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I have a motorbike with a wet battery. I use its electric starter to start the engine.

Is there any research done by others before to prove which one of the following makes the durability of the wet battery shorter?

Assume the motorbike is well-maintained and still in factory default settings.

Case 1: The lights are turned on before pressing the electric starter button until the engine starts.

Case 2: The lights are turned on after pressing the electric starter button and the engine starts.

Note: I am only interested in the scientific data because without it, I can say nothing to my debate partner.

I said to my debate partner that both methods are fine. However, my debate partner said the first case makes the battery life time shorter. He cannot give me the proof as well. :-)

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Actually with most bikes, there isn't much of a difference between cases 1 and 2 as they tend to cut the power to the headlight when you crank the starter motor. – Timo Geusch Dec 24 '12 at 22:12

Where possible, have as few electrical items switched on as possible when you start a car or bike.

You want to do this any way, as if the battery is a bit low, the load can drain it rapidly and you may not start the engine, but in any case you will require more recharge cycles, which will reduce its life.

Additionally, if the current drawn is too high you can start to cause chemical changes in the battery which may also shorten its life.

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+1 for reducing current draw. This is why some motorcycles (and all cars I've ever seen) use load-shedding relays to turn off accessories when the starter is engaged. The corollary to this, of course, is that if the bike in question uses such a load-shedding relay, it doesn't matter whether you switch the headlight on (immediately) before pressing the starter button or after. – mac Dec 18 '12 at 14:35
Standard procedure for starting an airplane is to turn on the beacon light (as a warning to anyone near the airplane) before starting. However, in cold weather that's not done, sometimes even that little extra draw can make the difference between the starter pushing the prop over the hump or not. – Brian Knoblauch Dec 18 '12 at 14:51
I am so sorry. I cannot mark it as the accepted answer until you can show me the technical proof. – kiss my armpit Dec 21 '12 at 15:25
Not sure what proof you want, dude - that's just the way it is :-) – Rory Alsop Dec 21 '12 at 16:16
References should be unnecessary, and likely won't exist, when you're talking about something so elementary. It's like asking for a reference to show that 2+2=4. Taken with the important caveat about load shedding relays, this simply is the way things are. If you want to know more, get a chemistry textbook and learn enough electrochemistry so that you can see how elementary this is. – Colin K Dec 24 '12 at 18:19

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