X-108 Info Portable operation with a 4S Lipo

Discussion in 'X-108 TRX' started by DD5LP, Feb 22, 2018.

  1. DD5LP
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    DD5LP Crack-Boarder X-108 Member

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    Hi Guys, here's something to look out for in case you make the same mistakes I did.

    The main reason I bought the X108G was to use it for SOTA activations. Now that we're nearly at the bottom of the Solar Cycle, 20w rather than 5w of SSB can make a difference. I have been taking my FT-817 plus a drastically modified Ramsey QAMP linear amplifier to give me between 20 and 30 watts on 15m through 80m (switched LPFs etc.). That as well as adding weight to the pack also adds complications with additional cables battery etc. Hence the X108G in one unit makes a lot of sense to replace the 817 and the amplifier.
    For the amplifier I bought a hard case 4S (4 cell) 5Ah LIPO battery. Yes I know LifePO4s are safer but they're still a lot more expensive than LIPOs. The other difference between 4S LIPO and LiFePO4 batteries is that the LifePO4 gives a nice 14v output whereas the 4S LIPO gives over 16v. For my amplifier this was fine as running the amp on 16v rather than 13.8v added about 5 watts to the output (the power transisters are actually meant to be run at 28v). However as I wanted to use this same battery now for the X108G, I needed to do something to reduce the, on full charge, 16.5v down to 13.8v otherwise this could damage the rig.

    On eBay I came across a voltage reducing unit with a nice LCD display and it was programmable to give a set voltage and up to a current limit out for a range of voltages comining in (always reducing the voltage however - this is what some call a "buck converter"). Once it arrived I attached my needed connectors to it, programmed it to 13.8v output and 3.5 amps maximum current output.

    Testing it, at first all seemed fine. It does not create RF hash as some of the voltrage-up converters do. When I took the power up on the X108G past about 13 watts output however I got a horrible noise seeping into the audio. 13 watts and below were fine but over that, the noise was there. I switched back from the battery and regulator to a shack PSU and there was no problem.

    My thought was RF ingress into the processor in the regulator was occuring. So I added ferrites to all leads to and from the regulator - still the problem was there. Then I thought decoupling the supply with a couple of 0.01uFd capacitors might help - no the problem was still there. It looked like I would have to mount the regulator in a metal box to screen it from RF.

    But then I did something that I should have done to start with. I watched the LCD display, and what happened when I turned the power up and transmitted? The voltage went down! KLING! How does the "buck" unit regulate an over current situation? It drops the voltage and it is known that the X108G does not like running at under voltage. I adjusted the "buck" unit to allow up to 5 amps current and no problems any more!

    I'm happy it was simply a miscalcualtion on my part as to the cureent needed by the x108G when transmitting at 20watts output and nothing more serious - here's a picture of the hard case LIPO battery and the regulator:
    upload_2018-2-22_15-47-43.png

    73 Ed DD5LP.
     
  2. Chrisbei
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    Chrisbei Junior Boarder X-108 Member

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    Hallo Ed,

    stört die Schaltelektronik nicht ganz extrem in den Funkempfang rein?
    Ich habe ein ähnliches Teil schon im Sommer 2017 in Kroatien dabei gehabt, extra verdrosselt sogar,
    aber das war viel zu wenig. Es wurde von mir dann noch in ein Gehäuse aus Metall eingebaut, brachte aber zu wenig
    Reduktion des Rauschens. Ich konnte mit dem Konverter so nichts anfangen an meinen 4s Lipos.
    Hab dann kurzerhand einfach nur 3 der Zellen angeklemmt....

    73 de Chris DL6SEZ
     
  3. DD5LP
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    Hallo Chris,
    Ich habe auch angst gehabt dass die "regulator" würden RF Störungen mitbringen aber es ist nicht so - da gibt absolute keine Störungen ! Wenn Ich früher für andere gerät ein 3S LIPO und ein umgestellter benutzt hab, dass war richtig schlecht. Es sieht so aus das Stromspannung reduzieren ist kein Problem aber 11.5v auf 13.8v bringen problematisch ist.
    In beider Fall konnte es auf die spezifische gerät abhängen. Ich habe ein anderer "buck converter" aus China gerade gekauft dass nur halb so teuer ist. Vielleicht gibt dass Probleme aber es sieht sehr ähnlich aus.

    73 Ed DD5LP
     
    Last edited: Mar 3, 2018
  4. DD5LP
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    Let me point out an error I made in this solution .... The fancy, LCD equipped voltage regulator shown in the picture above is rated at a maximum of 5 amps. When that limit is exceeeded it simply cuts off the power (thinking a short has occurred). The X108G can take up to 7.5 Amps! On my last SOTA activation running a digital mode at 20 watts in the awful radio conditions, the rig kept turning off!
    Only when I got home and looked at the specs did I realise my error.
    I have now ordered a regulator unit "Buck Converter" that is rated at a constant 8 amps with peak current allowed up to 10 amps. This one has no fancy display on it, but hopefully it will work. Chris - I hope the new simpler unit doesn't cause EMI - I wont know until I try it!

    73 Ed.
     
  5. DD5LP
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    Just to close this point out, the buck-converter, with no fancy LCD display has now worked fine for 4 months, no interference, no cutting out. I have it built onto a small plastic case with 2 5aH 4S hardcase LIPO batteries and a battey monitor / USB socket adapter and I also store the X108G power lead (with fuses in both lines) in the same box, so that I have everything available on the summit.

    73 Ed.
     
  6. DD5LP
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    X-108 could you please move this to a different thread as it describes increasing voltage i.e. using 3S lipos to provide 12-13.8v whereas this thread is related to reducing the voltage (14.5-16.7v) from a 4S LIPO down to 13.5/13.8v.

    There may even be such a thread already.

    The biggest question is whether the invertor - which I presume is what is used to do the voltage step-up is EMF-clean on both HF and VHF bands. I know some of the chinese built units are not.

    73 Ed.
     
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