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Thread: Field charging

  1. #1
    RC Champion
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    Field charging

    I have an xmaxx and the dual peak charger with 4s lipos how do I charge in the field? Id assume I need and inverter but how many watts?
    3.3 t-maxx, O.S. .18TM t-maxx, HV brushless e-maxx

  2. #2
    RC Champion Acidic01's Avatar
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    What batteries are you running?

    You can get a inverter but don't know how expensive it will be to do what you wanna do. And if you can find other uses for it to justify the cost...

    May be best to invest in a good DC/ DC charger. And make or buy a Ac/DC power supply. Or get one that has both options built in. Like hota or venom.

    To figure out what size inverter needed Charge both batteries at same time and see what volts and amps it is drawing. Then calculate. Watts per channel and then add both channels together then Add 20% or more on top for overhead as charger is not 100% efficiency more like 60 to 80% bet they don't say what efficiency they are at. (Like computer power supplies) Or easiest and most accurate if have a watt meter plug. Put charger into that and charge up to see what it's pulling from wall.

    Then you will know about what size inverter you will need for your charger.

    Watts = volts x amps.

    I have a icharger 406dou DC/dc, with a custom ac/dc power supply. I splurged for a good charger when I got my xmaxx as my old 80watt onxy 245 charger took 80 to 90 mins to charge my 3s 5000mha batteries for my erevo2. And didn't want to be waiting around for batteries to charge. And charger was limiting me. More so when I got 4 cars worth of batteries.

    I got 2 server power supplies that I modded into series to get me 24v. (Charger capable of 48v) so my custom psu gives me 1500watts at 24v 65amps.

    When I charge up my 9400mha 4s batteries for my xmaxx I charge at 2c. 18.8amps per channel.

    My charger is telling me at 24.4v it's drawing about 26.5 amps so it's taking about 648.19 watts.

    From empty batteries to ready to bash again in 20 to 30 mins depending on what balance mode I select and how out of balance they are.

    So I'm able to charge faster than I can use up my batteries which is what I wanted and why I put the $$$ and time to it.

    I got my server psu's from a local used gizmo store, for 30$. Then another 5$ or so for a old DeWalt drill case and other needed connectors and so on and a few parts from garage I had on hand and made my own feild charging case to house my charger and PSUs. I have a dc port in the back of my case I can plug in my alligator clamps to hook to my truck batteries so I can power the charger when not on AC.

    If someone does go this route get server psu's models with known Pin outs and and instructions. As it will save a bunch in testing what pins to short to get it to turn on.

    Spent a few days building my case, not as pretty as others but very cheap. And had to fab some brackets and other things needed. The prefabbed cases do look pretty cool. But $$$


    Also keep a eye on your 1:1 vehicles batteries as if you don't have a good battery in there you can drain it down and have to get a jump or have car running while charging.

    I haven't bothered with this but I have two large high end deep cycle batteries in my desiel truck. Much more of a issue on a little Honda or Toyota ect...

    Some guys have a whole separate marine deep cycle batteries. Or AMG cells they carry with their feild charger. And then charge that back up once home.



    Sent from my Pixel 3 XL using Tapatalk

  3. #3
    RC Turnbuckle Jr. olds97_lss's Avatar
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    As mentioned, your likely better off getting a charger that will run on 12V than you are spending money on an inverter.

    I recently picked up a couple Revolectrix GT500's for $75. Not sure why, but they only have them out of the Singapore site now. I run them off a 24V PSU. On 24V, they are capable of 500W/20A each, on 12V, they are capable of 250W. I see them on ebay for $99. I run them at 15A to charge 2x3S 5000-6200mah in parallel.

    Most DC chargers are similar with much lower output at 12V than 24V+, so if you do get a DC charger, keep that in mind. Many don't list the 12V vs 24V output which is odd, they only list the max output and if the specs say input from 12-24V, expect that the max output will be based off the max input listed.

    There's also the GT1200 for $180 on ebay that will do 600W on 12V, 1200W on 24V. Could go for that and a parallel charge board.

    What capacity are your 4S packs your charging? Which dual charger do you have specifically? I thought last time I checked that Traxxas has 2 of them.
    https://www.youtube.com/c/olds97lss

  4. #4
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    Once we get our toy hualer I’ll have access to ac power with the generator. I already have all the traxxas chargers and ID lipo battery’s. My buddy gave me a 2600 watt inverter just wanted to know if it was big enough to run the chargers when we go on day trips with the pick up. I do have an AMG battery in my Silverado and dual battery’s will be in my new diesel I been drooling over lol. This gives me a good look at what I need thanks guys.
    3.3 t-maxx, O.S. .18TM t-maxx, HV brushless e-maxx

  5. #5
    RC Turnbuckle Jr. olds97_lss's Avatar
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    Does it have a sticker on the bottom of it? Usually electronic devices show the input v/a and you can do the math. On rcplanet, they list it as 100-240V 2.35A. So at 120V that would be 282 watts.
    https://www.youtube.com/c/olds97lss

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