I'm still losing volts from my battery (they don't seem to be hiding in the battery box ), so I'm pretty sure the only thing left to blame is the battery itself. However, just to make sure it's not something else and I'm not going to knacker a new one, here's the story so far:

Ages ago I discovered by accident (I broke one) that the alternator wires were very unhappy, and replaced the the female spade connectors with new ones. I don't think this really has a bearing on what's going on but bear with me...

Some time later, at least a couple of months and many hundreds of miles, I came back home for the weekend to find that the battery was flat to the point it wouldn't throw the solenoid. Recharged it, checked the repaired crimps, all were fine and everything went OK.

Next time I came back, everything seemed OK.

The following occasion, I decided to measure the battery out of curiosity. 12.25V! Bike started, charging figures were not great but within spec. Re-crimped previous repair and soldered for good measure. Test ride charged battery a few tenths higher. Next day arrived at destination convinced something was amiss. Charging system appeared not to be working (lights not glowing when engine revved, no slight flicker when shutting throttle). Test rode twice during the day seemingly without issues, but both times charging seemed to work when setting out, but not working within a few miles. Leaving the bike for a little while and then running again seemed to bring it back to life. Rode home (25 miles), arrived with bike running on 9.5V at idle. Climbed to about 11.2 on turning off ignition.

Today, I have cut back, crimped and soldered new spades on the alternator connection by the right fairing bracket, and fitted a new connector. I have also put a new connector on the reg/rec, replaced the previous crimped repair on all the pins (this was done about 5 years ago or more) with soldered spade connectors, and the output is now direct to the battery via heavy multicore and a fuse on the positive, using proper battery connectors. Freshly charged batter applied, and the results were very good. System produced 14.5V at 2K never mind 5, with a few tenths less at idle. Haven't managed more than high 13s before, so I was really happy. I went out intending to put similar miles on as the last journey, however after I stopped to get petrol, I noticed that the headlights appeared to be dimming in time with the indicators, which is usually a bad sign, so despite having a few tools with me and a meter, I headed straight back home. 11.99V after less than 10 miles and one re-start of the engine. Nothing happened if I gave it a few revs, not even a tenth of a volt more. After switching off, it raised back to about 12.4V, and the bike would start if I tried.

I checked all the wiring again and everything was sound. I put it all back together, and once again it did the trick of suddenly working again, however I was not happy. Elsewhere, someone suggested that if a battery can't manage half an hour with full beam on with the engine stopped then it's junk. So I decided to put the meter across it and see what happened. It managed about 10 mins before there wasn't enough oomph to turn the starter (the solenoid still threw).

I'm fairly happy to say the battery is crap, or would be if it was a few years older! However, I'm a bit confused about it not charging, then charging, then not. If it charges from a charger, why not from the charging circuit, and also, if the charging circuit is working, why do I get such a low voltage when the battery is sulking? Does it somehow cause the difference between what should be about 14.5V output and what you actually read to become 'lost'?

Hi, I'd say your reg was knackered, if not totally then its on its way. You should get between 13-15v out the reg when engines running, the battery only starts the engine, once its running all the electric power comes from the reg. I had a simliar prob on my FZR but the battery was old( 7years!) so swapped it out anyway. Turned out the reg wasnt happy either so swapped it for a R6 one, i put a R6 reg on me NC30 ages ago and they work great never had a problem since.

Thing is, if I charge the battry before putting it on the bike, I get a good voltage at the battery when the bike is running - at least to begin with. Today I got the best output I've ever measured! Then it gradually drained when I went for a ride and wasn't charging when I got back. Then it decided it would a bit later... So confused! Sod's law says if I buy either the reg or battery, it'll be the other at fault!!

You may have an intermittent or heat related fault in the rect/reg or the stator that results in no or little output after traveling a few miles. An intermittent fault could be triggered by engine or road vibration or shock. Either fault condition would mean that the bike at various times would be relying on battery power, resulting a progressively flat battery and the symptoms you describe while riding. Would also explain why the problem then suddenly appears to correct itself after you stop or the rect/reg cools down.

Suggest you attach your voltmeter to the battery the next time you go riding and see if the charging system stops working at any time.

