Help! How long does it take to charge a flat battery by riding?

[Ixion]

The voltage isn't smoothed, it's not really DC. The 14.2V is peak, across the tops of the square wave, not RMS. Not sure if that's what Mr Motu meant. But I have charged batteries from flat (run and bump) on big bikes with apparently adequate results. Little ones may be another matter, their electrics are a bit crude.

[crashe]

Has anyone heard from Surfchick?

Did she sort out the battery.

I offered to lend her my battery charger but she never got in touch.
As I am only a few kms away from her, I could have gotten the charger to her within a few minutes.


And Yes I did send her a pm at the time.
But she hasn't read it yet.........!

[Motu]

Que?
I don't know about little bikes but all the big ones I've had will put 14.2 v across a battery at any thing above idle.
This WILL charge a battery and not give it a choice in the matter.

That's volts,you also need amps to charge a battery.It's a long time ago since I was told the theory and like most apprentices promptly forgot the long explanation and just remembered the impotant bit,if I get time I might try and brush up my theory.But an altenator gives a good initial charge and tops the battery up quickly and then cuts right back,never giving full charge.

I've seen homemade mobile battery chargers using washing maching motors and generators with twin spool regulators,they fully charge a battery.

[crazybigal]

should have charged enough to get it started one would think!
turn your light off if you can.
check your charging system your alternator or Rectifier could be shot.
most bikes do their charging just above idle, wont matter if your reving the shit out of it, the rectifier is going to spit out the same voltage to the battery anyway.
put a voltmeter over the batt at like 1500rpm and you should get between 13-14.5 volts depending on your charging system.
or maybe your battery is poked.
good luck

[davereid]

What a load of drivel this thread is full of ! Always good to see how the standard of science and physics is at our schools these days, I'll have a job for years by the look of it. Never mind, guess you are all good at kapa haka.

OK.. if your alternator has its magnetic field provided by field windings, if you have a flat battery you are stuffed. This is because you dont have any power to produce a magnetic field so you can push as fast as you like, but you will get no output.

But, on yer small motorcycle you most likely dont have field windings, chances are you just have permanent magnets built into the flywheel. So if you spin the engine, you'll get the 'lectricity.

In a "generator" you produce AC electricity, but mechanical contacts change over every 180 degrees to give you DC. In an "alternator" exactly the same thing happens, but instead of using mechanical contacts, electronic ones are used. (The rectifier.)

Your battery doesnt care. If the terminal voltage of the battery is lower than the terminal voltage of the alternator/generator/battery charger, then current will flow into the battery. If current is flowing into the battery its gonna charge. But as it charges its terminal voltage goes up, so the charge current decreases.

No probs for us mechanics, we know that as a good rule of thumb, if the terminal voltage of the battery when the engine is running is 13.8 to about 14.2, its going to be charging.

But, some of the charge is wasted, it just warms the battery up, and causes gassing.

The bottom line ?

Any bike with electrics in good nick can completely charge its battery - if terminal voltage is 13.8 - 14.2 its happening.

But, if your battery has a faulty cell, voltage may be OK, all you are doing is warming the battery and gassing the other cells, you need a new battery.

And NEVER NEVER NEVER charge a bike with the battery in. I know it says you can on the side of that flash "battery tenda" charger you bought, but you risk damaging your voltage regulator. Your voltage regulator sees voltages above about 14.2 and tries to short them out to prtect the bikes electrics. Lots of chargers are quite capable of detsroying the voltage regulator.

Cheers

Dave

[Waylander]

Has anyone heard from Surfchick?

Did she sort out the battery.

I offered to lend her my battery charger but she never got in touch.
As I am only a few kms away from her, I could have gotten the charger to her within a few minutes.


And Yes I did send her a pm at the time.
But she hasn't read it yet.........!

I imagine if she was having real problems she would be online so it may have been sorted out.

I could also be completly wrong and she can't get online lol. If I had her number I would text her but I havn't asked her for it yet and she hasn't offerd.

[mart1]

And NEVER NEVER NEVER charge a bike with the battery in. I know it says you can on the side of that flash "battery tenda" charger you bought, but you risk damaging your voltage regulator. Your voltage regulator sees voltages above about 14.2 and tries to short them out to prtect the bikes electrics. Lots of chargers are quite capable of detsroying the voltage regulator.

Cheers

Dave

Oops, I wondered what that clicking sound was

[lukelin250]

i ran mine flat as a pancake on the weekend. roll started it and went for a 20 min ride,,now all is fine. still not good for the batt though aye

[Finn]

As a rule of thumb, its 5 minutes per 100 cc's. So if your motorcycle has an engine capacity of 250cc that's 5 mins x 2.5 = 12 mins & 30 seconds. You don't have to worry too much about 30 seconds. You can round it up to the nearest minute.

Bummer if you have a Triumph Rocket. 5 mins x 23 = like forever.

[rok-the-boat]

How does a voltage regulator connect up? In series or in parallel. I imagine it is just in prallel, like, one side to power from the alternator, the other to earth. Would that be right?

[judecatmad]

When my ginny's battery was flat (due to the ignition being left on for a couple of weeks unbeknown to me...thanks Dave!), I jump started myself down the driveway and rode it to work at higher than normal revs (3rd and 4th gears most of the way instead of 4th and 5th), with the headlight off, and it seemed OK after that. Was about 45 mins to work and it seemed to do the trick.

My battery is only a couple of years old tho so that might make a difference?

Also, I guess if your headlight can't be switched off then that would change things significantly.

[sunhuntin]

When my ginny's battery was flat (due to the ignition being left on for a couple of weeks unbeknown to me...thanks Dave!), I jump started myself down the driveway and rode it to work at higher than normal revs (3rd and 4th gears most of the way instead of 4th and 5th), with the headlight off, and it seemed OK after that. Was about 45 mins to work and it seemed to do the trick.

My battery is only a couple of years old tho so that might make a difference?

Also, I guess if your headlight can't be switched off then that would change things significantly.

yeh...always use the key...not just the kill switch! learned the hard way. lmfao.
got it jumped by the roadside assistance guys...and being in an unfamiliar city, it was easy to charge...but i think 45 mins roughly was all it took. would likely take less than that though.