gonad
Well-Known Member
hi all how many amps should a solid panel produce? watts divided by volts? seem to be getting only one third of that equation ta
solar power
- Thread starter gonad
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sarabande
Well-Known Member
Hi G
Can you give us some figures and data please ?
What voltage are you getting off the panel's terminals when the sun is shining fully on it ?
How are you measuring the amps ?
Do you have any details of the panel ID number or markings ? There lots of reference stuff available which might help.
Can you give us some figures and data please ?
What voltage are you getting off the panel's terminals when the sun is shining fully on it ?
How are you measuring the amps ?
Do you have any details of the panel ID number or markings ? There lots of reference stuff available which might help.
gonad
Well-Known Member
BP solar no marking s but been told they should be 75 or 50 watt linked them up via electric cable to on board batteries ammeter in line gave 19.4 Volt at solar panel
G
Guest
Guest
If it is 19.4v at the solar panel then either the battery is not connected or you have dropped 5.4 volts or more across the cable. You should be seeing 13 to 15v at most at the panel if you want to get the power into the batteries. Otherwise 25% of the power is just turning into heat in the cable.
William_H
Well-Known Member
I would say obviously the 19.4 volts is correct for no battery connected.
When you connect a battery assuming decent cable then the solar panel volts is also essentially the battery volts.
Now wattage of a panel is the volts multiplied by the current. That is the open circuit voltage (19.40 X the max current in full mid day sun with the panel facing square to the sun. Even then UK high latitude may mean less than rated current. Or put another way 100 watt panel equals 5 amps at best.
So you getting 1/3 of what you expect under less than ideal conditions may be normal. (Well perhaps you think the panel has a higher rating than you thought.)
Anyway in the end it is current into the battery under your actual conditions that matters. I would suggest that panels usually work normally or not at all, unless you can see areas of corrosion damage which may reduce power while still delivering some power. olewill
When you connect a battery assuming decent cable then the solar panel volts is also essentially the battery volts.
Now wattage of a panel is the volts multiplied by the current. That is the open circuit voltage (19.40 X the max current in full mid day sun with the panel facing square to the sun. Even then UK high latitude may mean less than rated current. Or put another way 100 watt panel equals 5 amps at best.
So you getting 1/3 of what you expect under less than ideal conditions may be normal. (Well perhaps you think the panel has a higher rating than you thought.)
Anyway in the end it is current into the battery under your actual conditions that matters. I would suggest that panels usually work normally or not at all, unless you can see areas of corrosion damage which may reduce power while still delivering some power. olewill
Shanty
Well-Known Member
[ QUOTE ]
BP solar no marking s but been told they should be 75 or 50 watt linked them up via electric cable to on board batteries ammeter in line gave 19.4 Volt at solar panel
[/ QUOTE ]
To state the obvious: ammeters don't measure voltage. If you have a multimeter in line between the panel & the battery, and it is switched to a voltage range, what you will be measuring is the result of the open circuit voltages of the panel and the battery. Check the setting on your meter.
As Olewill has said, don't expect anything like the rated output - the actual output will be very dependent on the state of charge of the battery, and the amount of sunlight the panel can see.
BP solar no marking s but been told they should be 75 or 50 watt linked them up via electric cable to on board batteries ammeter in line gave 19.4 Volt at solar panel
[/ QUOTE ]
To state the obvious: ammeters don't measure voltage. If you have a multimeter in line between the panel & the battery, and it is switched to a voltage range, what you will be measuring is the result of the open circuit voltages of the panel and the battery. Check the setting on your meter.
As Olewill has said, don't expect anything like the rated output - the actual output will be very dependent on the state of charge of the battery, and the amount of sunlight the panel can see.
PeterGibbs
Well-Known Member
Hey, did anyone tell you that this is the wrong latitude for solar panels on boats? It's that Gulf Stream thing and all the cloud it produces....Panels - great for the green credentials, but in practical terms, a losing proposition. A hard judgement -after all they could be useful for extra propulsion in a following breeze....!
Give up and get a wind generator, if you really want to keep your batteries fat and happpy!
