I recently got a 2016 CBR300R and put in a new battery, though I can’t remember the brand. The problem is the bike won’t hold a charge overnight. Any ideas on what might be draining the battery?
I’m getting the battery tested tomorrow just in case it’s faulty.
UPDATE: I got a new battery that stays above 11.5 V when the bike’s off, but when I turn it on, the voltage drops to 8.2 V and the bike won’t start. It clicks aggressively but won’t crank. What could be causing this voltage drop?
It could be anything on a used bike.
Have you made any modifications or added electronic accessories?
I would check areas where mods are common, like around the taillight.
Also, if there’s a USB power cord connected to the battery, make sure it has an on-off switch to stop any drain.
@Tan
The bike is completely stock. I’ve been checking it over, and I plan to look at the stator, regulator rectifier, and starter relay. When I try to start it, it clicks and the dashboard flickers.
It could be a short to ground. Look for any loose wires or corroded grounds.
There could also be a parasitic drain, maybe from an aftermarket alarm.
Another issue could be that the battery isn’t charging properly, which could be a problem with the charging system.
Electrical problems are the worst.
@Drew
I checked a couple of spots but I’m not sure where else to look. I’ve never worked on a motorcycle before, and I’m stuck. The battery holds a charge when disconnected but drains quickly when connected. My friend thinks it might be the fuel pump solenoid, but I’m not sure about that.
@Bin
Start by checking the grounds; those are connections to the frame and engine. Look for loose or corroded spots.
To check for a parasitic drain, grab a multimeter and a friend. One of you holds the meter on the battery while the other pulls one fuse or relay at a time. No key in the ignition, of course. If there’s any change in the meter reading, that’s probably where the drain is coming from. Go through the entire fuse box, checking every fuse and relay.
Try leaving the kill switch in the off position overnight and see if the battery still drains. This might help narrow down the issue.
Kingsley said:
Try leaving the kill switch in the off position overnight and see if the battery still drains. This might help narrow down the issue.
I usually keep the kill switch in the off position, but it doesn’t make a difference. When I installed the new battery, the readings were the same whether the switch was on or off.
@Bin
When the bike is off, try putting a multimeter between the negative battery terminal and the cable. Is there any current flowing?
Kingsley said:
@Bin
When the bike is off, try putting a multimeter between the negative battery terminal and the cable. Is there any current flowing?
Yes, it starts at 0 and then gradually rises to around 13mA.
@Bin
Okay, so there is definitely a parasitic drain. Keep checking the meter while you pull the fuses one by one. The current should drop to zero once you find the right fuse.
Kingsley said:
@Bin
Okay, so there is definitely a parasitic drain. Keep checking the meter while you pull the fuses one by one. The current should drop to zero once you find the right fuse.
I tried that with every fuse in the box near the battery, but nothing seemed to draw power. I’m not sure where else to check. The first battery was bad, but the new one has the same problem. I think the issue might be with the starter motor, because the battery no longer drains, it just won’t turn over.
@Bin
It sounds like your starter is the problem. A 15mA draw isn’t too bad, but to confirm if it’s the starter, can you kick-start the bike?
Kingsley said:
@Bin
It sounds like your starter is the problem. A 15mA draw isn’t too bad, but to confirm if it’s the starter, can you kick-start the bike?
Yes, jump-starting works every time.
@Bin
So how does this make sense? What’s the difference between using the starter with a jump and without it?
Bin said:
@Bin
So how does this make sense? What’s the difference between using the starter with a jump and without it?
With a kick-start, you bypass the starter motor entirely.
The starter motor itself is what’s failing. It costs about $50 to replace. Once you remove it, I’m not sure how to test it, but that should be the next step.
@Kingsley
It seems the issue is with the starter motor then. The symptoms fit. Time to swap it out and see if that solves it.