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2004 Fat Boy Battery Discharged

badbmwbrad

badbmwbrad

Member
Last month, I parked the bike for 3 weeks w/o Battery Tender. Afterwards, the bike's electric start function was normal. BIKE model is Fat Boy FLSTF carbureted.

Last week, I parked the bike. 9 days later, the battery is nearly dead and won't provide enough power to crank the engine (used a booster battery to jump start engine).

When engine is running and it's revved up, battery voltage increases to >14 volts so I believe alternator/regulator/rectifier is good. The battery is a DEKA installed new in Nov., 2013. Battery voltage drops to ~10 volts when loaded during electric starter operation (engine cranking). I believe battery is good.

Bike's wiring harness is completely stock. There are NO aftermarket electrical accessories installed on bike.

I placed battery on an automatic charger/maintainer overnight to fully charge.

Checked for parasitic drain on the battery with engine off by disconnecting battery ground cable from bike frame.

Used an ammeter connected in series between battery ground cable negative terminal and the frame ground connection.

When ammeter leads connected, an electrical arc is observed and a faint whirring noise is briefly heard coming from the speedometer (speedometer needle deflects). Ammeter initially indicates ~400 milliamps then it drops to 20 milliamps then it drops to 0.4 milliamps which is very little parasitic load.

I don't know what's going on inside the speedometer but suspect this is perfectly normal for a Harley Davidson Fat Boy.

I also took apart the ignition switch; checking for resistance between the three connectors in various switch positions. Everything seems formal with no burned contacts or measured resistance when none should present.

The voltage regulator/rectifier wiring connection appears to be sound.

I can't figure out why my battery drained down to nearly dead in only 9 days...
 
I had the battery load tested and it's good. It's rated at 310 CCA but its output measured 345 CCA. Also looked at wires near oil tank and all appears well.

What ever killed my battery is not readily apparent...
 
badbmwbrad said:
I had the battery load tested and it's good. It's rated at 310 CCA but its output measured 345 CCA. Also looked at wires near oil tank and all appears well.

What ever killed my battery is not readily apparent...
Click to expand...

See post 3
and check this also
Harley Davidson Forums A bad diode can cause all kinds of problems. You say your battery passes a load test. Something is draining that battery
 
After reviewing the voltage reg. bleed test instructions, my understanding is this test will determine if battery current is able to flow from its positive terminal through either DSEI30 diode to ground; evidenced by a glowing test lamp.

A bad diode can cause all kinds of problems. You say your battery passes a load test. Something is draining that battery
Click to expand...
 
2004 Fat Boy Sluggish Engine Cranking w/ Electric Starter

The bike sat for about 5 days then it cranked sluggishly this morning with electric starter. I rode it to work 17 miles at highway speeds. An hour after arrival, I departed work. The engine was still warm yet it still cranked sluggishly...

Back home in the garage, I disconnected the battery positive lead and used an ammeter to check for parasitic electrical load (previous parasitic check was performed at the negative terminal).

When the ammeter's leads are first connected in series between batt pos terminal and pos cable, ammeter indicates 437 milliamps while speedometer hums audibly. Amperage then drops to 44 milliamps for several seconds (speedo quiet) then it drops again to a steady 0.75 milliamps.

I pulled out the 15 amp fuse (marked BATTERY) then indicated amperage dropped to 0.28 milliamps. None of the other fuses pulled caused a change in ammeter indication.

I presume if one of the rectifier's diodes is degraded and allowing battery current flow to ground then the ammeter's indication (prior to BATTERY fuse removal) would have been significantly greater than 0.75 milliamps. I conclude there is nothing wrong with my rectifier.

Thinking back to the last maintenance *operation I made on this bike before the engine cranking problem developed (*when I had added ~8 - 10 oz. oil), I revisited the engine oil level:

If there is too much oil in the tank then perhaps it can gravity drain into the engine crankcase over the course of several days then cause excess crankshaft windage and sluggish electric starting... My HD owner's manual procedure requires one to warm up the engine then let it idle for 1 - 2 minutes with the bike NOT sitting on the jiffy stand then shut off engine then pull dip stick from tank and confirm oil level does not exceed the high-level mark on the oil dip stick.

My oil tank level was even with the dip stick's high-level mark. Regardless, I used a suction gun to remove ~6 oz. oil from the tank. The oil level is now ~3/16" below the high-level mark during a subsequent hot engine oil level check. I don't know what else to check.

I understand the twin-cam 88B engine employs a dry sump lubrication system but what prevents oil in the storage tank from gravity draining into the engine crankcase when the engine is off? Am I doing something wrong when I check the oil on this HD Fat Boy (my other motorcycle engines have a wet sump lubrication system)?
 
The bike wouldn't crank over sufficient to start the engine 24 hrs after having removed 6 oz. oil from the tank. It turned over and stalled on the piston's compression stroke. This time, it definately sounds like the battery doesn't have enough power to operate the electric starter. The lights dimmed when it tried to crank. I am at my wit's end trying to resolve this problem.
 
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