Review of the Li-Pro Imax 6 balancer/charger

[Tim Mackey]

I recently purchased this IMAX B6 to add to my growing collection of chargers and balancers, and despite having read online some concerns about it's accuracy, at the price charged by a certain H/K hobby store ( £35 GBP equivalent ) it was worth a try. My standalone Flightpower "V-Balancer" did not work satisfactorily with my Astro Flight 109 Lithium charger, but was OK when used with the propeak prodigy. My budget JP "LiPo 2000 Pro" charger was completely devoid of any information during the charging process, but having checked it a few times against a DVM, I was suspicious of its claimed accuracy, so it was time to see what the latest generation of smart balancer/charger combos had to offer.

I lashed up a test rig, which comprised of the unit itself, and 3 seperate dvms.

2 of these meters were set to measure voltage at the battery terminals, and the third was set to measure current flow during either charge or discharge functions. I used 2 meters for voltage to eliminate errors in accuracy, and indeed both meters showed slightly different readings as expected, so I averaged out the 2 readings to arrive at a fair reading. You can see the setup in this picture

I first tried a straightforward charge of a small flightbox 12V lead acid ( PB ) battery which was showing around 12.3 Volts on the bench. The IMAX was programmed to charge it at .5A and according to the booklet ( not a very comprehensive instruction book I have to say, but I have seen much worse !! ) the charge should terminate when each cell reached 2.46V. On a 12 v battery ( 6 cells ) it should therefore stop at 14.76V. On initial hook up, the meter showed 12.31V and the IMAX display showed 12.40, an error of +.09V.

After 15 minutes a further photo was taken, and the readings were -

METER 12.60V  versus IMAX 12.67 +.07V  See Picture above.

After 30 mins the results were as shown here:

 I monitored the process for 1 hour.

The IMAX stayed true to an error of approx .06V throughout, and the current was accurate at .50A - .49A throughout with 502 m/a delivered during the 1 hour charge time. Photo here

 I then let it do its thing until the alarm sounded to signify the end of process, and the meter showed 14.23V and the IMAX displayed 14.31. ( + .08V ) This was all perfectly acceptable, and I have no doubt that the final terminal voltage was lower than claimed due to the age of the battery.

The next batch of testing was on a 4000 m/a NiMH cell, and will follow shortly.

I then did a 3s LiPo “storage charge” process, and this will be the third posting, followed by a summary and general observations.

[Tim Mackey]

Ok so on to the NiMH.

I chose the discharge program, to see if it would terminate at the correct voltage, which should be 1.0V for each cell in the pack. I only have individual 4000 m/a cells these days which I use in onboard glow systems, so I hooked one up and set the IMAX to discharge at 1A.

On hook up, the cell was showing 1.34 on my meters, and IMAX showed 1.27 ( .07v difference )

The current was 1.03A on the meter, and 1.0A on IMAX. After 1 minute things were as shown here

I then checked things again after 13 mins ( my timer went off early !! ) and it showed this

It finally finished with its good loud alarm at just under 2 hours in total. The final readings were …

METER 1.16V and the IMAX displayed 1.0V ( difference of .16V ) The Imax also displayed the total current drawn as 1998 m/a, which is quite accurate, as it was discharging at 1000m/a per hour for around 2 hours. The imbalance between my meter readings and the IMAX display was approx .15V throughout. This is only 15 one-hundreths of a volt and the current readings remained similarly accurate. So all in all, I reckon a pretty good result.

I have done, so far, 2 X 3s LiPo tests, comprising of a discharge process at 1.0A ( the highest I could set on the IMAX which is a bit limited ) and then a "storage charge" which is a program feature which is designed to stop the charge process at 3.85V per cell instead of the normal "full" figure of 4.2V. This is the optimum storage level recommended by most LiPo suppliers, but is something that I have to say, I have never done up to now....mainly because of the complications of doing so without a charger such as this !

I intend to do 2 further tests in LiPo mode, which will consist of one "balance charge" using a Hextronic 3s 2500 m/a battery, which happens to have a matching JST plug, and then one final program of a small 2s pack which I use in my Twister Bell indoor heli. This pack is one I modified by fitting my own balance plug. Incidentally, the IMAX comes ready fitted out with JST style balance sockets for any battery with matching balance plugs for 2s through to 6s packs.

Theresults of these final tests will be posted over the next few days after I have had a chance to perform them.

