# Transmit high current with low voltage on a lightweight system

I have a moving system at 20meters from, say, a base station. The system consumes more or less 200W at 12V. I used until now a battery to power the system. The main drawback is that I have to recharge the battery quite often.

Therefore I need to find a solution to power the system. The system should be lightweight. This leads to some limitations. I was thinking of leaving the battery solution and choose to connect the system to the base station.

If I try to transmit directly 16Amps at 12V, I will have to use a huge cable (and heavy). I would rather transmit a bigger voltage with a smaller current and then use a small DC-DC converter on the system.

I was thinking of these kind of lightweight DC-DC converters:

1. VPT DV200-2812S or DV200-2815S In 16-50V, Out 12-15V, Out power 0-200W, 115 grams, 6x6x1cm http://vpt-inc.com/Products/?prod=5

2. XP Power QSB35048S12, in 48V, out 12V, out 29.2A, power 350W, 114grams, 6x6x1cm http://www.xppower.com/pdfs/SF_QSB75-350.pdf

3. MTM Power 132-200W PMD200 48S12 UHB In 48V, Out 12V, Out max 16.7A, 6x6x1cm

4. VICOR DC-DC converters

What is your opinion on this solution?

Remember: Voltage 12V Power around 200W Distance from base station to main system 20m Main system must be lightweight

• An important part of being an engineer is learning to attach numerical constrains to a project. I keep reading lightweight, what is your definition of lightweight? Compared to a 12V car battery most everything I can think of is light weight. – Kortuk Jan 5 '12 at 10:46
• Yes, you are right. The weight of the parts that will replace the battery should not exceed 200g. The power cable going from the base station to the system should not exceed 1kg – Pelotudo Jan 5 '12 at 10:52
• IMO increasing the voltage and decreasing the cable diameter may be a bad idea: I suppose the cable has to withstand also some mechanical stress, so you can't just choose the diameter based on the current. Do you have a maximum weight for both the cable + the converter? – 0x6d64 Jan 5 '12 at 10:54
• AC cable and a standard power supply? – kenny Jan 5 '12 at 11:24

## 1 Answer

Why you don't use a normal AC cable and a PC power supply on the main system? I think that you can easily find one that gives 200W in less than 500 gr and you don't have to worry too much about the cable since you can just buy a good one in any DIY shop.

• Yes that could be a solution. However, I am not sure to find a power supply that would be as lightweight as the DC-DC converters (more or less 100grams). – Pelotudo Jan 5 '12 at 14:07
• I don't know that but i'm worried about the cables that you need for DC current handling, that might be bulky i think. Just to know, where are you from? Have you got 110V or 220V voltage? And the other consideration that i was making is that a PC power supply can be found everywhere, without having to buy it; maybe you can also find one for (an high power) laptop use, that may be less bulky... – clabacchio Jan 5 '12 at 14:27