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  1. #1
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    Duratrax Onyx 245 Charger Help?

    I'm not sure how many of you have or are familiar with this charger or not, but I have questions that I can't find the answer to in the manual.

    I have 2 Onyx 7.4v 5000mah 2S lipo batteries that I bought the same time as the Onyx 245 charger. The charger automatically defaults to a 5A current charge for Lipo batteries everytime you plug it in, which is what I need for my batteries, so I know they are being charged properly. The charger itself has a data button that allows you to cycle through different data points about the battery, such as the amps its being charged at, how long and the voltage of each cell in the battery, as well as the mAh rating.

    My question, or concern rather, is that after the charge cycle completed after charging both my batteries, I cycled through the data points and went I got to the mAh rating, one battery read just under 2500 and the other read 2699. My concern isn't the discrepancy between the two numbers, but rather that both my batteries are 5000mAh batteries. I wondered if maybe it was telling me that was the mAh of each cell, since mine is a 2 cell battery, which would work out math wise. But it doesn't make sense to me it would read that way since there is already a separate data point that will tell me the individual voltage of each cell and that's clearly marked by and indicator of which cell it is. This reads as a general overall mAh rating. So obviously my concern here is that my batteries aren't getting charged to their full milliamp capacity, therefore meaning my batteries are only lasting half as long as they should.

    So can anyone tell me, or preferably show me proof, as to whether or not the charger isn't charging properly or that the mAh data point is telling me what it is per cell and bot overall?

    Thanks in advance.

    Sent from my SM-G935R4 using Tapatalk

  2. #2
    RC Turnbuckle Jr.
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    Nope, but I think that number is the charge that you put in the battery, not what the capacity is. So if one says 2500 it was already half charged. And the one with 2700 on the display would've been less than half charged. The charger doesn't know the capacity of your batteries.

  3. #3
    RC Qualifier Bige4u's Avatar
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    Actually, battery chargers go by the individual voltage of the cells more than the MAH capacity, once it knows they top out @ 4.2v , it stops there... and as for your MAH readings, if there was a left over charge from prior use, it just builds up from there.

    If you would like to check the total MAH of your batteries is, put one on a storage charge and write down the finished capacity shown, then let the battery sit for 30min to cool, then do a full charge this time and again, write down the finished capacity shown and add them both and see what you get... then repeat this process for your other battery(s).
    Bashing along @ 30mph...

  4. #4
    RC Turnbuckle Jr.
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    Yes the mah is a calculated value of charge rate and, charging voltage.

  5. #5
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    Quote Originally Posted by Gripdog7205 View Post
    Nope, but I think that number is the charge that you put in the battery, not what the capacity is. So if one says 2500 it was already half charged. And the one with 2700 on the display would've been less than half charged. The charger doesn't know the capacity of your batteries.
    Ah. That actually makes perfect sense to me. Thank you Gripdog. I appreciate that. As well as everyone else's input. I feel better now. I was just afraid I was getting duped out of some battery life. Haha. Because neither battery was fully dead if I remember correctly.

    Sent from my SM-G935R4 using Tapatalk

  6. #6
    RC Qualifier Bige4u's Avatar
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    When it comes to lipos, never use them till they are, "fully dead", as you put it, thats how they get irreparable damaged and will start puffing(expanding)... just make sure to set your LVC(Low Voltage Cutoff) in the ESC to 3.4v, its the lowest you want to go while still maintaining the usable life of the lipo battery.
    Bashing along @ 30mph...

  7. #7
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    Quote Originally Posted by Bige4u View Post
    When it comes to lipos, never use them till they are, "fully dead", as you put it, thats how they get irreparable damaged and will start puffing(expanding)... just make sure to set your LVC(Low Voltage Cutoff) in the ESC to 3.4v, its the lowest you want to go while still maintaining the usable life of the lipo battery.
    Silly question; but i have 2 Slash 4x4 and a Stampede 4x4 that I just switched to lipo packs on. light years over nickel so far...I have been running them on the "factory preset" low voltage cut of the stock esc for the lipo setting.. when they hit the 50% speed portion I cruise them back to me and swap the pack.. that a good stop point? I dont go til the truck shuts down completely. I put the packs to storage mode by charging them back to 40% capacity. (ex 5500mah X 0.4 =2200mah... so i set the MAH capacity to that on my 5500mah 2S packs)... just wanted to be sure that was were I stop when running a truck is all.

  8. #8
    RC Qualifier Bige4u's Avatar
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    The factory traxxas esc has its own lipo voltage cut off built it, its not programable like aftermarket ESC's... so when it hits it preset, thats where you switch out the lipo for another to continue running your vehicle.

    The only time you would ever run a vehicle till it goes no more is when your using a NIMH battery, just make sure you set the ESC for that type of battery first before using, then switch over to the lipo setting when using that type of battery.

    Storage mode is good when you dont plan to use that lipo for a while, say like 1-2weeks or more, theres no point charging it to that only and using it right away... always go full charge if you plan on using the battery the same day or the day after.
    Bashing along @ 30mph...

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