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Charging Battery with Solar Panel
Scrumper
31-03-2012
Hi

Was thinking of buying charger here...
http://www.maplin.co.uk/solar-powere...charger-217850

The battery I want to charge is 12V and 86AH.

I assume that 12v at 12w would charge at 1 amp, therefore it would take 86 hours of daylight to charge, am I right? It seems like a awful long time.

I know little about solar panels, any idea if the charger would give more than 12w in direct sunlight, or is it limited to 12w?
ProDave
31-03-2012
No it will take longer. Nothing is 100% eficcient, so it will need more than 86 AH of input to fully charge an 86AH battery.

And in anything less than direct full sunlight the output will be lower.

That's the same panel I use to keep the battery on my boat topped up so I don't have to lug it home to charge it. So they do have some uses.
Nigel Goodwin
01-04-2012
Originally Posted by ProDave:
“No it will take longer. Nothing is 100% eficcient, so it will need more than 86 AH of input to fully charge an 86AH battery.

And in anything less than direct full sunlight the output will be lower.”

Assuming the rated output is only 12W, it will only very rarely reach that, and average output over a summers day is probably only a quarter of that during daylight - and apart from midsummer, a great deal less.

As you suggest, it would take a LOT longer than 86 hours to charge the battery - like you use yours, it's best considered for use keeping an already charged battery topped up.

If the OP wants to use a solar panel to actually charge the battery, he needs one (or more likely more than one) a LOT bigger, and LOT more expensive.
c4rv
01-04-2012
That is only designed to keep a battery topped up, not charge from scratch.

As nigel pointed out you would be lucky to average 1/4 of the output during daylight and that is assuming you can mount it in the most efficient position.

So say in March, you have 12 hours of daylight which gives potential generation of 12 amp/h @ 12v but in reality you will get around 3 amp/h @ 12v which would mean that battery would take a month or so to charge from scratch.
c4rv
01-04-2012
Even with this £200 60w kit, maplins state charging time of around 5 days for a battery the size you quote, that would be more realistic.

http://www.maplin.co.uk/60w-solar-power-kit-223250
Winston_1
01-04-2012
Solar chargers such as this are not worth it unless you have no access to a mains supply. The £50 odd that this cost will provide a lot of mains electricity for a long time.
c4rv
02-04-2012
Originally Posted by Winston_1:
“Solar chargers such as this are not worth it unless you have no access to a mains supply. The £50 odd that this cost will provide a lot of mains electricity for a long time.”

but what if you are nowhere near a power point ?
Nigel Goodwin
02-04-2012
Originally Posted by c4rv:
“but what if you are nowhere near a power point ?”

Fairly obviously (depending what you want to do) you buy large expensive solar panels, along with a suitable battery and charger system.
alan1302
02-04-2012
Originally Posted by c4rv:
“but what if you are nowhere near a power point ?”

That's what Winston said...unless you have no access to mains power....
Scrumper
02-04-2012
Yes it's far away from mains power (a cricket scoreboard actually).
ProDave
02-04-2012
The most wierd one I ever had to do was to wire up a solar panel AND a wind generator, just to keep a 12V battery topped up.

The battery ran a small fan to ventilate a composting public toilet, and a low power 12V light.

It was many miles from the nearest electricity supply.
Nigel Goodwin
03-04-2012
Originally Posted by ProDave:
“The most wierd one I ever had to do was to wire up a solar panel AND a wind generator, just to keep a 12V battery topped up.”

Nothing particularly weird about that - there are thousands of similar schemes in the UK for road signs and weather stations.

You can't possibly rely on just one source, so the mix of wind and solar gives you MUCH greater reliability.
ProDave
03-04-2012
Originally Posted by Nigel Goodwin:
“Nothing particularly weird about that - there are thousands of similar schemes in the UK for road signs and weather stations.

You can't possibly rely on just one source, so the mix of wind and solar gives you MUCH greater reliability.”

No, the weird thing was the application. A public composting toilet miles from anywhere. It was about a mile walk from the car park to do the job.

And when it was complete, building control STILL insisted on an EIC (electrical installation certificate) just for the little charger to run a fan and a light.
stylo
03-04-2012
Originally Posted by ProDave:
“No, the weird thing was the application. A public composting toilet miles from anywhere. It was about a mile walk from the car park to do the job.”

Probably unintentional, but that is funny!
ProDave
03-04-2012
Originally Posted by stylo:
“Probably unintentional, but that is funny! ”

ROFLMAO

Yes I must be more careful how I phrase things in the future.
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