rcnewb2004

my car never sems to completely run out of battery power... it just sortof... runs very slowly for a very long time >_< so not sure if they ar dumped or not

=MisFitz= NuKe

well, a very good quality pack, or very new, should run very strong then drop off almost immediatly, then run very slowly, or not at all.

etzkev

And that's the art of NiMH batteries!

=MisFitz= NuKe

you know it, lol, you know your batteries are worn out, when you can run them on a friend's bulb discharger and the lights dim and stay dimmed for about 5 minutes, lol, hrmmm....may be time for some new cells.

Cole Trickle

Are some of you using the auto repeak thing? What do you think of it?

=MisFitz= NuKe

when I had mine, I just used the charge and discharge function, and a FEW times I tried the turbo thing.

rcnewb2004

I just built my first pack last night, it was a frustrating battle. But I finally did it. Assembled using Silver bearing 60/48/2 solder, and Dean's Pro Bar 3s.

But i think i may've f*cked up.

Off the CDC these are my specs for my battery during its first cycle:

These are matched GP3300. (Green/Orange top cells).

The cells are matched to ~409s runtime at 30A discharge, 1.162+ V/cell. Cutoff 0.9V/cell, run for 5000s.

On the CDC I am using 4mV/cell drop, 3.0A charging, 20A discharging. 1 minute between charging and discharging.


Vp=10.187V
Va=7.097V
IR=30mOhms
Charging Capacity=4039mAh
Discharging Capacity=2900mAh

I am a bit concered about that discharge capacity.... is there something wrong or is it just me?

babytoy101

iTrader: (8)

you have a very good battery pack there!

etzkev

Yeah, that is a pretty good pack!

fatdoggy

Good pack. Look at what it peaked at, over 10 volts. A very good pack will peak below 9 volts. My gp3300 pack peaks around 9.3-9.5 volts with an ir of 30. The higher the voltage peak the higher the resistance in the pack. The 3 amp charge rate could have screw'd with the peak. Most people charge at 5-6amps.

Ooj

I have to agree with Fatdoggy about the peak voltage when charging. Also a good pack will have a much better average voltage on discharge - more like 7.2 - 7.4 volts. Just for comparison, my new promatch packs are 1.165, 1.5IR, 430sec. They are charged at 5A, 4mv cutoff and 20A discharge on the CDC - they ususally charge to 3800mah and discharge 3200-3400mah, 25mohm resistance, and average 7.3V. These are the kind of numbers a very good 1.165 pack should produce when built and cared for properly - overheating and excessive use of solder kills any packs performance. A pack will never show good numbers on its first cycle - it takes 2 -3 runs. Also cycling when the pack is new is not such a good thing according to some well renowned matchers. If anyone is curious, I am using promatch cells - cheapest of the well known matchers and the numbers are drawn from a 5A charge - much harder to get insane voltages when the other guys use a 6A charge

Cole Trickle

Capasity is good, but yes, I'll also agree that the peak voltage and the average voltage aint as good as supposed to.

Is your soldering iron hot enough?

I tend to say you have several bad solderings here. The solderings should be with very little soldering on them, and especially, almost no soldering between the bar and the batt.

Recently, I had only one bad soldering in my pack - it was enough to give higher IR. Not that I measured it, but it was noticably on the track.

Cole Trickle

In which way did you have bad results? Runtime problems?

I believe all other handling was good, since you can judge the EQ?

rcnewb2004

Thankyou all for the replies. This newb has definately picked up a lot from you guys in the past month.

Thanks alot once again, however, you guys have left me with more questions and I hope its not too much trouble for you guys to follow up on them if you guys have some spare time.


Cole - So the capacity from my GP3300s is ok?

I can have some crappy joints... would resoldering them make it worse?

how can you tell if the joints are cold? And how can you solder them without using overkill amounts?

Why would excessive solder cause joints to be less conductive?

Ooj - Your cells have some pretty impressive numbers. My cells however are 1.162V IR2.7 runtime 409s. My cells have higher IR to begin with.

So 7.097V is still a bad number to have given that I have higher IR to begin with?

Why is cycling bad on a new pack? I should just charge it fully before I use it?

My cells are pre-cycled four times before they got to my hands, does that mean that my cycle numbers are still inaccurate and I should run the pack 2-3 times before I cycle it again to check the numbers?

So charging at high amperage gives advantage on the track over slower charging?

And what do you mean by your last sentence Ooj?
" much harder to get insane voltages when the other guys use a 6A charge"



Also, since this is my "good pack', how frequent do you guys recommend that I should run this pack?

I run my packs usually twice a day. How much of a break time should I give the cells between charges?

and How many days should I give the cells to rest after the two charges in one day? (I hope my question worded is clear)

Cole Trickle

rcnewb2004: I did some re-thinking, maybe the average voltage aint bad - I'll check my own numbers tonight, I think I might have remembered wrong.

But that peak voltage definately sound too high - mine is around 9,10. Especially considered your low charge rate. My peak voltage is with 6 A charge (the higher the amps, the higher the peak voltage).

Follow the guidelines from the mathcers, like Fukuyama , and you should get good results.

Soldering: It's hard to explain, it's about experience. Probably, a picture will say a lot. But what I can say is to use a jig and a iron, which get hot enough. Maybe someone else can help...