Charger Behavior Question
 

I'm using my GT A6 charger to cycle the 7 cell, 1000 mAh, NiMH flight pack from my NitroPlanes PBY Catalina. I'm monitoring the process on my computer using the provided "Charger" software. All seems normal and predictable except for one characteristic that I don't understand.

While charging, the charge current drops briefly to zero every two minutes (variable) or so, then switches back to my selected charge current of 0.5 Amps.

Anyone know what's going on? Is it checking for something? It charged the pack to 10.41 V before switching to the discharge part of the cycle.

Just curious, thanks,

Frank

RE: Charger Behavior Question
 

It's probably normal on that particular charger and could either be a quick discharge (known as reverse pulse or burp or others) or it could just be an open voltage check on the battery every two minutes as a safety measure against overcharge. Many chargers do either , both or neither. Some of them can be programmed for preferance.

RE: Charger Behavior Question
 

Thanks for the reply, guver. Yes, I expect it's normal for this simple, inexpensive charger. The computer graph and the charger display both indicate the current goes to zero but doesn't reverse. I just wonder what the designers achieve with this action. Perhaps it is as you suggest, an open circuit voltage test for something??

Incidentally, looks like my battery is not too good. It hasn't been cycled much (haven't flown the plane yet) and the charger is only moving about 500 mAh into and out of the battery. Guess I'll cycle it a few more times and see if the capacity improves!

Frank

RE: Charger Behavior Question
 

It may be just parameters (settings) or could even be just one bad/weak/out of balance cell. I guess what I'm saying is that it may be a mistake to conclude that the battery is bad.

If I remember correctly , there were ideas about pulse,reverse pulse, ect charging that might have been good for batteries or to restore capacity. I've never found any amount of cycling, discharging,pulsing,burping to have any positive or negative affect on them. The thoughts are prevalent about breaking up crystals and such. It is too technical for me. [:o]

RE: Charger Behavior Question
 

And too technical for me also, guver!! But I'll take the easy route. Everything I read says NiCd and NiMH batteries need to be cycled initiallly to achieve their rated capacity, and that cycling them is not harmful. After only two cycles the storage capacity "seems" to have increased from 484 mAh to 642 mAh. Again, it's a 1000 mAh 7 cell NiMH battery. It was pretty warm when the charger shut off after 642 mAh.

So I'm going to set it up again on my computer desk to cycle 4 times at 0.5 Amps. I'll post back what happens.

Frank

RE: Charger Behavior Question
 

Here goes........

No great batteries should EVER GET warm at all, while being charged at 1C or less!!!!!!!!!!!!!

The batteries are probably Very old stock. send them back. Hope for newer ones.

Rich

RE: Charger Behavior Question
 

guver, Here's my results (if I can tabulate the data intelligently)

Charge (mAH) Discharge (mAH)
484 561
642 742
731 855
821 813
898 876
904

So, except for the 855 number it seems to make sense. Increasing capacity with exercise. Also, I've read that the actual numbers will vary depending on charge and discharge current.

cyclops2
The battery pack came from NitroPlanes as part of the RTF Catalina. Not likely I could get a replacement. But doesn't the temperature rise depend on the charger characteristics. I read that if I overcharge, the excess energy is given off as heat. So if my charger is overcharging to some small degree (delta peak sensitivity) I could expect the pack to warm up. It did so towards the end of each charge cycle.

What do you think?

Frank

RE: Charger Behavior Question
 

I'm not a big fan of cycling. How about trying a c/10 charge or 15 hrs and then a manual discharge test? Your battery really looks ready for use to me. ;)

RE: Charger Behavior Question
 

That 900 is about as good as The sales dept. will allow.
YES> Excess charging can show up as warming. What is your packs end of charge voltage ?

I have become spolied by the LIFEPO4's. No loss of power after 6 months.

RE: Charger Behavior Question
 

guver
I'd agree, the battery pack looks to me to be as ready to use as it will ever be. Since it's a flight pack, not RX or TX, C/10 is maybe not appropriate. What do you mean by manual discharge? Use the charger "discharge" mode manually?

cyclops2
End of Charge voltage was around 10.4 volts, about 1.5 volts per cell. That's probably pretty well fixed with excess charge creating heat and not increasing the pack voltage.
What's a LIFEPO4?

RE: Charger Behavior Question
 

This is a LIFEPO4 setup. The red charger is pure goodness. Plug the little gharger cord into it & everything is checked & fully charged & then it TURNS OFF.

At 71 this is love. Peaks to 100 % & no overcharges. :)

No fires on over discharges & recharges.

The C ratings are 30C with a LITTLE voltage drop.
2 sizes. this is the 1100 mahr..........also a 2300 mahr size..........HARD METAL cases. :)
These are from Black & Decker battery packs bigger units a DEwalts power pack.

NOT cheap. But they have NO self run down when stored for 6 months. Hundreds of full power cycles.

RE: Charger Behavior Question
 

Yep, Use the charger "discharge" mode manually.