another EV mystery

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Tom Thomson
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Joined: Fri Aug 31, 2007 12:48 am

another EV mystery

Postby Tom Thomson » Fri Jul 31, 2009 12:42 am

An unusual occurence this morn. I pulled out onto the road in 1st, shifted to 2nd and the car felt doggy. Pushed on the notgas pedal and noticed the amp gauge was displaying a low reading. As the car gradually gained speed, the amp draw increased. Normally the draw would start high and decline as the revs built up. For the remainder of the trip (21 miles) the system responded normally but the motor temp was 50 to 100 deg (F) above normal. 924 Porsche, Curtis 1221, D&D 15A-6, 84V lead acid system. Any thoughts????
tommyt

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Jeremy
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Postby Jeremy » Fri Jul 31, 2009 4:28 pm

Dirty brushes/commutator?

Sounds like a possibility, as they'd tend to clean up with use.

Might also be a loose connection, one that improved as it warmed up.

Jeremy

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ChrisB
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Postby ChrisB » Fri Jul 31, 2009 9:43 pm

Or maybe a battery with a high resistance cell ??

But I'd would have thought you'd have noticed this sometime before it got to this stage with other issues like poor range ?

ChrisB
I reject reality and substitute my own !!!!!!

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timpootle
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Postby timpootle » Sat Aug 01, 2009 5:38 am

I'm no technical help, I'm afraid.

Can we see a picture? I looked on evalbum.com and found several Porsche 924s but none owned by Tommy T.
Tim Crumpton

Tom Thomson
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Postby Tom Thomson » Fri Aug 07, 2009 9:01 pm

Thanks for the replies
Loose conn sounds unlikely. All terminals are crimped and soldered and wrench tite (5/16 scrs). In any event, getting hotter normally raises the resistance. The brushes could be the culprit; maybe some trash under one. That could happen quickly and with a lessening effect as it worked out or disintegrated???? A shorted cell also is unlikely as that would not correct itself in a matter of seconds. Yes, I have photos but I don't know how to do anything with them other than hold them by the edges and look at them. That's the reason the car is not on EV Album.
tommyt
ps Since that event, I am running at 239 w/mi so I think I'll pour another cup of coffee and forget about it.

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ChrisB
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Postby ChrisB » Fri Aug 07, 2009 9:41 pm

Tom Thomson wrote:Thanks for the replies
Loose conn sounds unlikely. All terminals are crimped and soldered and wrench tite (5/16 scrs). In any event, getting hotter normally raises the resistance. The brushes could be the culprit; maybe some trash under one. That could happen quickly and with a lessening effect as it worked out or disintegrated???? A shorted cell also is unlikely as that would not correct itself in a matter of seconds. Yes, I have photos but I don't know how to do anything with them other than hold them by the edges and look at them. That's the reason the car is not on EV Album.
tommyt
ps Since that event, I am running at 239 w/mi so I think I'll pour another cup of coffee and forget about it.


Maybe not a shorted cell but how about a cell thats got a cracked plate, must admit I've only had this with pretty old cells, one plate or plates fracture off the main interconnect spine, they ark for a moment and then weld themselves back up, my old Bedford CF electric did that to me several times, was a classic problem with these vehicles at start up just off charge, generally resulting in a hydrogen explosion blowing the top off half the battery pack :shock:
I had it happen a couple of times and got away with no more than a slight cracking sound and a hestitation.

Just a thought ?

ChrisB
I reject reality and substitute my own !!!!!!


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