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Author Topic: Solar chagers  (Read 996 times)

oilstain

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Solar chagers
« on: July 25, 2021, 04:25:59 PM »

Sollar battery chargers

I have 2, when in bright sunlight, but not connected to a car battery,
A small one with no control gear reads 17 volts when not connected but has maintained the battery well for a number of years.
A large one with built in control gear, I think, reads 5 volts.

Will both be giving a charge of 12V + when connected to a car battery but I cant get a reading as the battery voltage is part of the reading
 :stars
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autorover1

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Solar chagers
« Reply #1 on: July 25, 2021, 04:39:52 PM »

I suspect the one with control gear needs the battery voltage to be sensed to control the output and defaults to 5V when there is no battery , and the other 17V will drop once there is a load on it.
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Dormy

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Solar chagers
« Reply #2 on: July 25, 2021, 08:34:47 PM »

Wot he said ^^^^

I have both; The unregulated 2 watt job keeps my motorbike battery topped up in the shed. Reads more than 17v when not connected but drops to battery voltage when the plug is inserted. I monitor this with a plug-in voltmeter on bright days to make sure the battery doesn't get cooked.

The 80 watt panel's regulated control instructions are quite specific; "Connect the battery first, then the solar panel". So the control box needs the battery to then regulate the solar panel's charge voltage.

HTH
Ian

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oilstain

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Solar chagers
« Reply #3 on: July 26, 2021, 12:37:13 PM »

How can you read a charging voltage of a sollar panel when conected to a battery :stars

Its all magic to me :thud
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Herald1360

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Solar chagers
« Reply #4 on: July 26, 2021, 01:44:47 PM »

With an ordinary analogue or digital voltmeter across the panel's output.

When the panel is connected to the battery, the charging voltage is the same as the battery voltage, to be certain that charging is happening, you need to measure the current being delivered to the battery.

Low power "maintainer" panels operate more as if they are a current source with a maximum compliance voltage which is higher than 14V or so. The battery's long term well being depends on the current being low enough not to overcharge the battery.

Higher power panels feed the battery through a charge control regulator which will control the panel's output voltage depending on the state of charge of the battery for a "clever" one, or just limit it to around 13.8V which is the typical long term safe float voltage for most PbSO4 car or leisure batteries.
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Craig T

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Solar chagers
« Reply #5 on: July 26, 2021, 01:54:03 PM »

How can you read a charging voltage of a sollar panel when conected to a battery :stars

Its all magic to me :thud


In order to charge any battery you need to put in more volts than the battery already has so take a reading of the battery as it stands perhaps then connect the solar charger. If the voltage then goes above the battery voltage the charger is doing something. If it remains at 12v it isn't doing a lot but not doing any harm and if the volts drop below 12v, disconnect it as the panel is draining the battery.

Craig.
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TimV

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Solar chagers
« Reply #6 on: July 26, 2021, 07:25:29 PM »

Use the high amperage setting on your multimeter, put it in series between the battery and the solar charger. Make sure you're in sunlight, you should see the charging current. More useful than volts in this case.
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