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Electronics => Electronics => Topic started by: Mastermime on January 11, 2013, 08:22:50 PM

Title: Spark Eating Away At SLA Battery terminal
Post by: Mastermime on January 11, 2013, 08:22:50 PM

Hello everyone,

I'm testing my the functionality of my drivetrain (treads). I'm testing it using 2 12v SLA 50 amps batteries hooked up in series.  The scooter motor I'm testing is 24v 400 watt 23a peak current.  I dont believe thats the startup current though.

Anyways, I just went to test it and when I just touched the negative jumper cable to the negative battery terminal.  Everything spinned correctly, but when I touched the cable to the negative terminal, it appeared as if the connection was eating at the negative terminal. 

Is this normal when working with high amperages?

Could this have been because I didn't clamp it on the terminal, rather just touched it?

I just wanted to ask so I dont ruin anything.

Thanks

Title: Re: Spark Eating Away At SLA Battery terminal
Post by: waltr on January 11, 2013, 08:46:27 PM

Yea, that could happen for two reasons
1- the connection is arcing due to being slightly intermittent
2- the connection is heating due to resistance in the spot touching and not a good solid connection.

If the motor draws ~23Amps while running it could easily draw over a hundred Amps on start-up.
Do you know the Stall current or the winging resistance of the motor?

You may ruin is the battery terminal if you do this until there is not enough of the terminal for a proper connection later. Also, if the terminal get too hot it can melt the battery case and thus the terminal mounting in the battery could move or even get disconnected from the plates.

Its ok for a few quick, short tests (which have already done). Now its time to get a proper switch that can handle the current.

Title: Re: Spark Eating Away At SLA Battery terminal
Post by: Mastermime on January 11, 2013, 10:26:34 PM

ok thanks for your help.  I definitely believe its the first reason- the connection is arcing due to being slightly intermittent.  I tested with a battery connector and that seemed to work fine for what I was testing. Thanks again.

Title: Re: Spark Eating Away At SLA Battery terminal
Post by: Tommy on January 12, 2013, 07:50:35 AM

Quote

it appeared as if the connection was eating at the negative terminal.

Mastermime, to save your battery terminals you could use a car starter solenoid (or starter relay)
for testing the motor, most hardware stores stock them also.

Tommy

Title: Re: Spark Eating Away At SLA Battery terminal
Post by: Mastermime on January 21, 2013, 01:14:23 PM

Thanks for the suggestion Tommy.  I just put a temporary automotive connector and that served its purpose well and I accomplished all the testing I needed