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Batteries - NIMH - What's Best! Struggling with my Current Equipment 4 years 10 months ago #55135

Good Day All
So, just to be clear, I'm a 'greenhorn'...but improving, thanks to a lot of help, here.

I'm using a Duratrax Onyx battery (NIMH 7.2v, 5000mAh) and a Duratrax Onyx 210 Charger
Upon complete charge, or at least when the charger says: "End". I can scroll thru some info, using the 'Data Button'
Mine typically about reads about 900mAh (but many times much less like 283mAh) and 80.2v....I've contacted Duratrax 2x and they have told me that the voltage is what's important.
Please see copy/paste from their email below"

Michael,

- 283 mAh = The amount of MAH put IN to the battery since you started the charge. This number will likely not ever be 5000 that your battery is.

- 8.24 v = The current voltage on the battery, your battery is a 7.2v battery a full charge is approximately 1.0v higher than the labeled voltage.
8.2v is a full charge


My run times are short, just a few minutes. (Not any super-fast racing buggy, just a plain old VW Rally with stock motor etc)
What is your opinion? Is there a better option for a NIMH set-up? I really don't have too much invested in this battery and charger...I just think I should be getting closer to 10+ minutes.

Your thoughts are valued!

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Batteries - NIMH - What's Best! Struggling with my Current Equipment 4 years 10 months ago #55136

Short Version: A VW Rally should run for hours and hours on a 5000mAh NiMH battery. Something is amiss.

Long Version: Each cell of a NiMH battery is nominally 1.2V. A standard 6-cell pack is therefore rated at 7.2V. However, this "nominal" voltage is really the voltage when it is nearly empty, not the voltage when it is full. You can expect 8.2-8.4V when it is full. The mAh reported by the charger is how much of the battery's capacity the charger put into it on this charge. If you hook up a full battery to the charger, it will put in virtually nothing because it is already full. If you put a nearly empty battery on the charger, it should take close to the full 5000mAh of charge.

Old school Ni-Cd racing packs were 1200mAh so you should be getting 4 times the run time with your newer battery. If you are not, there are few possibilities:
  • Your charger might not be putting in a full charge for some reason. Sounds like you've already contacted Duratrax to investigate this.
  • Your battery might not be holding a charge. This happens when they get old.
  • Your car could be pulling way too much current for some reason. Does it roll smoothly?
  • As NiMH cells discharge, the voltage ramps down. If the car gradually gets slower and slower, that's the result of a depleted battery. If the car just suddenly stops, that's probably a low voltage cutoff on your speed controller. Low voltage cutoff is only for lithium batteries. This feature needs to be disabled for NiMH batteries. My guess is that this is your problem. What kind of ESC are you using?

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Last edit: by blakbird.

Batteries - NIMH - What's Best! Struggling with my Current Equipment 4 years 10 months ago #55138

I think that you lost a cell or more. A 5000mah should have largely more run time or your motor is dead.... i had the same matter with a 5200mah. I think that big capacity sticks are more fragile than smaller.

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Batteries - NIMH - What's Best! Struggling with my Current Equipment 4 years 10 months ago #55140

Stingray...Blak
Thanks much for your replies!!
The motor is the stock motor (this VW is my first car in 30+ years)
The ESC is the one that came with the model, the Tamiya TBLE-02.
Yes, the car does slow down, when I suspect the battery is becoming depleted (the steering servo works, but you can only get a few short bursts from the car) I'm assuming that's normal...BUT again the run time is short!
Yes, the car rolls smoothly, and actually faster than I anticipated, but, you can see the speed slowing soon and eventually petering out.

Duratrax, has explained that there is a "break-in" period. That there must be 10 or so, charges and depletions of the battery until it responds as intended. I'm at 20+ for this battery set-up.

So...back in January, before the snows of Northwest, New Jersey, USA (when I purchased the battery and charger) The mHa reported by the charger seemed to be rising after every battery charge/ run cycle...up to 1800mHa. So, I was thinking that this was the normal "break-in period" Now, I am questioning that.

So, the battery is new (and should be broken-in)

There is not any difference when running the same battery in my Hot Shot, which may has a slightly quicker motor, but same ESC as the VW.

I can press Duratrax, and will, but do you like a different battery and charger combo??....

I'll purchase a different battery/ charger, based on your experience and perhaps get the performance that's correct??
Frustrated, when running ,,,even though I enjoy building, more than running.

Thanks again for your input!!

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Batteries - NIMH - What's Best! Struggling with my Current Equipment 4 years 10 months ago #55142

I run with 2 2000mah sticks bought 3or 4 years ago. I run approximately 10 12 minutes with a tb02 or dt02. I have old esc inside. Teu 101 and a chinese esc.
Jonny retro adviced me a imax b6 charger. I am very happy with it. It works very well.

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Batteries - NIMH - What's Best! Struggling with my Current Equipment 4 years 10 months ago #55148

Thanks for the additional information, that helps. The TBLE-02s controller is in lithium cutoff mode by default. If you are using a NiMH battery you need to change the mode. Hold down the set button while turning on the switch and watch for the green light. When you see the green light, immediately release the button. You should hear a single long tone indicating the ESC is in NiMH mode.

If you are still having problems after that, it is probably a bad battery. Nothing wrong with the charger. I'd recommend a 3000mAh battery instead of 5000. They are less fragile.
The following user(s) Liked this: stingray-63

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Batteries - NIMH - What's Best! Struggling with my Current Equipment 4 years 10 months ago #55149

That battery is toast, no matter if the ESC is set on Life or Nimh, you should at least be able to run a 5000 for a couple of minutes.
The cutoff for the LiFe setting is 4.8 volt.
As mentioned better get a decent 3000 or 3300 mAh NiMh those will work better. I like the ones from Vapextech.

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Follow-UP!! Batteries - NIMH - What's Best! Struggling with my Current Equipment 4 years 10 months ago #55155

Thanks all for your replies
I contacted Duramax again...Please see the reply from Duramax below (bold)

The only reason a model would prematurely stop running after 5 minutes. Would be that the LVC (Low voltage cutoff) is being met because of the battery being dead.
Or the electronics overheating or having an internal malfunction and it shutting down. The battery voltage after a run would dictate is this concern battery related, truly battery related. Or is it something else in the system.

I'm sorry about the Duramax Tech's poor English, I struggled with it, as you likely are doing.

I was instructed to charge the battery and operate the model, and immediately after the model stops, to re-connect the battery to the charger and then check the battery's voltage. They said that if the voltage is 7.2 v or less then they would suspect a battery issue, if not, something else is going on.

I have done what I was asked to do and got, maybe 5 minutes runtime. (from my Tamiya VW Rally) The voltage reported by the charger was 7.13 to 7.28v
I tried the same battery in my Tamiya HotShot. I got less than 5 minutes runtime, and the reported voltage after the battery was depleted (the model stopped running) was also 7.2v.
Both models use the Tamiya TBLE-02 ESC

As suggested I have ordered two 3000mHa batteries.
Question: Is there something I'm missing here?? Is there some other issues that I should be looking at?

I don't mind just replacing the battery and sucking up the $25 I paid, if replacing the battery does the trick.

Thanks for reading!!

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Batteries - NIMH - What's Best! Struggling with my Current Equipment 4 years 10 months ago #55156

Sounds like a bad battery. After 5 minutes you should still be up over 8 volts.

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Batteries - NIMH - What's Best! Struggling with my Current Equipment 4 years 10 months ago #55157

Thanks Blakbird!
I'll have my new batteries by tomorrow...: :)

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