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Old 08-03-2006, 05:13 AM   #1
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Default transformer Q"

Hi guys
looking at buying a transformer to convert 240 down to 12 volts....
Is 20 amps going to suit my needs as I may be charging 2 batterys at the same time ? and what would be a min you would need ie....5 or 10 amps, just want to know to make sure I've got enough amps.
any help would be good....see ya timmey
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Old 08-03-2006, 05:21 AM   #2
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20 amps should be more than enough for you. If your only going to be running two chargers' that would be 12 amps @ amps per charger. the still gives you 8 amps for other product like a pelter cooler, tire warmers and/or discharge tray that require a power source. you might need a distrubution box if your power supply only has one set of banana plug. (there is a set of banana plus that you can plug another on into them there by much more.

Your min would be 12 amps for two chargers. I hope this helps eh.
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Old 08-03-2006, 06:07 AM   #3
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Are you converting 240 volts AC or DC? Chargers run off of DC power and if you are talking about just using a stepdown tranformer on a 240 volt wall outlet you are going to have some problems.
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Old 08-03-2006, 06:13 AM   #4
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Make sure you are looking at 12v DC power supply's rather than Transformers. I run a 20A pro-peak supply, does me ok for indoor racing with 2 chargers, motor cooler etc. Best thing to do is check with a multimeter the current draw of all of you equipment individually, then you will know what you can load up at once. Much more motor coolers draw about 4 amps and tyre warmers can draw quite a bit as well.
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Old 08-03-2006, 10:43 AM   #5
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More than meets the eye!
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Old 08-03-2006, 02:10 PM   #6
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I don't think that the transformer will be your problem, it will be getting a bridge rectifier that can pass that kind of current. Then you will want to use the correct value caps to filter out the remainder of the converted ripple. A ferrite core or two could also help prevent line noise from getting transferred to your charger, helping to prevent possible false peaking or other problems with sensitive things you may want to power up.
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Old 08-03-2006, 04:25 PM   #7
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A decent DC supply needs is regulated, not just rectified and filtered. Otherwise, the voltage will jump all around with varying loads.
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Old 08-03-2006, 04:46 PM   #8
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Old 08-04-2006, 03:30 AM   #9
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Quote:
Originally Posted by Iceracer
A decent DC supply needs is regulated, not just rectified and filtered. Otherwise, the voltage will jump all around with varying loads.
Sorry tim, its true. A full wave bridge rectifier to An RCR, LCR, LCL filter will yield a relatively flat DC voltage, but that voltage is entirely determined by the load presented to the ps circuit.

Switch mode power supplies are cost effective, compact and suitable for the relatively modest demands of RC racing. Although we have robust current requirements, ripple isn't a big deal.
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Old 08-04-2006, 06:16 AM   #10
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thank's all for the help......see ya all at the track some time
see ya timmey
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