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Nov 06

ImaxRC X350 Overcharging FIXED!



The Fix:

  • Use a high quality power supply with very low ripple/noise.
  • clean the lacquer off all terminals with a wire brush or fibreglass pen
  • replace the crappy deans connector with a genuine deans connector
  • replace the internal 10A discharge fuse if you have exceeded the rated 40W discharge and have the “Connect Break” issue

The Backstory:

After hunting around for hours on the internet to try and find the perfect LiPo charger, I purchased what looked like a winner from HobbyKing. The ImaxRC X350 Charger:

ImaxRC X350 Charger

It has a whopping 350W charge rating, 40W discharge, touch screen, multiple battery chemistries, etc.

The 2 days that it took to arrive were painful, I was way too excited about this charger… So when it turned up, naturally I fired it up immediately and started charging a LiPo! I watched the nice pretty graph climb to full charge at a rapid pace BUT… it didn’t stop at the typical 4.2V/cell that I was expecting, actually it climbed closer to 4.34V per cell which is a recipe for fire/explosion with Lithium Polymer batteries. The charge cycle terminated at around 4.34V/cell with an “Out Voltage Too High” error.

x350 voltage error

The next thing I tried was discharging the battery to bring it back within a safe voltage range but the discharge cycle only lasted a few seconds and then an internal fuse blew and the display reported “Connection Break” (read on for the fix).

X350 connect break error

I tried several other cells with the same results, different cell counts, capacities, etc and every now and then it would terminate at the correct 4.2V/cell but not often. After trawling the darkest corners of the internet and trying to contact the manufacturer and HobbyKing plus a few other distributors, I was getting nowhere. HobbyKing said that it is a known issue with that charger yet they are still selling them, not even a warning on the website. There were a few suggested fixes by other users on youtube and the hobbyking forums. Theuns Oosthuizen AKA “TheUnsie” in particular was very helpful in determining the cause of the “Connect Break” error but the problem with my charger was still not resolved.

Please see TheUnsie’s youtube videos to repair the “Connect Break” error which consists of replacing an internal fuse:


The other day I decided to take the charger with me to where I would be flying and charged up a few cells from my car battery and quickly realised that the batteries were charging to the correct voltage and not a millivolt higher! consistently, every pack. weird…

So that my car battery didn’t go flat, I started the engine for a while but realised that the batteries were now overcharging again… I thought this had to be something to do with noise from the alternator on the car while it was running.

To test this theory I plugged the charger into my very nice laboratory power supply which has a very clean output and it charged fine compared to my usual modified server power supply. I decided to measure the noise from each power supply and discovered that the server power supply was around 580mV peak to peak whereas the lab supply was around 8mV peak to peak.

The comparison looks something like this:
X350 Noise

Problem solved!

Now that this charger is working as it should, it is exactly the awesome product I was looking for!

Next I just have to find a high-current, low-noise power supply.. Any suggestions? Let me know in the comments below.

4 comments

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  1. Frank

    Have you tried putting a large capacitor across the charger inputs to reduce the ripple?

    1. James Finniss

      Frank yeah i did try that. Large cap for low freq noise and smaller filter for high freq noise.

  2. Martin

    Thank you so much for sharing!!
    I bought 2 of these chargers to charge 2 lipo 5000mah packs in one time.
    Al has been in build in an aluminium traveling case together with my EFEUL power supply (1200 W – 80A -18V)
    I have a lot of errors like to high voltage, connection break enz on both of the chargers.

    Time to do some fixing!

    Thanks!!!

    1. James Finniss

      My pleasure! hope it works for you.

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