Battery problem - Possible Short?

[LibTimothy]

My Pinz has been having battery problems lately. First the batteries went dead and had to be charged, but I caulked this up to the batteries being old.

Then the pinz has been hard to start, cranking slowly, but then catching and starting.

But this weekend, I went to start the Pinz and as soon as I turned hit the starter button, the lights on the dash dimmed. I pulled open the battery box, and saw smoke. Upon closer examination I saw that the positive voltage terminal was burnt and the battery has a crack in it. The terminal connector was burnt and melted.

Here is the battery terminal:



I can't decide it there must be a short or if this was caused by the starter current with a bad connection.

I will check the charging voltage as soon as I get new batteries. But before I put new batteries in the Pinz, is there anything I should check as a possible short? I traced all the wiring from the battery box to the starter, and did not find anything that looked burnt. (I assume that a short that can melt a battery terminal should have some burnt area around the short.) Could my starter have caused this?

Thanks for any ideas!

Timothy

[Jimm391730]

Typically, a "short" or high current draw from the starter (and I have seen this occur as the starter gets old and filled with carbon dust from the worn brushes) will heat the wiring, crimps, and other parts of the conductive path before it would be able to heat the lead of the battery post. From your picture I would guess that you just had a poor connection between the post and the battery clamp. In the small area where current was flowing it was concentrated enough to create localized heating -- in other words, the current was compressed into a smaller area at the post than anywhere else in the wiring, crimps, etc. The lead battery post is NOT the best conductor of electricity and this is why the posts are as large as they are (but lead is easy to work with in the manufacturing of batteries) so if current cannot flow evenly through the post then the lead is able to be melted. But the lead post has quite a bit of mass, and because of this it doesn't heat quickly (generally much slower than wires, crimps, or ring terminals which are of much less mass and material). Hence my suspicion that the connection between post and clamp was not good, or at least not good everywhere that the clamp touched the post.

Secondly, the battery positive runs through a heavy wire directly to the starter. When you push the starter button a small amount of current energizes the solenoid which extends the starter gear, but the solenoid also makes the high current connection to the starter motor from the heavy wire. From there the current flows through the starter motor and back to the chassis; so any "short" would need to be within the starter itself and this is not very likely. If you had shorts between the battery positive wire and the chassis somewhere then you would have "shorts" at times other than when you go to crank the engine.

So yes, as you say, a "short" would show up as a burned or hot spot somewhere in the wiring other than the battery terminal post.

It is also possible that the lead connections internal to the battery have aged and are creating heat, possibly directly under the terminal; this may have added addtional heat to the terminal. It gets really ugly when the battery internal connections melt as the resulting spark can ignite the hydrogen within the battery, causing a battery explosion. The resulting spray of acid is nasty in an engine compartment! (probably would be a much less drastic scenario within the Pinz battery box, but it could explode the box!). It might be time to invest in new batteries.

I've seen simple ammeters that just fit next to the battery cable and can measure the cranking amps and I suspect that many battery shops would have such a device; it would tell you how much current was being drawn during cranking. I wouldn't expect a Pinz to draw more than 100-150 amps although I haven't measured it. If the current is acceptable then I would definately say that the battery clamp connection was the culprit.

[LibTimothy]

Thanks Jim.

Your explanation is very similar to what another friend told me tonight on the phone after I posted here. I was worried that the starter could draw so much current that it would look like a short. Good to know that is unlikely. Good to know that there are not other common shorts either.

I plan to get two new batteries this week and I will put new terminals on the wires and make sure that they are clean with good electrical connections.

Thanks again!

Timothy