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Thread: Car Battery 12v for development (and not charging the LiPos every couple of hours)

  1. Car Battery 12v for development (and not charging the LiPos every couple of hours)

    Hello Everyone.

    i have the exapod Mark II. and, in order to avoid the constant use of the LIPOs i thought (or read at this point i do not remember anymore to use a car battery ( that can give a lot of energy, 12v- and any amps the hexapod could need)

    in the picture shows that i connected the Car battery but the Arbotix do not even power up, (no lights , nothing), according to the manual arbotix should manage DC 6v-16v no problem . But it does not turn on at all.
    meassured batery voltaje (its new), and it is ok, 12.6- 13v.

    any idea why does not even power up ? (if i came back to the LIpos everything works beautifuly)
    i check voltaje regulator in the arbotix does not get hot, and no lights are turning on.(as if dead)
    what am i missing ?
    what is the way to use either a direct power supply or what am i doing wrong here ?

    thanks in advance !


    Last edited by martinvecchio; 06-15-2013 at 07:21 PM.

  2. Re: Car Battery 12v for development (and not charging the LiPos every couple of hours)

    hi, it is because the motors are brushless dc and they may need the inverter that sometimes is included in the original battery. Let me know if I am right.

  3. #3

    Re: Car Battery 12v for development (and not charging the LiPos every couple of hours)

    the motors are brushless dc and they may need the inverter that sometimes is included in the original battery
    There is nothing in this sentence that makes sense.

    First, he's trying to power an Arbotix, which is a microcontroller board. It should run fine off a car battery.
    Second, the hexapod is obviously using Dynamixel servos, which do not need separate motor drivers.
    Third, I have never seen an inverter built into a battery pack.
    Also, the more common name for them in hobby circuits is "ESC" (electronic speed control) as "inverter" is typically used for heavy-duty equipment (house power, electric cars, etc) but I think it's technically correct to still call the hobby-size ESCs "inverters" just like BECs are really "DC DC power converters" :-)

    So, Arbotix not working? My only guess is that you're either hooking it up with reverse connections (switched + and -) or you have a break in your connecting wire or connectors somewhere.

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    Re: Car Battery 12v for development (and not charging the LiPos every couple of hours)

    Quote Originally Posted by EnrikDS View Post
    hi, it is because the motors are brushless dc and they may need the inverter that sometimes is included in the original battery. Let me know if I am right.
    WTF? This is a legged bot, not a plane or helicopter. The bot uses dynamixel servos (AX-series) which have all the brushed DC motor control internal to the servo. Just apply power and sends serial commands.



    Quote Originally Posted by martinvecchio View Post
    Hello Everyone.

    i have the exapod Mark II. and, in order to avoid the constant use of the LIPOs i thought (or read at this point i do not remember anymore to use a car battery ( that can give a lot of energy, 12v- and any amps the hexapod could need)

    in the picture shows that i connected the Car battery but the Arbotix do not even power up, (no lights , nothing), according to the manual arbotix should manage DC 6v-16v no problem . But it does not turn on at all.
    meassured batery voltaje (its new), and it is ok, 12.6- 13v.

    any idea why does not even power up ? (if i came back to the LIpos everything works beautifuly)
    i check voltaje regulator in the arbotix does not get hot, and no lights are turning on.(as if dead)
    what am i missing ?
    what is the way to use either a direct power supply or what am i doing wrong here ?

    thanks in advance !

    Have you checked your wiring's continuity with a multimeter? Is there actually 12V reaching the arbotix, or is it not making it past your masking tape splice? I do not trust twisting cables together and then applying tape to ensure a solid electrical connection. Crimp connectors and solder are both easy and inexpensive ways to ensure a very reliable connection. Also be aware that while the arbotix can accomodate up to 16V, the AX-series servos will probably not like a voltage larger than 12.6V (maximum from a fully charged 3S LiPo battery). The AX-servos were originally designed for 8S NiMH batteries (9.6V) and well regulated 12V power supplies.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

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    Re: Car Battery 12v for development (and not charging the LiPos every couple of hours)

    Martin, are you aware you built your Hex with the body upside down? Not that it matters I suppose, just a deviation of the assembly guide. Though it leaves your wires down the legs very loose and prone to getting caught in the legs. In regards to the car battery, I would agree with the others it has got to be the masking tape splice. Can you give us closer pictures of that wiring job?
    Last edited by KevinO; 06-15-2013 at 11:03 PM.

