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I heard this could happen - first time for me.

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I heard this could happen - first time for me.

  #1  
Old 02-02-2019, 02:54 PM
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Default I heard this could happen - first time for me.


reversed polarity
Always make sure you get the polarity right when charging a dead battery (don't hook it up in the dark).
 
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Old 02-02-2019, 07:00 PM
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Let's see the full length of the leads, may we, sir?
 
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Old 02-02-2019, 11:51 PM
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The chemical reactions of a car battery are completely reversible. The battery,
however, must be completely dead for this to happen as when a battery is completely charged one set of plates (Anode)- is composed of Pb (or plain lead) and the other (cathode)+ is composed of PbO_2 or Lead-dioxide. The chemical reaction for discharge is as follows:

(Anode)- Pb + HSO4− → PbSO4 + H + 2e −

(Cathode)+ PbO2 + 3H + HSO4− + 2e− → PbSO4 + 2H2O\

The half reactions show that both sets of plates become PbSO4 or Lead-Sulfate. A completely discharged battery would essentially be a "clean slate" that could be charged either direction (in an ideal scenario). But it is unlikely to have a completely discharged battery (0V). Plus special current control factors are required.

 
  #4  
Old 02-03-2019, 08:39 AM
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Originally Posted by derf View Post
Let's see the full length of the leads, may we, sir?
Sorry, I only have two hands. I was lucky to get as good a picture as I did. There's no funny business going on with the leads though.

In fact, I put this battery in my truck after mistakenly charging it backwards and sparks flew when I connected the cables. I found that if I disconnected the wire going to the alternator I could hook things up without sparks (can anyone here guess why that was?). Tried to start the truck and while it would crank just fine it wouldn't start. I checked the coil voltage and it was zero.
That was when I put a meter on the battery and discovered the reversed polarity. Just for kicks I swapped the battery cables and tried again and it started right up.
That was really weird watching that thing run with the battery connected backwards.
So, like I said, I originally connected the battery to the charger in the dark thus getting it backwards and it was in fact a completely dead battery. I had hoped to bring it back to life with a long slow charge. Well I did bring it back to life, just not like I planned. Now I have a light connected to the battery in an attempt to completely discharge it again so I can try to flip the polarity back to normal. I just hope the battery survives all this since it seemed to be in decent shape once fully charged.
 
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Old 02-03-2019, 01:08 PM
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You may have blown out a couple alternator diodes. Check for proper alternator operation after you get your battery sorted out.
 
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Old 02-03-2019, 07:04 PM
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Somehow the alternator survived it although I'm sure it's life has been shortened to some degree.
After I got it running I went ahead and pulled the battery (since I didn't see the point of letting it recharge again) and it ran fine on just the alternator.
I'm lucky I didn't appear to do any damage to the engine either since after some thought I realized I must have been cranking the engine over backwards before I tried reversing the battery cables.
 
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Old 02-03-2019, 09:14 PM
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You still need to check for proper alternator function. Have it tested for no a/c ripple and proper voltage regulating.
 
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Old 02-04-2019, 09:04 AM
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I got the external regulator but yeah, good idea.
I don't need to mess up the electronic ignition (it's a wonder I didn't already).
Everything else on this thing is old school so they should be fine.
 
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Old 02-04-2019, 09:16 AM
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Originally Posted by jamnar View Post
Somehow the alternator survived it although I'm sure it's life has been shortened to some degree.
After I got it running I went ahead and pulled the battery (since I didn't see the point of letting it recharge again) and it ran fine on just the alternator.
I'm lucky I didn't appear to do any damage to the engine either since after some thought I realized I must have been cranking the engine over backwards before I tried reversing the battery cables.
I don't think it's possible to crank the engine backwards by reversing the polarity on a battery. BUT, I'm not a mechanic.
 
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Old 02-04-2019, 05:42 PM
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I find it exceptionally hard to believe that the PCM and any other integrated circuits would possibly function properly what's the polarity reversed.

Yet here we are.
 

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