Battery drain & charge

Does the battery charge when the bike is running?

The battery seems really sluggish lately and if the bike doesn't fire after a few cycles the starter/battery just dies. One I kick it and get it running and kill the engine it starts again with the starter.

The battery seems like it has lost power. How do I fix this..? Slow/trickle charger..? What voltage and can I get a cheap one from Walmart..?

Battery is dieing, and/or self discharging between rides.  I have a Battery Tender and installed the battery end on the bike with connector routed into the air box; I open the air box door and connect it while in storage.    Now would be a good time to buy a LI battery and save 3 lbs of weight, and they don't self discharge like lead acid.  Or go to Walmart and buy another lead acid battery.

+1 on what Chuck said.   Lead Acid batteries even when well cared for only last about five years before they need to be replaced.



Or go to Walmart and buy another lead acid battery.

Checked the manual and the battery is a YTX5L-BS. Looked at Walmart - $33.00 but ratings are terrible

I'm riding this weekend and dont have time to order one. Is this the right battery? I'll look at my auto store.

Battery is dieing, and/or self discharging between rides. 

it is on a 2012 CRF250X so it is not that old. Can I charge it up?

Sure, you can use a trickle charger or better yet, go for a long ride<g>


The five years though is just an average and you need to take care of the battery.  In the off-season, it needs to be kept charged.   Batteries that are not deteriorate (and were talking lead-acid here).   Should be fully charging it once a month when it's not being used.



Sure, you can use a trickle charger or better yet, go for a long ride

I have a three day ride planned this weekend... will that take care of it?

That would be more than enough.   I've never figured it out, but a few hours should be enough.  Let's see, bike has 20 watts for charging, so at 12v, that's 1.6 amps.  Battery is 6 amp/hours or there about's I believe, so 3.6 hours to fully charge it if it was totally flat.  I doubt it is though, so riding for a couple of hours should be plenty.



You won't have 1.6 amps going to the battery the entire charge.  Reason being is that the current decreases as the battery voltage increases.  The current being delivered to the battery will be the voltage output of the stator (approx. 13.5V) divided by the resistance of the battery.  The battery's resistance increases as it charges, which decreases the current.  Therefore, it will take much longer than 3.75 hours of constant charging to fully charge a completely depleted battery.  Better just connect it to a wall charger overnight to be safe.


Here's a good analogy:


Let's say you're filling up a 5-gallon bucket with water via a pipe suspended above.  There is a valve on the pipe that is controlled by a float resting in the bottom of the bucket.  When the bucket is completely empty, the valve is fully open and the amount of water flowing out of the pipe is at its maximum.  As the bucket fills, the float rises, and the valve begins to close.  As the valve closes, the water flow decreases.  The more water in the bucket, the higher the float, and the less water flowing into the bucket.  So as you can see, when the bucket is entirely empty, the rate at which it is filled is at the maximum, and as the bucket fills up, it takes longer and longer to fill it.  It may take only a few seconds to fill the first half of the bucket, but several minutes to fill the second half and hours to top it off.  Same concept with charging a battery.  Current is at the maximum when the battery is dead and decreases as the battery charges because its resistance increases and slows the rate of charge going into it.  This example applies to when you are charging the battery off the stator, which has a fixed voltage (more or less).  If you charge your battery from a wall charger, the current remains constant as the battery charges in order to maintain a certain rate of charge regardless of the battery's charge.  That way it doesn't take days to charge it.  Case and point, if your battery is completely dead, then I would recommend charging it via a charger, not relying on the bike to charge it from a dead state because you never know what's going to happen out on the trail.

Edited by mossman77

That'll work.  I have one on my X with the battery end routed into the air box for easy access for charging. 

once a lead acid battery is ran very low, or dead, it is never strong or reliable for thought if you don't want to be kick start the third time you drop it in 5 mins on a tough section of trail

That'll work. I have one on my X with the battery end routed into the air box for easy access for charging.

I had one on my 250x and it just drained the battery and my bike doesn't like kick starting so it drained right before a race and I haven't put it back on since

I had one on my 250x and it just drained the battery and my bike doesn't like kick starting so it drained right before a race and I haven't put it back on since

I've owned and maintained a lot of lead acid batteries for vehicles and equipment that are stored for long periods without use and never had a Battery Tender or any other "smart" charger discharge a battery. 

I'm sure your sudden battery failure was frustrating,  I've also had a lot of lead acid batteries unexpectedly fail, some as soon as a few minutes after charging to a full charge.  Not uncommon for a lead acid battery end of life. 

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