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Discussion Starter · #1 ·
Hey guys,

I am trying to chase a massive voltage drop from the battery when I hit the starter switch. Battery reads 13v and when I hit the starter it will drop instantly to around 7.3 volts. When I stop hitting the start button it will go back up with a slight drain from the previous battery level.

Any ideas as to what I should be testing or looking for with this? Could it be the starter solenoid going out? Short somewhere in the ignition wiring?

Really not too sure what I should be looking for.
Thanks for the help
 

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You have a weak battery.

The best way to assess battery health is to take it to an auto supply store and have them do a load test. A load test determines if the battery can deliver its rated current to a resistance similar to that of a starter motor without dropping below a voltage threshold value.

Alternatively, you can simulate this test by first charging the battery (a healthy fully charged battery should measure about 12.6 volts) and then remove the fuse to the fuel pump so that when the engine is cranked it won't start. Measure the voltage across the battery terminals as it cranks. If the voltage drops to less than the upper-9 volt range, you need a new battery.
 

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Discussion Starter · #3 ·
You have a weak battery.

The best way to assess battery health is to take it to an auto supply store and have them do a load test. A load test determines if the battery can deliver its rated current to a resistance similar to that of a starter motor without dropping below a voltage threshold value.

Alternatively, you can simulate this test by first charging the battery (a healthy fully charged battery should measure about 12.6 volts) and then remove the fuse to the fuel pump so that when the engine is cranked it won't start. Measure the voltage across the battery terminals as it cranks. If the voltage drops to less than the upper-9 volt range, you need a new battery.
I just bought the battery yesterday from the store and actually returned another a few days ago as well. I don't believe it's all three of the batteries being bad unfortunately.
 

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Sounds like a typical bad cell in the battery. If it fails to hold a charge after a day or two as well, it's normally the battery. I would check over the wiring carefully for shorts and make sure the solenoid cannot touch the frame or engine during start. Does it crank & start ok? And does it show a charge when running? Seems strange after two batteries.
 

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Jump straight from the battery to the starter. If it cranks, the battery and starter are good enough.
 

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Discussion Starter · #9 ·
Sounds like a typical bad cell in the battery. If it fails to hold a charge after a day or two as well, it's normally the battery. I would check over the wiring carefully for shorts and make sure the solenoid cannot touch the frame or engine during start. Does it crank & start ok? And does it show a charge when running? Seems strange after two batteries.
The battery will hold its charge just fine it's only when I hit the starter that the voltage just drains out instantly. Two were agm batteries and the third was a more expensive gold something battery. All of them weren't cheap by any means though.

I'm leaning towards a short, but I have no clue how to look for it
 

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The battery will hold its charge just fine it's only when I hit the starter that the voltage just drains out instantly. Two were agm batteries and the third was a more expensive gold something battery. All of them weren't cheap by any means though.

I'm leaning towards a short, but I have no clue how to look for it
On both the Ducatis I have, there was a LOT of corrosion on the connections, at the engine ground and at the solenoid and especially at the starter connection. You should maybe check those out.
For the short, look for bad or worn insulation and burn marks where the wires might touch something. And DO try Duc96cr's idea of jumping straight to the battery for a test.
 

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Discussion Starter · #12 ·
What battery did you buy?
I bought three different batteries. Two were agm and one was some gold plus one. Cheapest battery was about $100 so it's tough for me to think it's a bad battery. All held a charge just fine, but the second I hit the starter button it lurches the engine slightly and voltage drops to about 7.

After I stop hitting the starter it jumps back to a normal voltage. It's stumping me
 

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Discussion Starter · #13 ·
On both the Ducatis I have, there was a LOT of corrosion on the connections, at the engine ground and at the solenoid and especially at the starter connection. You should maybe check those out.
For the short, look for bad or worn insulation and burn marks where the wires might touch something. And DO try Duc96cr's idea of jumping straight to the battery for a test.
I'll give the direct jump a shot tonight! I'll definitely check the wiring as well again. The bike was completely disassembled to the frame so it's possible I just missed bolting something in. I'll also try and make a video later of my issue
 

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I'll give the direct jump a shot tonight! I'll definitely check the wiring as well again. The bike was completely disassembled to the frame so it's possible I just missed bolting something in. I'll also try and make a video later of my issue
Yeah I would give that a shot, assuming you are checking the voltage at the battery a bad ground or connection would give you starting issues but shouldnt cause the battery to show that much sag. Try hitting the starter directly and see if it even turns over. Sounds like you possibly have a bad starter or something is binding and not allowing it to turn over.

And price is really irrelevant if you buy a high quality agm battery that is to small for the bike. As Strega said these bikes take a lot of CCA to start reliably.
 

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Discussion Starter · #15 ·
Yeah I would give that a shot, assuming you are checking the voltage at the battery a bad ground or connection would give you starting issues but shouldnt cause the battery to show that much sag. Try hitting the starter directly and see if it even turns over. Sounds like you possibly have a bad starter or something is binding and not allowing it to turn over.

And price is really irrelevant if you buy a high quality agm battery that is to small for the bike. As Strega said these bikes take a lot of CCA to start reliably.
Very true on price of battery, but they were what came up for the 1098 battery model so I'm unsure haha. I'll try bypassing it and seeing what happens when I am off work.

My starter solenoid was cracked as well so I'm wondering if that could be part of my issue.
 

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Very true on price of battery, but they were what came up for the 1098 battery model so I'm unsure haha. I'll try bypassing it and seeing what happens when I am off work.

My starter solenoid was cracked as well so I'm wondering if that could be part of my issue.
It could cause a slow start issue, but not what you are seeing. If you were having a short to ground straight off a battery cable you would know. That generate A LOT of heat.
 

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It might be a lot of things! Worn brushes on the starter motor, starter clutch on the way out, worn starter gear, the starter pinion might be worn or starting to burn out! Any of the above suggested faults are all also viable, the starter motor is an easy place to start by taking the end cap off and visually inspect the brushes and contacts 👍👍
 

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My 1098S had a bad sprag clutch, different symptoms all together.
The insufficiently heavy main battery cables on these were a known and common problem.
The wiring to earth and to the starter can’t handle the current flow, which makes the wiring get hot, and heat further reduces the ability of wiring to conduct current. A vicious cycle.
There are cable upgrade kits available, can’t remember the brand, but not hard to find on the net.
once you get the problem resolved, the bike has to be on a trickle charger when parked up or the anti theft system will sap the battery in just a few days.
 

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this is in german, so i explain in short
first measure the resistance of the Starter line:
instead* of the Starter put a Bulb and a DMM (10A mode) in line, H4 or so, note the current.
then measure the Voltage drop from Batt+ to Bulb+.
calculate Resistance R=U/I
should be in mOhm Range.
next
measure the Voltage drop from Batt+ to Starter+. when cranking.
then the Current I = U/R

this is more or equal exact then a dc current clamp i believe, but with the clamp it's done in seconds.
and you can measure at different points.
if the current near batt+ differs from near Starter+, you have a short somewhere between.
if its too high, the Starter is bad.
if too low, Battery.

*the instruction differs here because its a a car Starter with included relay.
 
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