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Old 08-25-2005, 06:24 AM   #1
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Default How to Tell is a Battery is Good?

Hi All,
I am new to electric and bought a pakage deal that included 4 matched 3300 batteries. They guy said they were like new but I think they look really worn out Anyway, I have a Duratrax ICE, how can I use this charger to test if the betteries are any good?

I did a normal discharge\charge on them at 3.3A and I get the following results for capacity:
Battery 1: 2507
Battery 2: 2954
Battery 3: 3523
Battery 4: 4002

What else can this charger tell me about them? Is Battery 1 & 2 any good for racing? I will be running stock and 19T. I'm thinking at least 1 cell is bad in Battery 1, any way I can tell with my charger?

Thanks
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Old 08-25-2005, 06:59 AM   #2
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You have to measure IR and average voltage. I know your charger can do it, but I dont have one, so I dont know how.

Also, you should charge at at least 5 amps, preferable 6 amps. This way the packs perform much better on the track. The discharge rate should be 10 amps.

For stock/19, capasity dont mean much. The packs with the highest voltage and lowest IR, are the best.

The pack with low capasity, it's not for sure one cell is dead. A way to check it out, is to ckech if one cell gets warm/hot before the others. Or use a voltmeter to check voltage individually of the cells.

Have you tried equalizing them? It might help quite some...

When you have sorted this out, you might like to use the graphic curve feature - the packs with the highest voltage/lowest internal resistance in the BEGINNING of the discharge, is the best. If you could discharge at 20 amps, it's the first 5 minutes, which is interesting... Not sure about when it's 10 amps, around 7 minutes I would guesstimate.
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Old 08-25-2005, 07:17 AM   #3
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Yea like Cole said...a 5 or 6 amp charge rate is a must......then your biggest concerns should be Internal resistance, and the cells average discharge voltage,(this simulates their performance on the track)....also make absolute certain to equalize them on a trey right before your planning on charging or cycling them......not treying the individual cells down to a nice even amount will give you lousy performance on the track and an inacurate reading when cycling.......you can trey your GP3300's down anywhere between .9 Volts per cell, and zero without harming them.....Im also not too familar with your brand of charger(I mean all of it's in's and out's) but you can always throw a cheap voltmeter on the individual cells while their charging to look for any hints of a bad cell.......and your average discharge voltage when cycling will tell you for sure if somethings "seriously" wrong....Rule of thumb is , any "Just decent" matched GP3300 pack should carry 7.00 Volts (or more) for the average discharge voltage , when discharging at 20 amps....if you don't come up with this when cycling, time for some new packs....good luck.......Joe
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Last edited by Joe B; 08-25-2005 at 08:15 AM.
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Old 08-25-2005, 09:08 AM   #4
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So discharging them on the charger is not good enough? It only discharges at 10 A, so what would be a good discharge rate? I charged at 3.3 A as whis was one of the "built-in" profies for the 3300 cells. I was told by the LHS that charging at 5 and 6 A would hurt the battery and cut down on the life. They recommended 4 A unless I was in a bind and then I could try 5. Why do I need this discharge trey? My charger is not good enought to discharge it?
Thanks
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Old 08-25-2005, 09:17 AM   #5
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not sure what your budbet is but if you plan to use batteries for a long time invest in a discharger (integy make a good one for around $50?) and battery tray lots of them out there to equalize the batts. everytime you discharge a pack you should equalize the cells. this will help maintain your mathched packs and make them last longer. as for charging the 33000s seem to like charging at high amps i would charge at5-6amps no less. you will have pleanty of run time and good voltage if taken care of.
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Old 08-25-2005, 09:52 AM   #6
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With a charged battery, hook it up to your Ice and run a discharge. Make sure that the cutoff voltage is set for 0.9 volts/cell and that you are discharging at 10 amps. Once the discharge is completed, the display will show that the cutoff voltage has been reached. Using your jog dial, scroll down the information an you will find the average voltage and internal resistance of your cells. Note: this data should not be used to compare the numbers advertised by cell-matchers. They are discharging at a higher rate and on different machines, so comparing the two sets of numbers will be like comparing apples to oranges.

Another good indicator of battery usefulness is the peak voltage a pack has after a charge. Believe it or not, higher is not better. The higher peak voltage indicates increased resistance, which is not good. SO, as you work with the batteries and condition them, you should see a fall in peak voltage after a charge.

The key numbers you want to work on while you are reconditioning these packs will be decreasing peak voltage, increasing average voltage, and decreasing internal resistance. Capacity will fall, but it is a small loss compared to the increase in punch. AND, since you'll running stock and 19 turn 5 minute races, you shouldn't have a problem with runtime.

As someone stated earlier, I wholeheartedly suggest a equalizer tray. I have a Novak SmartTray and am very happy with it.

Here is my battery regimine for my GP3300s that I have had good success with:

1) Discharge at 10 amps to 0.9volts/cell

2) Equalize on SmartTray to 0.7 volts/cell (this makes sure all cells are equal, but it does reduce runtime a little bit)

2) Four-Step Chrage (requires thermal sensor):
0-100 mAh => 0.5 Amps
100-2500 mAh => 7.0 Amps
2500-2600 mAh => 0.5 Amps
2600-3900 mAh => 5.0 Amps
3 mV/cell charge cutoff
130F Max Battery Temp
Trickle charge: off
dchg>chg: off
Imulse and Reflex charging turned off for all steps
Temp check turned on for all steps

Now, if you want to be safer, then you may just want to do a linear charge at 5.0 amps, which should be fine for your batteries.
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Old 08-25-2005, 10:19 AM   #7
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Thanks for all the information.

