Charging woes

Sorry in advance, I posted part of this last night but tacked onto another thread...

I appear to have a charging problem, having suffered a flat battery after filling up with petrol mid-week. I've checked the regulated output, having trickle-charged the battery for 18 hours first. These are the results with the lights off and on, at tickover and 5000 RPM.

No lights: Tickover 14.40v, 5000 rpm 14.08v
With lights: Tickover 13.94v, 5000 rpm 13.29v

The 'with lights' test at 5K revs gives a voltage across the battery that's beneath the range specifed by Mr Haynes.

Why is the voltage *dropping* as the revs increase? I do have recollection of reading something about this before - any ideas?

Is this the regulator, the battery or something else?

TIA.

[mister c]

Common fault on the SV, I would say the regulator/rectifier. Change it for a Gixxer one.
Someone will be along shortly with some proper mechanical knowledge to tell you, but thats what I'd go for.

With lights: Tickover 13.94v, 5000 rpm 13.29v

That is ideal .... if you are getting a flat battery, its coz the battery is naff ... those v-s look good to me (better than mine).

And yes, the regulator circuit cuts in and reduces output off idle .. mad isn't it!!

Originally Posted by Blue_SV650S

With lights: Tickover 13.94v, 5000 rpm 13.29v

That is ideal .... if you are getting a flat battery, its coz the battery is naff ... those v-s look good to me (better than mine).

And yes, the regulator circuit cuts in and reduces output off idle .. mad isn't it!!

Thanks for the encouragement. I'm hoping it's the battery: I've got a new one on charge right now... cheaper and quicker to try than a new rec/reg!

Originally Posted by chazzyb

I've got a new one on charge right now... cheaper and quicker to try than a new rec/reg!

New battery installed this moaning. Charge rates same as with old battery. Threw caution to the wind and went out for a ride this afternoon. Did 170 miles, with a couple of engine stops (wee and petrol). Bike still started on the button when I got home. I reckon 170 miles with headlight on should have drained the battery if it wasn't charging adequately.

Anyway, I haven't learned my lesson - the new battery cost £21.

Originally Posted by chazzyb

New battery installed this moaning. Charge rates same as with old battery. Threw caution to the wind and went out for a ride this afternoon. Did 170 miles, with a couple of engine stops (wee and petrol). Bike still started on the button when I got home. I reckon 170 miles with headlight on should have drained the battery if it wasn't charging adequately.

Anyway, I haven't learned my lesson - the new battery cost £21.

Glad it seems sorted, where did you get a battery for £21?

Yeah tell us, when my battery went dead and stranded me I paid more than double that!
Pointy battery is cheaper than curvy battery for some reason...

Originally Posted by Blue_SV650S

where did you get a battery for £21?

My local motor factor is run by couple of blokes who ride bikes. They keep a few bike batteries - a cheap and cheerfull(?) make (Wun Hung Lo, or similar). YTX9-BS/CTX9-BS is the right size, even if its longevity is rather suspect.

Ah, OK. I bought a yuasa which is original fitment I think.

[Spanner Man]

Morning all.

Sounds like there's nothing wrong with your charging system. The figures quoted in manuals are a general guide, so basically if you're getting a charging rate that is 10% over the batteries standing voltage at low RPM (which you are) then all is well.

One point worth mentioning is that the YTX-9BS battery you have fitted is only 8 amp hour, as opposed to the O/E YT12-ABS which is a 10 amp hour battery.
Back when YT12's were only available from Suzuki at a cost of around £85 a lot of people fitted YTx9's, & had trouble starting on cold mornings.

As a general rule it's ok to install a larger capacity battery where possible, but not a smaller capacity one. For as a smaller battery will reach full capacity earlier, the regulator will be working harder losing the excess charge in the system. As it does this by getting hot, you may well shorten it's life somewhat.

Cheers.