15 RT Battery question..

rvint · Nov 13, 2017

My 2015 RT has about 40k miles and is ridden nearly everyday. I've recently noticed that if the bike is not ridden for more than two/three days consecutively, it is hard to start. Sometimes to the point that the battery seems to become so weak that it seems as if it's going to give out all together. I began putting it on the Battery Tender when I know I won't be riding for a couple of days but most often, that doesn't seem to make any difference. I've given in to the idea that I simply need to replace the battery but, I'm wondering if I should be surprised by this? This is my third BMW but my first RT. Are the RT's harder on batteries for some reason? Or, is a couple of years all that I should come to expect from the life of a modern battery? Both before and after I began using the Battery Tender, the voltage indicated around 9 but very quickly climbs to 14 once the bike fires up. I commute daily for right at 30 minutes/15 miles one-way and the garage remains at a consistent 72-75 degrees.

wbrownell9 · Nov 13, 2017

When I had a boat the conventional wisdom was that more batteries were killed by neglect than died of old age. How far do you ride when you go out - enough to restore what you took out starting it? What's the resting (before starting) voltage after it's set a few days? If it's on a tender, unplug it and give it a half hour to settle before you measure the voltage. The OEM AGM battery should be 12.8+ (100%); 12.6 is 75%, 12.0 or below is basically dead. Even if resting voltage is good it may not be able to deliver enough current and you (or a shop) need to load test it to verify that. So many variables there's no "right" answer but I regularly have at least a half hour with the revs over 3500 and have had no issues keeping mine charged. Very seldom do I go places just a few miles apart without "needing" to go somewhere 25 miles away by curvy road too

Something is wrong either with your battery or the charging system, several times I've let a WC boxer set for for over week in a cold garage with no tender and it started fine.

pglaves · Nov 13, 2017

rvint said:
Are the RT's harder on batteries for some reason? Or, is a couple of years all that I should come to expect from the life of a modern battery?

Que the "my batteries last 9 years" and the "I'm lucky to get three years" guys and gals. Also the "I always use a tender" and the "I never use a tender" folks.

t6pilot · Nov 13, 2017

I’ve been happy using optimate 4’s on my bikes and Porsche
Does its magic and desulfinates battery and cycles through charging
That said my 15RT battery will be 3 years old next spring and will get changed before summer riding season
Anyone have a recommendation for quality replacement?

AKsuited · Nov 14, 2017

rvint said:
I've recently noticed that if the bike is not ridden for more than two/three days consecutively, it is hard to start.

Maybe it's something other than the battery.

rvint · Nov 14, 2017

wbrownell9 said:
When I had a boat the conventional wisdom was that more batteries were killed by neglect than died of old age. How far do you ride when you go out - enough to restore what you took out starting it? What's the resting (before starting) voltage after it's set a few days? If it's on a tender, unplug it and give it a half hour to settle before you measure the voltage. The OEM AGM battery should be 12.8+ (100%); 12.6 is 75%, 12.0 or below is basically dead. Even if resting voltage is good it may not be able to deliver enough current and you (or a shop) need to load test it to verify that. So many variables there's no "right" answer but I regularly have at least a half hour with the revs over 3500 and have had no issues keeping mine charged. Very seldom do I go places just a few miles apart without "needing" to go somewhere 25 miles away by curvy road too

Something is wrong either with your battery or the charging system, several times I've let a WC boxer set for for over week in a cold garage with no tender and it started fine.

Both before and after I began using the Battery Tender, the voltage indicated around 9 but very quickly climbs to 14 once the bike fires up. I commute daily for right at 30 minutes/15 miles one-way and the garage remains at a consistent 72-75 degrees.

patm · Nov 14, 2017

rvint said:
Both before and after I began using the Battery Tender, the voltage indicated around 9 but very quickly climbs to 14 once the bike fires up. I commute daily for right at 30 minutes/15 miles one-way and the garage remains at a consistent 72-75 degrees.

That means the charging system is working as expected but the battery is dead. There are many resons why a battery fails, some last for years, others fail quickly. They all fail eventually. At 9 volts, I would suspect a defective cell in the battery. Replace.

rvint · Nov 16, 2017

patm said:
That means the charging system is working as expected but the battery is dead. There are many resons why a battery fails, some last for years, others fail quickly. They all fail eventually. At 9 volts, I would suspect a defective cell in the battery. Replace.

Thank you Pat for the blunt, no BS answer. You've been most helpful.

mojoman · Nov 16, 2017

Hard to Start

Take it to a garage and have them check the battery. That should tell you if you need a new one or not instead of just guessing.

rvint said:
My 2015 RT has about 40k miles and is ridden nearly everyday. I've recently noticed that if the bike is not ridden for more than two/three days consecutively, it is hard to start. Sometimes to the point that the battery seems to become so weak that it seems as if it's going to give out all together. I began putting it on the Battery Tender when I know I won't be riding for a couple of days but most often, that doesn't seem to make any difference. I've given in to the idea that I simply need to replace the battery but, I'm wondering if I should be surprised by this? This is my third BMW but my first RT. Are the RT's harder on batteries for some reason? Or, is a couple of years all that I should come to expect from the life of a modern battery? Both before and after I began using the Battery Tender, the voltage indicated around 9 but very quickly climbs to 14 once the bike fires up. I commute daily for right at 30 minutes/15 miles one-way and the garage remains at a consistent 72-75 degrees.

strataj · Nov 16, 2017

mojoman said:
Take it to a garage and have them check the battery. That should tell you if you need a new one or not instead of just guessing.

You can do this at WalMart, Auto Zone, all do it at no charge, you need a load test

Jay

gsinnc · Nov 16, 2017

strataj said:
You can do this at WalMart, Auto Zone, all do it at no charge, you need a load test

Jay

My dealer will do it for no charge as well.

pauls1150 · Nov 17, 2017

Just a little head's up re the load test - When I took a battery over to my local O'Reilly's, they hooked it up, and started the machine based on a book they had that defined all (?) the available batteries, ok that's fine...
But the very first part of the test was that it actually gives the battery a small boost before testing. I immediately had them stop that - I (we...) want to know the condition of the battery NOW, in it's worst case state. They understood, and disconnected the battery, waited a few minutes, and hooked it up again - it failed.

15 RT Battery question..

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