Battery Issues - YBR125

[kawakid]

Hi,

Not my bike, its my sons and I think I might know the answer.

Middle Son 19, bought a YBR to learn on.

Last week, he travelled to work (4 miles), then to his girlfriends (16 miles) and back and his bike failed to start after his return Quick charge on battery and all was fine.

The battery is a Yuasa and no more than 2 months old. (We swapped to this as his battery conked out, during a winter ride).

Looking at his battery with a multimeter, it is getting a charge and the reg/rec seems to be doing its job, giving no more than 14v.

I've put the multimeter to amps and I can't see an obvious leak.

Tbh, he's had this issue since around the time he got the bike, but it was cold in winter and he's just got used to topping his charge up. To the point his(my) trickle charger goes with him.

Now the only thing I can think and I will swap it out, is when he got his bike, we swapped his dull bulb for an Osram (H4).

Other things of concern, his journey to work is really short like 4 miles.

The battery is tiny.

There is heated grips, but he isn't using them, the multimeter didn't detect a leak. (Though i've not checked for a relay)

Any help/pointers appreciated.
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I've a twin and a 4.

[WD Forte]

Yuasa has a good rep but it may be at fault or a chinese knock off.
No parasitic drain when turned off suggests it may well be the battery.
the stock YBR battery is only 6AH

Some thoughts on checks and tests

H4 is just the fitment what power?
the YBR is intended to use a 35/35W H4 bulb not a 55/65W H4
I've know people often fit these instead of the stock ones
At a 14V running voltage, a 55/65W bulb will use 4 to 4.5 amps
while the 35/35W will use only 2.5 amps

I cant find any data on the YBRs stator current output or wattage
but there may not be that much over capacity to run heavier lights ( if fitted)
and fully charge the battery.

Also, the stock efi type stator has 18 coils in 3 phases while a lot of after market ones
look to have have fewer slightly bigger coils.
Without knowing the actual output of these stators we cant know what we can get out of them
without running them into a dummy load through say a 30A ammeter.

I'd do a diode test on each phase of the rectifier
If say one diode goes open circuit, you may have a less than full 3 phase system
without knowing it and have a reduced charging system.
The regulator is downstream of the rectifier and will try and hold the same output voltage
for 1, 2 or 3 phases but put out less current/power.
This will probably not be obvious to the rider.

Finally as always, check and clean all connections and grounding
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bikers smell of wee

[stinkwheel]

An ammeter with it running would be useful to see what it's drawing/putting in. Most multimeters have a 10A setting and input. Be an interesting exercise to plug it in in place of the main fuse and see what it's drawing with the engine off and ignition on then with the engine running. Then plug it into the output for the reg rec and see if it's pushing out more than it's drawing.

Shouldn't pop the meter fuse and if it does, if it's drawing more than 10A and you've found the problem.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Robby]

Is it still charging after a run?

Reg/rec failure can be gradual, and get worse with heat.

I don't know the specifics of this bike, but in general for bikes with 3 phase charging systems:

The alternator has 3 phases, each of these outputs AC voltage on its own wire to the reg/rec. Usually 3 yellow wires, and it doesn't matter if you get them mixed up.

The reg/rec has 3 shunts - diode pairs - that convert this AC voltage to DC.

Over time the shunts fail, usually one at a time and gradually. They fail worse when hot. Each dead shunt means less of the wattage from the alternator is making it through the reg/rec.

However, because the reg/rec also regulates the voltage down to 14.5v, you can still see 14.5v at the battery with no load. You're missing current, but the voltage still checks out.


So test it hot with some electrical load and see if the voltage drops. Or just replace the reg/rec.

The higher wattage bulb won't help here, but it shouldn't cause the problem with an otherwise healthy system.

[stinkwheel]

You can also get little LED voltmeters on ebay for under a fiver. You could jury rig one on the bars so you can see what it's doing on the fly.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[kawakid]

Thanks all for the pointers.
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I've a twin and a 4.

[MCN]

It's easier not to have to phaph about connecting an ammeter inline to measure amps.

Clamp on meters are far simpler and quick to use.

https://www.ebay.co.uk/itm/155503862555?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=dmtycvyosz-&sssrc=2349624&ssuid=bRtIGP-LTU2&var=&widget_ver=artemis&media=COPY

I got one of these a while ago.

It also measures in micro too.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[kawakid]

Hi,

Just an update on this, firstly thanks for all the help.

I thought I was going mad, I tested for loss using a multimeter, but it wasn't showing as any drain. I even had a mate who is a spark make sure, i'd connected it correctly.

I then considered taking the bike to someone who knows what he's doing, rather than a 50 year old IT guy (moi).

In the end, the bike failed to start after being on charge over night.

I cranked it over and on the mulit meter, DC volts went from around 12 to 7.

Yup a dead battery.

Now this battery was brand new Yuasa and purchased from a very reputable Car Parts place.

They tested it and confirmed it was fubar, ultimately a new battery has fixed it.

The battery is really small, the other thing that concerned me is that the acid had already been added. (Perhaps something to do with recent acid attacks).

Not sure what to think, I just hope he can soon pass his test (A2) and move on to something decent and more supportable.

Once again thanks.
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I've a twin and a 4.

[A100man]

[stinkwheel]