I have a battery that has 18,000 miles and 27 months of service on it. I am checking voltage at my plug for my battery tender, and reading 12.88 volts with ignition off. The bike never sets more than 2 days without being on a tender.

The service manual tells me a battery reading 12.7 volts is 100% charged. The obvious answer is that all is well.

However, I will be taking a mountain trip in October and the morning temps will most likely be low 40's. The bike will set outside all night, a big change from my basement garage with pretty constant temps.

Based on everyone's experience, should I replace the battery before the trip for peace of mind, or would I just be throwing good money away for no real good reason.
Thanks for any advice.

 

Having sufficient voltage is just one part of the equation. You could also get it load tested. They do it for free at most auto part stores.

If it passes both tests, it should be fine.

Have a fun and safe trip!

 

Bill, I found (the hard way) that leaving my bike on a Tender most of the time *can* give a false sense of security.
I test voltage in my batteries on the tender pigtail every so often. After being fully charged I wait a few hours, then turn the ignition on to activate the headlight for a minute or so to remove the surface charge, then turn it off and check voltage.
12.7 = 100% charged (AGM batteries run about .1 higher so 12.8)
12.6 = 90%
12.4 = 75% (marginal)
12.2 = 50% replace

 

Some good info here...


http://www.yuasabatteries.com/faqs.php?action=1&id=30


rule 1... You must wait at least one hour after charging your battery to conduct this test.

 

I just replaced the original battery in m bike. It's an '05, so I figure I got my moneys worth out of it. The tender will keep it at peak capacity, as long as the battery can hold it. Take your voltage reading after removing the tender, and letting it sit for 24 hours. That will give you a truer sense of what the battery has left in it. If it drops to the low 12's ,it on it's way out.,,

 

Bill, you should really wait 24 hours or so after charging a battery before testing for voltage. They need a little time to settle out before a true voltage reading can be made. A battery that reads 12.8V right after a charge will actually read 12.6V or lower once it settles. 12.6V or better is a good battery. At around 12.4V you've got a battery working around 75% capacity at best. Anything lower than that and it's time to consider changing it.

After the battery settles and reads 12.6v or better, you can then test the battery voltage during a start up. The voltmeter reading should not drop below around 9.5 volts. If it does, you're likely to have issues starting up in colder weather.

If the battery passes that test, you can then do a charging test. A good battery will read between 14.0 and 14.5V with the engine running at 3000 RPMs.

If the battery passes all 3 tests, I see no reason to replace it. If any are borderline, it's a judgement call on your part so far as peace of mind goes.

 

Thanks everyone, good advice and ideas.

To be clear, my 12.8 reading was a couple of hours after riding about 25 miles and approx 12 hrs after I took it off of the the tender. I will check voltage again after a longer period with no activity, riding or charging.

I found some good info on performing a load test at home with a volt meter and will use Mikes process for checking load at startup, and output voltage at 3,000 rpm.
Thanks again for all replies and advice.

Ride safe everyone.

 

Ok, the latest.

The bike sat 24 hours without a tender hooked up, and read 12.77 volts at the battery terminals. Volt meter on the battery terminals and cranked to start. Dropped to 9.77 on first start, 10.3 on another start immediately after the first.

I think I am good to go.

Any opinions?

 

Probably good. The only thing is that after sitting 24 hours I would have turned the key to run the headlight for two minutes then off before checking. Then, assuming it's an AGM, if the voltage is around 12.65 or higher it should be fine.

 

My, 19k mi, 3y 4m old spend the night outside in winter at 30°F , with no tender. When I put it into a unheated garage during the 3 coldest month, i only charge the battery every 3-4 weeks and it's fine.
Although it would be better to keep it attached to a tender as much as possible, I doubt your bike will have any issues for a day or two in the cold.

Also the battery discharges less with the cold than when it's warm.