/ motorbike charging problem is it the battery

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colina - on 20 Sep 2013
ok so havin problems with my classic moto guzzi!
the thing is I don't know whether it needs a new battery or whether the alternator is not charging.

I have a volt meter fitted on the bike and is showing about 10 volts whether riding or stationary.
now im thinking if its a broken battery it wont charge anyway and if its a bad alternator the same applies
any easy way of telling which it is.thanks.

the bike has been standing 4 years so its a good chance its the battery but I have also had alternator problems in the past.
RCC - on 20 Sep 2013
In reply to colina:
Sounds more like a faulty volt meter to me! A healthy battery at 10V is unlikely to start the engine.

Is there a problem with the running or starting of the bike?
Andrew Wilson - on 20 Sep 2013
In reply to colina:
Hi,
I have an Aprilia RSV in the garage that would not start after a week if not on trickle charge. I admire your optimism. Obviously if you have had a problem with the alternator in the past and not replaced it then it could be that but it is more likely the battery. Does it start? Mine needs around 14v to start but its a big twin.
I would not buy a new battery now anyway if its running, unless you plan on riding it through winter.
Andy
colina - on 20 Sep 2013
In reply to Andrew Wilson: the guzzi is a big twin also !however the only way I can start it at the moment is to keep charging the battery,tempted to just buy a new battery but don't want the same thing to happen ,waste of money etc
any more ideas?
colina - on 20 Sep 2013
In reply to RCC: !bike runs fine and yore right in saying the bike wont start with 10v ,the voltmeter is fine it shows 10v cause that's wot it is!
Andrew Wilson - on 20 Sep 2013
In reply to colina:
Thought it might be! Check the battery terminals and earth for corrosion. If not a sealed battery does it need topping up with fluid? Sounds very much like a dead battery anyway, before I last put a battery on mine it would start straight off charge in the morning, and only just start when leaving work. If I had to stop for petrol I was knackered.
Good luck
Andy
RCC - on 20 Sep 2013
In reply to colina:
> (In reply to RCC) !bike runs fine and yore right in saying the bike wont start with 10v ,the voltmeter is fine it shows 10v cause that's wot it is!

OK. Sounds more like the alternator then. A knackered battery will normally shoot up to 13-14V once the engine is on and drop off equally quickly once the engine is off. Is it firing OK?

adam11 - on 20 Sep 2013
Clean all your Earths first. The check the AC voltage from the alternator, no idea what the spec is but I'd expect between 30-50v. My money is on a knackered regulator/rectifier - they're not the best quality on Italian bikes of that vintage. If you can adapt the harness, then fit a Yam R6/R1 reg/rectifier, they're very reiable with a good heat sink.
Shorai batteries are the future for cranking over big twins :)
colina - on 21 Sep 2013
In reply to RCC: ok its not shooting up at all! staying constant at about 11 v and gradually getting lower and lower when using indicators horn lights etc to the point the battery is flat.
so still don't know if the batt is bgggered or the alternator is not doing wot it supposed to do.from wot your saying regarding the voltage goin up to 13v is correct it does sounds like the alternator,although if the battery was at fault im assuming it wouldn't go up anyway.
Dominion - on 21 Sep 2013
In reply to colina:

I had a dud car battery, which I removed from the vehicle, and charged up, so it was showing about 14v

Left it overnight (out of the vehicle) and checked the next morning, and it was showing about 11 volts

So it was clearly not holding it's charge, even with no load on it.

If your battery behaves like that, then it's a dud battery.

Martin W on 21 Sep 2013
In reply to colina: If the voltage at the battery terminals isn't going up when the engine is running then there is definitely a problem with the charging circuit: either the alternator itself, or the regulator/rectifier.

However, if you've let the battery go completely flat a number of times then there's a risk that that could have become damaged as well. I always keep my bike plugged in to a battery tender when it's in the garage. You need to be careful which one to use, though. I lost two batteries to an Optimate trickle charger before I dumped it and got an Acumen Platinum smart charger instead. That works like a charm, and does seem to be really "smart", unlike its predecessor. I've been on the same battery ever since I started using the Acumen.

To hook the charger up to the battery I use a 12v socket on a fly lead. I use one designed for marine applications which has a rubber bung to seal the socket when it's not in use. I route the wiring out under the saddle. It has the advantage that I can also run 12v accessories off it if I want to, such as satnav, or heated gloves/waistcoat. You need to make sure that you get the polarity of the socket and the plug on the charger the right way round - or the "wrong" way round in the case of the charger plug, otherwise you either won't charge the battery, or your accessories won't work.

