Issues charging NiMH BATTERY - RC Groups
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Dec 30, 2017, 04:38 PM
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Issues charging NiMH BATTERY


I have a IMAXBAC6 when I try charging a 8.4v 3000MAH it shows that is full after 3:15 minutes. It happens everytime

Any ideas

Thanks
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Dec 30, 2017, 09:42 PM
Space Coast USA
hoppy's Avatar
What charge rate?

What is pack voltaage before charging?
What is the voltage right after charging?

Charge pack at 300ma for 16 hrs to balance cells.
Dec 31, 2017, 05:03 AM
Registered User
Charge rate = 3.0
Before charge volts = 7.5
After exactly 3:15 minutes = 10.2 volts

Does this sound like a faulty charger?
Dec 31, 2017, 08:01 AM
Space Coast USA
hoppy's Avatar
10.2V is fully charged. (that's shortly off the charger voltage, it will drop some more with time)
7V is discharged.

What problem are you having with pack performance?


More questions:
What is voltage the next day? Has it dropped a lot?
What is the battery used for? What happens between the 10.2V and 7.5V readings?
Are you charging at 9A?

You can try the 16hr 1/10C balance charge to see if that improves battery performance.
Last edited by hoppy; Dec 31, 2017 at 08:22 AM.
Dec 31, 2017, 08:04 AM
Registered User
Charge rate 3.0 is very high you should be charging at 0.3 amps.
Dec 31, 2017, 08:12 AM
Frankenstein recycled packs
rampman's Avatar
Agreed. Charge low and slow until you get some cycles on it.

Rick
Dec 31, 2017, 08:21 AM
Space Coast USA
hoppy's Avatar
From his other thread he is indicating perhaps it is 3C, not 3A.

But anyway, forgetting the charge current for a moment, what is the problem you are having with the battery?
Dec 31, 2017, 09:11 AM
Registered User
Quote:
Originally Posted by hoppy
From his other thread he is indicating perhaps it is 3C, not 3A.

But anyway, forgetting the charge current for a moment, what is the problem you are having with the battery?
The battery is a brand new Traxxas 8.4. 3000 After my first of over 10 minutes at 3/4 throttle I put it on the charger and the charger says it is full after 5:00 minutes. I know this is not right
Dec 31, 2017, 09:23 AM
Registered User
If it's NiMh and new I would charge it overnight at .1C for the first couple charges. The charger shuts off when it thinks it is charged and it gets fooled by false peaks when the batteries are new. NiMh charging does not work on voltage like Lipo charging does. It uses a delta peak detection on most chargers. You can adjust the sensitivity of this on some chargers. Read up on NiMh charging if you are not familiar with how it works.
Dec 31, 2017, 10:47 AM
Space Coast USA
hoppy's Avatar
[QUOTE=jhamm;38900421]The battery is a brand new Traxxas 8.4. 3000 After my first of over 10 minutes at 3/4 throttle I put it on the charger and the charger says it is full after 5:00 minutes. I know this is not right[/QUOT

Problem............
If the pack voltage is 10.2V after charging and off the charger, the pack is fully charged.
But this contradicts with the before charging voltage of 7.2V and a 5 min charge time.

Something is missing in the info.

First, what is the voltage of that 10.2V pack now? If you fly with that 10.2V battery after the short charge, how long does it fly?

My suggestion:
1 - Charge the pack at 300ma for 16 hrs.
2- Discharge pack at 1A till pack voltage is 7V. Record mah out.
3. Charge pack at 1A and record mah in.
Dec 31, 2017, 12:03 PM
PGR
PGR
Low AltiDude
PGR's Avatar
Quote:
Originally Posted by hoppy
3. Charge pack at 1A and record mah in.
Keep in mind that a NiMH (or NiCd) pack isn't like a LiFe or LiPo pack where mAh in equals mAh stored. The NiMH charging process is notoriously inefficient and a pack will only absorb somewhere around 80% of the energy it takes to charge it. In other words, if a charger says it took 3000mAh to recharge a pack, that pack only absorbed something like 2400mAh of energy. The rest was lost as heat.

That doesn't indicate that anything is wrong, though. That's just the nature of Nixx battery chemistry.

Pete
Dec 31, 2017, 02:47 PM
Space Coast USA
hoppy's Avatar
Right on Pete, but right now we don't know anything about what's happening. How do you fully charge a pack (10.2V) in 5 min after flying till it's down to 7.2V. which is what appears to be happening but of course can't be.
We need data to clarify what's happening. Something is amiss, right?
Dec 31, 2017, 06:30 PM
PGR
PGR
Low AltiDude
PGR's Avatar
Quote:
Originally Posted by hoppy
Right on Pete, but right now we don't know anything about what's happening. How do you fully charge a pack (10.2V) in 5 min after flying till it's down to 7.2V. which is what appears to be happening but of course can't be.
We need data to clarify what's happening. Something is amiss, right?
Absolutely. I'm not disputing that at all.

My personal SWAG is the charger is false-peaking, either due to incorrect settings or a pack that needs a good forming charge or two. But without more data, all any of us can do is make SWAGs.

(SWAG = Silly Wild-A$$ Guess).

Happy New Year!

Pete
Dec 31, 2017, 06:54 PM
Registered User
is it a genuine or clone imaxb6.

the clones as far as i know are terrible with nimh packs, my b6 would not charge nimh probaperyu it would always false peak even at 0.1c and even with taking the delta peak settings lwoer.


i replaced it with another charger and it charged nimh fine
Dec 31, 2017, 07:02 PM
PGR
PGR
Low AltiDude
PGR's Avatar
Ignore
Last edited by PGR; Dec 31, 2017 at 07:03 PM. Reason: Double post


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