The Mystery B6 balancing LiPo/LiFE/NiCd/NiMh/Pb charger (review, sort of)
Posted by Akom • Tuesday, October 21. 2008 • Category: Reviews
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.
Results:
Charger claims:
Voltage: 12.58 Cells: 4.19 4.20 4.20
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.
Overview
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.
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.