Solar panel charging

saxo_man

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I have a small 7.0Ah 12v battery attached to a motor that runs a small door. I also have a solar panel connected directly to the battery. During bright sunny periods I have measured that the solar panel delivers 21-22v to the battery.

The battery has been going flat after a couple of days so I assumed it was a duff battery (although brand new) so I bought another one.

The new battery is now exhibiting the same behaviour.

As a test I charged up the first battery using a 240v charger, and plugged it into motor. I also unplugged the solar panel from the system. Yesterday I checked and it’s been two weeks, and it’s still working.

Can a solar panel drain a battery?
If I was to replace it can anyone recommend a suitable replacement panel?

Thanks
 

Marc

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Would 21/22v not be too much for the battery? I think you can feed it 13.5v/14v MAX and watch to make sure you not sending too many amps to the battery.
Can you restrict the output on the Solar panel to be 13v output?
 

stevieturbo

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There's no way you should be getting such high voltage at the battery whilst it is connected and charging.

Although if the battery was open circuit, there may appear to be such no-load voltages at the charger itself.

Is it a car charger type solar panel ?
 

saxo_man

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saxo_man
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Would 21/22v not be too much for the battery? I think you can feed it 13.5v/14v MAX and watch to make sure you not sending too many amps to the battery.
Can you restrict the output on the Solar panel to be 13v output?

Hi Marc. Not sure how I would go about doing that.

There's no way you should be getting such high voltage at the battery whilst it is connected and charging.

Although if the battery was open circuit, there may appear to be such no-load voltages at the charger itself.

Is it a car charger type solar panel ?

Hi Stevie.
This is the voltage I get if I unplug the solar panel from the battery and connect a multi meter to the terminals of the panel itself.

I didn’t buy the panel, it came with setup I bought. It’s rated at 2.4W at 17.5V
 

-Pete-

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@saxo_man If I read that right you said you have the panel connected directly to the battery with nothing in between? I have very little first hand experience with them myself but from what I know, you should have a command unit between the panel and your battery in order to regulate the voltage into the battery. Its definitely the case with power walls and charging batteries for drones etc too when people knock up their own.

something like this would probably sort you out and stop you cooking the batteries.

 

saxo_man

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Thanks for all the help so far.

This was bought as part of a pre-made kit, but it sounds like something must have failed going by the responses.

I've attached some photos. The battery is meant to sit behind the metal case, below where the shutter controller switches are. But as i've had to remove it couple of times, and it was difficult to connect when it was in position within the metal case, I just extended the wires to allow it to be connected/disconnected more easily. If I fix this problem i'll move the battery back into it's proper position.

The solar panel wire comes through the wall to the right of the panel in the photo, and goes into a cigarette lighter type outlet on the front of the panel. Behind this there are 2 red wires and 2 black wires - one pair goes to the battery and the other pair to the circuitry for the motor. The shutter controller also has a bluetooth adapter to allow it to communicate wirelessly with another control panel located in a different place.

I have noticed there is a crack in the glass of the solar panel. What sort of power would the replacement need to be to ensure this battery stays topped up.

TIA
Adam.

shutter-01.jpg
shutter-02.jpg
 

-Pete-

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that looks very basic at best and still doesnt look like it addresses the issue of a regulator/controller to adjust the power being fed from the panel but I could be wrong. I'm just making best case assumption based on the pictures there.
I would think the solar panel would need to feed into a controller of sorts which would then feed into your battery and then run your door/motor directly from the battery itself.
I'm basing this off the normal car setup of a 12v system with the panel and controller being equivalent to your alternator charging your battery to provide a constant 12v source.
Doesn't sound like there's a charge controller anywhere? To save it over charging or discharging the battery? Is there anything like this in the set-up?

Amazon product ASIN B071ZZ2S84
thats exactly the sort of thing I was suggesting was missing from the chain, something to funnel the power from the solar panel into a usable current/voltage for the battery. definitely looks like the missing link.
 

stevieturbo

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Hi Stevie.
This is the voltage I get if I unplug the solar panel from the battery and connect a multi meter to the terminals of the panel itself.

I didn’t buy the panel, it came with setup I bought. It’s rated at 2.4W at 17.5V

The unloaded voltage doesnt really mean much. What happens when it is attached to a load is a different matter. You could connect a flat battery to it and see if any current is actually flowing, and also measure voltage with it connected...it should be higher than battery voltage itself if it is to have any hope of charging.

Could always try something like this ? It's designed for that purpose.

The shutter controller also has a bluetooth adapter to allow it to communicate wirelessly with another control panel located in a different place.


So at rest, with whatever comms the adapter is doing and power using etc....how much current is it actually using ? ( disconnect the charger )

Any charger is going to have to supply more power than that to prevent the battery draining.
 

saxo_man

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@-Pete-
This is a commercial product, not something made up, so I don’t think there is anything missing from it. But there is definitely something not right.

@stevieturbo
I’ve found the same panel on eBay. The 21v I measured seems consistent with the open circuit voltage in the literature. I didn’t realise it delivered different amounts of voltage depending on if loaded or not.

I’ll need to check again with it connected but assuming it’s working ok, how do I go about measuring current?

D2D15F0E-F66C-4B2D-BA74-2FCB9AC91903.png
4263BA90-9F99-4AC4-B71D-279D7BAD21EA.png
 

-Pete-

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it may be a package but In my opinion it still looks a bit janky but anyway, it says there 150ma as operating current. If you can get your hands on a meter or clamp meter and check it as its in operation to see if thats what you're getting out of it or close to.
ALso, whats the red crimp terminal for in the middle? is there something connected to that panel?
would be worth checking the cigarette socket too, its pretty common that the internal connections can be loose or barely on (unless its a fully moulded version which theyre usually not as they have a small internal glass fuse)
I would go over all the connections thoroughly and if you have a meter, check for continuity everywhere.
 

saxo_man

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saxo_man
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it may be a package but In my opinion it still looks a bit janky but anyway, it says there 150ma as operating current. If you can get your hands on a meter or clamp meter and check it as its in operation to see if thats what you're getting out of it or close to.
ALso, whats the red crimp terminal for in the middle? is there something connected to that panel?
would be worth checking the cigarette socket too, its pretty common that the internal connections can be loose or barely on (unless its a fully moulded version which theyre usually not as they have a small internal glass fuse)
I would go over all the connections thoroughly and if you have a meter, check for continuity everywhere.

There are switches that stop the door at either direction of travel. They break the contact to the motor. I’m working in ballymena today but will check this evening. Thanks again
 

stevieturbo

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Even most cheap multimeters will measure current, passing it through the meter.

Or you can get a DC clamp meter for around £20-30, although probably a waste of money buying one specifically for this test.
 

Apis

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Looks like one I used to have. I left it on a battery for 8 months while I was overseas and when I got back the battery was dead and wouldn't recover.
Some of the motorhome places or fb groups would be worth asking. They are well into solar chargers the last few years.
 

stevieturbo

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Looks like one I used to have. I left it on a battery for 8 months while I was overseas and when I got back the battery was dead and wouldn't recover.
Some of the motorhome places or fb groups would be worth asking. They are well into solar chargers the last few years.

Was the battery connected to anything else ? If it's still connected to the car, it will likely still drain faster than it can recharge unless it's a fairly big panel.
 
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