RandomFellow, will my runtime decrease _each_ time I use the discharge tray? MIght I use the ICE to discharde to 1.1, then use the tray to drop to .9? Would that keep my run-time? So you think the higher capacity batteries are the worst batteries I have? If I follow you correctly, I should maybe cycle battery 3 & 4 like 5 or more times? I am looking for at least 5 minutes of run-time without "falling off".

Thanks for answering all my newbie questions.
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Old 08-25-2005, 10:37 AM   #8
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Discharge treys properly used shouldn't directly cause runtime to fall off....cells just do this naturally to some extent.......I have GP 3300 cells that have been treyed to zero for well over a year....and they haven't lost more than 5 to 10 seconds of runtime.......and even a pretty terrible GP3300 pack will give you WAY more than 5 minutes at full power in stock and 19 turn
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Old 08-25-2005, 11:31 AM   #9
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Quote:
Originally Posted by LosiSuperTruck
Thanks for all the information.

RandomFellow, will my runtime decrease _each_ time I use the discharge tray? MIght I use the ICE to discharde to 1.1, then use the tray to drop to .9? Would that keep my run-time? So you think the higher capacity batteries are the worst batteries I have? If I follow you correctly, I should maybe cycle battery 3 & 4 like 5 or more times? I am looking for at least 5 minutes of run-time without "falling off".

Thanks for answering all my newbie questions.
No, the higher capacity batteries may be your better batteries, but it all depends upon average voltage and internal resistance during discharge (remember, there are three states batteries are in: charge, discharge, and at rest). What I was saying was that peak voltage (after a charge, peak voltage will be listed in your data display) will increase as resistance increases, so, having a high peak voltage will indicate a battery with higher resistance, which will impede the current flow of the battery and lower average voltage during discharge. Think of it this was, as resistance in the battery increases over time due to crystalization of the chemicals inside the battery, voltage will have to be increased to overcome the resistance. This is Ohm's Law (R = V / I, where R = resistance, V = voltage, and I = current) in action.
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Old 08-25-2005, 11:41 AM   #10
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One more question, I am not supposed to charge the battery before first using a discharger? If I am cycleing the battery 5 times, I must stop between cyles and discharge it?
thanks
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Old 08-25-2005, 01:44 PM   #11
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A "cycle" is (normally) a discharge and then a charge. You should allow your batteries to cool prior to charging. The Ice can be programed with a delay between discharge and charge.

There is no need to charge the battery before discharging. After a race, I usually just throw my batteries in their storage case. You should always (normally) store your batteries with at least 0.9 volts/cell in them, and there should be more than enough voltage after a five minute stock or 19-turn qualifying heat or main. You can check with your Ice to make sure, and if they are low, then just put a few minutes charge in them to bring up the voltage before storing them.

Avoid cycling your batteries more than twice at a time, as this will have a detrimental effect on battery performance. And, if you are in the off-season (like I am right now with Electric TC), you should pull your batteries out and discharge then charge them once a week. NiMH batteries don't like to just sit - they need to get used to keep up their chemistry.
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Old 08-25-2005, 10:42 PM   #12
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Ok, I set the charger up to discharge at 10A and charge at 5A. I had time to cycle 3 batteries. Battery 3 was not cycled.

Cap Charged @ 3.3A Cap Charged @ 5A
Battery 1: 2507 2375
Battery 2: 2954 2701
Battery 3: 3523 ????
Battery 4: 4002 3104

Average voltage for B1=6.485V, B2=6.534V, B4=5.456V
Peak voltage for B1=9.382V, B2=9.290V, B4=9.395V
Battery Resitance Average B1=102, B2=94, B4=???? (battery was dead when charged)

Looks like it really hurt the capacity of the pack by charging at 5A

I have a Novak Smart tray on order, but until then I can only discharge by the charger. I need them for this weekend, any ideas. Does my data look bad?
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Old 08-26-2005, 01:04 AM   #13
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Return battery number 1 and 2. You can't race with those....... the battery might be flat before the race end.
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Old 08-26-2005, 01:16 AM   #14
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Yea the packs don't look too good...first off don't pay much attention to the capacity figures untill you have a equalization trey(they can be way off)........according to your info even the higher average voltage packs you have, only have around 6.50 volts (average voltage) at a 10 amp discharge......At a 10 amp discharge they should be WAY ,WAY higher......I'll post some 10 amp figures a little later.....or if anyone else has some figures for just some (fairly good) matched GP3300's cycled @ a 10 amp discharge to give you a good base line
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Old 08-26-2005, 01:34 AM   #15
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Sorry to say, but yes, these packs dont look too good.

Returning them is probably not an option?

One thing came to mind...

I'm pretty sure, your charger is able of charging/discharging single cells.

If you number each cell, and then discharge/charge/discharge, and record the data, you'll find out which cells are good and bad.

It's time consuming, 1 hour plus pr. cell, but if you are familiar with soldering, you actually have the option of matching your cells.

It's hard to say if it's worth it... but according to my experience, there usually only is one, maybe two bad cells in each pack. So chances are good, you are able to assemble one or two reasonably packs. If you're real lucky, 3 packs.

One thing is for sure, if you get a couple of packs out of it, they're already stress tested !

EDIT: Even if you dont re-assemble these packs, the process of charging/discharging each cell individually, might wake them up a little - this process is more effective, than just equalizing them. Except it's very time consuming
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Last edited by Cole Trickle; 08-26-2005 at 04:13 AM.
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