Akom's Tech Ruminations

Various tech outbursts - code and solutions to practical problems

The Mystery B6 balancing LiPo/LiFE/NiCd/NiMh/Pb charger (review, sort of)

Posted by Akom • Tuesday, October 21. 2008 • Category: Reviews

The Mystery B6

I got this charger because the little unit that was included with my R/C plane just did not inspire a lot of confidence. It did charge, just took hours, and gave no hints about why. So I figured I'd go and buy something that gives me a little more information. And I found it. In Hong Kong. But now it's on my desk.

For being able to charge anything, the $50 and two weeks of waiting simply doesn't seem excessive.

As far as I can tell, the Mystery B6 gets a fair amount of negative commentary on the forums. People seem to question its voltage precision and balancing accuracy. So I thought I'd run a very simple test.

It occurred to me today to double check how well it works for several reasons.

  • A friend told me that people have issues with it
  • I just crashed my plane (today), and failed to notice that two of four balancing connector wires ripped clean off my lipo (3 cell). After about 5 minutes, the charger loudly objected, saying something about Battery Voltage being invalid

The latter event impressed me enough to look into it further. The charger connects to the battery through both the main power connector and the multi-wire balancing plug, simultaneously. At first I thought that it would balance charge via the balance connector, and monitor overall voltage through the main plug... But now that I ran it with the balancing connector half-missing (only one cell was connected), I checked the cells and they all went up in voltage approximately evenly!

So I realize that it charges through the main connector now... which suggests that it balances by lightly discharging through the individual connections to each cell (the balancing connector) during charge. Interesting. I soldered the battery wires back on and let it finish charging. Then I compared the readings with my manual measurements with a DMM.

Normal Charge Display


Charger claims:

Voltage: 12.58 Cells: 4.19 4.20 4.20

Balancing Detail Screen

My DMM claims:

Voltage: 12.56 Cells: 4.17 4.18 4.21

Discounting any included errors due to variation in wire resistance and connector quality (and the fact that I am holding the leads for the DMM in my hands), the measurement error, if any, is 0.05%. Perhaps the critics got defective or miscalibrated units, but I'm not seeing the issue here.

Current battery temperature


That aside, the unit does offer a decent array of features and charge/discharge modes, most of which I don't seem to need. It will do a quick charge (disregarding balancing) to about 95% capacity for those times when you really, really want to get back in the air right away. It lets you tweak the nominal voltages for each battery chemistry it supports (you select the battery type/charge mode). It lets you configure a bunch of stuff too:

  • Safety cut-off total mAh
  • Safety cut-off charge time
  • Safety cut-off temperature (a temperature sensor is included)
  • Low input voltage threshold
  • The charge rate (duh!), which is used as a mean high rate, the charger will exceed this rate momentarily as it varies the charge current depending on the state of the pack. This actually caused me some problems because the wall-wart I am using with it cannot provide more than 1.5A, causing the charger to stop charging and scream "Input Voltage Error". It's nice that they have all these error messages. Note that the charger didn't come with an AC adapter, this is something I dug up in my goody bin. When you charge it from a battery (in a car), there are no issues charging at high rates. Naturally, as the battery nears full state, the charge rate drops off until it's basically 0 just before charge finishes
  • Specific things for each type of battery, like peak detection, etc
  • Charge/discharge sequence delays, and stuff like that (I haven't needed any of this yet)
  • Additionally, it lets you store several profiles of configuration in memory (Though I am not finding this very useful so far, perhaps because all my batteries are very similar)

It seems to have a USB connector to allow it to be monitored (controlled?) via a PC, though I am not entirely certain regarding why I'd bother. The user interface is not bad at all, though the key beep is pretty loud. I can understand how this is useful though - in the field with gas birds buzzing around, you'd never hear a weak beep.

