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Electronics => Electronics => Topic started by: MaltiK on February 17, 2009, 04:55:41 PM

Title: SLA Battery Spark?
Post by: MaltiK on February 17, 2009, 04:55:41 PM
I plugged in my 12v 24AH batteries into my wheelchair motors, not realizing the brakes had to be disengaged, I saw a huge spark as I disconnected, and some got on the floor. The motors ran fine after wards. My question is, is this normal for such a high current drawing device to draw a spark when disconnecting?
Title: Re: SLA Battery Spark?
Post by: Trumpkin on February 17, 2009, 06:36:31 PM
Yes, I think so.
Title: Re: SLA Battery Spark?
Post by: SeagullOne on February 17, 2009, 06:52:49 PM
You mean disconnect the electronics or disengage the the brakes? ???

I'm building a similar robot and just want to make sure... :)
Title: Re: SLA Battery Spark?
Post by: ArcMan on February 17, 2009, 08:30:19 PM
Dude, how could you not know to disengage the brakes before running your motors after all this...

http://www.societyofrobots.com/robotforum/index.php?topic=6706.0 (http://www.societyofrobots.com/robotforum/index.php?topic=6706.0)
Title: Re: SLA Battery Spark?
Post by: HDL_CinC_Dragon on February 18, 2009, 12:53:23 AM
High currents will tend to spark.
Title: Re: SLA Battery Spark?
Post by: MaltiK on February 18, 2009, 04:54:52 AM
Dude, how could you not know to disengage the brakes before running your motors after all this...

http://www.societyofrobots.com/robotforum/index.php?topic=6706.0 (http://www.societyofrobots.com/robotforum/index.php?topic=6706.0)


I was getting so many different answers, so I just assumed all were correct and worked from there. The only answer regarding them as being brake wires however, said that applying voltage to them will turn on brakes, however, it is vice versa. Where applying voltages turns off the brakes, and must keep the voltage applied to run.
Title: Re: SLA Battery Spark?
Post by: ArcMan on February 18, 2009, 06:14:34 PM
You are mistaken.  This is a direct quote from my post.

"The thin wires are to release the brake.  Just apply 24VDC to them and the brake will release.  Make sure you energize (release) the brake before you try to run the motor."
Title: Re: SLA Battery Spark?
Post by: MaltiK on February 19, 2009, 07:27:59 PM
Oh sorry I guess I catch that, I apologize. But what I wound up doing is taking the brake+the wire off completely. Apparently underneat is a hexagonal nut bolted to the end of the drive shaft, and it sits inside the brake pad, and the brake pad is sandwiched between two metal plates. When electricity is applied to the coil spring, the plates separate, allowing the brake pad to spin (along with the drive shaft). When there is no power in the coil spring, they then hold the brake pad between them, which in turn hold the nut, which in turn keeps the drive shaft from spinning. So when my motor goes vrooom the hexagonal shaped nut goes vrroooom with it since I didn't bother going deep inside the motor. But it works nonetheless. Placing two 12 AWG wires in one Sabertooth 2x25 terminal block is very challenging.