Fixing your Lumea Battery Charging Issue, for less than $1/£1/€1

My original post about how to repair your Lumea when the batteries are dead is becoming quite popular. As a result an electronics designer from the UK, Shamus Husheer, reached out with another, cheaper solution.

He was handed a dead Lumea and just like you did, searched for a solution online. He found my original post and noticed that the Lumea is using a LiIon battery. As an electronics designer he knew a better, cheaper way to fix the battery that he would love to share:

 

The background (you can skip this if you like):

The underlying problem with the Lumea is that it uses a LiIon battery, yet the charger circuit in the device breaks some fundamental rules for designing such things. When fully discharged, a LiIon battery needs to be gently charged at a small constant current (e.g. 0.02A) until it reaches approximately 3V, after which point it can be safely charged at the full current (e.g. 1.0A).

The Lumea detects that the battery is discharged to below 3V, and so for safety reasons won’t apply the full 1.0A charge unless the battery voltage is over 3V. But for reasons either of design incompetence or commercial cunning, it does not apply a low-current charge to fully discharged batteries, hence the problem when you leave one discharged for months.

We will make an incredibly simple current-limited charger from the Lumea’s own power supply and a single component – a resistor. The Lumea power supply is 8.5VDC, which is about what two fully charged LiIon batteries can deliver in series (which is how they’re wired). Worst-case, if you get the power supply around the wrong way, we want to limit the current to a safe level (less than 0.1A). That means we need a resistor of about (8.5+8.5)/0.1 = 170ohm, and in this worst-case scenario would be dissipating 1.7W of heat (enough to feel, but entirely safe). A convenient, easily available value is 180ohm, which has the colour code brown-grey-brown, and easily available in a 2W power rating for a few cents.

When fully discharged, this resistor will allow us to charge the batteries with (8.5-0)/180 = 0.047A, and when at 3V per battery (with two in series) we will charge at (8.5-6)/180 = 0.014A. Because only a small amount of charge is necessary, on my Lumea this took only about 15 minutes from dead to alive enough to charge normally.

The total charge delivered over 1 hour, after the batteries reach 3V each, will be less than 0.014AHr. The batteries are rated for >1Ahr each, so it’s entirely safe to leave them charging through this resistor for an hour (but don’t leave them over night).

 

The solution:

There is nothing wrong with your battery – you just need to give it a tiny bit of juice, at a safe level of current, then the Lumea’s own internal charging system can take over. The easiest way to do this is to use the Lumea’s own charger, and a 180 ohm, 2W resistor (available from any electronic shop for a few cents, e.g. £0.76 for a pack of 10 here: http://uk.rs-online.com/web/p/through-hole-fixed-resistors/7078833/) or here at Amazon.

Open your Lumea as per the photo [in the original blog post], but don’t even bother taking the battery holder fully out. All we need to do is locate the red and black terminals at the bottom of the battery pack (not the terminals of the charger inlet).

Hold the outer ring of the charger barrel against the black (negative) terminal – this can be held in place using e.g. a clothes peg.

Push one end of the resistor into the inside of the barrel (it’s easier to do if you bend the resistor lead back onto itself to make a snug fit).

Connect the other end of the resistor to the red (positive) terminal, and hold it there with e.g. a clothes peg.

Plug in and turn on the plug for the Lumea charger.

Leave charging like this for about half an hour.

Disconnect your resistor from the battery pack, and try plugging the barrel into the usual socket on the Lumea. It should light up and charge normally – if not, try repeating the connection between barrel, resistor and terminals in case you didn’t get a good connection the first time.

Once charging normally, let the Lumea charge up fully. And you won’t forget to keep it charged every couple of months again, will you?

If this article helped you to fix your Lumea, please donate a small fee to keep this site running so I can write and help others to. Thnxs!

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32 thoughts on “Fixing your Lumea Battery Charging Issue, for less than $1/£1/€1”

  1. After two years of having changed the batteries I couldn’t believe my lumea died for the second time . This time I tried this batteries charging trick and it’s charging again. I was very worried about having to tear it apart again, it was the most difficult part in the first fix, so I tried to do it only opening the purple plastic at the bottom, where the charger goes, and the two screws that hold that part. I didn’t have any resistors on hand so I cut an USB cable, connected the red to the red battery pole, the black to the black, and plugged it to a 0,5 A plug that I use to charge my smartwatch. I’m definitely setting a reminder for this to never happen again
    Thanks again for all the work behind these fixes!!!

    • Hi Rudd,

      When dismounting the small black component on the black wire to PCM was broken. Can you tell me what it is. I am reading on the posts it is a thermistor
      Is it a simple resistor 10kΩ or a mix resistor thermistor ?
      Someone mentioned 10 K Ohm B = 3380 NTC , can you help ?
      Many thanks
      Kind regards
      Claude

  2. Hi Rudy, thank you for the information. My wife`s Lumea was death and I managed to charge the battery. when charging with Lumea´s charger it doest not blink the green light. when i turn it on, the fan works, but power selector does not work, it does not “shoot” either. Full charged I measure 8.11V, might this be the problem? thanks. Jorge.

  3. It works great, very easy and very simple. Do it just you see on the pictures above and leave it for a 1/2 hour and you will see the result.

  4. Hallo Rudy, Het werkt fantastische. Het apparaat werkt weer.

    Waanzinnig dat je dit hebt kunnen ontdekken. Kan i nog doneren met bovenstaande link.

  5. Hi Rudy. Can you share any video of how to use the resistor. Don’t want to make a mistake. I am zero at electronic stuff.

