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Low voltage at RPM

R

rumple

Joined Mar 2012
70 Posts | 0+
Morning all,

Bike has been a little reluctant to start with the colder weather, starter seeming to run out of speed too quick.

Expected it to be battery related but figured I would check the voltages prior to getting a new battery (from the paperwork I can see this battery has been in 8 years)

At idle I'm getting 13.3 across the battery but as soon as I pass 2000k revs the voltage drops.
After about 2500k is down to 12.2v which means the charging voltage could be lower than that as 12.2 was the voltage the battery started at!

I only ask as all other bikes I have owned usually put out above 12v at idle and increase to about 14k and levelling off at maybe 4000k rpm


Sound normal for the APE or does this warrant further investigation?
Rumple
 
Sounds normal.. mine does the same. Worried me for a while... but I haven't had any issues..

Check the voltage of the battery under load.. ie. When cranking the starter.. anything in and around 10v or less and the battery is done... some can be saved with a good charge but with it being so old I'm going to say its coming to be coming to the endof its like if its ggiving bother...

Also check the connectors to the reg/rec for corrosion... and purchase a 100amp starter relay

Bye bye starting issues
 
Thanks for the quick response,

Glad to know this behaviour seems normal for the bike even if unusual compared to other bikes.
The behaviour has not really given me any issues either, the battery is producing good volts, just not for long enough

Reduced charge capacity is usually a good sign the battery has seen better days, and given its age its probably better to change it before winter.
I have had mixed results using a deep charge battery charger, i guess some batterys get so encrusted with lead sulphate that there is just no saving them.

Anyways i was thinking of getting a motobatt MBTX12U as a replacement.
 
I was under the impression the number in the battery reference coincided with the current output of battery...

The 14 is too tall in the sense that you'll no longer be able to use the little clamp of the battery tray... but the seat clears no problem and it makes starting that much easier
 
turbopresh said:
I was under the impression the number in the battery reference coincided with the current output of battery...

The 14 is too tall in the sense that you'll no longer be able to use the little clamp of the battery tray... but the seat clears no problem and it makes starting that much easier
Click to expand...

excellent, thanks for the info.
Ill get a battery on order
 
sorry lads but that charging rate isnt normal, anywhere from 12.8 to 14.5 is acceptable.... down to that level when revving the motor would suggest theresa problem im afraid...

can you confirm those readings or have i read this wrong?

wouldnt supprise me....hehe

griff
 
Fitted the replacement battery and rechecked the voltage across the terminals
idle is 14.4v
4k is 13.5v

I'm unsure why the voltages have improved by changing the battery, and also unsure why the voltage diminishes when RPM is increased...
The usual M.O. for a R/R on most bikes would be to increase output along with stator output until the voltage threshold is reached then level off somewhere around 14v-14.5v

At least if the R/R is operating incorrectly it is undervolting, and not cooking my loom. My firestorm failed the bad way and gave me the pleasure of spending a weekend rewiring the bike... grumble grumble
 
I get a solid 14.5 at idle and all the way to around the 4.5k rpm mark, then it tails off. Been running on a 10amp like this for a year now without issues.
 
Maybe another indication of the battery be on its last legs... mine does it to.. and tbh I was the same at first.. but if anyone else's is different t I'll look into it.. but I think I remember reading that it was the norm..

If it ain't broke don't fix it lol
 
sorry ads theres still something not quite right....

im gonna stick my neck out and say please check the browm block connectores on the RR line from the generator, its usually high resistance that will cause this voltage dropping as the revs get higher....

just remeber theres two of em one at the RR and one between the cylinders (bit fiddly to get too)

let us know how you go!

Griff
 
Is that the big white cylinder type connector? Last time I tried to pull it apart it wouldnt budge.. I bet its melted to **** lol
 
turbopresh said:
Is that the big white cylinder type connector? Last time I tried to pull it apart it wouldnt budge.. I bet its melted to **** lol
Click to expand...


the big white connector will be on a 99-03 bike the brown block connectors will be on the 03-onwards bikes (gen2)

sounds fave to me!!

stay in touch!

G
 
managed to get the connector apart... not looking too healthy.. lol

IMG_20120918_183612.jpg


just going to chop it out and hardwire it...
 
just a tad... lol now to find out what this knocking noise is coming from the front cylinder intake valves... and fit my titanium akra system :D
 
For rumples issues, i'd try reg rec. mine did exactly the same, Griff spotted it in a heartbeat, I hadnt noticed because I had only one headlight bulb connected for ages, and it was okay.. connected both up, sent it in with a mate to see griff and the problem was instantly evident as it failed to charge and start.

I had already cleaned and greased all cable connections, soldered the stator on direct, the problem with the dropping voltage was purely the regulator, new one fitted following day.. all sorted. its now high 13v all the time it runs.

Still, bought a Mosfet FH011 regulator to send problems to the sin bin for ever more
 
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