Halfords 12v / 20w Solar Charger - output 19.6v ?

[markob]

Hoping some of the solar experts can help with this one..

Just bought the above to keep a car battery topped up whilst not being used, thought I would check the cigarette socket stays live on the car with a voltmeter (luckily it does) and also thought I would check the output of the solar panel. In not particularly bright sunshine it was outputting 19.6v on the 12v cigarette plug !

I presume this would not be good for the car battery ?

Should I add some kind of MPPT charge controller ?

 

[markob]

This is a link to the Halfords unit :

Halfords Solar Maintainer 20W | Halfords UK

Shop the latest Halfords Solar Maintainer 20W at Halfords UK

www.halfords.com

 

[Pete C]

Try measuring the voltage when it is connected to the battery - it will be a lot lower, as the load on the cell pulls the voltage down.

Pete

 

[Dellmassive]

Hoping some of the solar experts can help with this one..

Just bought the above to keep a car battery topped up whilst not being used, thought I would check the cigarette socket stays live on the car with a voltmeter (luckily it does) and also thought I would check the output of the solar panel. In not particularly bright sunshine it was outputting 19.6v on the 12v cigarette plug !

I presume this would not be good for the car battery ?

Should I add some kind of MPPT charge controller ?

running any panel direct to a battery is not realy a good idea.

esspecialy is its not fused or has a internal blocking diode.

as you say you can run it through a solar controller to get around that problem. . .

either PWM or the better MPPT controllers. .


also on that note 20W is very low power, in testing you need about 50W min to counter act any static discharge.

but i suppose 20w is better than no watts right. . . .

see here for some back ground.



******************************************************************

SOLAR:

• Solar Pwm & Mppt Controllers - How I Done It -
• Mobile Solar Panels ? . . . - How I Did It -
• What Solar Panel & Controller? - How We Done It -
• Solar Panel Cutting Hole In Roof !!! - How We Done It -
• 300w Plus Solar Club -- How I Done It --
• Solar Sheds & Other Non-t6 Solar Projects - How We Done It -
• [Guide] Solar Cables? . . . - How I Did It -

.....



and the rest: Dellmassive’s "How I Done It" blogs.

.

 

[rod_vw]

And don't put it on the dash to collect the sunlight as modern windscreens block most of the useful 'charging' rays.

 

[markob]

Thanks for the advise, very interesting.

I didn't like the idea of an unregulated voltage going straight into the battery and your info above seems to back that up

I might return the Halfords solar panel and buy one from Amazon with an MPPT controller built in - any suggestions?

I don't this the car needs much to keep it topped up, but perhaps if doing this it makes sense to buy a bigger panel too?

 

[Dellmassive]

Various panel kids are shown here:

[Guide] Mobile Solar Panels ? . . . - How I Did It -

Mobile Solar Panels ? . . . - How I Did It - There is loads of background to this . . . . . but for now here is a vid for you all. =] Just remember W = V*A and as a general rule a good 100W panel will give you up to 6A charge with good sun. 25w = 1.5A 50W = 3A 100w = 6A 200w = 12A 300w = 18A...

www.t6forum.com

Look at around 50w for a dash trickle charge.

And 100-400w for a leisure battery mobile charge.

 

[Pete C]

I agree with the 50W spec. You lose 50% if it goes inside the van behind the tinted windscreen.

Pete

 

[markob]

Just as a follow up to this, I am considering my options…

This solar panel was only bought to keep a battery topped up in an old car I don't use very often

It has started me thinking though.. I might add solar to the T6 in which case investing in a decent (Victron?) MPPT controller now for future use might make sense...?

Are there any Solar controllers that also allow for DC-DC charging? I might add a second battery to the T6 later too...

 

[rod_vw]

I've got a RING RSCDC30 in my T6 which works reasonably well, it is a very early version (5+ years old) and has had a few firmware hiccups but better now. There must be more modern units available now.

 

[AussieMick]

I have a redarc unit that does both mppt solar and dcdc at the sametime. , used it for over 4 years sometimes in extreme conditions.

It's a Redarc BCDC 25D. Mine is 25A model also available in 40A and new 50A models.
Don't know if it is available in the UK.
I'm sure Victron will have something similar.