Portable Solar Panel working but not charging
Discussion
Bought a 30W solar panel, mainly to trickle charge my car when not in use, it was meant to be a 10W panel but I bought the wrong one. The controller says it is charging 12V nearly 13 and checking the voltage at the battery clips it is right. However left the interior light on over night and the battery is at 52%, so connected it to the solar panel on the car expecting it to charge over a day or two especially in the sunny weather, but it hasn't, four days later it still at 52%. Could anyone explain this, an I doing something wrong?
Used to have an electric trickle charger, but having driven off a couple of times without disconnecting I trying out the solar pannel.
Sorry if there are spelling errors, spell checker not working
Used to have an electric trickle charger, but having driven off a couple of times without disconnecting I trying out the solar pannel.
Sorry if there are spelling errors, spell checker not working
Edited by Oliver Hardy on Monday 16th June 23:59
A few things.
52% where are you getting that from? that's one hell of an accurate reading for a lead acid battery. I've not even seen a solar regulator that is that precise (and there is no way they can be).
Which solar regulator are you using?
A simple test is to put a meter on the battery, THEN attach the solar. If the voltage starts to climb, even slowly, its charging,
12v panels tend to be around 20v, and then the voltage drops in the regulator to a little over the voltage the battery requires. This drags down the metered voltage on the panel.
Finally, failed solar panels often meter at half their max voltage under load, but full voltage when not loaded. So a 21v panel might meter at 11v - ish under load, if damaged
52% where are you getting that from? that's one hell of an accurate reading for a lead acid battery. I've not even seen a solar regulator that is that precise (and there is no way they can be).
Which solar regulator are you using?
A simple test is to put a meter on the battery, THEN attach the solar. If the voltage starts to climb, even slowly, its charging,
12v panels tend to be around 20v, and then the voltage drops in the regulator to a little over the voltage the battery requires. This drags down the metered voltage on the panel.
Finally, failed solar panels often meter at half their max voltage under load, but full voltage when not loaded. So a 21v panel might meter at 11v - ish under load, if damaged
A 30W solar panel will only produce 30W when directly facing full sun.
I have one on my boat to keep the batteries float charged over winter. Mines 25W I think, but in reality the most I can get from it is a few amp-hours per day, because of shading, not facing the exact optimum direction etc. That's brilliant for avoid self discharge over winter, but takes a very long time to actually charge a battery.
A car battery is typically about 50Ah, a few days of a few Ah is not making much difference, especially as cars tend to keep drawing current after being switched off. Some cars draw a fair bit of power for the first hours or day or so, even after that they keep drawing some power for the ECU and central locking receiver and whatever else.
If you're starting to see problems, possibly your battery is getting old?
If it's down at ~50%, it needs either a decent drive or a proper charge.
Or possibly a new battery?
I have one on my boat to keep the batteries float charged over winter. Mines 25W I think, but in reality the most I can get from it is a few amp-hours per day, because of shading, not facing the exact optimum direction etc. That's brilliant for avoid self discharge over winter, but takes a very long time to actually charge a battery.
A car battery is typically about 50Ah, a few days of a few Ah is not making much difference, especially as cars tend to keep drawing current after being switched off. Some cars draw a fair bit of power for the first hours or day or so, even after that they keep drawing some power for the ECU and central locking receiver and whatever else.
If you're starting to see problems, possibly your battery is getting old?
If it's down at ~50%, it needs either a decent drive or a proper charge.
Or possibly a new battery?
a 30w panel will EASILY charge a car battery in the summer, certainly over a few days .You can run a compressor fridge with 80w of solar and a 75ah battery - indefinitely in the summer. Any kind of shading absolutely knobbles a solar panel. Even shading a small corner can knock it down to a tiny amount of power.
From a 30w panel, expect around 1.5 - 1.8 amps, during the day, pointed roughly at the sun, NOT behind a windscreen.
From a 30w panel, expect around 1.5 - 1.8 amps, during the day, pointed roughly at the sun, NOT behind a windscreen.
Many thanks for all your replies, battery is new, a couple months old, the car is old (26 years old) so apart for the clock and the interior light, I do not think it draws much power.
It is showing a more or less state of charge on the controller, but max charge of 12.9v, mostly 12.8v, does not make a difference if it is in the car or outside.
I have got Ancel battery monitoring gizmos on my cars. Seem to work OK if with some delay. Barrery looses about 2% per week according to Ancel.
Edit:
Connected the panel to an old battery and was getting 13.4v, so took off the positive terminal and now charging at 13.2. So will connecting with O rings help?
