BMW R1200R R1150R/T F800 K1200R R1100R/T R1250R RnineT Message Board

My R1150R lives in an inclosure that has no electrical outlet. Each week my battery loses .6 volts. In my experience if it reads even a little below 12 volts the bike may not have enough juice to start. I ride most weekends, but if I can't, I run a cord to the enclosure and plug in a charger. This weekend, because of weather, I did not ride or charge. I predict that if I do nothing, next weekend the battery should read 11.6 volts - which is fine, I'll plug in the charger when the weather clears. I'm wondering...how low can the battery go before it is compromised ?

If your battery looses .6 V in a week, that's a bad sign. Do you use an alarm system? When it gets close to 12 V it's only charged for 50%.
The clock on the dashboard doesn't use that much power.
It shouldn't get below 12V or your killing the battery. Unless there is something draining your battery, it's almost ready to be replaced.
Getting below 12V regularly, really shortens the life expectancy of the battery.

What drains my battery is the usual: motronic and the clock. Plus.... what exacerbates the parasitic drain is the Kisan signal monitor I installed. When I leave town I pull the motronic and clock fuses and the Kisan unit; the battery stays charged for over a month. Nice of those genius German engineers to bury the battery do I can't just disconnect.

Have you considered a solar panel? I have a couple smaller rectangular, about 4” x 12” on my shed to maintain my ATV and Riding lawn mower batteries. They work great and do not need direct sunlight to charge.

Glad you brought that up, Tundra. I installed a 2.5 W solar panel from a company called NOCO and modified the connector to fit the wiring running from my battery. Under a clear sky it would put out 18 volts; I thought that was sufficient but that wouldn't charge the battery. Maybe it wasn't sending enough amps ? Without access to the battery, I didn't know how to read the amp output. What brand do you own ? What's the W rating ? You say you have two; are they connected ? FWIW I fought through the snow and took a reading; the battery had 12.1 V. I thought it best to run the cord and connect my charger.

https://www.homedepot.com/p/Coleman-2-W ... /203241468

I have 1 of these, they only work if the battery is fully charged. It's a maintainer, not a charger.
Kept my battery fine for 3 months. The clock will drain the battery.

The rule I heard is 11 volts, it's toast.

That 2 watt Colman is the exact panel I use on smaller Batteries. I use a larger 6 watt square panel in a car port where I park my Truck. It sits for weeks at a time, here in sub-Zero temperatures and starts right up.
The mower Battery is twice the size of most Motorcycle batteries and the crank over speed is noticeably faster if I had the 2 watt panel connected to it.
That being said I use a Deltran battery tender on the garaged Motorcycles. Running it on each until the light is green every couple weeks. I even bought 3 ft. SAE connector extensions to hang down under the Motorcycle covers.....Hey...winters are long on the Tundra.

My Clock seems to drain down enough of the battery in three weeks that it turns over but won't start.

Thanks for the info. I'll look into the Colman panels; they seem to be readily available and inexpensive. Since I've had a bad experience with a 2.5 charger maybe I should spring for a larger unit that's used on cars - we'll see. Sjbmw stated that if the battery descends to 11 volts it's sayonara. I assume that's a flat 11.00. I've charged a battery that read in the high 11s that worked for years.

My pal Motorcycling Mo with his enormous GSA and me with my Rockster both solved the problem of trickle-discharge of a lead-acid or gel battery by fitting a readily-avavailble cheapo accessory called "battery isolator switch".
Look on The Bay...
It fits between the NEG pole of the battery and a nice clean bare-metal point on the chassis. When you park up the bike in the garage and won't be using the bike for a week or two, just use the seat-key to lift up the seat, switch off the isolator and replace the locked seat.
A lovely simple anti-theft device.
Then, next month / fortnight when you want to dig out the bike, just lift the seat, switch the isolator back on, turn the ignition key BUT DON'T FIRE THE BIKE UP.
Twist the throttle from one end to the other, slowly, three separate times, to make the ECU learn the recently forgotten throttle position parameters.
Then turn off the ignition key, count five, turn back on, then fire the bike up.
Kushtie.
Or splash out as I did on a Lithium-Ion 'Shorai'-brand lightweight new-tech battery for 240 snoojits.
Doesn't self-discharge. Spins that crank like gangbusters....
AL in s.e. Spain