AX100 overcharging

[Squiggles]

Hanne's wee AX100 appears to be overcharging (Lightbulbs blowing, Battery stuffed (Now have a replacement) and looks to be trying to charge at over 9V instead of ~7)

Where should I start looking? It has a 3?ohm resistor mounted next to the coil and the heatsink is getting pretty brittle although I doubt that is related and I'm not sure what is regulating the current on it or i'd start there

Parts fiche is here

[Squiggles]

Diode appears to be working fine or at least it is the same as the diode I took off another AX (Infinite resistance one way and less resistance the other)

[CookMySock]

The "diode test" function on the multimeter should show "no change" when you connect the diode reverse-biased, and about 0.6V when forward-biased.

Is there no regulator? Often the action of the connected battery is enough to prevent over-voltage to the lighting.

[Squiggles]

Is there no regulator?

Not that we're able to locate (either in the parts fiche or on the bike)


A bit more background...

The AX came to us with a fooked battery and when we finally kicked it into life promptly blew a couple of bulbs.

Replaced the battery with a cheapy and fitted new bulbs. A couple of months later the bulb blows again, new bulb lasts another 2 or so months. At somepoint we noticed the battery had run dry, topped it back up etc and with a good charge we're away for a bit longer.

That battery is toast (0.7V iirc) and won't charge. When we ran the bike with that battery (not knowing it was toast) the bulbs blew soon after.


What on earth regulates the voltage on this thing? It doesnt appear to be a zener diode (2 wires and no ground)

[Drew]

If it's anything like an "A"100 then it only has a 12vDC power source coming from behind the flywheel.

Get that critter off and you should find a regulator rectifier of some description I think.

[Squiggles]

If it's anything like an "A"100 then it only has a 12vDC power source coming from behind the flywheel.

Get that critter off and you should find a regulator rectifier of some description I think.

Interesting... A100 has the same battery and rectifier as the AX100 (6V)

[CookMySock]

If the stator output is less than about 1/4 to 1/10 the AH rating of the battery then you don't need a regulator.

That is, for example, if you have a 6 AH battery, then you can (over)charge them continuously at about 0.5 to 2A without damaging them (much.) As you have discovered, this will boil the battery dry in short order, and this is the price you pay for an inexpensive charging system. The simple solution is to regularly top the battery up with distilled water.

Quite likely you could rig up a conventional shunt regulator and even dispense with the battery completely.

[gammaguy]

i own a factory manual for one of those wee fellas

let me know if you need a copy on CD rom

make sure you have a new battery fitted,or all the tests will be useless

[Squiggles]

i own a factory manual for one of those wee fellas

let me know if you need a copy on CD rom

make sure you have a new battery fitted,or all the tests will be useless

Thanks, i'll give you a bell if we haven't gotten ontop of this soon.

Checked the charging voltage on the other AX100. Can get up to around 9.5V at higher revs but it's more stable than on Hanne's one. Then again, hers is a 1987 and the other one is a 2003

[Drew]

Interesting... A100 has the same battery and rectifier as the AX100 (6V)

I'm pretty sure from a couple posts on here, that it will simply have a rectifier behind the flywheel and that's it.

It might not be regulated, as I know an "A" will run with lights, without a battery but they are dim as hell unless you are revving it.

[Flip]

A lot of small jap bikes from the 70's just used to use the battery as a kind of generator ballast resistor. The battery was always charging and some times over charging. In practice they used to boil their batteries especially when used with the lights off. Just keep topping the battery up with purified deionized or distilled water. When the battery ran dry the full alternator voltage was output to any bulb and it used to blow them very quickly.