warning SkyRC 4P3 charger - voltage too high Phantom 3 Batteries error

jamesb72

jamesb72

Member
I bought this very expensive 4 way charger as a Christmas present to myself, it appeared to be a clone of the Smart PowerCharge 4 way charger which is even more expensive and hard to get in the UK, so a slightly less expensive version which automatically charges/discharges to storage voltage appealed to me.

Unfortunately it outputs much too high voltage (18.8v - should be 17.5v) so causes over voltage warnings on all my Phantom3 batteries video shows this at 7mins in. I have not left the batteries charging to find out what happens as potentially charging to 4.7v/cell could be bad !

I contacted SkyRC a couple of weeks ago, they refuse to accept this is a problem ;(

 
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theGreenOrange

theGreenOrange

Member
A typical lipo cell has a nominal voltage of 3.7V and charges to 4.2V. They should not be discharged below 3.2V (3.0V might be ok). I don't know anything about those proprietary DJI packs, but a normal 4S lipo battery should stop charging at 16.8V. Are the DJI ones really 17.5V?
 
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jamesb72

jamesb72

Member
SkyRC have come back with this explanation, which doesn't make sense to me - why would their be a voltage drop on DC-converter, surely they would drive to target voltage (18.8v) just at reduced current, which would still overcharge LiHV 4S lipo past 17.4v ?

"charging system adopts Buck Converter, if we use 17.4V in the BUCK converter, the battery will not be fully charged."
 

theGreenOrange

theGreenOrange

Member
It appears that the DJI batteries include an IC which may internally drop the voltage sent to the cells during chrging? It looks this way to me because the batteries have an on/off switch, LEDs, diagnostic indication, etc. Just an educated guess, as I am not familiar with "buck converters".
 

jamesb72

jamesb72

Member
I suspect the DJI battery IC just monitors voltages, I would be surprised if it can disconnect the terminals or drop voltage as batteries don't get warm during charging or make any click noises you'd expect from a relay.

The DJI and non-DJI chargers I have which work normally all measure 17.5v which is the final charge voltage of the 4S LiHV cells, which makes more sense to me.
 


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