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01-14-2015 | 02:53 PM

#16

Yosh70

Tech Master

iTrader: (17)

Joined: Jul 2009

Posts: 1,618

From: Sask. Canada

Quote:

Originally Posted by Brandon1977

And all I'm saying is, rather it be a 2s or 4s, it should charge at 6A not 3A. Which would lead me to believe there's an issue with the internals of his charger

I hope you dont think that charging requirements for different cell count lipos are all the same....try a friends 4/5 or even a 6S lipo and see what amperage your charger can output.

01-14-2015 | 03:56 PM

#17

Dave H

Tech Champion

Joined: Oct 2007

Posts: 7,342

Quote:

Originally Posted by cutting42

Well if we are being precise (or pedantic ;-) ) the max voltage overstates the requirement as the LIPO charge cycle is only done at MAX amps for the early part of the charge as you can see by watching the display during charging. By the time the batteries get over the spec voltage (3.7v per cell) the charger does not dish out the full amperage so in reality calculating as I did is pretty accurate which is why the calc max amps for 4s was the same as the observed - 3.3A

We are kind of splitting hairs here, we agree on the premise that the 50W charger cannot deliver 6 amps into a 4s battery but can into a 2s.

All of the lipo chargers I have, of several brands, charge at full amperage all the way up to 4.2 volts per cell. Then begin the CV portion and start decreasing the amps. For the vast majority of the charge cycle the cells are above the 3.7V nominal, a lot of it is above 4V even. The voltage rises quickly and significantly when charging.

Nominal voltage is intended as a representative voltage during discharge, while under load when the voltage sags or drops. Opposite of charging.

If the amps are dropping around 3.7V per I suspect it is due to power limiting, as correctly alluded to by previous posters. A 80W charger would not be able to maintain 6 amps on a 4S to full voltage. Would still charge it, and probably work fine for many, but it would take longer and is under powered to a degree.

01-14-2015 | 05:13 PM

#18

cutting42

Tech Regular

Joined: Mar 2013

Posts: 261

From: London UK

Quote:

Originally Posted by Dave H

All of the lipo chargers I have, of several brands, charge at full amperage all the way up to 4.2 volts per cell.

I have not seen this, I see a peak of max amps initially dropping quite quickly and way before it reaches 4.2 volts. I have the Hitec 4 x 80w charger so will take a look at it tomorrow at race night as I am intrigued now. No 4s batteries to charge just 2s but the principle should be easy to see.

01-14-2015 | 05:45 PM

#19

Dave H

Tech Champion

Joined: Oct 2007

Posts: 7,342

Quote:

Originally Posted by cutting42

Please do and let us know. With 2S packs it should be a good test.

01-15-2015 | 10:36 AM

#20

cutting42

Tech Regular

Joined: Mar 2013

Posts: 261

From: London UK

Quote:

Originally Posted by Dave H

Please do and let us know. With 2S packs it should be a good test.

I did video it to confirm but you are correct, the charge current remains at Max amps set until 4.2v is reached and then rapidly drops off as the charger goes from CC to CV. Interesting, I had never monitored it closely before, you learn something new every day!