Charging battery whilst still connected

[FJRider]

Or pump for the air bed...

[Max Preload]

Or pump for the air bed...

Now you're thinking!

[Squiggles]

You could do some of the electrical mods listed on the tl forums, theres a charging one amoungst others

[davereid]

Its not a good idea to charge a battery while its connected to your bike, I'd suggest you disconnect the earth lead.

The reason is, that most motorcycles use a "Shunt" type of voltage regulator. These regulators are the modern equivalent of the zener diode used on older bikes, and indeed usually use a zener diode as part of their design.

A shunt regulator is a heat-sink which diverts excess energy from the charging system from the battery to to heat.

For reasons known only to the designers, they are often wired so they are connected across the battery, even when the key is is off.

If you attempt to charge a battery that has a shunt regulator across it, your charger will be working against the regulator.

Your charger DOES NOT produce DC. Its an AC device, with a rectifier. A recifier gives you a varying current, but with a peak voltage much higher than its rated output. This varying current flow is all travelling in the same direction, so it suitable for charging a battery.

That little 4-amp 13.8 volt rated charger you got from repco will actually have a peak output voltage of almost 19-20 volts.

50 times a second, your bikes regulator will attack that peak voltage, trying to turn it to heat.

If the charger is small enough, the regulator will win. It, and the charger will get hotter than normal, but you will get away with it. If the charger is too big the regulator will loose. Then the full charger voltage of up to 20 volts will be applied to your battery, and anything else in circuit at the time.

Bottom line ?

Take 20 seconds to take the earth lead off.

[jonbuoy]

Its not a good idea to charge a battery while its connected to your bike, I'd suggest you disconnect the earth lead.

The reason is, that most motorcycles use a "Shunt" type of voltage regulator. These regulators are the modern equivalent of the zener diode used on older bikes, and indeed usually use a zener diode as part of their design.

A shunt regulator is a heat-sink which diverts excess energy from the charging system from the battery to to heat.

For reasons known only to the designers, they are often wired so they are connected across the battery, even when the key is is off.

If you attempt to charge a battery that has a shunt regulator across it, your charger will be working against the regulator.

Your charger DOES NOT produce DC. Its an AC device, with a rectifier. A recifier gives you a varying current, but with a peak voltage much higher than its rated output. This varying current flow is all travelling in the same direction, so it suitable for charging a battery.

That little 4-amp 13.8 volt rated charger you got from repco will actually have a peak output voltage of almost 19-20 volts.

50 times a second, your bikes regulator will attack that peak voltage, trying to turn it to heat.

If the charger is small enough, the regulator will win. It, and the charger will get hotter than normal, but you will get away with it. If the charger is too big the regulator will loose. Then the full charger voltage of up to 20 volts will be applied to your battery, and anything else in circuit at the time.

Bottom line ?

Take 20 seconds to take the earth lead off.

A cheap charger will do that, they don't regulate the voltage much, a decent quality one will be current and voltage regulated. You can get battery tenders to hook up to your bike all the time your not there, as long as the output voltage is limited to around 13.8v your regulator won't be fighting it all the time. I wouldn't leave a cheapo one connected 24/7.

[Max Preload]

If the charger is small enough, the regulator will win. It, and the charger will get hotter than normal, but you will get away with it. If the charger is too big the regulator will loose. Then the full charger voltage of up to 20 volts will be applied to your battery, and anything else in circuit at the time.

That's fair enough, I guess. But why would you get 20V applied from the charger when the bike's regulator fails - a track to earth? Wouldn't the rectifier diode pack prevent that?

I don't claim to be the most clued up in the intricate details of electrics (I know enough to be dangerous...) but I know this. My bike is equiped with a 3-phase alternator which puts out 50V AC (presumably so that it doesn't have to deliver a higher voltage to clip at the 14.5V for the full waveform), which is rectified and regulated to ~14.5VDC. I presume it's rectified first, then regulated. So it's a steady DC. How is the charger different to that? Presumably it's only single phase, rectified and regulated to say 13.8VDCish. But isn't it too a steady delivery?

Also, the diagram below from the genuine Kawasaki workshop manual for my bike, shows 24VDC being applied to the regulator to test it. Of course, that's the normal flow of alternator output, but wouldn't the regulator be equipped to take the full output voltage of the alternator applied in either direction, so in my case at least 50V (shouldn't matter AC or DC I wouldn't think).

Take 20 seconds to take the earth lead off.

Not in my case - the battery is under the tank. It's not that simple - I should know - I had the starter solenoid stick ON one time and had to strip it to take the terminal off the battery while it cranked. That certainly gave the battery a good test.

[Skyryder]

I just bought myself one of these. $41 at Super Cheap on special.


http://store.voltelectronics.com.au/...er%20-%20750mA




Skyryder

[mark247]

Getting a new one today, so no worries there

If you are having charging problems, it might be a good idea to get the charging system fixed before you fully kill another new battery. I know when my reg / rec fried itself it fully killed my battery as well because i just kept running it fully dead again and again.

But in saying that, I dont really know what your exact charging problem is.