Scooters - 125 to 300 > Downtown 300

DT 300 Battery warning light, bad rectifier?

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julio:
Hey guys!

I left my Downtown 300i parked and couldn't started due to low battery. I took the battery to a shop to charge it and diagnose it, it was at 80% health, so I took it back to the scooter, started without problems and went for a ride, after 15 minutes the battery warning light came on.

I thought ok, maybe the battery is bad, it was 3 years old, so I bought a new one, went to another ride and again after 15/20 minutes the battery light came on.

I checked the manuals to test the chargin system and did the following tests:

1. Checked battery wiring, got voltage from battery and continuity test on the gound.
2. Checked resistance on the wires coming from the stator, got 0.4 between each of the 3 wires.
3. Checked continuity between the wires coming from the stator, no continuity.
4. Started the engine and check the AC current coming from the stator, got 24v on each of the 3 wires.
5. Check the battery voltage and got: 12.5v with the bike off, 13.2v with the engine at idle and 13.8v with the engine at 4000 rpm.

During the tests I had the engine running for around 20 minutes mostly in idle and the light didn't came on, but I don't trust it :P

The manual says that battery charging voltage should be between 14v and 15v, so I guess my issue is that my battery is not getting enough charge. I think since cabling seems good, stator seems to be generating those 24v and battery is new, the only thing left is the rectifier? What do you think?

I found similar posts here that seems to indicate the rectifier is the issue, but unfortunately rectifiers are quite expensive in my country so I don't want to spend the money if its not a good chance to fix it!

Thanks in advance!

Ruffus:
@julio welcome here!
Maybe read in this link before we go into matters...

https://www.kymcoforum.com/index.php?topic=33785.msg236991#msg236991

From your scoots stator are three yellow cables via a connector coming to its regulator/ rectifier.
(where you measured 24 VAC, good sign all the same VAC)
Check this 3-prong connector for corrosion!
Check this connector for burn signs! (pls see links)

https://www.kymcoforum.com/index.php?topic=33740.0

https://www.kymcoforum.com/index.php?topic=31878.0

From reg/ rec are two cables, black/ red via a connector leading to scoots battery.
-open this connector
-connector NOT corroded?
-start scoot
-measure how many volts you get there at 4000 rpm
-less than 14 VDC = regulator faulty = new reg
-more than 16 VDC = reg faulty = new reg

One more point to consider:
- minus direct cable from battery to scoots motorblock (loose or corroded)
- plus cable from battery to scoots starter relays
(loose or corroded)
Maybe give us a feedback to learn.

julio:
Hi Ruffus!

Thanks for the quick answer and help.

I checked all the connectors and they look really good, corrosion and burn free.

I was measuring the voltage directly from the battery and getting max 13.8v DC at 5000 rpm and 13.2v DC at idle. Tomorrow I will check directly from the connector from the reg/rec that goes to the battery.

I will also check the cable from the battery to ground and battery to starter.

I read on the threads you kindly shared with me that any regulator with 3 cables for the stator and 2 for the battery would work. Is that like from any motorcycle?

I can get one for like 20% of the price of the one from Kymco, it is 3-phases, 12v but only 12 amps, maybe is too small? Should I buy it at least to try it and see if it fix the issue and then buy the right one?

Again thanks for all the advise!

mousejunks:
The regulator-recitifier is known to fail on the Downtown 300. Follow the steps above to ensure it's not the stator. The first symptoms is as you said, the red battery warning light due to low voltage. It is too weak to handle the required current draw and cannot comfortably handle the two low beams which are 35W X2 = 70 watts.

Replace the rectifier with a genuine part. Kymco has fixed this issue with the Downtown 350 by changing to a different design.

Ruffus:
Yes, any modern reg/rec will do if it has, like I wrote 3 yellow in from stator and red and green out towards battery.

12 AMPS is hefty enough to test, for longer I would take something stronger, even I havent any amperage on my NO NAMES.
Assuming your new battery is healthy.

There are a few reg/ recs which have seven ( 7) cables attached.
This is only to split 2x red and 2x black/ green in thinner cables to reduce  heat.

If possible get the one with 5 cables (3 yellow, red/black/ green) and with matching connectors.
I have good experience with aftermarket regs when they have a big enough cooling back.

Take what you can get and afford. Depends where you are located at, but AMA*ON is a good source for such things.

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