Dear all,
So as part of my electronics adventure I decided to build a small off grid power supply in my “lab” (bedroom) for testing and build purposes. I picked up a tiny 10W solar panel and a 12v 60ah car battery. After reading about the dangers of car batteries I put in an automotive fuse box on the output side with fused outputs for 3A, 5A and 15A.
Having read about battery conditioning I went and purchased a cheap PWM solar charge controller from ebay which I have established is complete rubbish and doesn’t work - probably because my solar panel is so small but possibly because it’s junk - pending investigation.
I want to build my own charge controller but in the interim my battery is going flat and I want a quick and dirty solution for hooking up the panel but being middle aged I’m a scaredy cat so I thought I’d ask an expert.
Now I realise that at 10W I can probably just hook that panel directly to the battery without a charge controller, it came with a diode soldered across the plus and minus terminal (1N4004) which I think is for polarity protection so I went ahead and soldered on a blocking diode (1N4004) on the positive terminal of the panel for reverse current protection.
The panel came with standard battery connectors so I’ve set up a couple of connecting posts on my windowsill to connect those to with wire running directly to the battery.
My concern is that if I was to accidentally short those 2 uninsulated connecting posts then I would be shorting my battery out which would be very bad - so I want to put some protection in as close to my battery as possible to prevent that happening.
I’ve read that I can safely give my 12V (6 cell) car battery 14.1V even if it is fully charged (
http://www.powerstream.com/SLA.htm) so I was wondering if a simple short term solution would be to hook up a voltage regulator in the battery box at 14.1V - I’ve got some of those LM2596 regulator modules (example:
http://www.ebay.co.uk/itm/DC-DC-Buck-Converter-Step-Down-Module-LM2596-Power-Supply-Output-1-23V-30V-2014-/171369032731?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item27e663ec1b) sitting around which I thought might be fit for this purpose. I’ve examined the board and it has an SS34 surface mount diode which I’m sort of assuming is for reverse current protection but it seems to be mounted on the input side so I’m concerned it isn’t there to protect the regulator? I’m not very good at reading data sheets yet.
So my question is: Can I use this regulator and if I can then do I need to add an extra protection diode on the output side (and have to suck up the extra voltage drop) OR can I get away with just putting a blocking diode in close to the battery and forget about the regulator altogether? - this is all for a short-term solution.
My solar panel is: 12V, 10W with a nominal voltage of 17.5V - at 12V the current is P/V = 833ma (it’s just over 0.5A at 17.5 volts)
The non-heatsinked version of the LM2596 which I have is rated at 2A.
Sincerely,
Middle aged scaredy cat