Gel Battery will not start when engine hot

[Mike.Craft]

Hi Guys,

I would appreciate your help with this one and to know if anyone else has had the same problem.

I have a BMW R1200RT with a genuine BMW gel battery. The bike starts fine when it has been parked for a while or overnight, but once I have been riding for a while and the bike has warmed up, the engine struggles to start if I turn off the ignition and then try to restart. It begins to turn over, then all of the LCD display lights go out and the starter motor stops turning. Then after about half a second of "dead bike", the starter turns the engine again and it starts as though nothing is wrong. If I leave the bike parked for 30 mins or longer, it starts normally as it did before riding it.

This problem happens even if I have left the bike in the garage with my Optimate 4 charger plugged in all night. I have tried riding with a small digital volt meter plugged into the accessory power socket and I get about 14 volts at all times, even in slow traffic or when idling, so it seems to be charging ok.

This battery is only about a year old and replaced a previous gel battery that exhibited similar problems. For a while changing the battery seemed to cure the problem, but it has developed the same fault over this past year. The bike is used reasonably regularly and I keep the battery topped up with the Optimate charger every couple of weeks if I have not been riding it.

Has anyone else had a similar problem with gel batteries or has any suggestions??

Regards,
Mike

[mogu83]

Assuming it's not the battery. Did you try removing and cleaning the connections of the cables coming off the battery (both ends). That's what I would do next.

[Mike.Craft]

Thanks Mogu83,

I will give that a try and let you know what happens.

Regards,
Mike

[dbrick]

A heat-related failure in the starter relay might show the same symptoms. If you've a friend with a bike that uses the same relay, you might trade parts overnight to see if the failure migrates to the other machine.

[deilenberger]

Or - the starter is binding up when warm. There is a nose-bushing in the starters that is known to wear with time/use. It might be worth pulling the starter out to take a look at it (and lube it while it's apart- it's likely an oil-lite bushing - sintered bronze - so soaking it in engine oil overnight will work just fine.)

BTW - the age and miles on the bike might be significant in this case - and I don't see that info given anywhere..

I think your best bet is to sell the RT and just buy an R.. but I might be biased..

[Bob Ain't Stoppin']

Agree on the info posted so far. You should put the voltmeter right on the battery terminals (not the cables) and watch it during a hot start. If the battery voltage is going low at that time, you have a bum battery that can't supply normal current or starter needing attention that causes excessive current flow (per Don's post). If the voltage stays high, you have a poor connection that is limiting current flow to the starter (per Mogul post).

[zackvis]

Hi
It is your starter motor take it off and clean it out espesialy the brushes and the commutator .I had the same problem ,changed the battery and it seems better for a while but started the same nonsence again .Since cleaning it ,which by did not look too bad as i have a 2009 it has never played up again.
The com gets dirty and the brushes sticky and the do not connect as well as they should thus not allowing enough current thru into the coils
of the motor.