As you can see from the pictures, it shows you a wealth of information while charging, including time, mah delivered, current rate, current voltage, etc. You can flip to the battery cell detail, as well as look at temperature of the sensor, and even review some of the safety parameters without interrupting the charge.

The unit also comes with a mesh of wires and adapters for connecting to Deans plugs, JST plugs, some very weird hex plug and your plain old alligator clips. Actually its "normal" connector is the Deans, so if you have a 15C or higher battery you'll probably not have to carry any adapter wires (unlike me - all my batteries are 10C with JST plugs).

In summary: great charger, does a lot more than I need (and I used to build my own peak detector NiMh/NiCd chargers in the past). It would have been nice to have something like this back in the days when I used AA cells for everything. I am certainly less concerned about lipo explosions since this thing actually tells me what it's doing, and it has now greeted me with 3 different error messages, catching my errors, as opposed to the other way around.

For the curious, here are the error messages I've gotten

  • INPUT VOL ERROR: My poor wall wart couldn't deliver and dropped below 10 volts. (Note that the manual (below) incorrectly defines this particular error)
  • CONNECTION BREAK: I didn't connect both battery connectors, thinking that it worked like my E-Sky charger
  • BATTERY VOLTAGE CELL LOW VOL: My balancing plug got partially ripped off the battery in a crash

Since the Manual Seems to be pretty hard to find,

I decided to scan/include it here.

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2 Trackbacks

  1. I have a hand-me-down Garmin C330, the el-cheapo, no-text-to-speech teletubby-looking GPS unit that every online store was liquidating a few months ago. Mine also has a dead battery, and while it used to run for 1-2 minutes on it, now it barely runs 5 se
  2. I have a Dewalt 18V cordless drill, which was very expensive ($200 back in 2001), came with two batteries (heavy, NiCd packs), and I've used it extensively for just about everything when we bought our house. Now both packs are dead.


Display comments as (Linear | Threaded)
  1. Hi: I have a MYSTERY B6 charger, but have no USB connector cable!! Could you let me know the part no. or where I can find one?? Thax: Bill J.

  2. Cursory scan of forums shows that the USB cable is pretty hard to find. This place did sell out of it: http://wattsuprc.com.au/product_detail.asp?pid=EAC200

    Some people also claim that this works too: https://www.hobbycity.com/UNITEDHOBBIES/store/uh_viewitem.asp?idproduct=2119

    As far as software goes, there is definitely open source stuff available in addition to whatever the first item comes bundled with... http://www.logview.info/cms/e_logview_info.phtml (Claimed to work).

    In summary, I personally don't have a need to monitor the charger with a computer, so I haven't tried any of this myself

  3. Hi, Many thanks for info. do you have a URL for the B6 charger MANUAL. Id doesn/t seem to dork on page describing charger. Thanks, Steve K. Hi, Sorry to do 2 comments, BUT any info on temperature sensor? WHere to get one? WHat does circuit look like? Is it a thermistor?, ...or temp sensitive switch? Are only 2 of the 3 pins used?? guys I got it from on ebay, no help. Cheers -SK

  4. The owner's manual is on this page. Scroll up and use next/prev buttons to flip pages.

    As for the temp sensor, I don't know what type it is. Mine came with it, and it looked like all 3 pins were used (Maybe it's a one-wire style chip?). I'll try to do some measurements in a bit.

  5. Akom do you have anouther link to the manual, will not let me turn the pages. or can you send me a copy to my email. really need this manual. thanks

  6. I'm rather curious what browser you're using. Works for me in Firefox, Chrome, and even my Blackberry Storm2 browser I'm also rather curious why someone would really need the manual :-)

  7. The temp sensor is a LM 35 0-100 degree cel., the cable is a futaba servo cable for remote control vehicles.

    If in need mail me, i have the complete sensor in stock for 9,95 euro ex shipment.

    greetz franco (franco -=at=- home.nl)

  8. Akom, I've had my Mystery B6 (same as your) for almost 2 years now and have never had a problem or concern about it's charge/balance or discharge abilities and results. I too checked it with a DMM and still do once in a while just for accuracy sake and it is always spot on.

