Battery Medic - how to ID the REAL vs FAKE

methods

methods

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Joined
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Location
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Recently we ordered a batch of Battery Medic knock-off's. Hobby City was out of stock (though they are back in stock now) so we went to Ebay. As we were about to close the deal - my Chinese vendor warned me that I was buying the "poor quality" version :shock:

For a dollar more I was offered the "high quality" version -> so of course this sparked our interest. We ordered 29pcs of the high quality and 1pcs of the low quality.

View attachment 4


VERDICT?

Yes there is a difference
Yes one is better than the other - both in design and accuracy

THE GOOD ONE:
Red PCB
Green tinted LCD with sharp characters that are easy to read
Good spacing on the shunt resistors
Dead on accurate
Clean PCB

THE BAD ONE:
Yellow Green PCB
Grey tinted LCD with weak character display
Shunt resistors are packed in - clearly the layout guy did not know what he was doing
Pretty poor accuracy, +/-30mV on a quick test
Flux on the PCB

That is about all you need to know. I expect someone to chime in and tell us what version Hobby King is carrying. We of course will be using and selling the quality version here at MethTek. They will be available just as soon as we characterize them and figure out what sort of "value added" modifications we want to do.

I did a quick test with a 4S pack.

Fluke 87
4.083V
4.15V
4.16V
4.15V

Fluke 87V
4.082
4.147
4.158
4.152

GOOD UNIT
4.08 Perfect
4.15 Perfect (rounded up)
4.16 Perfect (rounded up)
4.16 Good (3mV error then rounded up)

BAD UNIT
4.07 OK (rounded down, so off by 10mV)
4.15 GOOD
4.19 BAD (High by 30mV)
4.12 BAD (Low by 30mV)


That was by no means scientific - but that is all I need to see. Exactly what I expected to see from what I have read. If you have one - its fine... just understand its limitations.

Also realize that precision was not measured here (accuracy is how close it reads, precision is how constantly it reads). Both accuracy and precision are affected greatly by heat... but that is a test for another time. For the record - those (quite beautiful) results were not engineered in any way. I literally grabbed the top two units out of the box, grabbed a battery off the shelf, grabbed two DMM's, plugged in and wrote down numbers. (i.e. I did not pick a reading that would make the bad one look bad... or try to find worst case)

Here is some pRoN for you


IMG_20120209_113717-1.jpg
IMG_20120209_113850-1.jpg
View attachment 1
IMG_20120209_114113-1.jpg


MethTek at your service.... buying crappy stuff so you don't have to :p

-methods
 
I just bought 4 from HobbyKing like 2 days ago, still wating for them. Any chance they can be the fake ones?
 
****ing awesome, Methods. Thanks for doing some footwork here.

http://www.hobbyking.com/hobbyking/store/__10328__Hobby_King_Battery_Medic_System_6S.html
The hobbyking unit *looks* like the "good" one, just going off these pics, but we'll see.

The eBike world has needed a decent quality standalone balancer to make bulk charging vastly easier for... how many years now? :) If you can put lipstick on these pigs, you'll be a real american hero(tm).

I wonder if the tolerances of components ( IE resistors ) is just awful or what. Will stay glued to see what you can do with these.
 
Hey Methods,

Thanks for the info.

I got same as your Battery medic with green LCD and red PCB in back as similar your GOOD Battery medic picture.

I bought 14 dollars with free shipping from ebay under HKRC (seller name). He is excellent guy and easy communication.
 
I have a HobbyKing labeled one that is about a year old, mine is a third variant but very close to the "good" one above, same color etc but not identical. I'm guessing methods is just a newer revision and I have an older "good" version. Waiting on a better DMM to check accuracy of mine.
 
Yep - my guess is that Hobby King will carry better units (though I would not be surprised if some of the early units are of poor quality...) When Hobby King took over the Chargery BM6 they ruined the design. My very old units were right no (Chargery is a good company) but when I later bought a few form Hobby King the readings were all over the place. Now - I believe they had enough complaints that they brought the quality back up.

I suspect that when Hobby King first starts carrying something manufacturers are going through some growing pains trying to meet the heavy demands of mass production.

If anyone has other variants - please post up a picture and short description.

When we have more time we will do a more comprehensive test.

-methods
 
I just recieved 2 from hobby kind that seem to be yet another variant of the battery medic
View attachment 2
Green screen like methods "good one"
WP_000455.jpg
Green pcb like the "fake one" :?:
WP_000457.jpg
The layout of the back of the pcb looks different than both of methods.

my readings of a 6s pack
fluke 88
4.16
4.15
4.17
4.16
4.15
4.16

medic 1
4.16
4.15
4.16
4.16
4.15
4.16

medic 2
4.15
4.15
4.15
4.16
4.14
4.16
 
damn, just bought 2 of the yellow ones. anyone know of sources other than HK for the 'good ones'?

my tests havent been as accurate (using a cellog 8 as a control + some rather long wires :? ) but for me the 1 yellow ive tested proved pretty good, balancing to within ~10mv, even getting 1 pack to less than 5mv, lower than the 6mv accuracy of the cellog. (so it could be as much as 17mv worst case scenario). However, it did have a 20-30mv difference between it and what a red BM balanced to, slightly over-discharging the pack vs the red slightly under-discharging it (~4.095 vs ~4.105 for yellow vs red respectively). both had been modded with larger parallel resistors for faster discharge

what kind of upgrades are you thinking of adding meth?
 
