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  1. #1
    RC Enthusiast
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    Cool Can I charge 2 batteries at same time with one charger?

    I will be recieving my erevo vxl with an extra traxxas battery and the series adapter and was wondering if it is possible to charge both batteries at the same time with the traxxas series adapter?

    If so what charge rate should I put into my hyperion eos5i.
    By the way that charger is capable of charging 14 cells.It autodetects the cell count I just have to enter the charge rate.
    Thanks for the help.
    Last edited by camaro97; 06-13-2009 at 03:36 AM.

  2. #2
    RC Champion
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    Yes, you can charge them both. Set the charger for the same rate as if you were charging just one pack. I think I read that the packs are 1100mAh... so a rate of 1.1 amps.
    If I'm wrong about the pack capacities, naturally some one will correct me. Either way, a rate of 1C to charge.
    English. It's your language. Learn to type it.

  3. #3
    RC Champion
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    From talking electronics dot com
    FAST CHARGING
    Fast charging a cell involves a very high current and this causes the cell to heat up.
    When the cell becomes fully charged, the charge-current is converted to a "gassing" process. The cell has the capability of re-combining the gasses but not at the rate of production during fast charging.
    Re-combination of gasses creates a lot of heat and as soon as the cell becomes fully charged, it heats up considerably.
    This characteristic can be detected to turn off the charger.
    No cell likes to be fast charged and there is some limitation to the life of a cell that has been repeatedly fast charged.
    Fast charging a single cell (of the type: 2400mA-hr AA) requires a current of about 2.4 amp. This equates to a wattage of about 2.8watts.
    This means you require a 2.8watt power supply for each cell you want to charge (at the same time).
    For a 10 cell battery, this requires a 28 watt power supply (plug pack). This type of plug pack is not available.
    That's why fast chargers only charge 1, 2, 3 or 4 cells at a time.
    There are a number of fast chargers on the market. They deliver a high current to the cell and detect the terminal voltage or the rise in cell temperature. And the cells must be taken from the equipment and fitted to the charger. These chargers are also very expensive.
    For a 12v battery, 10 cells are needed and this requires a lot of work to recharge them.
    Our solution is to use the SLOW CHARGE method and keep the current below the "10-hour rate" so the cells will not be damaged.

    SLOW CHARGING
    If the charge-current is 1/10th the ampHr rating of the cell (this is called c/10), the cells will be charged in approximately 14 hours. After this time nearly all the gasses generated in the cell will be re-combined but the pressure will not build up very slightly. For this reason, the cells must be removed from the charger after 18 hours.

    TRICKLE CHARGING
    If the charge current is 1/40th the ampHr rating of the cell (c/40), the gasses generated in the cell will be re-combined and the pressure will not build up.
    The cell can be kept in a state of trickle charge for a long period of time without damage.
    Normally, TRICKLE CHARGE was referred to as the "14-hour" charge-rate, so that a completely exhausted cell would be fully changed if the current was one-tenth the amp-hour rating of the cell. For instance, if the cell was 1.2 amp-hr, the charge current would be 120mA for 14 hours. This referred to a NiCad cell, but for a NIMH cell, the trickle charge time is "40 hours."

  4. #4
    RC Racer
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    charging that 1100 mah battery at a 1c rating for the first charge isn't recommended. I use an 1100 mah batt in my rc18t and i have an onyx 240 dual charger. i set the charge rate for 0.8 amps which takes over an hour. In the manual it says to do a "slow charge" the very first time you charge the pack using the included Associated cheapo wall charger, takes about 4-6 hours.
    5608 3905 5805 7108, DF-03RA, 2x AX-10, MRC

  5. #5
    RC Turnbuckle Jr.
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    Quote Originally Posted by camaro97
    I will be recieving my erevo vxl with an extra traxxas battery and the series adapter and was wondering if it is possible to charge both batteries at the same time with the traxxas series adapter?

    If so what charge rate should I put into my hyperion eos5i.
    By the way that charger is capable of charging 14 cells.It autodetects the cell count I just have to enter the charge rate.
    Thanks for the help.
    I would use a charge rate of 0.2 to 0.4 for the first couple charges to condition the packs...

  6. #6
    RC poster
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    Quote Originally Posted by Slasher
    Yes, you can charge them both. Set the charger for the same rate as if you were charging just one pack. I think I read that the packs are 1100mAh... so a rate of 1.1 amps.
    If I'm wrong about the pack capacities, naturally some one will correct me. Either way, a rate of 1C to charge.
    When charging them both do it in parrellel or series?

  7. #7
    RC Racer
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    I think you'd want to charge the NiMh packs in parallel. This would be the equivalent of a 2200mAh batt, so a 1C charge rate would be 2.2amps.

    but you only have the series adapter? I think I recall somebody in the forum saying that they charged their NiMh's with the series adapter. You should do a search. If using the series adapter, the two batteries will appear as a single 14.4V battery and a 1C charge rate would be 1.1 amps.

    Upon further research, I guess it's better to do them in series. See this post.

    LiPos are a whole different story and would require special wiring adapters.
    Last edited by RC-Now; 12-29-2009 at 12:55 PM.

  8. #8
    RC Racer
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    I charge my nimh packs in series for my Rustler to double up on charging.
    I also charge my lipos in series for my merv, but those I run in parallel.

    To be safe, I series charge the nimh packs to about 90%, then charge them individually the rest of the way. The reason is I run those packs individually, so they do not both start at the same leftover capacity.

    As I run the lipo in parallel in the merv, i charge them fully in series, and the balancer does the rest. You can charge lipo in either parallel or series, but I prefer series as each cell gets a separate connection to the balancer. This way if just one cell has an issue, the charger will pick this up immediately and cut the charge.

  9. #9
    RC Competitor
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    i was told by a few people that i should never charge in parallel. So i don't. After a quick search most of the internet says that you shouldn't charge in parallel. I don't have a clue why but there you go

  10. #10
    RC Champion
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    1st .... NEVER try and charge NiMH in parallel. They can be charged in series IF you have extremely well matched cells.

    You are much better off charging NiMH packs as single packs!

    Lipos can be safely charged in series or in parallel. I mostly charge and balance in parallel .... but sell and use rigs for series and parallel. Both methods are safe if done correctly.

    Bob
    I make tap adapters and power harnesses.

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