    Further, this unit is very likely made by the same company that makes many other well known brand chargers, because the configuration of buttons and output jacks are the same as is the firmware charging program displayed on the LCD. I had to laugh that Hobby People is selling essentially the same charger with their brand name for $80 and one with the AC/DC power supply built in for over a $120!

    Incidentally, I only paid $39 for mine with all the various battery connector pigtails and the 12V power gator clips from a Hong Kong dealer on eBay nearly 2 years ago and then found the AC/DC power brick at a local surplus electronics store for $5. I now wish I'd bought two or three of the Mystery B6 chargers.

  9. keith

    how do you us the balance charging for lipo battery ? do you need to plug the balance charging socket and the black and red plug all the same time


  10. Yes.

  11. can you help me with the low voltage alarm ? what should I do to solve this problem ? thank you

  12. Fixing the low voltage alarm is easy - get a better power supply! :-) Alternatively, reduce the charge rate until your current (inadequate) power supply no longer fails to sustain voltage above 10V (Check what voltage your B6 is set to alarm at) You should not experience low voltage alarms if you power the charger from, say, a fully charged car battery

  13. my B6 charger is work with another lipo battery that I have without any problem ,but it didn't work with 4 battery that I use for the first time and need to recharge them and give me that alarm ("battery chck ... Low voltage")

    thank you for answer my comment

  14. I have found a temperature probe for the Imax B5 B6 can it be used on Mystery Charger? They use different connections can the Imax one be modified to suit the Mystery one? Thanks

  15. Where do you get the software to go with the charger I have the cable but mine didn't come with the software. I love the charger it is very nice and the case is excellent.

  16. You guys without balancing problems are lucky. I bought two, and when charging 3s batteries, one gives: 4.16v, 4.18v, 4.27v. The other gives 4.14v, 4.19v, 4.24v. Anyone who is expereinced with Lipo batteries knows this is dangerous and could cause an explosion. I only use mine to charge my transmitter NiMH batteries, and if I need to charge a Lipo, I use the Li-Ion setting, because this is 0.1v lower, and so it does not go over 4.2 volts.

  17. Hey Akom,

    Great review of this product. I recently puchased one of these items on Ebay only it did not come with much except for the unit (of couse), DC power cable w. no connector, and a manual. . .all for .99 cents, plus shipping which was 20 bucks. Anyways, I need to buy a power supply for this unit but the one shown on the site where I bought this thing does not mention the size of the plug or the exact specifications of the recommended power supply. Would you by chance be able to take a quick close up pic of your power supply sticker and email it to me? It would really help me out in tracking down the right one. Also, since the device did not come with cables, do you know of a place online that I can pick these up. I know I should have probably researched some of this before I purchased the item but hey. . . I didn't. I just hope once I get the device mine will exhibit a simliar behavior as yours. I am happy to hear of others that have had success with this device. Thanks again, great review!


  18. The output cables you can buy on ebay, eg: http://cgi.ebay.com/Set-Wires-and-Cables-B6-Balance-Charger-/320409020387?pt=Radio_Control_Parts_Accessories&hash=item4a99dda7e3#ht_3051wt_907 You can make them yourself obviously also - banana clips, wire and whatever you want on the other end.

    My power supply is an old laptop brick that happened to be of reasonable voltage (under 16V seems to be a requirement) - I soldered a barrel connector to it. Taking a pic of it wouldn't help you. You can buy 12V switching power supplies for under $10 on Ebay - the only things you care about are: 1) Current. More is always better - eg 3A, 5A, should be higher than your desired charge rate. (even more if pack voltage is above 12V) 2) Connector. You can solder your own, but it's nicer to buy the right one - I believe that it's 2.5/5.5 for this one, but it may have been the next size down, I'll have to check - or you can measure yours.

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