PWG
Give up and get a wind generator, if you really want to keep your batteries fat and happpy!
PWG
Richard10002
Well-Known Member
[ QUOTE ]
Hey, did anyone tell you that this is the wrong latitude for solar panels on boats?
[/ QUOTE ]
which bit of location: Spain puts him in the wrong latitude?
Hey, did anyone tell you that this is the wrong latitude for solar panels on boats?
[/ QUOTE ]
which bit of location: Spain puts him in the wrong latitude?
William_H
Well-Known Member
Hi Shanty thanks for the reference however. You state current depends on battery charge state......No
As a result of the high open circuit voltage (20 volts) the solar panel wil pump in pretty much the same current regardless of charge state.
This assumes that there is no regulator fitted. This is good in that you get a battery that is eventually fully charged (and as fast as possible with the current available) but of course can be harmful to a small battery with a large panel. The battery overheats and boils the water away.
Current into a battery is essentially a function of the difference between the inherent voltage of the battery (charge state varying between 11.5 and 13.5 aprox.) and the voltage of the charge source.
A standard alternator regulator is set at 14 volts so when the voltage of the battery comes up you have like .5 volt difference to push current in so not much current.
But with your solar panel if the battery is inherently 13.5 volts you have over 6 volts difference from the max voltage of the solar panel.
However if you fit a regulator to the solar panel it looks just like an alternator regulator ie 14 volts max volts so current falls with charge ie only .5 volt difference.
good luck olewill
As a result of the high open circuit voltage (20 volts) the solar panel wil pump in pretty much the same current regardless of charge state.
This assumes that there is no regulator fitted. This is good in that you get a battery that is eventually fully charged (and as fast as possible with the current available) but of course can be harmful to a small battery with a large panel. The battery overheats and boils the water away.
Current into a battery is essentially a function of the difference between the inherent voltage of the battery (charge state varying between 11.5 and 13.5 aprox.) and the voltage of the charge source.
A standard alternator regulator is set at 14 volts so when the voltage of the battery comes up you have like .5 volt difference to push current in so not much current.
But with your solar panel if the battery is inherently 13.5 volts you have over 6 volts difference from the max voltage of the solar panel.
However if you fit a regulator to the solar panel it looks just like an alternator regulator ie 14 volts max volts so current falls with charge ie only .5 volt difference.
good luck olewill
PeterGibbs
Well-Known Member
Richard,
I could have made my point better had I been more detailed.
Weather is only one consideration for solar panels. True, Med Spain has quite a lot of clear skies in the summer, Atlantic less so. Winter sky cover is often heavy as depressions roll in.
Other factors: panels deliver their (small) rated output when perp to the sun - not easy on a boat. Furthermore, any shadow falling on the panel (boom etc) will cause the output to fall, reducing the charge still further. Wire runs from panel to battery will also absorb precious output.
Hence my comment about a wind generator. Most likely to be the better solution to power generation.
PWG
I could have made my point better had I been more detailed.
Weather is only one consideration for solar panels. True, Med Spain has quite a lot of clear skies in the summer, Atlantic less so. Winter sky cover is often heavy as depressions roll in.
Other factors: panels deliver their (small) rated output when perp to the sun - not easy on a boat. Furthermore, any shadow falling on the panel (boom etc) will cause the output to fall, reducing the charge still further. Wire runs from panel to battery will also absorb precious output.
Hence my comment about a wind generator. Most likely to be the better solution to power generation.
PWG
G
Guest
Guest
Can I point out that if there is moderate wind we go sailing and generally down wind so wind turbines are quite useless.
If it is good weather we need more Fridge (cold drinks) fans (cooling etc) and water from the watermaker to wash off after the hourly cooling down swims.
If it is a windy anchorage we learn our lesson and try harder picking one next time.
So Solar wins for passive luxury.
If it is good weather we need more Fridge (cold drinks) fans (cooling etc) and water from the watermaker to wash off after the hourly cooling down swims.
If it is a windy anchorage we learn our lesson and try harder picking one next time.
So Solar wins for passive luxury.
