Dec 23, 2014, 12:32 AM Registered User Joined Nov 2014 177 Posts Discussion Power Supply Voltage Why would you choose a 24v power supply over a 12v? Wouldn't the wattage really be the important variable? For example, would a 1000w-12v supply be the equal of a 500w-24v supply? They would both supply the same max current, right? Am I thinking this correctly at all?
 Dec 23, 2014, 02:59 AM Registered User Letchworth, Great Britain (UK) Joined Jul 2004 12,815 Posts You're right that wattage is important. A 24v supply that can deliver 20A, for example, will deliver twice as much power (watts) as a 12v one delivering 20A. I'm afraid your numbers are wrong; a 1000W 12v supply will be running at 83A at full output, whereas a 500W 24v supply will only be running at 20A. If that 24v supply were to run at 1000W though (i.e. the same power), it would be 41A. Amps is usually what kills an electric or electronic circuit, so it's often advantageous to keep them low by building a circuit that can use a higher voltage.
 Dec 23, 2014, 03:25 AM Registered User Joensuu, Finland Joined Mar 2002 1,712 Posts All of the above. Plus, some chargers are limited by max power or max input amps, whichever comes first, and can't output full power with 12V input.
Dec 23, 2014, 07:01 AM
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Quote:
 Originally Posted by jkettu All of the above. Plus, some chargers are limited by max power or max input amps, whichever comes first, and can't output full power with 12V input.
+1
This is true for all higher power chargers. To realise their full power output potential you need to supply them with a higher voltage DC supply, over 30V in some cases.
 Dec 23, 2014, 07:14 AM Registered User Barbados Joined Jan 2011 2,581 Posts Lets say from the I Charger 106b 250 watts down are rated 12-18 volts,so a 24v PS is useless for small chargers,you have to get into the mid range and up for chargers to be spec'ed 24volts and up.So it's also relative to what power bracket you are in.
Dec 23, 2014, 07:58 PM
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Quote:
 Originally Posted by go_hercules Why would you choose a 24v power supply over a 12v? Wouldn't the wattage really be the important variable? For example, would a 1000w-12v supply be the equal of a 500w-24v supply? They would both supply the same max current, right? Am I thinking this correctly at all?
Many power supplies are rated for maximum watts capability. They also come in a range of voltage outputs. Standard voltages are 5, 12, 24, 48 and 120 Volts DC output.

Since watts equals volts times amps, Amps will equal watts/volts.

So, your 500 Watt power supply will put out 500 W/5 V or 100 Amps at 5 Volts. Or 500/12 or 41.6 Amps at 12 Volts, or 20.5 Amps at 24 Volts.

The higher powered chargers such as the Cellpro Powerlab 8 charger is rated at 1344 Watts, but only with a 24 Volt DC input voltage. (I've got two of the '8 chargers)

Also be aware that not all LiPo chargers can handle a 24 Volt DC input. If you apply 24 Volts to a unit rated at a maximum 15 Volt DC input, you'll blow the charger. And it won't be covered under warranty.
Dec 23, 2014, 09:03 PM
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Quote:
 Originally Posted by abenn Amps is usually what kills an electric or electronic circuit, so it's often advantageous to keep them low by building a circuit that can use a higher voltage.
That's kind of misleading. Excess Amps, excess Volts, and excess Watts will all kill electronic circuits, if any one of them exceeds the ratings of the devices.
Dec 24, 2014, 12:04 AM
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Quote:
 Originally Posted by Wintr That's kind of misleading. Excess Amps, excess Volts, and excess Watts will all kill electronic circuits, if any one of them exceeds the ratings of the devices.
Add to that static discharge. Just walking across a carpet, and drawing s spark can easily create a voltage well over 20,000 Volts. The current is very low, but damage can result to electronic equipment. They even have a ESD (Electronic Static Discharge) test for making certain your TV, DVD player, all electronic equipment can handle this.

So when reaching inside your desk top computer with its side panels off, touch its metal frame first.
Dec 24, 2014, 02:47 AM
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Letchworth, Great Britain (UK)
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Quote:
 Originally Posted by Wintr That's kind of misleading. Excess Amps, excess Volts, and excess Watts will all kill electronic circuits, if any one of them exceeds the ratings of the devices.
It's a generalisation, I know, but I don't think it's misleading in the context of this discussion, namely model aircraft systems.

But you're right, almost anything can kill an electronic circuit if it exceeds the circuit's spec -- we need to include temperature, humidity, vibration, etc. if we want a complete list
 Dec 24, 2014, 07:15 PM Registered User USA, MO, Florissant Joined Nov 2010 2,151 Posts It's not likely a charger will draw excess Amps; sure, there will be a bit more loss when charging a battery with a higher Voltage than the input, but not that much. And, most 'smart' chargers will shut down when the input Voltage drops too low, so that leaves Voltage that is too high. I'd sooner run a charger rated for up to 24V input at something less than that, if only to avoid any damage if the power supply rose above it's normal range when the current shuts off. As for static discharge - Volts is Volts, and you can't always feel the discharge that can kill electronics. Before touching any unprotected device, safely grounding oneself to a common point is always recommended.
Dec 27, 2014, 12:52 PM
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Ohms Law

Quote:
 Originally Posted by go_hercules Why would you choose a 24v power supply over a 12v? Wouldn't the wattage really be the important variable? For example, would a 1000w-12v supply be the equal of a 500w-24v supply? They would both supply the same max current, right? Am I thinking this correctly at all?