Q: 0610iDUO - 3s FP - Bouncing Amps?
 

Very interesting issue I'm having. When charging my 3s FP 5k pack, the charging amps are set at 5A, but it's bouncing all over the place between 4A and 6A. I switched it to the other side of my DUO and it's still doing it. My 2s FP 5k pack is charging just fine on either side as well as a few other lipos I've tested. It's just this one pack.

I have tried unhooking the power supply to alow the charger to reset, but that didn't change anything. I have the latest firmware installed.

I know I have the settings right.

Quick update: After about 5 minutes of charging, it's still bouncing a tiny bit, but now it's only between 4.9 and 5.1 which is significantly better, but still a little odd.

Any ideas on what could be causing this?

http://i192.photobucket.com/albums/z...rgeproblem.png

Pulse charging? Depending how long the bounce timeframe is, the charger could simply be measuring no charge vs charge voltage differences (if the difference is too great, the setting may be wrong). Aside from that, I couldn't say as I don't have that charger to see for sure.

I assume your power supply is holding up to the load ok? I can see it cycle if pushed at or over its rating, or if the load is causing the voltage to drop below the charger's min input...

Thanks for the quick reply, Brian.

The power supply is 35A. I've charged 6s2p a123 at 10A with no problems as well as 5s lipo at 8A with no problems. Right now I'm only charging 3s lipo @ 5A.

I know the settings are correct. The same settings worked earlier today without a hitch. Man, this is just really odd. Right now it is charging as it should, so maybe it was just an odd hiccup. Very weird.

Here is the charge graph now. You can see the chaos for the first few minutes and then it's been great since. It will be interesting to see if this happens again.

http://i192.photobucket.com/albums/z...geproblem2.png

Just for fun, here is the final graph of the charge for anyone who'd be interested to see it.

http://i192.photobucket.com/albums/z...geproblem3.png

Well, in the last pic, the overall curve looks right: constant current charge and voltage rises slowly until 4.2v/cell, at which time the voltage is held constant and current falls to a set shutoff value (0.1C?). The pulses must just be part of its measuring algorithm. Either that or the data capture feature isn't working quite right.

I would hook an analog meter up across the battery to see if there are in fact pulses. I say analog because the needle can sometimes show brief changes better than a digital meter due to sampling rate. If you have two meters, hook the other in series with the battery to measure current for the same reason.

I have no idea what that "noise" is at the beginning of the charge though. Maybe the charger varying the rate and monitoring the resulting voltage to ensure proper settings? If the charge rate is too high for a particular cell, there will be a large voltage difference between charge and no charge. That's the only reason I can think of...

I have that same charger. I guess I have not looked into it, but I take it you can have it hooked to a PC while charging and see these graphs?

Thanks again, Brian.

The noise at the beginning is definitely atypical. Here is a full charge of a 2s 8k pack. This is what is normally looks like. The Amps just go straight to where they're set and stay there until it hits 4.2v/cell. Well, they do go to zero consistently as part of the charging algorithm, but you know what I mean. :-)

http://i192.photobucket.com/albums/z...2s8kcharge.png

I will definitely try the meter, but I only have a couple of digital multi-meters, so I'll just do the best I can with them.

Thanks again!

I'm sure you know this, but measure voltage in parallel with the pack, but current in series with the pack. Not trying to insult your intelligence, but I've seen numerous cases where someone attempts to measure current by placing the leads in parallel to the load. In case you don't know, a meter has a VERY low resistance (just enough to measure a tiny voltage drop to calculate current) and that basically shorts out the supply.

Good call, Brian. It never hurts to remind people especially when it's important.

Thanks again for your help.