I also have a small digital voltmeter on the inner fairing so that I can keep an eye on the charging voltage when I'm on the bike. That way I can see if the regulator/rectifier is on the way out (a common problem with the model of bike I have, but I've been lucky so far, touch wood). It would probably also let me see if any accessories I did have plugged in were causing too much of a current drain.
gethin_allen on 21 Sep 2013
In reply to colina:
First thing, buy a multimeter, you've got an only bike so you'll need it again at some point.
Then, you should be looking at +12 when not running, then this will drop to ~10 while starting then jump to ~13.5 when running.
If you aren't getting this jump when running then it's likely the altnator or something it the charging system. If if drops far below 10 turning it over then it's likely the battery.
Try cleaning all the terminals and checking wires for corrosion.
You should be able to check the battery condition by looking what it charges at, otherwise, if you go to a proper battery shop rather than just a place that has batteries they could probably do a drop test or a hydrometer test if the cells are serviceable.
Have you checked the fluid levels in the battery?
banksy - on 21 Sep 2013
In reply to colina: I had similar problem with my vfr. Took a age to find problem. initial thoughts were alternator. garage then checked for possible short circuits through frame which may have been 'dumping' the battery charge. Eventually found that the charge regulator was dud. Changed and been running perfect ever since.
auser - on 21 Sep 2013
In reply to colina: Start it up, let it idle.
Put the headlight on
Rev it over 2000 rpm - if the headlight gets brighter then the voltage is rising from the alternator so it's likely to be the battery.
teflonpete - on 23 Sep 2013
In reply to auser:

^^^This^^^
richyfenn on 23 Sep 2013
In reply to banksy:
> (In reply to colina) I had similar problem with my vfr. Took a age to find problem.... Eventually found that the charge regulator was dud. Changed and been running perfect ever since.

I had this on my CBR. Tested all the connections and voltages which were perfect, but it was an intermittent fault which only ever occurred while riding and never while testing at a stand still! Suddenly the lights would dim and I had to rev it to keep it going, then a minute later it was fine again. Changed the regulator and has been her lovely self since.
JD84 - on 23 Sep 2013
In reply to colina: Well, if all else fails, I had a similar problem with an old motorbike of mine and it was the starter motor. Simply take it off, strip it, clean it with brasso, put it back together again and it should work fine.
Charging the battery sometimes helps, or fiddling with the solenoid, but I was told the above by a colin appleyard mechanic and it worked well. Hope that helps!!
colina - on 25 Sep 2013
In reply to colina: ok some good stuff there .will maybe look to getting a trickle charger over the winter.cant do it no harm anyway .thnks 4 everyones suggestions
KTC - on 25 Sep 2013
1. If when the bike is running above idle, say at 1/3 revs, you don't have 14V or so, the generator is at fault - or the wiring to the generator.

2. If when the bike is running at 1/5 revs the voltage goes above 14.5V ish the the regulator is knackered, and your battery may well be damaged by it.

3. If the battery, disconnected from the bike entirely, drops it's charge overnight from around 12V to 11V then I'd say the battery is dead - though a good smart charger may be able to recover some life from it.

4. If a battery showing 10V is starting your bike, your multimeter is knackered, or your battery is full of magic.

Clean all plugs and wiring, check all earth points. Look for heat damage and corrosion.
M0nkey - on 26 Sep 2013
In reply to KTC:

>
> 4. If a battery showing 10V is starting your bike, your battery is full of magic.
>

Is it possible to get refills if this is the case? Which colour pump do you use at the esso garage?
ads.ukclimbing.com
teflonpete - on 26 Sep 2013
In reply to M0nkey:
> (In reply to KTC)
>
> [...]
>
> Is it possible to get refills if this is the case? Which colour pump do you use at the esso garage?

The tartan one.
deepsoup - on 26 Sep 2013
In reply to colina:
> (In reply to colina) ok some good stuff there .will maybe look to getting a trickle charger over the winter.cant do it no harm anyway .thnks 4 everyones suggestions

Actually a trickle charger can do it some harm. Bike/car batteries really don't like being on a constant trickle charge.

If you want something you can plug in and forget about you'll be better off with something like an Optimate/Accumate/Oximiser etc.. Rather than trickle charging, they'll charge at a slightly higher rate until the battery comes up to around 14v ish, then stop until it drops back below 12v ish, and cycle that way indefinitely.
colina - on 27 Sep 2013
In reply to deepsoup:
> (In reply to colina)
> [...]
>
> >
> If you want something you can plug in and forget about you'll be better off with something like an Optimate/Accumate/Oximiser


wow !an "optimate/accumate/oximiser" sounds like something captain kirk would use .
8-)


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