Not a XK X251 review ( This is battery related ) - RC Groups
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Dec 08, 2017, 10:53 PM
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Not a XK X251 review ( This is battery related )

Hmmm , Yep ! ( I blame those sales )
I got me a XK X251 ( See Pic 1 ) , but this post is not about the quad ! But rather the battery and charger it comes bundled with ..
As well I am becoming a little disillusioned with many of the reviewers that are sent product on a regular basis .
So I will just have to take on the roll of the DEVILS advocate ...

If you look at Pic 2 you will notice the battery only has a balance plug , and the supplied 2s charger ( Pic 9 ) does NOT balance charge .. In fact it does a horrible job of charging and I would rate this charger @ POS ( Pic 9 ) . The only other charger I had capable of charging this battery is a half decade or more older charger that came with one of my first 450 heli bundles ( Pic 10 ... and yes it was on special ) . Now this charger also does not balance charge , but does a better job than the supplied charger ( Pic 9 ) .

I found the situation some what intolerable so decided to add a plug so I could charge VIA my hobby charger ( Pic 8 ) . The first thing to do was get out a sharp ( Thats very sharp folks ) knife to peel away the coverings of the supplied battery ( Pic 3 ) . What I had to do was get to the positive and negative terminals so as to solder on a plug . ( Pic 5 ) Generally I dont throw away plugs , I sort of collect them for just in case circumstances ( like this one ) . Pic 6

Pic 7 shows the completed job . We all know how to solder and we all know not to short the lipo ( Right ? )
Pic 8 shows the lipo being discharged .

So thats where I am at right now , discharging the battery .
Whats important is that I can now BALANCE charge the battery ..

I have to Po Po XK for this one , the supplied charger overcharged one cell and created a some what serious imbalance in the battery . If you did this enough times there could be a problem . ( Could )
As far as the battery and charger go , it is my humble opinion that XK has used poor judgement ... I sincerely hope that nothing bad happens as I am some what concerned by this ( hence the post ) .

The battery and charger bundled with the XK X251 is a thumbs down from me ..
Last edited by old4570; Dec 08, 2017 at 11:15 PM.
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Dec 10, 2017, 08:40 AM
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Ok I have done some discharges and can confidently say this battery is poorly cell matched ( Capacity ) ..
After some 3 discharges ..

0.5A discharge x 2 = A serious imbalance kicks in at around 3.7v
1A discharge x 1 = A serious imbalance kicks in at around 3.7v

Once cell is about 3.67v and the other is 3v = This is bad ju ju folks .
The cells in my battery are very poorly matched .
At least my hobby charger kicks up a warning when one cell reaches 3v and stops , otherwise it might go by the Voltage and damage one of the cells ...
Damaging a cell in a lipo could = Puff the magic Dragon !

So this brings to light a some what of a flaw in the X251 design !
How can you run a battery monitor ? If the quad uses the balance plug to power it ?
Some one needs their beehive kicked !
( As well better batteries for the X251 )

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