It is showing a more or less state of charge on the controller, but max charge of 12.9v, mostly 12.8v, does not make a difference if it is in the car or outside.
I have got Ancel battery monitoring gizmos on my cars. Seem to work OK if with some delay. Barrery looses about 2% per week according to Ancel.
Edit:
Connected the panel to an old battery and was getting 13.4v, so took off the positive terminal and now charging at 13.2. So will connecting with O rings help?
Edited by Oliver Hardy on Tuesday 17th June 13:45
Hoofy said:
Griffith4ever said:
Low voltage solar is my business.
Prepare for me to barrage you with inanely dull, noob questions in future. 
Griffith4ever said:
Hoofy said:
Griffith4ever said:
Low voltage solar is my business.
Prepare for me to barrage you with inanely dull, noob questions in future. Hoofy said:
Griffith4ever said:
Hoofy said:
Griffith4ever said:
Low voltage solar is my business.
Prepare for me to barrage you with inanely dull, noob questions in future. Griffith4ever said:
richhead said:
Ive tried a few solar charges over the years, never found them to be much use tbh. They are ok for maintaining a charged battery but not much else.
Then you've just tried ones that are too low wattage. Low voltage solar is my business.I am by no means an expert.
Griffith4ever said:
Hoofy said:
Griffith4ever said:
Hoofy said:
Griffith4ever said:
Low voltage solar is my business.
Prepare for me to barrage you with inanely dull, noob questions in future. There's a lot of (e.g.) 30W panels on ebay which are in reality a lot smaller.
I bought one which was comically cheap, sold as 25W, it's more like 8W.
Which is what I expected, and what I wanted.
The quick way to evaluate a panel is to aim it at full sun and measure the open circuit volts.
Then measure the short circuit current.
The max power current and the current into a 12V battery will be lower than Isc. 3/4 is a fair guess normally.
There are also a lot of terrible cheap 'controllers' on the market, which confuse the issue, and may be set to restrict charging when you don't expect that.
Also 12V batteries are subtle and complex things, a quick measurement can often tell you very little.
They take time to respond.
They are not all quite the same, subtle differences in chemistry!
It's worth buying a cheap multimeter so you can check the current
The biggest panel I have is a decent 50W one, into a 12Vbattery with no regulator it gives a peak of just under 3A.
I've used it on my boat, horizontal with virtually zero shade. In sunny weather this time of year I can get about 15Ah from it in a single day.
Which on its own would take about a week to charge the battery.
Which is fine, I can use the fridge and the battery will recharge after the weekend, or with a combination of solar and an hour a day with the engine running, I can run the fridge indefinitely.
My mate with a bigger boat has about 600W of panels and can go for a long time without using the engine, running a fridge and freezer, even when it's fairly cloudy.
Lead acid batteries take a lot of current in the early stages of charging, then want a smaller, diminishing current to get them fully charged.
(that's the very basic abridged version!).
Solar panels are ideal for that final stage of charging.
A good alternator is ideal for the early stage of bulk charging.
I bought one which was comically cheap, sold as 25W, it's more like 8W.
Which is what I expected, and what I wanted.
The quick way to evaluate a panel is to aim it at full sun and measure the open circuit volts.
Then measure the short circuit current.
The max power current and the current into a 12V battery will be lower than Isc. 3/4 is a fair guess normally.
There are also a lot of terrible cheap 'controllers' on the market, which confuse the issue, and may be set to restrict charging when you don't expect that.
Also 12V batteries are subtle and complex things, a quick measurement can often tell you very little.
They take time to respond.
They are not all quite the same, subtle differences in chemistry!
It's worth buying a cheap multimeter so you can check the current
The biggest panel I have is a decent 50W one, into a 12Vbattery with no regulator it gives a peak of just under 3A.
I've used it on my boat, horizontal with virtually zero shade. In sunny weather this time of year I can get about 15Ah from it in a single day.
Which on its own would take about a week to charge the battery.
Which is fine, I can use the fridge and the battery will recharge after the weekend, or with a combination of solar and an hour a day with the engine running, I can run the fridge indefinitely.
My mate with a bigger boat has about 600W of panels and can go for a long time without using the engine, running a fridge and freezer, even when it's fairly cloudy.
Lead acid batteries take a lot of current in the early stages of charging, then want a smaller, diminishing current to get them fully charged.
(that's the very basic abridged version!).
Solar panels are ideal for that final stage of charging.
A good alternator is ideal for the early stage of bulk charging.
Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff