The lamp icon lights up when starting the engine.

[jung]

When I press the on button and start the engine, (Cold start)
The engine starts with difficulty, and at that moment, the lamp icon shown in the picture appears, and then disappears after the engine starts.

Is it because the battery voltage is low?
My motorcycle is 3 years old, and when I press the on button, the voltage comes out to about 12.2~12.5 depending on the temperature.
Even if I fully charge the battery with Optimate 4, it's the same.

Some people say that when they start the engine, they briefly kill the lamp to fill in the insufficient voltage, and then make it normal again.

If the battery is the problem, the battery icon should light up, but why is the lamp icon on?

Has anyone experienced the same problem?

 

[Anibal]

Sorry, I can’t help you out as the B does not have that symbol, however, if you consult your operator’s manual (free download from BMW Motorrad) and search for “warning lights” in the Index, you should be able to see what the symbol means.
I agree with you, a battery symbol would be the expected icon if the battery was the issue.
A light bulb in my eyes will indicate one bulb is about to die or something. Having said that, a faulty light bulb on the B is not displayed as a bulb icon, it is an amber triangle and a message.
Also a faulty bulb would not hinder the engine start up.
Keep us posted and hopefully another Classic owner will be able to shed some light.

 

[Star-Lord]

It might be a good idea to replace your battery if getting within the 3 to 6 year mark; especially, if the bike is struggling when starting.

It looks like your bike is complaining about a Bulb; have you visually inspected all of the Lights?

Also, it might be a good idea to inspect all wiring Ground connections (Typically Brown color wiring)

The below image is from Page 25 within the manual:

 

[Petr Kunc]

R18 have various options for lights. Daylight or driving light. Might be that your bike is set to use driving light in prior and the Amp consumption goes up during starting. LED main unit can be switched off to save more Amps for starter and main ECU can then evaluate it as a broken bulb. BMW electronics is black magic i must say. Do you have alarm system installed and active, maybe? (Red ''ladder'' icon flashing when bike is off) It can drain the battery. Also the key close to the bike can drain both bike and key battery (personal experience ) as they are constantly chatting. I am connecting my R18 to the BMW charger once in a month and it's always charging for at least one hour even though everything is off.
Last but not least - modern batteries are crap

 

[jung]

R18 have various options for lights. Daylight or driving light. Might be that your bike is set to use driving light in prior and the Amp consumption goes up during starting. LED main unit can be switched off to save more Amps for starter and main ECU can then evaluate it as a broken bulb. BMW electronics is black magic i must say. Do you have alarm system installed and active, maybe? (Red ''ladder'' icon flashing when bike is off) It can drain the battery. Also the key close to the bike can drain both bike and key battery (personal experience ) as they are constantly chatting. I am connecting my R18 to the BMW charger once in a month and it's always charging for at least one hour even though everything is off.
Last but not least - modern batteries are crap

I think the problem is that the battery voltage has dropped compared to the beginning.

I turned off the alarm system a long time ago.

Could this be because the r18's system draws insufficient voltage from the lights to start the engine?

You can find out by replacing the battery with a new one.
I fully charged it and can still use it.

 

[jung]

It might be a good idea to replace your battery if getting within the 3 to 6 year mark; especially, if the bike is struggling when starting.

It looks like your bike is complaining about a Bulb; have you visually inspected all of the Lights?

Also, it might be a good idea to inspect all wiring Ground connections (Typically Brown color wiring)

The below image is from Page 25 within the manual:

View attachment 16572

If you test after the engine is completely started, there is no problem with the turn signal or lights.

 

[Petr Kunc]

Might be, i am not sure if drive light is dimmed during start. I am using day light and automatic switching to driving light.
But i had this problem on my Triumph Speed Triple, where the main light is dual and it's turned on with main ignition switch. I had to install time delay relay, because starter was caughing. 2x H7 bulbs =100W and even with new gully charged battery i was not never sure if it will fire or not

 

[RhoXS]

I have received lamp alarms on my TC due to low voltage on startup. It clears immediately after start.

 

[Star-Lord]

What is the battery voltage once the bike is started and has been idling for a few minutes? Should be around 13.8 V from the alternator.

Also, why not leave your battery tender plugged in continuously? The charger - tenders are a LOT smarter than older trickle chargers, where they maintain the battery's float voltage and goes into standby mode once charged.

 

[jung]

What is the battery voltage once the bike is started and has been idling for a few minutes? Should be around 13.8 V from the alternator.

Also, why not leave your battery tender plugged in continuously? The charger - tenders are a LOT smarter than older trickle chargers, where they maintain the battery's float voltage and goes into standby mode once charged.

After the engine starts, about 14.4v comes out. It's the same even when the battery is fully charged.

 

[jung]

I have received lamp alarms on my TC due to low voltage on startup. It clears immediately after start.

It seems to be the same symptom. I think it's because the voltage is low. After fully charging the battery, it seems to have improved slightly.