Voltage Regulator/Stabiliser/Indicator for Portable Radio

**CU55TM Disco** · 4th September 2012, 07:58 PM

Hello Guru's.

I recently finished my "portable/Work site radio" project utilising a 12V 12AH Gel-Cel Battery, a Car Radio with AMFM/AUX Only (no cd), and a single 6" coaxial Speaker. It all enclosed in a Fiberglass box, that i moulded from a 99c Coles Mop Bucket.

what I am wanting is a circuit that will regulate the output of the battery and supply a solid 12v (@ about 1 to 1.5a) and also give an indication of battery condition via a single tri-colour led (green - good, yellow - ok, red - flat)

the SLA battery starts its day at about 13 ish volts and ive run it to about 11.5 volts, what I am hoping to achieve is a longer play time from my given battery, and a low voltage shut off at say 10.5 or 11 volts. I figure if I can reduce my supply voltage to 12v down from 13 ish and then hold 12v as the voltage tapers off, i should be able to drop down to a 6 or 7 AmpHr battery and still get a similar run time to the 12AH one I currently run.

From my current limited knowledge and general out-of-touchness, I was looking at something like a LM2577-12 or I have also heard of a MAX1771 which appears similar.

as for the battery condition indication, integrating something like THIS: LED Battery Voltage Indicator Kit - Jaycar Electronics

Into the whole shebang would be sweet.

Am I on the right track, and is there anyone here that can steer me in the right direction?

Cheers,

Robert.

**Wallyb** · 4th September 2012, 09:01 PM

I do not believe you will see any advantage in introducing a regulator.

The losses it would introduce would be far greater than any potential gain in trying to keep a constant 12V. The battery does not have a wide range of opperation compared to say a solar cell.

Remember that the nominal voltage of a lead acid battery is 13.8V

That box looks great!

You would be better of:
-increasing the battery capacity or
-attaching a solar cell or three to the top and sides
-using more efficent speaker (SOMETHING PEOPLE FORGET ABOUT)

Not sure what you can do with the car stereo with out some electronics knowledge but they are certinaly not built for efficiency. A iPod or similar with a simple amplifier would be better.

Hope that helps

Wally

**JDNSW** · 5th September 2012, 07:34 AM

Just adding to what Wally says (almost all of which I agree with), you should note that most gel cell batteries will not stand deep discharge, and will have a very short life if discharged below about 11.5 (although note that actual voltage depends on current being drawn). And you won't get much more length of play anyway.

I think most modern car radios are in fact fairly efficient, but as they are designed to provide high power to inefficient speakers they can still use a lot of power. Hence your biggest improvement will be to use efficient speakers.

John

**CU55TM Disco** · 6th September 2012, 07:19 PM

So should I aim towards something like a low voltage cut off circuit, so that I can turn off the radio as the battery hits a specified voltage? That way ill KNOW that the battery is indeed flat and wont risk damaging it further.

The unit will play fine for an entire 10hr shift at work, but I have no idea what the voltage is at the end of the day (without opening it up which is a MASSIVE task), if I had the above cut-off circuit I could gauge how long the current battery plays for, and, downgrade if I feel the need.

Can anyone recomend a speaker that is particularly designed to be More Efficient than others. The current Clarion Coaxial I have in there is crapping out at a fast rate of knots, its an old 2nd handy that Ive had stashed away for (5?) years and the suspension is slowly flaking away.

Thanks for the replies!

Perhaps something like this?

http://www.extremecircuits.net/2010/...2v-sla_18.html

Could I combine the above circuit, and the previosly mentioned jaycar LED battery Indicator KIT together somehow???

That'd be sweet!

**CU55TM Disco** · 12th September 2012, 05:58 PM

Had to treat the "bass bucket" to a new speaker as the suspension on the old clarion I had in there turned to dust and made it sound like arse.

I got a set of Jaycar RESPONSE 6.5" Coaxials, I did have a google for something that was super efficient, but couldnt find anything that suited the bill, nor that was notably more efficient.

Only drama is that the diametre was slightly larger by 10mm, which means I had to get a new front panel water-jet'd.
Whilst i was getting bits cut, I CAD'd up a handle and got a couple of them cut.

Also bought the Jaycar Battery indicator kit, but need someone to elaborate on the circuit in previous post, and see if the 2 can be combined somehow.

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