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Discussion Starter · #1 ·
Went out to get on my RT yesterday and the battery wouldn't turn it over; just kind of grunted a couple of times and then nothing... I had ridden it a hundred miles or so a week ago. I had it fail to start one time back at the first of the year and the dealer checked it at the 12K service and reported that the battery was good. So the battery is two and a half years old and not dependable. I charged the battery on a Battery Tender and when I took it off, it registered 14.1 on the meter on the dash. Also, the battery tender was too hot to hold, which I had never noticed before.

So, I have a new battery coming tomorrow and also have a new starter relay. Mechanic work in my un-air conditioned garage has to be done early when the predicted high is 100. We'll see what transpires.
 

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2021 BMW R 1250 RT, 2020 BMW R 1250 GSA, 2014 HD FLHTK, 2005 Honda Goldwing
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Battery power at rest and under load (cranking power) are not one and the same. A bad battery does not generate enough of the later. Had a very similar problem with the 2020 GSA during the first year of ownership. Defective battery! Apparently not entirely uncommon with newer BMW bikes. Annoying but an easy fix. Hope your bikes starting issue can be remedied just as easily. Good Luck!
 

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In your comment, hot garage. A hot climate also shortens battery life. The only real way to test a battery is check voltage under starting load. It should not dip below 10 volts. There are electronic battery test units out there but expensive. And the testing (unless using the bike starting as the load) should be done with the battery disconnected from the bike circuits. BMW bikes are very good at using up a battery. Your alternator in the bike runs at about 14.3 or so. As mentioned a decent VOM ( (volt ohm meter) is needed to really get an accurate reading. I'm also concerned about your comment on your smart motorcycle trickle charger being hot. You need a reasonable quality unit there also.
 
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Discussion Starter · #4 ·
Thank you both for your replies. Deltran says that it is normal for Battery Tenders to get hot, like 130f or so, during the heavy phase of the charging. Just remember to not set it on your seat...
 
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