[Myron Beaumont]

Well done Timbo

If you write an autobiography you must call it " I'm charging ahead  and want to meter"( meet 'er)

[Erfolg]

I to must congratulate you Timbo.

I also have had concerns, regarding what is happening with my set up. In the past you have reassured me with your considered view of the results I have obtained.

I am looking to purchase Imax B6 ,within the UK or a Foreign web (site where the postage costs are not to large). At present I am still debating the offering at BRC, you have previously mentioned, the JP Lipo plus, which is obviously a badge engineered rendition of the same thing.

I am hoping that someone such as Giant Cod or Robotbirds (as they both organise their own local suppliers) will import and sell the Imax direct, missing out the handling/wholesaler roll of JP, thus achieve even keener prices.

As to the alamists on some other sites, I would suggest they learn to understand the significance of the values obtained from their instruments, and what are normal functional accuracies, repeatability and performance. I am suspicious of those who claim their measuring instument are certified and calibrated (unless they are a large industruial organisation/research establishment). By whom. The National Physical Laboratory (NPL), if so when and what are the calibration results of their equipment. Did thet use a temperature controlled etc. workshop?

Please keep us all informed, again, excellent work and iniative.

Regards

Erfolg

[Tim Mackey]

TY Erfolg. Thats exactly why I used 2 x DVMs to get a truer readout of the figures.

The next installment will be early next week - building, and entertaining guests is occupying my time at present.

[Tim Mackey]

Ok so here is final section of the review - LiPo balance charge, and then "fast charge" and finally summary. The same test rig was used, with fresh batteries in each of the 3 meters.
First off I setup for the “balance charge program” - this appears to be a time controlled charge of 2 hrs, where the charge current is set manually. I first discharged the 1200m/a 3s pack to 10.25V and then rigged up the unit. ( I chose the normal 1xC rate of 1200m/a ) but the charge current drops right off to trickle after 1 hour when the pack has reached an acceptable level. Charging then continues at this low level until the cells have balanced satisfactorily.  I deliberately chose a pack whose cells were unbalanced to begin with - the individual cells were checked manually just before starting the process, and were…

CELL 1 = 3.97

CELL 2 = 3.07

CELL 3 = 3.18

Picture 1 is at 15 minutes into the process - and shows 12.38V on the meter and 12.48 on the IMAX, with matching current displays. Total charge in so far……299 m/a.

The cells were checked ( by simply pushing a button on the unit ) and read.....

CELL 1 = 4.14

CELL 2 = 4.14

CELL 3 = 4.15         ( remember..... clicking the image shows it full size )

This is good balancing so far, although there is a small discrepancy with the units own claimed voltage of 12.48v as these 3 figures total 12.43v - not huge…but slightly odd ?

The next test point was at 30 minutes, and the picture tells it all.

I did check the cells again ( but forgot to photograph ) and they were now showing…

CELL 1 = 4.18

CELL 2 = 4.18

CELL 3 = 4.18    which equals 12.54.

The IMAX voltage shows 12.60, but my own meters showed 12.55 - Excellent!

Note also at this point the charge current has dropped off to .88A.

Total current put in so far is 579 m/a.

[Tim Mackey]

The next shot is at 55 mins and again picture is here - ( slightly off focus - sorry ! )

The pack is now considered full, and current has dropped to just 240 m/a. The cells however are slightly off balance, and the unit continues until termination at the 120 minute mark, where 2 pictures were taken showing final voltage, and cell balance figures of..

CELL 1 = 4.20

CELL 2 = 4.20

CELL 3 = 4.20

 

Spot on as they should be, and the IMAX shows 12.59v, and my meters show average of 12.48v

Close enough to full, 908 m/a put in ( remeber the pack was not empty to start ) and the slight difference in voltage is probably down to immediate small drop off after peaking. 

All in all, a very good result     Next up is "fast charge" - New posting  as this bloomin forum still restricts me to a miserly word count - when is this gonna get fixed David ??

[Tim Mackey]

OK so here goes for the final leg

The chosen process here was "LiPo fast charge". This is slightly mis-leading, as it takes the normal 1+  hour which we all use on our liPos  - DONT WE !! I first discharged a 2 year old, well used, small 2s 800m/a pack from my twister bell heli. I dropped it right down to 6.3 V ( pretty well empty ) using the IMAX discharge feature, which it performed perfectly satisfactorily. At the end of discharge however the cells were quite badly out of balance at…..

