Jump to content

Key on voltage drop


jstehman

Recommended Posts

I've been chasing this electrical system for the 2 years I've had this bike.

 

First thing was change the R/R to a mosfet unit and wire straight to the battery.  Also redid a connection from the ignition to the harness that was getting hot.

 

First thing I did when I purchased the bike was charged the battery and check the voltage.  12.6 overnight off the charger.  Hmm.  Not great.  So I put in a new Yuasa battery.  

 

Rode for the rest of the season.  Then comes next season.  Having starting issues.  Seems like a weak battery, so I check the charging system and it's weak but the stator checks out good.  So I change the R/R and wire it with a kit from roadster cycle direct to the battery.  Great!  14.03 at idle.  14.1 ish above idle.  Battery voltage 12.85 overnight rest.

 

Past few days it's been a little cooler outside..I go to start her up for a ride, and the starter turns maybe 2 times then dash blanks and starter stops.  I release the start button and try it again.  Fires right up. Hmm

 

Hot restarts give me no problems.  Fires right away.

 

*******

 

Did a key "on" position, battery voltage test and got 11.7 volts after the fuel pump primes and it slowly drops from there, plateaus around 11.6 

 

Seems a bit low or is it in the ok range?

 

Could my battery have taken a hit when it was new with the crappy charging voltages for the one season?

 

Headlights are Not Stock.  

They are a Xenon bulb kit with ballasts supposed to pull 35w per bulb.. could the headlights be pulling more juice causing funky startups?

 

Screenshot_20201003-225130_eBay.jpg

Link to comment
Share on other sites

  • Member Contributer

Jsteham

 

I would suggest that your battery is either not holding its charge overnight or you have a sacrificial drain. You haven’t mentioned if you have changed the stator but I assume you have conducted the Drill and with a 14.03v charge rate at idle it doesn’t seem as if it is the culprit.  
 

The only other area that may be worth looking into is the starter switch and relay.  If you are hitting the start button and it only cranks twice and then the dash goes blank and you then try again and it starts with no issues it may be high resistance across the switch/relay or connectors.

 

by the way I have the same set up as you - roadster cycle R/R, direct feed to battery and 4 x 35 w Hid lights and have no issues.

 

let us know how you get on

Link to comment
Share on other sites

The stator is the original stator @27000 miles.

 

I forgot to mention the red wire in the connector to the starter solenoid was hot enough to melt through the plastic connector.  I removed and crimped and soldered a new spade connector to the wiring and reinstalled to the original starter solenoid. 

 

Starting to think it's the battery.  The volts dropped quickly when I turn the key on.

 

And I have not had the battery load tested, but I tested cranking voltage drop and it was minimal.  Definitely above 11v

Link to comment
Share on other sites

  • Member Contributer

Agree with  Marooncobra sounds a bit like you still have a battery issue, In between seasons is your battery placed on a charger/maintainer? Do you have extended weeks of no riding and no charging of the battery as this can cause damage to a battery?

Cold starting will test out a battery low in capacity = poor cranking.

 

Your lights are not an issue. If you're saying they are 35w each then you've actually reduced the load by 40w in total (OEM=2x55w H4's). Don't forget, the first thing that happens when you press the Starter Switch is your headlight relays are de-energised = No headlights while cranking.

 

Make sure ALL major Power and Ground connections are good and tight. Starting at the Battery, across to the Starter Relay, the Main Frame Ground and the heavy cable connections at the Starter Motor.

 

Attached is the Leakage Current test. With Ignition to OFF you should not read any current greater than 2.5ma. (Meter set to read lowest DC Amps range)

 

 

 

Leakage_Current.JPG

Link to comment
Share on other sites

Thanks guys.

 

Yes battery is on a tender if the bike is down for more than a week.  But I fear that first season with the poor charging circuit may have taken it's toll on the new battery.

 

I was surprised that the voltage dropped that fast, so I initially thought the headlight ballasts we're grabbing voltage, but the actual wattage difference makes sense that it is lower, my understanding is that the voltage should not drop beyond 12.

 

I will check my main ground to the frame.  That is the green wire collection that is bolted to the frame under the gas tank, correct?

 

And check the main lug on the starter motor for corrosion.

 

Battery connections and starter relay connections are clean and tight.

Link to comment
Share on other sites

I went for the low hanging fruit first and got the battery load tested.

12.9 volts, and dropped under 10v at 10 seconds of load 😔

 

Looks like she's toast.

 

Will get a new battery shortly.  Which Is What I Should Have Done when I replaced the R/R and it's wiring.

Link to comment
Share on other sites

  • Member Contributer

As mentioned, there may be shorts and sacrificial drains when bike is off. That’ll sap battery when sitting for while. 

Link to comment
Share on other sites

  • 4 weeks later...

Just wanted to update to this thread.

 

I got a new battery installed.  Whammo!  She spins over faster than before on starting.  Definitely a big difference in cranking speed with this battery.

 

Voltage is definitely not an indication of cranking ability.  Lesson learned here. 

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...

Important Information

By using this site, you agree to our Privacy Policy.