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Old 06-09-2019, 04:12 PM   #1
CarloL
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Battery Voltage

1997 M900

Battery is the Yusa , 11 months old, I also removed the butt connectors a few weeks back and replaced with crimped connections , slightly larger gauge wire

I had to put in an older battery (3 years old) the other morning as the battery went flat but bike is used daily, the battery should not be going flat

Testing with the older battery (3 years old)
  • Static Voltage is 12.90
  • Static Voltage with GPS Tracker is 12.86
  • Idle 13.81V

I expect we should see higher voltage at idle, 14+? I suspect the battery is not getting charged enough when driven?

Last edited by CarloL; 06-09-2019 at 07:20 PM..
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Old 06-09-2019, 05:10 PM   #2
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More importantly, what's the charging voltage at, say, 3-5000 revs? If it's 14.2v-14.5v then that's normal. If it's still 13.8v, then your charging system may be getting tired.

A single lead-acid cell will start to charge at anything over 2.15v so, as the battery will have six cells, that's 12.9v for a complete battery, (although at that voltage, it would take ages to charge - like a trickle charger). While 13.8v would be at the lower end of what would be expected, under normal circumstances, it should be enough to maintain a healthy battery with no abnormal power drains.

If the maximum charging voltage is actually less than 14v then that, coupled with the tracker, may mean that the battery just can't quite keep up.

Rather than measuring the battery voltage with the tracker active, it would be more revealing to measure the current draw in amperes. Anything more than 50 milliamps could cause problems
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Old 06-09-2019, 07:03 PM   #3
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What year is the bike? The old single phase system on the older bikes is marginal at best. Anything over 12v is charging but I would expect 13-14v but not much more and it will be overcharging which will kill the battery just as bad as undercharging.
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Old 06-09-2019, 07:19 PM   #4
CarloL
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Sorry its a 1997 M900

Thanks

Checked again at revs , voltage does not change , stays at 13.4V this time regardless of RPM

How do I test the amp draw , I tried it and just got a blank screen

Was using this
https://www.halfords.ie/workshop-too...tal-multimeter
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Old 06-09-2019, 08:18 PM   #5
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That sounds about right for a single phase '97 like my 748 i put in on a trickle charge because unless you are going on long run outs you will be using more battery power to start it than you can put back in. Get a decent trickle charger and put it on that to keep the battery topped up.
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Old 06-09-2019, 08:23 PM   #6
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Quote:
Originally Posted by CarloL View Post
How do I test the amp draw , I tried it and just got a blank screen
To test the current draw, push the black lead into the COM socket of your multimeter and the red lead into the AMP socket. Set the scale to amps.

You'll need to disconnect the negative terminal of the battery and then put the meter in series with the battery i.e. black meter lead on the negative terminal and red lead on the negative lead of the battery. With the tracker on, you'll see how much current it's drawing on the meter. 50 milliamps will show as 0.050.

NB! Don't whatever you do try to start the bike with the meter in series; they're usually only rated for 10A max and the heavy current for the starter will fry it

I think the 1997 Monster still used the single phase alternator. I don't know what the expected DC voltage output of a healthy example should be but I think the AC output should be around 30v at idle, 70v at 3000 rpm and 140v at 6000 rpm (Haynes manual?).

This is a useful source of reference for the charging system:

http://ducati-upnorth.com/tech/chargingfailure.php
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Old 06-09-2019, 10:12 PM   #7
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Great thanks for the info

I am in a place I cannot get a trickle charger on it , might just take the battery put every 2 weeks and charge it
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Old 07-09-2019, 09:10 AM   #8
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Something doesn't sound right there to me- my 1997 900 can easily be left two weeks or more without being on charge and still start ok and that's with a seven year old Motobatt.

Especially since I replaced the fuel pumps and hoses so the carbs fill quicker when the button is pressed.

But clearly you have an electrical issue to begin with, so I would certainly start by going through all the electrical connections (particularly the grounds), cleaning them up and putting them back together with a little Silicone grease- same goes for all the fuses.

As these bikes get older they do need a little more attention to keep them happy and it is things like this that get overlooked and will end up failing when you're out miles away from home which is why I went through mine and replaced the starter and ground connection leads a couple of years ago- it spins up a lot quicker since doing so meaning less pressure is put upon the somewhat marginal charging system.

I will start mine up later and take some readings for a reference for you.
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Old 07-09-2019, 09:53 AM   #9
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Thanks

Mine is a vacuum mechanical fuel pump

I constantly drive with the headlight on , maybe not too much draw on the battery when driving

In general everything on the wiring harness looks in good condition, I try to keep things topped up with ACF50 to prevent corrosion
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Old 07-09-2019, 12:35 PM   #10
CarloL
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Tested if anything is putting a draw on the battery (with GPS attached), nothing

GPS has an internal battery, not too sure if it only uses the bike battery when it's internal battery gets below a certain capicity

Might be time to get the exact fit battery cable setup,

Gps

Power Draw At 12V < 5 mA (Ultra Deep Sleep), At 12V < 9 mA (Deep Sleep)
At 12V < 11 mA (GPS Sleep) ,At 12V < 26 mA (nominal)

Working Voltage 10v – 30v DC with overvoltage protection


Last edited by CarloL; 07-09-2019 at 12:40 PM..
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Old 08-09-2019, 03:18 PM   #11
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My M750 had an odd fault, similar to yours, the battery going "flat" quickly on layup. Key in, ignition on, dim dash lights. I thought battery, did the tests all ok but had convinced myself that the battery was the issue, changed it, still the same. waste of money, eventually worked out it was the main relay (under the seat) going high resistance internally, opened it up, cleaned the contacts, still the same. Changed it for a new one and, fingers crossed, it solved the issue.
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Old 08-09-2019, 03:50 PM   #12
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Could that or you could just have a failing battery that wont hold charge and rubbish charging on the 2 wire system, taking out more than you can put back in.
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Old 08-09-2019, 05:14 PM   #13
CarloL
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Quote:
Originally Posted by larsen View Post
My M750 had an odd fault, similar to yours, the battery going "flat" quickly on layup. Key in, ignition on, dim dash lights. I thought battery, did the tests all ok but had convinced myself that the battery was the issue, changed it, still the same. waste of money, eventually worked out it was the main relay (under the seat) going high resistance internally, opened it up, cleaned the contacts, still the same. Changed it for a new one and, fingers crossed, it solved the issue.
Thanks , might be worth the few euro to get a new one

I changed all these on my 748s , main relay , starter solenoid

I also purchased some uprated starter cables , grounding cable ; it helps alot but so far she is going great , CTEK LED battery indicator is consistently green

I gave her good clean the weekend , cables all look good ,will put some conductive lube on the grounds , cabling when the new cables arrive

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Old 11-09-2019, 07:48 AM   #14
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Thanks

Mine is a vacuum mechanical fuel pump

I constantly drive with the headlight on , maybe not too much draw on the battery when driving

In general everything on the wiring harness looks in good condition, I try to keep things topped up with ACF50 to prevent corrosion
If everything is working as it should then running with the headlight on will not draw anything from the battery. The battery only exists to start the bike and the alternator takes over when the engine is running.
As you have stated that you have 13.8 volts at tick over then the alternator IS working.
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Old 18-09-2019, 08:00 PM   #15
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Fitted the Exact Start Cables, bike fires up at a wiff of the button , running great , I still have to install the earth and Starter Solenoid to Starter cable(Nut is seized)

Cable from the Battery to starter solenoid is just fitted, it is nearly twice as thick as the OE
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