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MegaBlade voltage problem
MegaBladeMatt - 20/10/15 at 12:23 PM

Looking for some help with my MegaBlade.

I've not done much night driving since buying the car, but having had some rectifier issues I was testing the voltages with different electrical parts on and off.

Annoyingly when I switch everything on my voltage drops below the 14v required for a charge to occur.

Car ticking over = 14.5v
Fan on = 14.2v
Lights on = 14v
Both lights and fan on = 13v

In most situations this is never going to cause me a problem as the fan is only on when stationary and I dont usually drive at night.

But I'd like it to be working properly, and with the winter closing in being able to drive in the dark would be easier to live with.

I replaced the battery when I bought the car 6 months ago with the same battery it came with:

Varta 530 030 030 motorcycle battery

So, any ideas what I can do to fix?

Thanks
Matt

CosKev3 - 20/10/15 at 04:02 PM

Does it rise if you rev the engine up?

I know the Haynes manual for my R1 engine lists the voltage at 5000rpm.

MegaBladeMatt - 20/10/15 at 04:06 PM

Yep, It will raise with the revs but I am concerned that with any stop start driving my battery will be losing charge.

I am assuming it should be closer to 14v with the lights and fan on at idle.

Be interested to know what anyone else with a BEC is getting at idle...

MikeRJ - 20/10/15 at 06:28 PM

quote:
Originally posted by MegaBladeMatt
Yep, It will raise with the revs but I am concerned that with any stop start driving my battery will be losing charge.

I am assuming it should be closer to 14v with the lights and fan on at idle.

Be interested to know what anyone else with a BEC is getting at idle...


I would expect the voltage to drop at idle on a bike engine when the system is loaded; they are very basic alternator systems and bike engines don't spend much time idling!

However, check to make sure you aren't getting excessive voltage drop across the wiring from Reg/Rect to battery. Also check the connector from the stator to the Reg/Rect to ensure there's no corrosion or loose contacts etc.

BaileyPerformance - 20/10/15 at 09:14 PM

Most bike charging systems max out at around 25amps.

So, more than 25amps load the voltage will start to drop off, even if the engine is revving.

If you have a car type cooling fan fitted then it probably pulls 15A on its own.

Remember all the electrical load is on the alternator not the battery when the engine is running, do the battery type / size has little effect on the battery voltage.

:-)

britishtrident - 20/10/15 at 09:53 PM

Old style car dynamos didn't charge at low speeds and it wasn't a great problem.
If it worries you there is the option reduce how much current the fan draws.

[Edited on 20/10/15 by britishtrident]

MegaBladeMatt - 21/10/15 at 10:03 AM

Thanks guys,

I will do some more testing over the weekend at higher revs with everything switched on, and take it for a local drive to see how it handles the load.

Hopefully it can manage,

Ill let you know how it goes.

Matt