24v to 12v

Joined: 18 Aug 2003 Location: Perth

Have just recently purchased another 24v MQ patrol and was wondering if anyone out there knew where i could get a 24 to 12 volt reducer at a good price. To run mainly 12v accesories like fluro lights etc

Marc

Joined: 09 Nov 2002 Location: Traralgon Vic Aust.

Jaycar, Dick Smith, Tandy. We sell Redarc units at work. These are good units but a bit exxy!!!!

Joined: 24 Feb 2003 Location: Melbourne

I got a decent one from jaycar at about the $80 mark if I remember correctly..

puts out some decent current too, so yer Cool

Joined: 30 Dec 2002 Location: Adelaide

If you don't require much current capability and are into DIY, then you could rig up a three terminal voltage regulator on a heatsink and get around 5 amps.

Jaycar sell the LM338K which is adjustable 3-35v at 5amps for $14. Only a small number of cheap components would be needed to set it up for 12-13V operation.

Let me know if you want details on how to do it.

Joined: 16 Jan 2004 Location: WA

i saw the jaycar one this week.. $78.95

Joined: 27 Feb 2004 Location: Meadowbrook, Brissie

Why not just run a fused and if you want switched wire to just one of the batteries for your fluros and whatever else. I've done it in my 24v gq and havent had any hassles

Joined: 25 Oct 2003 Location: Melbourne Australia

Sir Rollsalot wrote:

Why not just run a fused and if you want switched wire to just one of the batteries for your fluros and whatever else. I've done it in my 24v gq and havent had any hassles

If it were mine I'd do this too, but there is an argument against it.

The problem is that when you have two batteries in series, the stronger battery draws the charging current instead of the weaker one.

Therefore if you have one battery consistently doing more work than the other, it will consistently get LESS charge than the other (when it actually needs MORE), ultimately killing the battery.

Still, I personally think this is an overrated concern, but I couldn't recommend it to someone else in good conscience Smile

Jason

Joined: 18 Aug 2003 Location: Perth

Had a battery go today. So sick of the electrical hassle i have had with 24v patrols. Considering going the whole hog and converting the car to 12v.

Marc

Joined: 24 Feb 2003 Location: Melbourne

Shark wrote:

Had a battery go today. So sick of the electrical hassle i have had with 24v patrols. Considering going the whole hog and converting the car to 12v.

Marc

what other problems have you had with your 24V patrol? you dont run anything dirrectly off the battery such as spotlights do you?

Joined: 30 Dec 2002 Location: Adelaide

I thought I'd be smart and wire a relation's car alarm to just one battery on his 24V Isuzu truck. Anyway a few months later one of the batteries died and Isuzu immediately blamed the alarm hanging off only one- it causes charging problems as mentioned. Rolling Eyes

Do it properly and save some money in the long run. The three terminal voltage regulator idea I posted earlier is a dirt cheap option.

Joined: 27 Feb 2004 Location: Meadowbrook, Brissie

I also have an 24v to 12v inverter in my car that runs my immobiliser and a couple of other things but since my 12v feed from straight from the battery only runs a fluro above my back door and a couple of cigarette lighter jacks in the back i wasnt to worried about the whole battery draining prob

Joined: 30 Dec 2002 Location: Adelaide

Car alarms only draw around 20-30mA (0.02 -0.03 Amp) unless they're triggered and going off; your average 12V fluoro draws around 1 Amp. So be careful or you may have similar problems and kill one of your batteries.

Joined: 18 Aug 2003 Location: Perth

Has anyone actually done this conversion. It cant be that hard!!

Marc

Joined: 05 Dec 2003 Location: Brisbane Australia

a switch mode power supply would of course be the best

you can get kits for this too

a switch mode is about 70-90% efficient

where as a regulator simply dissapates the extra voltage as heat... (50% efficient)

if you grab a variable voltage regulator you can normally get about 5amps through the big suckers, throw a couple in parallell with a big heatsink (sheet of alloy?) and you got a good powersupply. Its a simple resistor setup to get the correct voltage, could get it to 13.7 perfectly.

something like this thing would do the job

http://www.national.com/pf/LM/LM338.html

Joined: 30 Dec 2002 Location: Adelaide

Yep, that's exactly what I was suggesting earlier. Very easy to set up and reliable.

Joined: 25 Jan 2004

Having had a 24v system in my Humvee there is no way I'd want to change it back to 12v even if it could be done. Current drain is halved on all components compared to 12v. The lights are always bright, the starter turns over like it has no load, the Autofridge pulls about an amp on 24v, no more probs with poor connections.
I do run a lot of 12v accessories, Barret HF, Thomas compressor, 12-240 inverter, GPS, stereo, CB, AA battery charger, camping lights, Laptop through switchmode power supply etc.
To avoid running one battery down I fitted a Redarc Charge Equaliser, basically it just floats both batteries at the same level regardless of power drain from either. It has behaved faultlessly for over two years now.
Full info at http://www.redarc.com.au/ce-techspec.htm
As stated you can even use it to run a third 12v battery as a stand alone system.
Peter

Joined: 16 Jan 2004 Location: WA

or you could knock this one up for under 25 rodneys Smile

http://www.oatleyelectronics.com/kits/k168.html

Joined: 25 Jan 2004

No that is a 12-24 converter, what I use is a Charge Equaliser which floats both 12v batteries at the same potential regardless of current drain from either.
I can run 12v accessories from either battery, the Equaliser then levels the power stored in each battery to the same level avoiding discharging one of the batteries more than the other.
Peter

Joined: 16 Jan 2004 Location: WA

Quote:

Have just recently purchased another 24v MQ patrol and was wondering if anyone out there knew where i could get a 24 to 12 volt reducer at a good price. To run mainly 12v accesories like fluro lights etc

Marc

I was referring to the original post...

Joined: 25 Jan 2004

Yes I realised that but the converters are not particularly efficient, they use more power than required due to losses in the unit and they usually have a current draw limit.
With a Charge Equaliser there are very minute losses as all it is doing is floating the potential BETWEEN the batteries. The Equaliser is NOT supplying the accessory.
The 12v accessories are connected directly (through a fuse with appropriately sized wiring) to either 12v battery.
Peter

Joined: 05 Dec 2003 Location: Brisbane Australia

ozhumvee wrote:

Yes I realised that but the converters are not particularly efficient, they use more power than required due to losses in the unit and they usually have a current draw limit.
With a Charge Equaliser there are very minute losses as all it is doing is floating the potential BETWEEN the batteries. The Equaliser is NOT supplying the accessory.
The 12v accessories are connected directly (through a fuse with appropriately sized wiring) to either 12v battery.
Peter

im sure theres a price tag that follows aswell O_O

Joined: 16 Jan 2004 Location: WA

haha

here you go

http://www.solarsystemsaustralia.com.au/the_solar_community/products/redarc/charge_equalisers_etc.htm

Laughing

the equalisers are cheaper than the swithed mode supplies for the same power output Rolling Eyes