Solar panel controller for nominal 5W panel - Unisolar SmartChargeFLX

[David]

I bought this in 2001 to play at maintenance charging a battery (car, I think).

I never got very far with it (as far as I can remember) and it has been in the box for a long time.

seems to be for that model.

It claims that there is a blocking diode included to prevent reverse current flow.

Does this mean that I don't require a charge regulator?

For example, if I plug a USB 12V charge adaptor into the supplied cigar lighter socket should that be all I need to charge a power bank? Or, for that matter, a mobile phone?

I note that the operating voltage is listed as 16.5 volts, which seems a little high for a battery maintenance charger, so does it need some kind of voltage regulator in front? If so, what?

I looked up charge regulators and found cheap stuff like

and which have some interesting reviews.

However these might rely on a 12V battery being present.

Hmmm... V * A = W; A = W/V. Assuming it is chucking out 16V then power output might be: A = 5/16 or 1/3 of an Amp charging rate.

Anyway, is there a recommended solution to turn this panel into a solar charger for small devices?

I'm thinking for camping where there is no mains hookup.

Cheers

Dave R

[Harry Bloomfield]

David formulated on Saturday :

No, that simply means it will not discharge a battery, when it is unable to charge it (in the dark).

You probably wouldn't need a charge regulator to use it to charge a 12v car battery, its output is quite small at 0.30 amps.

A 12v to USB cigar lighter adaptor will include a 5v regulator.

[David]

Thanks.

The remaining question is "Is it safe to feed 16.5V into an adapter?". I am assuming that it can cope with 14V+ as that is what an alternator allegedly pushes out, and I assume that this gets as far as the cigar lighter socket.

Cheers

Dave R

[tabbypurr]

Modern cars disconnect the cig lighter socket when the engine isn't running, so that won't work. 5w is such a low charge rate that it can be left on indefinitely, albeit not ideally.

NT

[Martin Brown]

The nominal open circuit voltage will plummet as soon as any real power is taken. The purpose of a charge controller is to maximise the power delivered to the load and protect it from overcharging. But for a 40Ah battery it will barely notice 300mA peak charge rate which is <C/100.

It might well be broadly comparable with the average modern cars daily discharge rate when averaged over 24 hours and UK weather. A lead acid

40Ah in good condition self discharge rate is around 1W or 5% lost charge per month. Batteries that are on their last legs won't start a car if it is left unused for more than a couple of weeks.

[dennis]

8<

Mine doesn't, I run the dash cam 24x365 from one of the sockets.

[Brian Gaff]

And also some kind of over current drain protection as well. Brian

[Brian Gaff]

I'd imagine it would be OK assuming the device does not run hot already, and most these days do not, it was the old series regulated ones that used to get hot and hence waste a lot of the heating up the heat sink!

Brian

[Marland]

At only 5w output a good proportion of that will be running the charge module itself leaving hardly anything over to charge any battery, it will only be giving 5w in really ideal conditions which will be rare in the UK.

GH

[David]

For clarity, I'm not proposing to plug it into a car. I was using the car cigar lighter socket as a comparison with the solar panel feeding a directly connected cigar lighter socket.

The solar panel will work a 12V USB charger when fitted into the cigar lighter option on the output lead from the solar panel.

Testing suggests that about 300mW is the output. Testing also suggests that this will struggle to keep up with the discharge rate of a modern mobile phone whilst "doing stuff". It did give a marginal increase in battery charge to a phone which was turned off.

On the basis of that testing I won't be carrying it around to act as a backup charger when away from the mains.

Given that it is around 18 years old, I am reasonably sure that there is better technology around these days.

Cheers

Dave R