DT 300 Battery warning light, bad rectifier?

[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

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.

[Ruffus]

Mouse, you are right about battery weak and handling this two headlights of 35 W each, makes a amp consumption of about 5.83 A only for this items. Plus ignition, position, brake, lights etc.

In this range, KYMCO stators produce appr. 280 -350 W = 23 to 29 amps load to the reg/ rec which has to be digested by a couple of diodes and a small ECU within this reg.
KYMCO changed some years ago the outer appearance against a bigger/ deeper cooling element. FWIK and measured, internals were not measurable changed. Think they changed from black cable to green cable, not 100% sure.

IMHO, of course if you can get an OEM part its nice to have warranty.

But none of NO NAME regs I changed last 3 years failed until now and if, guys would have called me.
So I take that one for €28,- to 35, - and change them if neccessary for free.

[julio]

Hola amigos!

Thanks again for all your help! I have updates!

So I got a rectifier a little bigger, 20 amp, it's a universal rectifier so I had to attach the connectors, but it was good enough for the test!

I connected everything started the bike and immediately got 14v on the rectifier and 14v on the battery with the engine idle! That's a lot better that the 13.2v I got with the old one. I did a test ride and everything seems to work, so I think the rec/reg was bad.

Based on your comments Ruffus, I think this would be just for testing, since the cooling element is smaller than the original and it's also only 20 amp.

I'm attaching some pictures of my test setup, please don't laugh at my connections, I used heat shrink tubing after taking the picture :p

I can't get the original from Kymco here. This one cost me 20 usd and one from the same brand but made for the Downtown costs 120 usd, it has a bigger cooling element and 35 amp.

One more time thanks for your help!

[Ruffus]

Congrats Julio, I love your setup!

One more thing(s) you could to do,  is:
a) put a fan on this reg and drive it as long it lasts

b) take from old (faulty) reg this cooling element off (hacksaw, flex) and attach it on top of your 20 amp regulator with crumbled aluminium foil between to enlarge cooling factor, fix it on with metal wire and drive it until it lasts.

A later feedback would be nice. Hola.

[mousejunks]

One very important note about heat affecting the regulator-rectifier - in the Downtown 300, the regulator is located directly above the exhaust pipe manifold so it is exposed to a lot of hot air, especially when the scooter is not moving. Heat is bad for electronics, even more so when it's excessive exhaust heat.

Julio that looks like a good job - I would've done the same if I didn't have a genuine part. Some ideas to help with the cooling:

1) Airflow. Remove or cut out the plastic guard just underneath where the regulator sits to the right side of the seat tub. This will allow more air flow to the regulator. In the Downtown 350 there is no plastic guard and a huge gap under the body panel so airflow is really good. Also mount it where there's more airflow - if you can move it somewhere else using longer wires.

Airflow from a moving bike is superior to a fan, engine radiators work the same way.

2) Heatsinking. Ruffus's idea to combine heatsinks is really good. You can also use thermal tape and bolts to join two heatsinks together for more cooling capacity and heat dissipation. Don't be afraid to drill holes in the metal where there are no electronics.

I have added photos of the Downtown 350's regulator location - the left side under the left body panel, above the airbox where it is not exposed to either engine or exhaust heat.

[julio]

Hola amigos!

Just wanted to post an update on my issue. Good news; it seems to be resolved!, I have been using the generic 20 amp rectifier and battery is charging without issues, so that's good!

Bad news; new problem appeared and I'm not sure what it is. When I was putting everything back together I plugged my underseat led light and it didn't worked, the cables were really hot and I unplugged it, I think the light was shorted.

Just after that, the met-in red light from the dashboard stopped working and the check engine light.. is not on, it's more like slightly illuminated.. it gets a bit more stronger when accelerating, it doesn't turn on completely, it is just a very dim yellow light only noticeable during nighttime, but I think something is not working ok there.. also I noticed that my blinkers seem to varies their speed with the engine idle, they get faster when I accelerate.

I think I might have introduced some kind of electrical problem, but hey, the battery is charging perfectly!!

Thanks for your help guys!!
 

[mousejunks]

Hola amigos!

Just wanted to post an update on my issue. Good news; it seems to be resolved!, I have been using the generic 20 amp rectifier and battery is charging without issues, so that's good!

Bad news; new problem appeared and I'm not sure what it is. When I was putting everything back together I plugged my underseat led light and it didn't worked, the cables were really hot and I unplugged it, I think the light was shorted.

Just after that, the met-in red light from the dashboard stopped working and the check engine light.. is not on, it's more like slightly illuminated.. it gets a bit more stronger when accelerating, it doesn't turn on completely, it is just a very dim yellow light only noticeable during nighttime, but I think something is not working ok there.. also I noticed that my blinkers seem to varies their speed with the engine idle, they get faster when I accelerate.

I think I might have introduced some kind of electrical problem, but hey, the battery is charging perfectly!!

Thanks for your help guys!!

I think the underseat light is shorted, maybe a pinched wire during installation.

Hard to say but the first step is to measure the voltage output of the regulator. Use a multimeter to measure the voltage at the battery at idle and acceleration, should not be more than 14.5V.

Voltages too high or low can cause weird issues.

[Iahawk]

another great thread from all..good reading and learning. Nice work, guys!

[Ruffus]

I think the underseat light is shorted, maybe a pinched wire during installation.

Mouse, I might be inclined to go this way and search for a ground failure in this strand.