weak battery?

[Patrick_Krivacka]

went out to start my bike after not having started it for a week and the battery was so weak it couldn't get it to run. Do i really need to put the bike on a tender if it's going to sit for more then a few days? Does this seem odd? The battery is new.

[Bob_Roller]

It all depends on how you ride the bike .

The Bosch charging system on airhead BMW's, doesn't really start to charge the battery, until you get to around the 3500-4000 rpm area, so if you a lot of slow riding in traffic, get stopped by traffic lights, the battery will not get charged up .

What kind of battery do you have ?

[Patrick_Krivacka]

thanks for your quick reply Bob. I honestly don't know what kinda battery I have. I'll have to check when i get home. the PO put it in. There's a few stop lights on my commute, but there is long stretches of higher speeds as well. do you keep your bike on a tender? if so, what do you recommend? i love a kickstarter on a Motorcycle.

[Bob_Roller]

I just got a battery tender about 2 months ago, up til then, didn't worry about the battery, never had a problem, until the relentless desert heat finally takes it's toll on the battery .

The '81 R65, only gets taken out on weekends, as I have collector insurance, so it technically can't be ridden to work, so it would sit for 5 days between being ridden .

I don't know about battery sources in your area, but three of us here, have installed a generic AGM type battery from Staab battery, located in the Chicago area .

Don't know about it's service life, but it was only $42 plus $16 shipping to Phoenix .

http://www.staabbattery.com/product/UB12220-V.html

Seeing as you've just gotten the bike, you may want to spend some time, and check the battery cables for condition, corrosion, security of hardware, electrolyte level and specific gravity of the electrolyte, if it's a serviceable type battery .

A good general looking over of the electrical connector condition may be a wise thing to do, when you get the time .

You never know what previous owners may have done to the bike .

After living in a desert for the last 17 years, I've forgotten about problems with corrosion on electrical connectors .

[Barry]

A good battery should not discharge to the point where it will not start the engine after 1 week however it will discharge to some extent depending on type of battery, temperature and age. If you want a battery to last you have to keep it fully charged and that might mean leaving it on a battery tender or using an ordinary charger once per week particularly if it only gets used on short runs. This applies to a much lesser extent to AGM batteries which have a lower internal discharge rate.   The highest internal discharge rates will occur with standard wet batteries and very high ambient temperatures.

[Bob_Roller]

There's one battery cable connection, that gets overlooked .

It's a bit of an odd set-up .

The positive cable from the battery, goes to a threaded stud on the starter, the output from the diode board, also goes to this same stud .

It's hidden under the top engine cover .

Seeing as how these bikes are approaching 30 years old, hard to say what condition the connections are in .

[Patrick_Krivacka]

It seems odd to me that it would be low. I guess I'll look it over. I was planning on getting to that spline lube this weekend, so I hadn't been riding it much until I had time to get to it. After that I plan on riding it nearly everyday for my 32 mile round trip to and from work. Motorcycles are primarily transportation for me (not to say I don't love riding! )

[nhmaf]

If it is a wet battery with caps to add distilled water, it might be low on electrolyte/fluid and needs topping off with distilled water.

[Yikes]

You might want to check the operation of your voltage regulator to see if you are getting a charging voltage to the battery even when the revs are up.  It's a simple test (that I don't exactly remember right now, but I think you can find with a quick search of the forum site) that my regulator failed.  My charging problems were fixed by a replacement regulator from Motorrad Elektrik.  

[Bob_Roller]

The test, is to connect a voltmeter to the battery terminals, start the engine, increase the rpms to around 4000,  the battery voltage should be around the 14v dc area .

But this needs to be done on a fully charged battery .

[Bengt_Phorqs]

There's one battery cable connection, that gets overlooked .

It's a bit of an odd set-up .

The positive cable from the battery, goes to a threaded stud on the starter, the output from the diode board, also goes to this same stud .

It's hidden under the top engine cover .

Seeing as how these bikes are approaching 30 years old, hard to say what condition the connections are in .  

+1 on that advice.  You won't believe the crud that can get into that area.  As long as you're doing a spline lube go ahead and pull the starter cover off and give everything a good cleaning.  Your bike will thank you for it.

[Patrick_Krivacka]

came home from work. decided to try and start it to see what happened. cranked strong and started right up. it was a little chilly this morning (the condensation on my trucks window was icy). what do you folks make of this?

[Rob Valdez 79 R65]

Batteries don't like cold.

[Patrick_Krivacka]

are r65's know to be cold blooded? I had a ninja 500 that was ridiculously cold blooded, but ran great in warm weather.

[nhmaf]

I'd still check the electrolyte level (if wet cell battery) AND go through and recheck all your electrical connections at the battery, the ground cable to the back of the transmission case, and the wires up to the starter relay and the starter.  Possibly something is loose and/or corroded and wasn't making a good solid connection before (high resistance = less juice to spin starter) and sitting in a cooler environment mave have cause something to ever so slightly contract..

Oh, and if you don't have a multimeter, go to the hardware or electronic supply store and get one - even a "cheapie" for ~ $20 will work well enough for debugging these (and other) sorts of electrical gremlins.