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Discussion Starter · #1 ·
I had been having a difficult time starting my 98 900CR and was bump starting the bike.
I used a battery maintainer on the year and a half old motobat the night before my rides.Long story
short I replaced the battery with another motobat. however when I removed the old battery I noticed
the battery case had deformed showing expansion bulges along both sides. it seems as if I switched
batteries just in time preventing a meltdown. Has anyone else experienced this? I never had an issue
with the flooded batteries and the lasted much longer than these motobats.
 

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The charging system might be in question. Sounds like the VR. It can't regulate a 14.4v steady charge, but goes past 15v so as to overcook the battery, causing excessive heat and expands the battery case.

I'd let it idle and then check with a volt meter what it pump out at idle.
 

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Discussion Starter · #3 ·
Bott...thanks for the suggestion. I'd meant to check the system when I replaced the battery. Both old and new batteries showed 12volts although the old one was obviously compromised. When I checked the voltage with the bike at idle it was at 12.5 volts but would spike to 15v when I increased the rpm. I just replaced the Electrosport VR with the OEM part and it did show a charge increase but nothing like the Electrosport. So, hopefully the bike and battery will play nice. Thanks again!
 

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I'll throw the generic numbers at it, meaning, ideal real world numbers of a charging system and the 3 components you can point to just by watching the volts to the battery and out of the battery.

12.8v is a well charged battery off the charger and sat a few days off it.
11.1v is a load test at the starter motor, and the return back to a battery that can PUSH [means volts] is 12.8v.
It happen so fast watching the meter hooked to the battery, the VR now kicks in at 14.4v.

If the volts show 12.1v after a load test, this is considered no longer a battery that holds volts, can take a charge, nor can PUSH [think] to push the starter motor over, but the dead, 'tick' 'tick' 'tick.'
After the bike starts, there is an immediate 14.4v charging away at idle. If you see a number of 14.7, this would be the peak range of a good working VR. If the charge is past 15v, the VR has Burned out and no longer can ground extra volts to it's ideal number(s).

If the volts remain at 12.8v after the bike starts up and does not change immediately, this points to the stator not charging and part of the coil windings are burnt out.

In abstract math and not really how the stator works in that electrical theory, but you can more see WATT is going on if we use a Harley 32a stator. So magnetically speaking, there is the sweep North is 180°, and a sweep South 180, where 16v went up the one wire, and the other 16v up the other wire. 16+16=32. So its like seeing 16v or your 15v at full on Heat at the battery, and his lost that balance effect of the system. Thus a VR in question.

12.6v is in need of charge and this usually the cutoff number to begin charging the battery to its 12.8v number.
12.4v is more in need of a smart charger and see if it can recover to 12.8v. Can't think of the name but Jay Leno uses that kind of charger. Long story short, I had a 12.4v [new] and could not get it to 12.8 with my old clapped. Bought one and because it can recover an old battery. I took a chance on it, and it brought it up to 12.8 in the static [off the charger sitting for days].

For what is worth.
 

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Just to add some info personal /experience (if relevant - 2-phase vs 3-phase) . If your 98 900 is a 2-phase bike then the charging voltage at lower RPM may be lower than ideal as they aren't the best charging systems , even with a decent Mosfet Regulator. But the voltage should still rise with engine revs , I've found when I've fitted later 3-phase Ducati Mosfet Regs to my 2-phase 900SL & 916 the max charging voltage I see at the battery when revving the engine is about 14.2V (memory recall used but it certainly in the low 14's not high 14s) and at lower /idle rpm it was mostly around the charged battery voltage of 12.5V+ taking some decent rpm to get a charging voltage over 13V (memory says over 2.5Krpm maybe higher) . A '98 900SS, dependant on market it was sold new in ,may be a 3-phase bike rather than the earlier 2-phase so you I'de expect that you should see an increase in charging voltage at lower RPM than I have and possibly higher max charge voltage too. PS I strongly recommend using later Mosfet based Ducati RRs (2nd hand) as they are usually very reliable (famous last words) and IME cheaper than dubious origin RRs that arent clear if they are mosfet or otherwise, & the Duc Mosfet RRs appear to have decent voltage control that should allow use of appropriate Lithium based batteries if desired.
 

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Discussion Starter · #6 ·
My 98 is a three phase system and I had replaced the regulator out of caution many years ago. The aftermarket regulator worked fine with flooded batteries but perhaps was confused by the AGM battery. We'll see how things pan out...and thanks for all the assistance!
 
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