  6. Re: Car Battery 12v for development (and not charging the LiPos every couple of hours)

    Thank you all for the replys !

    QUOTE=KevinO;58441]Martin, are you aware you built your Hex with the body upside down? Not that it matters I suppose, just a deviation of the assembly guide. Though it leaves your wires down the legs very loose and prone to getting caught in the legs. In regards to the car battery, I would agree with the others it has got to be the masking tape splice. Can you give us closer pictures of that wiring job?[/QUOTE]

    thks KevinO, ... (good eye you have ) !

    i checked voltage and continuity on the wiring at the end plug (that connect to the harness wire to the arbotix.), and it was 12.6v /13.2v. But after what i read, i will double/triple check on it tomorrow (the battery is at the "office" ). i will include pics.

    here goes the question:
    " Is there some protection circuit in the arbotix board that cuts off the power if voltage goes over 13v, that would be the reason i seeing Nothing when i connect the mower battery ?
    ....it was my guess that the battery is a little bit higher voltage and there is something protecting the board. so i was shooting for a voltage regulator.... hopefully is just a bad assembly on my side.

    thks for the reply , more to follow.

  7. #7

    Re: Car Battery 12v for development (and not charging the LiPos every couple of hours)

    What I do is keep a wire that has both a male and a female Deans Ultra plug, that goes out to the connector to my 'bot (not an Arbotix, though.) I plug in the battery to the male, and my power supply to the female (as it has a male plug that mates to the battery for charging as well.) Then I set the power supply to a safe "float" voltage for the LiPo -- 15.8V or so for a 4S LiPo, 11.8V for a 3S LiPo -- and run them in parallel. While the bot is just idling, the power supply provides all the current; when a servo current surge happens, the battery provides the raw brawn but immediately gets floated up to the power supply voltage.

    Note that it's not a good idea to "trickle charge" a LiPo battery, but a float voltage is different from a trickle charge, so this hasn't ruined the battery so far. It does require a power supply with good voltage adjustment, though.

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    Re: Car Battery 12v for development (and not charging the LiPos every couple of hours)

    I ended up getting a 12V 25A fixed voltage supply from CircuitSpecialists.com for $50. I made an 8ft "umbilical cord" using doubled up 16ga speaker wire with a Deans connector on the end. There's a small voltage adjustment range on the supplyso i set it to 11.1V at the servos under load. It works like a champ. The hex runs identically to how it does on lipo power even when crawling all over the ground at full speed.

  9. Re: Car Battery 12v for development (and not charging the LiPos every couple of hours)

    I did the soldering now is a neat job (please do not mind the colors, i know they are inverted realize after soldering, .... so i inverted black and red in the battery). still nothing on the hexapod Mark II.
    i also tested on the arbotix included in the robo turret as well. same issue.... nothing turns on, not even the light on the board.

    STILL NOT WORKING.
    im buying now the VARIAC 12v 25Amp recommended.


    -----------------
    here goes my thoughts:
    • all the lipos i meassured at open circuit and they look like a 15v-16v
    • the transformer that came with ROBO TURRET (that feed and arbotix with only two servos AX-12) as well is about 17v OPEN circuit.
    could it be that the arbotix does not recon anything unless over 14v or so??

    anyway im buying the VARIAC,... i thought... but it should have been easier is DC, and 12v...


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    Re: Car Battery 12v for development (and not charging the LiPos every couple of hours)

    The power supply is definitely the way to go.

    I notice you don't have any shrink wrap on those exposed solder joints. Be very careful what that touches. Sparks will fly if that shorts itself.

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