Looking at the back of that Hobby King model I am going to guess that the balance current is lower. This may actually help improve accuracy...

Since you have a fluke - I think you and I need to get a measurement of the average shunting current. We can do this several ways:

1) Measure the shunt resistance, then measure the *average* voltage developed over the shunt during discharge (easy and close method)
2) Directly measure the current by inserting the meter inline (best method)

I am sure there is some sort of duty cycle going on so measuring the shunt resistance and dividing by the cell voltage will *NOT* result in an accurate estimate.

Depending on the frequency of the duty cycle the Fluke will probably average it for you. IF you get some jumping on the measurement you need to try a different measurement.

-methods
 
I'll get an inline reading later tonight and post the results.
 
Ok -BALANCE CURRENT DATA

Fist off - this is poor test data - but hopefully we can get a *relative* comparison

FLUKE 87V
DC mA setting

4S battery wired up
Fluke inline with line 5 - the most positive line
4.15V on the cell being tested

BAD UNIT
quiescent current is 861uA (on that line - this says nothing of the total quiescent current)
Discharge current is 367mA (NOTE: This is turning on and off... actual average current will be much lower !!!)

GOOD UNIT
quiescent current is 917uA (on that line - this says nothing of the total quiescent current)
Discharge current is 373mA (NOTE: This is turning on and off... actual average current will be much lower !!!)

The Duty cycle runs at about 0.45hz on both units. The frequency really does not mean anything though.... what is important is the % duty cycle which appears to be about 70%

Correcting for duty cycle we have:

370mA * 0.70 = ~260mA

So these units run at about 1/4 of an Amp when the "discharge" button is pressed with 4.15V present

Again - not scientific data but data none the less.

NOTE: The HZ and % functions on my DMM were used to capture this data... this is not as reliable is using a scope because there is a certain level of assumption involved. A better test is to watch the discharge function on a Scope... but my awesome 4ch 400Mhz scope caught the leaking cap disease and died. :(

-methods
 
So what does this mean?

250mAh is the balance rate
That is 1Ah in 4 hours

If your pack is off by an Ah you are hurting bad.... so my guess is that these things can correct just about any problem you have in a few hours. Just hook them up and go eat dinner.

-methods
 
Mathew and I broke out 6 of these and did some testing unit to unit.
The results are very good :p

Out of the 6 units they all displayed the exact same readings!
Even better... one channel was toggling between 3.68V and 3.69V. Across all 6 units 4 of them were toggling and only two had settled on 3.69V.

This gives me great confidence - these things are very consistent. Way better than I expected - and way, way better than many of the dongles out there.

-methods
 
Don't forget to mention it's in your best interest to ensure the balancer is in a well ventilated area as they do get very hot if left running for a while.

Just read another thread where the seller I got my balancers from is currently selling the bad ones so I will not recommend him. :) Hope more people get the good ones and are not shafted with low quality knock offs.
 
Methods,
When you are ready to be selling the Battery Medics I'd like three (3) of them.
thanks,
Joe

edit : bah! that was supposed to be a pm.
 
I suggest setting them so that the resistor side is up. Even the slightest breeze in the room (ceiling fan) can make a huge difference.

-methods




FastDemise said:
Don't forget to mention it's in your best interest to ensure the balancer is in a well ventilated area as they do get very hot if left running for a while.
Click to expand...
 
We need stickeys here on ES and this should be one for sure. Thanks for this guys!
 
yeah I got two bad ones recently from ebay. green pcb. Difference of 50mv between this an my one red pcb medic :(. I want another two good units for my 18s3p setup :(. If you sell any methods let me know I'm in.
 
I have a dozen of them, all form hobby king, there can be a significant range of accuracy between units...

Not sure if this is documented somewhere ( I think i recall reading it at oen point.. ) , but anyone got a link to details for the non-engineer on how to install a on/off switch on these so they can remain hooked up to ballance leads without being a parisite ? will cutting the negative most wire in the ballance plug do it ( using a small switch ) ?

I usually try to set them up vertical when in use, to let the heat out.. vs horizontal with screens facing up.
 
Nice work methods. Another way to potentially tell them apart is some say "made" instead of "mode" on the bottom left button.
I'll have to start checking my sources, I've used several and noted that some come in a plain white cardboard box, some in a nicer looking blue and black coloured cardbox box with a picture on the frontand some in a clear hard plastic case - that almost always arrives cracked from postage!
 
Ypedal said:
I have a dozen of them, all form hobby king, there can be a significant range of accuracy between units...
Click to expand...

These are different than the units from hobby king.... We are seeing perfect consistency unit to unit.

We just finished the first soak test.
4S 5000mAh hard pack
Charged up to 4.2V/cell

Discharge Balancer set to 4.00V

After a few hours we came back to read:

Good Medic
4.00
4.00
4.00
4.00

Fluke reads
3.995 (perfect - considering LSB rounding)
4.004 (perfect)
4.005 (perfect - medic reads <4.004 so rounded down 1mV difference)
4.003 (perfect)

Tell you what... I will open up 10 of them and hook them up to 10 different packs and set them all to 4.00V and tomorrow morning we will see what is really up :mrgreen:

To be continued.......

-methods
 
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