CELL 1 = 2.84

CELL 2 = 3.46   So it appears that during a discharge process, balancing is not very key?

 I then hooked it up at 800m/a on “Fast Charge” and took the first shot at 6 minutes here

Next was 30 minutes,

I also took a cell reading, and was pleased to see them each at 4v !

 
Next shot is at 45 minutes, 600 m/a put in so far, and throughout all the stages, input charge current has remained steady at exactly what I set = 800 m/a. Voltage variation between my averaged meters and the IMAX display has been negligible at around .06V

Final 2 photos show both the termination voltage at 8.40 ( which is spot on ) and the individual cell readings of 4.19V each - again pretty much perfect.

Total charge put back in was 734 m/a  - quite good for a 2 yr old pack I reckon!

 So to summarise.....

 

[Tim Mackey]

This is a great unit for the money. OK so I bought from Hong Kong - which I do a lot of, and if your not comfy with that, well several UK dealers are selling these ( and other clones of the bantam which this is really ) for quite keen prices. I have found it pretty easy to use, although I do have 6 different LiPo chargers / balancers in all, which I have used a lot over the last 5 years, so I guess I am fairly experienced. Having said that, although the booklet is not brilliant ( it leaves out some of the terminology used in the display LCD screen ) it is adequate. The unit itself is verstaile, well made, and has only a few limitations considering its budget price, such as the current setting for discharging is limited to 5 watts, which means that although it states discharge currents of up to 1A, when doing say a 3s Lipo you will find it will NOT go above .5A due to the wattge limit. ( 12V X .5A = 6WATTS )

However, this is small niggle, and the other features far outweigh it. I have not finished experimenting with it, but a few worthy of mention are - you can program into memory up to 5 different types of batteries - and when you come to charge them, simply select the right memory point, and all your settings are automatically invoked. Input voltage can be from as low as 11.V right up to 18V, and you can set an alrm to warn you of low input V, to prevent your source battery running low - although I run all my chargers at home, on simple and almost free, home made PSUs. Storage mode settings, cycling of nickel and PB batteries, and an optional extra accessory allows you to connect a temperature probe to monitor your pack temperature, and terminate the process if a thresold is exceeded, etc etc.  Its verstaile, its inexpensive for its ability, and I certainly recommend it

[Mike Wyatt]

Well done, Timbo.  An extremely interesting and informative analysis/review.

 I've never heard of "storage charge", although I did hear say that LiPo's should be stored at about half charge - I generally charge mine after getting home form a flying session, then I don't forget to charge them before flying (as happened yesterday - when after a 6 minute flight, without caning it - a 3300 mAh 4s pack took 2975 mAh - it's known as sailing close to the wind !!).

Going to be in UK later this month, and may very well get one of these LiPro gizmos.

Haven't done too much flying af late, as November has given a new meaning to the expression "Rainy day".  Finished trimming out an EFlite Diamante with EFlite Power 32 motor and 4s pack - what performance.

 Go well.

[Tim Mackey]

Hi Mike and thanks for the comments. The storage charge level is, I think, only "necessary" for fairly long term storage such as perhaps a few months over winter or whatever, and takes them to around 90% of full. This is also advisable for when you are charging them at normal room temperature, and then taking them out into the cold weather to use. liPos should not be fully charged to 4.2V per cell when the temperature is low, as this shortens their life, and is the reason that packs are shipped only partially charged due to the very low temperature they are likely to encounter in a cargo hold.

I too generally just fully re-charge straight after flying, then they are pretty much ready whenever I need them.

[Mike Wyatt]

Hi Timbo

Interesting what you say about LiPo's and low temperatures.  Fortunately, the mercury very seldom falls below 15C here, and in fact winter is far and away our best flying time, although Aug/Sept?oct tend to be the "windy months".

Omitted to mention that I joine the "Spekky Brigade" over the weekend, and used the gear in the Diamante yesterday. 

[Tim Mackey]

Well done -good choice IMO

Incidentally where are you..... 

[Chris Bradshaw]

Hi Timbo

So how would you rate this against something like a propeak Prodigy ?

Or your other chargers for that matter

[Mike Wyatt]

Timbo

South Africa - Durban, on the Indian Ocean coast. 

[Tim Mackey]

Lucky blighter !

Chris. The pro- Peak prodigy has served me well for several years and is a very good basic charger.

