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Forum Index : Solar : Panel for car boost

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M Del
Senior Member

Joined: 09/04/2012
Location: Australia
Posts: 155

Posted: 07:50pm 11 Sep 2013

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Hi

I have an old BP 5w (10w seen) panel I have used for years to maintain/boost car batteries when the vehicle is not being used.
I now have three cars

, one with all the gadgets the other two with radio and clock(old school).
I am going to buy some more (10w?) panels to fit to them when not in use, 2 batteries died last month.

My question, do I need to use some sort of controller on them, or will that size panel be ok for long term use without?
I have never used a controller on a vehicle before and had no dramas but one of the vehicles will not get a lot of use and will sit idle for up to a month at a time.

Connection previously has been through an aux lighter socket or dual pins.

thanks

Mark

Mark

Downwind

Guru

Joined: 09/09/2009
Location: Australia
Posts: 2333

Posted: 12:07am 12 Sep 2013

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In most cases a solar panel can over charge a battery, as its not a regulated output.

Although a slightly over charging is far better IMO than leaving a battery go flat.
You will need to watch your fluid levels with over charging as it can boil the fluid away.

I would suggest a simple circuit to monitor battery voltage and disconnect the solar when a max voltage was reached.

My choice of circuit to do this would be a Opamp or a Picaxe to monitor the battery voltage and disconnect the solar via a relay, should the high voltage level reached.

I take it that its a 12v battery being charged, on average 13.8 is the float voltage for a lead acid battery, and they will handle 14.2 volts on a boost charge level, if you start getting above that you will boil the fluid away and perhaps cause excess heat that might buckle the cells and render the battery useless.

Again it also comes back to amps and voltage and what each battery can handle before damage is done.

Although 5 watts is bugger all energy and the battery should soak that up with little problems.

Pete.

Sometimes it just works

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