100 watts from your cigarette lighter?

Discussion in 'Amateur Radio News' started by WJ6F, Jul 29, 2020.

ad: L-HROutlet
ad: l-rl
ad: abrind-2
ad: Left-3
ad: Subscribe
ad: L-MFJ
ad: Left-2
  1. W0PV

    W0PV Ham Member QRZ Page

    Correction - staring at the schematic harder I see now they are six 25 Farad lower voltage caps in SERIES making the total for the bank 4.16 F. That is still a very impressive energy storage tank. Plenty for this application. Lower voltage super-caps are SMALL can be easily found by googling around like this example. And the OP vid pic of the insides clearly shows a big honkin' stone 15w resistor, probably the bleeder.
  2. KF5LJW

    KF5LJW Ham Member QRZ Page

    Your Majesty :) I present for your inspection a manufacture data sheet for Ultra Capacitors ranging in size from 1 to 3000 F. Quite small Form Factor for a capacitor, but like all capacitors have piss poor energy density.

    However your skepticism is well founded. To power a 12 volt toy from a super cap is no small affair and would require a Power Converter. You would need a capacitor to charge up to at least 100 volts or more. All one has to do is look at the discharge curves of any capacitor to understand why. If you were to only charge a capacitor to say 14 volts like an vehicle, none of the energy below 11-volts is not available to you. It forces you to leave roughly 80% of the energy inside without a noisy Buck Converter.
    Last edited: Jul 30, 2020
    G3SEA likes this.
  3. PA0MHS

    PA0MHS XML Subscriber QRZ Page

    So when I do the math again, using 4.16F, this thingamabob would power your rig for a whopping 45 milliseconds during 100W peaks!
    G1UFM likes this.
  4. KF5LJW

    KF5LJW Ham Member QRZ Page

    This thread makes me laugh. It is snake-oil looking for pigeons to pluck with very bad science. Super and Ultra Capacitors certainly have their applications, but this is not one of them. It is such a misuse of a technology, makes me wonder who the fools are? The one making them, or the ones buying them. Once you set the objectives, examine the options, cost, and complexity, Super Caps get eliminated very early as there are much better alternatives.

    Example, lets say we want to use a Power Port in a modern vehicle to provide 12 volt power to a small Transceiver like a VHF/UHF that requires 100 watt input. From a safety POV nothing needs to be done except fit the radio power cable fitted with the Port Connector. Consult Owners Manual but most Power Ports are limited to 150 watt maximum load which is a bit over-stated because the fuse will be 10-amps. So a 100-watt design limit is reasonable safety margin while getting the most power you can safely draw from the circuit.

    However from a Power Quality POV using the Power Port is unacceptable. The voltage loss, and common mode noise levels are just not acceptable. Well a Super Cap can resolve the noise issue, but cannot do squat about voltage loss unless you use a Noisy Power Converter. Doh!. Not only very expensive and complex, does not meet the objective.

    A better option and extremely effective is a Battery Pack. Same concept RV's, Telecom, Engineering, LMR, Competition A/V using a house battery, just on a much smaller scale. Use the vehicle alternator to keep the battery charged and supply power when running. Any power interface requires some precautions be taken. In this application a method to limit charge current, prevent house or auxiliary battery from back feeding, and a fuse between battery and radio. Two battery types come quickly to mind because they use the exact same voltages your vehicle uses. Either a small sealed AGM @ 20 AH range, or 4S LFP @ 10 AH. You could go as small a 4S LFP @ 5 AH.

    Eliminates voltage loss and noise using isolation from current limiter. Battery voltage will be roughly 14 volts at rest, and full load only dropping slightly outperforming a direct connection to the vehicle SLI battery in permanent installations. Can even work for a few hours with the Power Port turned off by the ignition. Not only would meet the objective, you blew them away for less cost.

    A few ways to get it done, but Super Caps is not one of them.
    PA0MHS likes this.
  5. W0PV

    W0PV Ham Member QRZ Page

    Not applicable - a stiffening capacitor only needs to dynamically compensate for the inductance and resistance of the leads to the lead-acid car battery. It NEVER should be expected to supply 100% (100w) of the power. Instead only the fraction needed to make up for instantaeous upstream power feed loss. An autotranformer in voltage boost configuration on an AC feed, far lower power rated then the actual load, is a loose analogy.

    Of course nothing is for free. The operating mode is important. It only enhances to a higher point SSB with its complex waveform, 10-20% average vs PEP. CW Morse code is derated (based on QRQ WPM? ;)) No benefit for RTTY, SSTV, nor even FT8 :(
    Last edited: Jul 30, 2020
  6. PA0MHS

    PA0MHS XML Subscriber QRZ Page

    I disagree with you. Every transceiver has a few large capacitors directly connected to the power socket/leads. This is imperative for proper operation. So at the power leads you will never see a high frequency transient/peak in current draw. So any inductance of the power leads plays no role at all. Mind you: my FT-897 and IC-9700 each came with a 3m power lead, much longer than you will ever find in a car between the battery and the cigarette lighter. So the only thing this device and its capacitors will do is compensate a tiny little bit for the resistance of the fairly thin wires you find in a car. It forms an RC network with a small R and a large C. The only thing that happens if the transceiver needs 100W for a brief period of time, and the voltage drops from, say 13.5V to 12V across the internal car wiring is delay that drop for 45 milliseconds, based on the drop of 1.5V from a 4F capacitor. Anyone can do that math. And in my opinion, 45ms is way to short to have any positive effect on the peak output power of the transceiver, as the envelope of the peaks in a voice last much longer than that 45 ms.
  7. KC2YMO

    KC2YMO Ham Member QRZ Page

    Although I don't like the cigarette lighter/powerport connection for high current applications because of contact resistance, would be nice to see a real BEFORE and AFTER comparison with a volt meter at the radio power input and a watt meter at the radio antenna output. Show the benefit or lack there of using this device.
    AC0GT likes this.
  8. VK6HIL

    VK6HIL Ham Member QRZ Page

    Utter engineering and marketing cobblers. More MFJ overpriced rubbish

    The only reliable solution is a direct feed off A battery. As someone else also alluded to, modern cars [anything in the last 20 years] REALLY do not like low battery voltage levels : all sorts of malfunctions and weirdness can occur if it drops just a little.

    And if you do feed it off the primary battery, make sure the engine is running.

    People who know what they are doing in Australia run separate batteries for accessories so they also don't run the chance of killing their starter battery and this dying in the middle of nowhere.
    WB4NQF and PA0MHS like this.
  9. G3SEA

    G3SEA Ham Member QRZ Page

    I don't smoke but hopefully nothing else will :cool:
    W1YW and K3XR like this.
  10. N3HGB

    N3HGB Ham Member QRZ Page

    This is a second life for capacitors that were sold to make cars faster by "insert some weird jibberish about the fuel injection" that actually did absolutely nothing :rolleyes:
    As has been pointed out, cars to run really small wiring for the load. I am always amazed at how hard the wiring is pushed when I work on a car. The lighter outlet is a really bad place to tap radio power if you have ANY other way to do it.

Share This Page

ad: cq2k-1