You'll prob just have to bite the bullet and start somewere. If you charge the battery does it hold charge? If it goes flat just sitting there over night its deffo the battery (unless you've got a short in the loom somewere). If the batterys keeping charge for a day or two then starting ok then I'd start with the reg. For the sake of £35 I'd be doing the reg just for peice of mind. Is it still got the OE one on it?
Cheers
Ian

Reg/rec is a relatively new one I got about two years ago. One of the aftermarket ones with fins on. Not the utterly cheap and cheerful Chinese crap that's to be avoided, but a middle of the road one that I'm sure other people on here have used quite successfully. I do have a spare one that came with the stator and flywheel I picked up, but I don't know for sure if it's healthy, and it's one of the non-finned ones. I guess if I put it on to test it, and it works, I could at least rule out the intermittent reg/rec theory and blame the battery. The battery lasted less than 15 mins with high beam on when I got back, although to be fair it wasn't fully charged so that will have affected the results. When I took the battery out to charge it, I tested the loom for leakage, and the meter read absolutely zero. However, I don't know if you're supposed to turn the ignition on when you do so - I didn't.

The reason I'd like to blame the battery is that on the facebook page, someone had a similar issue with zero additional voltage at the battery when it should have been charging, and changing the reg/rect made no difference, and the battery was the issue. However, in that case, the system NEVER did anything different, whereas mine does. For some reason, I didn't think to measure the output from the alternator before I ran the battery down, probably because everything seemed fine before I left and I was convinced it was the battery.

When cold, I had 0.5 ohms resistance across each pair at the alternator connector, and 0.6 ohms at the reg/rect plug end of the circuit. The AC output has been checked previously and was within spec. If it wasn't for the fact that the trains are being crappy this weekend, I'd still be at my parents place now, and able to do some more checking. I've picked up a cheap LED volt display so I can keep an eye on it while out. My current plan is to charge the battery and then go out and wait for the output to fall off, then get back quickly and measure what I've got where.

What sort out output per pair of wires should I get from the alternator when connected to the charging system? It's around 12 at idle and 50 or so at 5K, but that's disconnected, and I'm wondering if being under load might make a difference and help cause the fault, if it turned out to be the alternator....

A simple multimeter will not give a meaningful measurement of stator output (yellow to yellow wire) when the rect/reg is connected.

A fully charged battery should give 15 minutes of high bean headlights with voltage remaining higher than 12 volts.

Given you have a spare rect/reg, try it to eliminate a possible source for your problem but check it first to make sure it holds the battery voltage below 15 volts.

Fully charge the battery and leave it disconnected from the bike for 2 or 3 days. Test the voltage with a multimeter and see if it has dropped significantly.

Often a knackered battery will self discharge in a couple of days.

I'll see if I can arrange for this to be done. Don't really want to wait a fortnight until I'm back home again...!

Out of curiosity, what sort of shelf life would you expect on a new but unactivated MF type battery - ie leave it in the box and not add the water? I don't want to buy or use a new battery unless the current one really is the issue, but at the same time, if it turns out to be the case, I don't want to have to wait even longer for a new one to arrive when I find out. I wouldn't object to having a spare one if it turns out to be fine, however it would be a waste of money if it can end up being past it's best after long storage, even if you haven't activated it.

I've also pondered getting an Optimate. I don't have a bike battery charger, but have to rely on a car one. Most people say that over 1A charging rate hurts a bike battery, however this one has an ammeter in it, and it never delivers that amount of current when on the normal charge rate setting. Supposedly, these things even when only used as a charger as opposed to an optimiser/trickle charger can help recover a slightly iffy battery, or at least check the condition. I don't have much faith in the ability of one to fix a dodgy battery, but being able to check the condition might be handy. Do they really do anything like the claims?

speedy231278 wrote:I'll see if I can arrange for this to be done. Don't really want to wait a fortnight until I'm back home again...!

Out of curiosity, what sort of shelf life would you expect on a new but unactivated MF type battery - ie leave it in the box and not add the water? I don't want to buy or use a new battery unless the current one really is the issue, but at the same time, if it turns out to be the case, I don't want to have to wait even longer for a new one to arrive when I find out. I wouldn't object to having a spare one if it turns out to be fine, however it would be a waste of money if it can end up being past it's best after long storage, even if you haven't activated it.

I've also pondered getting an Optimate. I don't have a bike battery charger, but have to rely on a car one. Most people say that over 1A charging rate hurts a bike battery, however this one has an ammeter in it, and it never delivers that amount of current when on the normal charge rate setting. Supposedly, these things even when only used as a charger as opposed to an optimiser/trickle charger can help recover a slightly iffy battery, or at least check the condition. I don't have much faith in the ability of one to fix a dodgy battery, but being able to check the condition might be handy. Do they really do anything like the claims?

a car charger can knacker the standard battery easily, the plates are too thin inside and the extra juice destroys them, this causes the battery not to hold as much charge.. if the plates melt and flake away they can cause micro shorts in the battery that self discharge it overtime.

Optimate is the best way.

When you first get a new battery, fill it with the acid and wait 30 mins, put it on an optimate until it is fully charged, if you dont break it in properly they are never quite as good.