Modern Vespa

HELP!

Quick story... Couldn't get the scooter to start and found that it was an old/bad battery. Bought a brand new YUASA YTX12-BS, followed the instructions and put it on the tender overnight (Not installed in the scooter). Light turned green, so I then put it in the scooter, wired up the tender and it started right up.

The issue... Now that the battery is in the scooter and lead to the tender is installed, the light never reaches green. Just stays solid red (charging) for days. Almost seems like it can't reach 100% in the scooter because something is pulling power??? I'm clueless.

I have no electronic modifications installed on the scooter.

Battery is brand new.
Battery tender is brand new (800mA, 12v, weatherproof).

Scooter is a 2022 GTS Super.

When you installed the pigtail lead for the tender, did you get the polarity right?

Looks pretty good to me.

Yup, that looks correct.

Does the scooter still start?

Yes. Starts right up!

Just odd to me that I can top it off when the battery is out of the scooter but not when it's in the scooter.

Was just hoping to get the reassurance of the little green light after having to push the scooter home when the old battery died on me. Haha.

Is there a fuse in the pigtail lead? Maybe that's blown.

Is there a problem with a " parasitic" drain on the scooter. Maybe thats why the first battery failed. If it was a straight short it would blow the fuse on the Vespa AND it would blow the fuse on the charger. Its like there is a small voltage drain eg ignition on and speedo light on.

Just checked the fuse in the lead, and all of the fuses in the glove box. They all look good.

This is what I was thinking because the battery seems to be able to get to full charge when it's not installed in the scooter.

Not sure what could be the drain or how to troubleshoot that.

Scooter is mechanically and electronically stock. I've only ever performed minor cosmetic mods.

Ignition position is at "CLOSE" and there are no lights on anywhere, minus the immobilizer light blinking.

Maybe I should pull the battery and see if I can fully charge it again to prove my theory???

But if I get the battery to full charge out of the scooter I'm not sure where to look next.

Obvious question, with your new battery does the scoot stay charged over night, do you have a display of voltage on your screen?


Lastly and an obvious one are your screws and leads from the bike to the battery poles clean and debris free, eg no corrosion or thick grease.

If you have drain on the scooter it will be hard to diagnose and I for one would be enlisting either an auto electrician or a friend with a multimeter who understands what they are doing.

One time my scooter battery was dying over night (after some like 2-3 days of not use it) and the reason was that the light bulb under the seat never turned off. The switch was bad in my case, I changed it and that's it, but I saw a case in friend scooter where the battery tender cable prevented the seat from closing completely and that's why the light stayed on. That's easy to check

The 'old' dead battery was the first clue... as is, why was it dead as it wasn't exactly 'old'! I suspect a duff regulator.

There should be a main 30A fuse. Remove this and see if it charges now.

Quick update. Did a test. Left the scooter unplugged for around 48 hours. And it still started right up. No hesitation.

Happy to test the regulator, but I don't have a 30 fuse. Is the 25 the one I should pull???

Hmmm. I don't seem to have a light under my seat. Am I missing something?

Test by noting battery voltage with out scooter running, should around 12.6V, start scooter battery voltage should go up above 13v, rev to 3k rpm battery voltage should not go above 15. Report what you find

If you do not have a light under the seat, then that cannot be the cause for battery charge consumption.

It is a 2022 GTS 300. That means that "old" battery you replaced was only like 2 years old. That is not old. Probably it did get discharged but was still OK.

What I would do:
Disconnect the battery and measure the resistance between the plus and the minus of the connecting cables (you need a multimeter for that exercice. Or you have one, and if not buy one, it is a very useful tool that you can use for many other testing in vehicles and in your house).

With the contact off you should measure an open circuit, so infinite resistance.

If not then you have a leak somewhere.

The 25A fuse could be your main fuse with the smaller fuses as slaves behind.
(In my BV it is a 30A main fuse)
So test the 25A first. If it is the main fuse the reading should be infinite.

If so, then but it back in and redo the measurement removing the smaller fuses 1 by 1 until you have the infinite reading. The last fuse you did remove is the circuit where the leak is in.

The main fuse (30A) at a GTS 300 HPE (pre-Facelift MY23) can be found in the battery compartment.

The fuses in the glovebox are (left to right):

7.5A = Power supply via ignition lock: front indicators, "Vespa MIA" device, diagnostic plug, rear parking light.

7.5A = Power supply via ignition lock: horn, tail light, USB socket, remote light relay, flasher unit, pre-installation for accessories, Bike finder

7.5A = Power supply via ignition lock: ABS control unit, immobilizer antenna, engine control unit, injection charge relay (coil)

25A = Power supply from battery to ABS control unit


15A = Power supply via battery: cooling fan relay (contacts), 5A fuse (see below), instrument unit, remote light relay, pre-installation for accessories, bike finder.
Via ignition key: seat bench opening adjustment device.

10A = Supply via battery:
engine control unit, remote relay for injection charging, heater

And there is another 5A fuse below the pet carrier (slave behind the 15A fuse) for the diagnostic connector.

Lead batteries self discharge, but also the immobiliser must be using some power.

If the battery tender is very weak, maybe it can't keep up with the demand of these tiny but normal draws?

I'm sure my battery tender / charger is 20 amps, which would be 20,000mah. 800mah seems very low.

.8 is fine.

https://www.interstatebatteries.com/blog/motorcycle-battery-chargers

in a gts the ecu and dash always have power. this allows the flashing of the immobiliser light.

Can you post the model of your battery tender? Some will stay in a charging cycle and are designed that way.

It's bad to keep the battery at 100%, and more intelligent chargers will let the voltage drop and keep topping it up every so often.

I had a similar problem like this a while back where I could not get the light to turn green.. It turned out to be the battery tender itself. I changed it out with another one I had and all was good after that.

Not saying this is your problem but worth trying another one if you have another tender.