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lew247
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Posted: 08 January 2018 at 6:15am | IP Logged Quote lew247

I have protected LI batteries with the protection built in

4 of these



I have a 12V solar charger going into this



The charger part is based on the LT3652 solar charger IC and charges lithium batteries (Li-Po, Li-ion, LiFePO4) at a rate of 1000mA (can be set to 2A max)

Tomorrow when the sun is out I'll measure the current coming from the Solar cells

In the summer I was using one of these fev via a 5v regulator to drop the 12V down to 5V



This was working fine during the summer but once autumn came it stopped working, I thought it might be the module so changed it for another and then eventually got the proper solar charging board I'm using now


Edited by lew247 on 08 January 2018 at 6:18am



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Posted: 08 January 2018 at 7:42am | IP Logged Quote TassyJim

Your charger has a limit of 1 amp at 4.2 volts
Allowing for losses in the conversion, lets call that 5 watts required.

Your solar panel is 25 watts so even allowing for the London smog, there should be plenty available from your solar panel for a reasonable period of the day.

You need to measure the current coming from the solar panel and the current going into the battery with the load disconnected at (roughly) the same time. Also need the battery terminal voltage.

Measuring the output with the battery disconnected will confuse the controller.

With one amps out of the unit, there should be approximately 300mA coming from the solar panel.

If ned be, discharge the batteries a bit so you should be getting the full one amp charge.

The 14.9V you are seeing will be the 'Maximum Power Point' of the solar panel which is set by the trimpot on the controller. 14.9 sounds about right. The rating plate on the panel will have the correct figure for your panel.

Jim


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lew247
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Posted: 08 January 2018 at 10:25pm | IP Logged Quote lew247

I measured the current as well as the voltage from the solar cells today just after midday
Voltage 14.9V but the current is only 8.9mAh
I guess the sun really isn't strong enough to give any decent amount of current out of this cell pack
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redrok
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Posted: 09 January 2018 at 1:35am | IP Logged Quote redrok

Hi lew247;
lew247 wrote:
I measured the current as well as the voltage from the solar cells today just after midday
Voltage 14.9V but the current is only 8.9mAh
I guess the sun really isn't strong enough to give any decent amount of current out of this cell pack
Just to characterize the solar panel:
1. The panel Open Circuit Voltage? I.e not connected to anything.
2. The panel Short Circuit Current? Ya, dead shorted current through the meter.
3. What type of panel? Silicon or thin film?

Silicon generally has visible cells.
Thin film is generally made with Stripes.

This will give us a lot of information.

redrok
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kg4pid
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Posted: 09 January 2018 at 4:00am | IP Logged Quote kg4pid

lew247 wrote:
I measured the current as well as the voltage from the solar cells today just after midday
Voltage 14.9V but the current is only 8.9mAh
I guess the sun really isn't strong enough to give any decent amount of current out of this cell pack


I think your logic is flawed. You're not showing much current because the load (your charger) is not attemping to charge your battery. Either your charger is bad or your batteries are. The supply voltage and load determine current flow. Without a load you have no current.

Connect a small 12V light bulb or any small load that would draw about 1 amp directly to the solar panel. You should see the solar panel voltage drop some. How much it drops depends on how much sun your panel is receiving. Now measure current. I suggested a light bulb because you will see instantly that your panel is working or not.

Max
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lew247
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Posted: 09 January 2018 at 4:02am | IP Logged Quote lew247

Iíll try that tomorrow once the sun returns 😊
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redrok
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Posted: 09 January 2018 at 4:13am | IP Logged Quote redrok

Hi lew247;

Do the measurements I suggested.
We will get more information.

Measuring current while the load is present can be very misleading.

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Posted: 09 January 2018 at 7:27am | IP Logged Quote TassyJim

lew247 wrote:
I measured the current as well as the voltage from the solar cells today just after midday
Voltage 14.9V but the current is only 8.9mAh
I guess the sun really isn't strong enough to give any decent amount of current out of this cell pack

I agree that open circuit voltage and short circuit current readings are needed.

You don't need much sun to get better readings than that. A shadow on one of the cells will really shut the whole panel down.

Are you sure a squirrel hasn't shat on the panel?

Jim

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MikeO
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Posted: 09 January 2018 at 8:25am | IP Logged Quote MikeO


Squirrels in Manchester? LOL

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lew247
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Posted: 09 January 2018 at 9:20pm | IP Logged Quote lew247

It's the sun, or lack of sun and lots of clouds

I just went outside with a bulb and meter and with the solar panel laying in the middle of the garden with no shade whatsoever (other than the clouds) it is giving only 23mA of current





Guess I'll have to figure a different way to power it

Edited by lew247 on 09 January 2018 at 9:22pm
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MicroBlocks
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Posted: 09 January 2018 at 10:07pm | IP Logged Quote MicroBlocks

23ma is incredible low. Is the module damaged? And did you short circuit the panel while measuring current?


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lew247
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Posted: 09 January 2018 at 10:11pm | IP Logged Quote lew247

MicroBlocks wrote:
23ma is incredible low. Is the module damaged? And did you short circuit the panel while measuring current?

No it wasn't short circuited, it was just the solar panel connected to a bulb via a meter to measure the current
No it's not damaged as far as I can see
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