Flat battery

[speedy231278]

Somewhat ironic considering some of the thread I've contributed to very recently, but last night I got back to Sussex, fitted a new clutch switch to the bike as I was fed up with it not working, and then found the battery was flatter than a Witch's left tit. I'm assuming it's related to the recent issue I had with broken/corroded wires on the stator and the fact that I did a temporary fix pending my two month window next month to pull bits off the bike without worrying about not fixing them immediately.

Anyway, the battery was removed for charging. I checked the fix I'd done to the wires coming off of the stator and there was no obvious sign of them having failed, however as they were only crimped (albeit they seemed very secure when I checked earlier) I do wonder if maybe one of them wasn't as happy as it should have been for at least part of my last journey. I did hit the mother of all lumps in the road on the way back so it's possible it might have upset one of the connections.

As of now, the wires from the stator have been cut back, made good with new 2mm wire, and had new spade ends crimped and soldered to the ends. All pairs are 0.5 to 0.6 ohms between them. I also investigated the other end, and measured to within 0.1 of the same figure where the wires plug into the reg/rec. None of the wires at that end appear to be in bad shape, and they were all done about five years ago. Admittedly, they are plain crimp jobs, but those used were far better that the ones Halfords do these days.

I'm now getting mid to high 13s at idle at the battery, and if I turn the idle up to about 1500, I get 14+. Whether or not part of this is because the battery has come fresh off the charger I do not know... At 5K the figure is roughly the same, although it does seem to fluctuate a bit, and once or twice it dipped down under 10V for a split second. However, when you have the meter probes wedged against the battery terminals and everything is vibrating, I tend to find it doesn't help the readings in the least!

The last four times I've used the bike, it has been for the same journey and return. Since I 'fixed' the dodgy wires it hasn't missed a beat, and has started first time without any issues. After each return trip, it has been left a full week before doing the same again. While I am happy at this moment to put the problem down to not fixing it in a more solid manner, if it happens again, what should I start looking at? Has the battery given up the ghost, or might I have a short somewhere that's draining the battery? I don't run any plug-in electrical goodies, so any drain would be a fault with the standard kit.... I'm off to put roughly the same miles on it as the last trip, and will measure the thing again when I get back....

[magg]

What was the voltage of your flat battery?

[speedy231278]

Well, if I'd had the brains I was born with, I'd have checked it before I charged the bloody thing! If it dies again I'll be sure to do so....

I've got back without event, and the bike was happy to start again shortly afterwards. I'm a little curious about the readings I'm currently get, however I don't see an issue as I'm not sufficiently clued up on the finer points of the charging circuit:

Off: 13.24V
Idle 12.8V (RVF - lights are on)
2.5K rpm 14.4V
5K rpm 13.8V

I'm wondering why I'm losing volts after about 4K? Is the ignition simply drawing more juice when the engine revs faster (I'm guessing more sparks means higher load) ? It seems to become stable at around 4K, and I'm certainly revving the thing into five figures while stationary to find out!!

Is there anything suspicious in the above figures to those in the know?

[speedy231278]

Went out again just now to try and fnid some split pins (no luck with those), I've done about another 15 miles and the bike has been started at least half a dozen times and ridden in short hops between various places around town, followed by half a dozen miles back at reasonable speed. I didn't measure the battery with the engine running, however with it switched off it was 13.12V. Very slightly less than earlier, but as it's over 12.8 which is allegedly the magic number for a happy battery I am not too concerned. Now, if I find it's flat tomorrow morning it'll be a different matter. I'll be happy to be able to avoid getting soaked going to and from where I'm going, but annoyed that there'll be something else to fix somewhere!

[speedy231278]

Just checked as I'd left soemthing in the garage. Now has 12.98V. Is it usual for a battery that's got more than 12.8 or so on it to drop back fairly quickly to that level? I know that there's a slight loss over time (I read somewhere that it can be up to around 1% a day), however right now it seems to be losing about .1V every few hours. Right now I'm hoping it's usual for a battery to drop back from in excess of 13V fairly swiftly then level out, otherwise things might be rather bleak in the morning....

If there's something draining the battery rather than the battery simply being knackered and giving up the charge, is there any way of measuring it?

[RandomDan]

I think lead acids lose about 10% a month from what i remeber.
Straight after charging the voltage might be higher than usual.
Is the battery hot? Smell of rotten eggs?
It can smell of egg if it is overcharging as it burns the sulfur inside the battery!

[speedy231278]

Nope, no excessive heat, no funny smell. It's no spring chicken, but I don't think it's more than two or possibly three years old. Should have another couple of years before it gets weak, I would hope. The previous one lasted about 8! I did see a document that suggested if I disconnect it and measure current across the loom connectors, any more than 50mA indicates a wiring fault that's leaking current. If, heaven forbid I find it flat again, I'll measure that and see what I get.

[RandomDan]

You got an alarm on the bike or anything?
I would imagine a shitty alarm could drain it.

[speedy231278]

Nope, nothing electrical added.

[speedy231278]

12.97V this morning, started without any fuss. Will find out for sure if there's any issue next weekend.....