    • Hi Uzma,

      Sorry I can’t really make a video. Even I havent used the resitor before, I replaced the batteries. Just scroll trough the comments for photo and tips and you will fine.

  6. Big thanks for this tricks. 1 hour plus 180Ohm(2W) and I have 4V on my batteries. After that’s they charges from original power supply. Good work!!!!

    ps: The most difficult thing was to disassemble the device.
    pss: My original IMAX B6 mini refused to charge these batteries separately.

  7. Hi Rudy and Shamus,
    Thanks so much for posting this solution! I gave it a try and it revived my battery. However, my Lumea now shuts down every couple of seconds when I try to use it (I can get a couple of flashes out of the machine, but then it turns itself off). I am able to start it up again, but the same thing happens. Any ideas as to what is going on? Did I perhaps not charge it right with the resistor? Or is meu battery so “dead” that I should replace it (as per the original post)?
    Thanks once again!

    • It’s hard to say from here, but I would try to change the batteries. If it first didn’t charge and now it does but not fully then my first guess would also be the batteries.

    • Hey Amaral!
      I’ll share my experience that I believe might be similar to your situation.
      One of the two batteries in our Lumea got drained. So I did similarly to Shamus/Ruud’s suggestion and used 350 ohms resistor connected for about 1 hr and then attempted to charge w/o resistor. Attempted to turn it on, fan would kick in for 1-2 sec and then lights would go off.
      Checked batteries and each read about 3.5-3.7 Vdc. It got me puzzled for a while.
      Then I thought that perhaps the two tiny wires (black connected to black negative terminal of battery and white one connected to the common plate “+” from one battery and “-” from another) is meant for monitoring charge of one battery, and if it drops below certain threshold value, then some circuitry shuts off fan and lights up red “charging needed” light. To see if this was the case I soldered off white tiny wire from the baterries common bridge and soldered it onto the red wire that is connected to “+” of battery. Whoohoo, this actually solved the problem. Now I get Lumea work like new.
      My explanation to this is that the black and white tiny gauge wires are part of some protection circuit. When this circuit doesn’t read let’s say 3.5V from one battery, it automatically shuts off fan and the rest of equipment.
      Also, after many years of cycling charge/discharge, Li ion battery doesn’t get to 100% of 4.25V and stays at around 3.5-3.7 instead. That in turn triggers the safety circuit. By wiring white wire as I described above, it sort of cheats the protection circuit because 3.5+3.5=7 Vdc, thus it will take a long time to drop both batteries to 3.5 V.
      It would be great if Ruud and Shamus could comment on this and either confirm or disprove my suggestion.
      P.S. I used 350 ohm resistor because ac to dc adapter’s voltage is 12 Vdc and 12/350=34 mA. S
      Thanks and good luck!

  8. Hi guys!! I fixed Lumea battery failure with your precious experience, but unfortunately the protection component ( NTC or PTC? ) was broken durin removal… Can you help me to identify this? Thank you and have a nice day!!

  9. So pleased this worked! It’s tricky to get it open but definitely worth the effort. Thank you so much for the instructions : )

  10. Hello ! after error in the Charger plug end, I followed your procedure, 30mn after my Lumea charge works again! Thank you very much !!

  11. Brilliant, thank you ever so much! Found my Lumea dead yesterday, heart sank. Googled for a way to resuscitate, found this page. Picked up a resistor for 20p today, followed your procedure, Lumea works again! Means I don’t have to bin a device I paid hundreds of pounds for and that I don’t have the means to replace at the moment. This is what the internet is for 🙂 Thanks again.

  12. can you please share video of how to fix it.. its kind a hard to understand your technical terms as i have no electronic knowledge

    • Hi Hala, I’ve just managed to work it out, followed the procedure and my Wife’s Lumea is back up and running. Brilliant! So here’s what I did. I ordered the resistor fro RS components and for a total of 91p they arrived the next day (Smallest quantity pack of 10) but heyho)

      1st Follow the instructions to open the Lumea. It is a bit tricky and I’m afraid I scratched the body of ours, but a small price to pay to get it back up and running.

      2nd Take the end of the charger cable with the connector on it. The bit that looks like a small rod with a hole in the centre and obviously not the Charger plug end.

      3rd At the very bottom of the battery pack you can see 2 terminals. One red and one black. Use a peg or similar to hold the cylinder to the BLACK connector.

      4th Take one of your resistors and bend one end of the wire back on itself and push it into the hole of the cylinder. (If it feels loose, open the the wire bend you just made a little and try again. You want to make a good contact with the inside of the cylinder.)

      5th Again using a peg or similar, hold the other end of the resistor to the RED terminal (I learned by the way that it doesn’t matter which way round your resistor is as they are apparently non polar)

      6th Plug your charger in and turn on the power supply.

      7th Let it charge for about 30 mins. (Apparently it shouldn’t be more than an hour. Mine worked with 30 mins)

      8th Turn off the power and disconnect the resistor.

      9th Put the charger connector into its correct socket on the Lumea and turn the power back on and you should now see the green charger light flashing.

      I left the Lumea charging overnight and all that was left to do was close the body up again. Takes some doing and ours hasn’t closed as neat and tidy as new, but doesn’t appear to be much of a problem as it now works perfectly. Fantastic!

      Hope this has helped and good luck with your repair 🙂

      • Thank you for the help, it’s working cant believe I managed to do it myself. Followed the instruction. Thank you made my day 🙂

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