltage at the battery terminals to get the true voltage.

 

To add to this, try and get a DC clamp multimeter - it will allow you to easily measure current in a wire too - can be useful for some diagnosing.

[robtheplod]

I like our new member Heather, she keeps the info coming, loving the phone screen captures!...   Heather is also the name of my wife so I'm not biased!

[Tony Brooks]

5 minutes ago, robtheplod said:

I like our new member Heather, she keeps the info coming, loving the phone screen captures!...   Heather is also the name of my wife so I'm not biased!

 

I agree, and I am not biased ----------- apart from against those who do not conduct themselves like Heather.

[Rob-M]

The main voltage on those pictures look like well charged batteries over the last few days.  What electrical items are you using...?

[Tony Brooks]

4 minutes ago, Rob-M said:

The main voltage on those pictures look like well charged batteries over the last few days.  What electrical items are you using...?

 

I think that depends upon when the reading was taken. 13.2 charging voltage suggests to me that they are still drawing charge, but unless we know the potential solar output we don't know if it is 13.2 volts because it is still drawing lots of current or 13.2 because the panels can only produce that voltage (shade, low sun angle, etc.)

[Rob-M]

1 minute ago, Tony Brooks said:

 

I think that depends upon when the reading was taken. 13.2 charging voltage suggests to me that they are still drawing charge, but unless we know the potential solar output we don't know if it is 13.2 volts because it is still drawing lots of current or 13.2 because the panels can only produce that voltage (shade, low sun angle, etc.)

My understanding, and how I use the Victron solar app, is that the min voltage is the lowest reading of the batteries in the last 24hrs.  Ours usually shows 12.5v on the min when I get up in the morning.

[DShK]

Odd question but are you plugged into a shoreline? You said you were previously. The low output and consistent output from the panels looks like my output when I was using lead batteries and plugged into a shoreline. The fact that your minimum voltage is 13V leads me to believe you're plugged in, as this would drop lower over night.

 

If this is the case, the charger and solar are competing to top your batteries up. There isn't an easy solution to give your solar panels priority, other than manually plugging in when the solar output isn't keeping up with your needs.

[Rob-M]

3 minutes ago, DShK said:

Odd question but are you plugged into a shoreline? You said you were previously. The low output and consistent output from the panels looks like my output when I was using lead batteries and plugged into a shoreline. The fact that your minimum voltage is 13V leads me to believe you're plugged in, as this would drop lower over night.

 

If this is the case, the charger and solar are competing to top your batteries up. There isn't an easy solution to give your solar panels priority, other than manually plugging in when the solar output isn't keeping up with your needs.

That is what we do when we stay in the marina, shore power only gets plugged in and the battery charger switched on when the solar output starts dropping off and failing to meet our daily usage, usually Oct to Mar.

[DShK]

2 minutes ago, Rob-M said:

That is what we do when we stay in the marina, shore power only gets plugged in and the battery charger switched on when the solar output starts dropping off and failing to meet our daily usage, usually Oct to Mar.

I'm lazy so I've programmed my system so that the shoreline will be used automatically if the battery SoC drops to a certain point. But this isn't a particularly easy solution for a noobie just getting to grips with things. Perfectly doable though, especially as they have victron equipment.