An investigation about ripple current of Kunkin KP184

[vehiculeselectriques]

Hello,

mine is not functioning normaly, in CC mode 40A to battery load, it does not keep 40A constant current !
it goes immediatly down to 36A and less with minutes passing 
 

[electr_peter]

mine is not functioning normaly, in CC mode 40A to battery load, it does not keep 40A constant current !
it goes immediatly down to 36A and less with minutes passing 

I have not noticed such behavior yet, my unit was capable to sustain CC load of 40A from car batteries or power supplies.

What kind of batteries are you using, can they supply 40A? Are cables/connections sufficient for 40A? Can you check voltage drops across cables and voltage at battery terminals? If high resistance develops in a chain, it may not be possible to reach 40A.

[vehiculeselectriques]

thanks  i'm using voltage drop sense probes mode

my lifpo cell is capable of +200A no problem

copper wiring is 60cm long 2,5mm2 with Ø8mm ring connectors rated 25A ...
will try beefier cable and connectors 

[Everbrave]

Hello,

mine is not functioning normaly, in CC mode 40A to battery load, it does not keep 40A constant current !
it goes immediatly down to 36A and less with minutes passing 
 

If you post to the proper thread, you may get better answers; here, it’s about ripple

[electr_peter]

my lifpo cell is capable of +200A no problem
copper wiring is 60cm long 2,5mm2 with Ø8mm ring connectors rated 25A ...

Is it a single 3.7V cell? Current wise it could be sufficient, but voltage may be too low after voltage drop in cables and connectors.
DC load requires at least ~1-2V at the input terminals to reach full rated 40A. DMM can check this quickly.

[Everbrave]

I looked-up the prices: IRFP250N is around 1.5USD, IRFP264 is around 5.3USD

And there we go... 

Hey, at least they seem to have sprung for the genuine article.

I got in touch with the one of the developer and talked to him on several topics:
MOSFET type: they use IRFP250 for production and the IRFP264 when they are temporarily out of stock
Ripple: the modification made in board V7 to minimize ripple was to move the display 5V ground, since the display draws a significant amount of current. The ripple is at 100Hz
Firmware: FW2303 on V7 is not applicable to V6 (seemingly, different Beeper driver)

Hence, I repeated my ripple measurements using a low ripple power supply, Rigol 832, and optimizing the wiring in the set-up and obtained for my V6 Board a 100Hz (distorted) ripple value of around 2.8mV rms (see pic.). The high frequency noise is around 800uV.
I can live with this amount!

[torch]

Firmware: FW2303 on V7 is not applicable to V6 (seemingly, different Beeper driver)

I don't know what the earlier beeper sounds like, but the V7 emits charming musical chimes instead of an annoying beep. Quite a nice touch actually, and different chimes for different functions.

[Everbrave]

Firmware: FW2303 on V7 is not applicable to V6 (seemingly, different Beeper driver)

I don't know what the earlier beeper sounds like, but the V7 emits charming musical chimes instead of an annoying beep. Quite a nice touch actually, and different chimes for different functions.

I forgot to mention that the ripple value is almost independent of the load current and voltage, which supports the hypnosis that it is actually due to the display current. The picture I made is at 30v,2A load. Once the developer approves, I can post his exact reply.
I don’t know what the pictures you posted show, since it is not periodic! May be you can extend the time base until you capture the periodic 100Hz ripple?

[torch]

I'm not at home right now, but I'll try to remember to do that when I get back there.

[torch]

I don’t know what the pictures you posted show, since it is not periodic! May be you can extend the time base until you capture the periodic 100Hz ripple?

I got nothing. On the Siglent or on my old school analog Tek 475.

If I extend the time base to 2mS to match your capture, that brief pulse I showed just gets lost in the noise. The only way I can track it all the way to 2mS is to set the triggering to trigger on that specific pulse AND to use averaging to minimize noise. It seems to have a weird period of 68.5 Hz. It is definitely caused by the Kunkin; it disappears when the unit is powered off, appears at about the same point the boot reaches the model/version/ID splash screen and is there independent of whether the load is on or off.

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[Everbrave]

I don’t know what the pictures you posted show, since it is not periodic! May be you can extend the time base until you capture the periodic 100Hz ripple?

I got nothing. On the Siglent or on my old school analog Tek 475.

If I extend the time base to 2mS to match your capture, that brief pulse I showed just gets lost in the noise. The only way I can track it all the way to 2mS is to set the triggering to trigger on that specific pulse AND to use averaging to minimize noise. It seems to have a weird period of 68.5 Hz. It is definitely caused by the Kunkin; it disappears when the unit is powered off, appears at about the same point the boot reaches the model/version/ID splash screen and is there independent of whether the load is on or off.

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Well, that is interesting!
I can’t even explain where this pulse comes from; weird