Motorcycle Battery overheating, diagnosing the cause

Question

After trying to start the bike for about 30 seconds to no avail, I found that the screws attached to the battery had become hot to the touch. Taking the battery out and testing it with a voltmeter sparks began to fly off the battery. Needless to say I need a new battery.
I see 2 possible culprits for the battery overheating. 1: There's a short in some wires on the bike. 2: The battery itself has gone bad.
To support theory 1, the bike's been sitting under an awning for a while, with some parts unplugged. Covered it with a tarp but that isn't perfect protection from the elements. In addition, the front fairing of the bike as well as one of the horns, are not currently plugged in. Could these unplugged wires cause a problem with the battery?
As for theory 2, the battery is over 2 years old and I've charged it with a battery tender quite a few times. I'm hoping my problem can be fixed as easily as buying a new battery.
Some might suggest that the problem could be with the R&R but I doubt this. I had it replaced very recently and it showed no problems, plus I've successfully tested it with a voltmeter.

juhist · Accepted Answer

I suspect the sequence of events is the following:

The bike has developed some non-battery-related fault which prevents it from starting but doesn't prevent the starter motor from running.
You tried to start the bike with a good battery for 30 seconds. The current it takes to rotate the starter motor is very high. That current over 30 seconds heats all conductors that conduct electricity from the battery to the starter motor. In particular, screws holding the current conducting clamps around the battery posts will become hot to the touch.
You though the battery is faulty because the screws were hot.
You measured the battery with a multimeter, but with the wires accidentally in the current (Amperes) measuring positions.
Sparks began to fly.
You supposedly had further evidence for the "bad battery theory"

Why do I think this sequence of events is what happened? Firstly, if you tried to start the bike for 30 seconds, it is an indication that the starter motor was turning. Nobody would attempt to start the engine for more than 10 seconds if there's no sign that it's attempting to start.
Secondly, there's no reason for sparks flying with a multimeter with the wires in the proper voltage measuring positions. However, the wires in the current measuring position do in fact every time cause sparks to fly when misused that way.

I don't have a motorbike but my last car had 5.5 year old battery when I sold it. It was still going strong. My current car has 4.5 year old battery. Neither car had any battery changes in my ownership period.
I suspect motorbike batteries would be similar in quality to car batteries.

Motorcycle Battery overheating, diagnosing the cause

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