However, it does not have the facilities that this one does - in fact none of my other chargers have, even the Astro flight 109 which cost a small fortune a few years back is limited. having said that the A/F can charge/ discharge at a higher rate, and handles more cells than the B6, - but thats all it does - charge discharge! 

As I have gone exclusively lipo now for everything including all radio gear, I was in need of more features, especially as the modern packs are all balance capable.

I think as I said, it is an excellent and versatile unit especially for the money, prividing you are patient about discharging ( and why would you not be ? ) and that you don't plan on using huge capacity 8 cell and above packs in a hurry

[Chris Bradshaw]

Sounds good to me Timbo.

I was thinking about getting the e-Station BC6. Has all the features of the one you reviewed above plus a built in transformer and balancer. All for less than £100 too

[Tim Mackey]

£65 sounds a lot for a transformer -this is the same charger otherwise!

[Mouldy]

Bought a BC8 and find it excellent. However if Id have seen this one Id probably have bought it instead!

[Royden Baker]

[img s=60¬50]http://www.modelflying.co.uk/members/images/5044/homer.gif[/img]

Hello again Timbo

You really put some effort into your reviews!! I cannot claim to understand all of your excellent scribing (I am a production engineer), although I do have an understanding of electrical technology which is exponentially reduced when it comes to electronics!

Because it is loosely relevant to your review, I wonder if you would be kind enough to give me some advice regarding the subject of my glider and the li-po and charger required.

I had a long conversation with a guy at Inwoods who seemed to give me good advice which did not seem geared to selling me something (which threw me a little), but with my memory as it is I would appreciate advice written where I can refer to it.

The battery I believe is not a problem, but he said if \i had a charger, it might suffice and I would only need the balancer. I duly enclose a picture of the charger for your perusal and advice.

The next thing is the speed controller. I have a Ripmax EXTRA 50 which he said would do the job, but he also said it had a little switch on the end that would need to be moved sideways to the other position.

WEll, mine has a little black socket sticking out of one end which you can pull out to reveal two very tiny (0.5 mm x 0.3 mm rectanular section) pins. This plug and socket does not move sideways, so that raises the question of whether I have the right controller.

Finally, I suppose if I last that long I might wish to move on to a higher voltage at some point, so even if this charger I have is suitable for a 2s li po, it might be useless for a 3s.

Really finally, what does the s in li po speak refer to - it seems to suggest the word cell?

[Royden Baker]

Hi again Timbo

I made the usual mistake of forgetting to insert the attachment.

Now I have to apologise again as I do not seem to have mastered the art of copying and pasting images into this forum.

My charger is a GWS from Grand Wing Servo-tech.  It has a 4 to 6 cell and 6 to 12 cell switch and a pot meter to control the fast charge (the meter reads up to 6 amps).   on the front it says GWS-MC2002.  It also says NI-CD & HI-MH DC U-CON CHARGER.

I hope that helps, although you could probably tell me what it is from half that information!!

[Tim Mackey]

Royden ,this is off topic, so I will read and respond to your post a little later this evening with answers in a new thread called "GWS-MC2002" over in "electric flight".

[Doug Ireland]

Hi Timbo,

Very impressive review, very informative.

You mentioned the input voltage range of between 11 and 18vdc in the review but did not mention the max current. I would like one of these chargers and knocking up a power supply for it would not be too much of a problem providing I knew what rating of transformer to look for.

Thanks in advance.

[Chris Bradshaw]

You can get  good cheap power supply by using one from a pc.

Output voltage is usually 3.3v, 5v and 12v 

Just looked at a brand new 550W one for £18

[Tim Mackey]

I run all my chargers off any of 3 PSUs in my workshop -all ex PC and cost nothing - see here for one of them - this one is hooked up to my Astro Flight 10, but the others are all prettty much the same.

My local PC shop is always chucking out duff cases, and the PSU is often fine. You usually need to tie down a 5V line somewhere in order to get the 12V output working, but the whole job is a half an hours work and a few pence worth of resistors. Here's a link to one of several "how to do its"

free home made PSU

It really is simple and you dont need to be a electronics guru - honest!

Heres the one thats hooked up to the IMAX B6 - I also use this one for charging my on board glow NMH cells ( 3v output at 250 m/a )

The IMAX charger is capable of up to 5A output, and the specs say max charge power is 50 Watts.

Most of the PSUs are good for at least 8A constant on the 12 V line, and even an older 200Watt unit will be fine for what we need

I seem to remember they sold the chargers as "motorcycle accessories" as they are switcheable for 6v or 12v