Battery charge/discharge question

[El motociclista]

I think I might need a new battery but wanted to verify first with some of y'all. I bought my bike back in May 2007 and have not had to buy a new battery since. I do not know when the current battery was installed so to my knowledge it is at the very least 2.5 years old. Anyways, I have been checking the charge periodically with my multimeter and it seems to lose a lot of charge in a short period of time.

To verify, a couple of nights ago I charged the battery with my battery tender until it indicated a full charge. I checked the reading, which was at 12.88V. (I've gotten higher readings in the past after a full charge, right around 13.0V). The following morning (without any starting or riding of the bike between then) the charge fell to 12.33V, a 4%+ drop in charge from just the night before. In the following day-and-a-half it has dropped only to 12.30V, a much slower rate than the first night.
Soo, is this initial drop from 12.88V to 12.33V an indication that I need a new battery? Just as a note, I have not ridden the bike since fully charging the battery two nights ago so that I could track its discharge.

Thanks for your help.

[Big Shot]

As far as your testing is concerned, the second reading (12.33 - 12.30v) you have listed is a true representation of the condition of the battery.  And it's indicating a 55% or so state of charge which means its seen better days.  Kinda like Michael Jackson.

The drop you specified in red is irrelevant.  The first test you made (12.88v) fresh of the charger contains what is called a surface charge.  The surface charge needs to be removed to get a proper indication of your battery's health.  One way you can remove the surface charge is to simply allow time to pass and it will magically disappear by itself.  Just like you did but didn't realize it.  12-24 hours or so should be sufficient.  You can also speed up this process by putting a load on the battery to remove the charge if you, "Have to know now!" what the condition of your battery is.

Have you checked the electrolyte light levels?  If not, do so.  And if you find any of them to be low use distilled water to refill them back to the proper levels and recharge your battery again.  If you find you have to do this retest it once you've removed the surface charge to see if it improves.  (i'm assuming you don't have a sealed battery)

Not trying to oversimplify this for you but, when the battery no longer starts your bike it is an indication that you need a new battery.  After of course you've determined the battery to be in fact bad and that it's lack of charge condition isn't related to a poor or faulty charging system.  In your particular case here, i'd keep it as long as it's still capable of doing its intended job which is start your bike.

Have you ever pushed started a car or motorcycle before?  If not, you should learn.  It might just help you out of a bind sometime.  This should be on the test!

I tried to find a link to something a little more layman in regards to batteries but i couldn't because it's late and i'm tired.  If you can digest this stuff you'll know all you need to know about batteries so...  http://www.batteryfaq.org/


Good Luck - Bob!

[El motociclista]

As far as your testing is concerned, the second reading (12.33 - 12.30v) you have listed is a true representation of the condition of the battery.  And it's indicating a 55% or so state of charge which means its seen better days.  Kinda like Michael Jackson.

Hey, just curious, how did you you get that number of 55%?

The drop you specified in red is irrelevant.  The first test you made (12.88v) fresh of the charger contains what is called a surface charge.  The surface charge needs to be removed to get a proper indication of your battery's health.  One way you can remove the surface charge is to simply allow time to pass and it will magically disappear by itself.  Just like you did but didn't realize it.  12-24 hours or so should be sufficient. 

Hey, cool, interesting.

Have you checked the electrolyte light levels?  If not, do so.  And if you find any of them to be low use distilled water to refill them back to the proper levels and recharge your battery again.

I sure did. I've been checking it pretty regularly and made sure to fill the cells with distilled water to the top fill line before I charged it up. I've been noticing that one or two of the cells seem to lose electrolyte rather quickly. After a couple hundred miles the level in a couple of the cells will decrease down from the top line to about mid-way or lower between the lines. Maybe this is another indication that my batt is gettin old.

Not trying to oversimplify this for you but, when the battery no longer starts your bike it is an indication that you need a new battery.  After of course you've determined the battery to be in fact bad and that it's lack of charge condition isn't related to a poor or faulty charging system.  In your particular case here, i'd keep it as long as it's still capable of doing its intended job which is start your bike.

Actually, the bike has not been starting up very easily. I usually have to crank it a few times, wait 10-15 minutes or so and try again and even then, it sometimes doesn't start. I didn't begin to assume it was a battery issue until just recently. It's always been a bit stubborn to start given its cold bloodedness but now that I think about it it has been more difficult than usual.
It seems from what you're telling me and what the battery is doing I should start shopping for a new one. I appreciate very much your taking the time to explain this all. I wanted to make sure that I wasn't going to go out and buy a new battery unnecessarily.

I tried to find a link to something a little more layman in regards to batteries but i couldn't because it's late and i'm tired.  If you can digest this stuff you'll know all you need to know about batteries so...  http://www.batteryfaq.org/

Thanks a lot for the link. 

[Flanders]

Actually, the bike has not been starting up very easily. I usually have to crank it a few times, wait 10-15 minutes or so and try again and even then, it sometimes doesn't start. I didn't begin to assume it was a battery issue until just recently. It's always been a bit stubborn to start given its cold bloodedness but now that I think about it it has been more difficult than usual.
It seems from what you're telling me and what the battery is doing I should start shopping for a new one. I appreciate very much your taking the time to explain this all. I wanted to make sure that I wasn't going to go out and buy a new battery unnecessarily.

If the bike cranks with no problems, then it's most likely not the battery!

[BaltimoreGS]

A fully charged battery measures 12.6 volts.  That is the maximum capacity a battery can hold.  After charging the battery will have higher voltage but it can not hold it, that is known as "surface charge."  When a battery gets to 12.0 volts it is fully discharged.  So if you are at 12.33 volts you are slightly above 1/2 charge, about 55%.

-Jessie

[El motociclista]

A fully charged battery measures 12.6 volts.  That is the maximum capacity a battery can hold.  After charging the battery will have higher voltage but it can not hold it, that is known as "surface charge."  When a battery gets to 12.0 volts it is fully discharged.  So if you are at 12.33 volts you are slightly above 1/2 charge, about 55%.

Hey, thanks for that bit of information. I wasn't aware of  'surface charge' nor that the max charge for our batteries was 12.6. I measured mine immediately after a ride one time at just over 13V so assumed that was max. Didn't know that was just 'surface charge'.

[Big Shot]

(55% State of Charge)  Jessie nailed it above.  He did the math, i usually just use a chart, lol.

12 volt batteries are made up of 6 cells.  Each cell when new and in proper working order measures out to 2.1v.  So 6 cells x 2.1v = 12.6v = 100% state of charge.  Once a battery reaches 12.0v or 2v per cell it has no charge.  With this info you should be able to figure out the condition of any other 12v batteries you test.  Or like me, when in need, go find a chart : )

And based on what you've described about the battery's voltage and the trouble you're having starting the bike, have no worries mate, it's time for a new batt 

Thanks for the appreciation.


I'm giving her all i got captain! - Bob!