Charging

[hairygit]

If pressing the starter gets it back, check your earth cable to frame connection from the battery

[Fairview]

OK I will.

Thanks!

[madoc]

Thanks for the replies everyone.

Steve, this is the sort of step by step idiot guide I was hoping for, so here are the figures

1. 12V
2. 11.25V
3. 11.60V (fluctuating)
4. 11.78V (fluctuating)
5. 12.26V (fluctuating)

Is that 12v with nothing on ?
That's not good, a decent 12v battery should be around 12.7v.
Put it on charge overnight, then disconnect for a few hours and see what it reads then.


 

[SteveD CB500K0]

1. 12V
2. 11.25V
3. 11.60V (fluctuating)
4. 11.78V (fluctuating)
5. 12.26V (fluctuating)

Firstly, 12.0V is with nothing switched on is the sign of a dead battery. It should be at least 12.6V
Try disconnecting it completely and measuring it. As Madoc says, charge it overnight and then see what the terminal voltage is.
Looks like the first thing to do is buy a new battery.

Secondly, under revs the charging circuit should be regulated to 14.5V or thereabouts. 12.26 is not enough to charge your battery. In fact, its probably discharging at that stage.
So you need to look at the charging circuit as well.

We can try some more tests on the charging circuit if/when you've sorted out a decent battery.

Steve

[Fairview]

Thanks Steve, battery already on charge as per Madoc advice will check it when i get home but it sounds like it's knackered anyway. I'll pick up a new one and run the tests again and re-post the results.

Thanks again.

[Bryanj]

With batteries a Yuasa will cost about £10-15 morw than a Generic cheapy but will last longer as long as you dont forget to charge it after filling and before fitting

[madoc]

Thanks Steve, battery already on charge as per Madoc advice will check it when i get home but it sounds like it's knackered anyway. I'll pick up a new one and run the tests again and re-post the results.

Thanks again.

Let it stand after charging and stabilise. A few hours or overnight.
If it's around 12.7, then you're good.

Having a decent battery in the charging circuit is required.
Mine looks like it's fading (around 12.3v) and my charging system won't put it up over 13v now.
Um .

[Fairview]

Hi Madoc/Steve,

It's stood for 24 hrs and is still showing 12.7V. I haven't connected it to the bike yet in case that's draining it for some reason (although I don't think it is).  So it seems the battery is ok, should I run those tests again or can we go from here?

Thanks for your help.

[SteveD CB500K0]

Yes.  Install it and check with no ignition on.

If the voltage sags quickly, remove the +ve connection and measure any current draw.

[madoc]

If the voltage sags quickly, remove the +ve connection and measure any current draw.

Let me explain that.
If you have a reasonable multimeter then it will serve as an ammeter (usually to 10Amp).
There are usually three terminals on the bottom of the meter, one black/two red.
One of the red one does everything voltage related and the other measures current/Amps
You swap the red lead over to the ammeter one and select the right setting on the meter (most have a dial for the different functiions - voltage, resistance,contunuity and current).

Disconnect the positive terminal of the battery. Connect the battery terminal to the positive lead of your meter and the negative lead of the meter the wiring (you just unscrewed from the battery) which is hanging in lose. You should get no reading.
Now turn on the ignition and current will flow through your meter and give a reading - that proves it is working. You can probably turn on your lights and see a larger number.

Don't hit the starter - it's likely to pull more than 10amp and blow the fuse in the meter.

Now, turn off the ignition and NOTHING should be shown.
If it does show a number then something is shorted somewhere and that will drain your battery over time.

I have a AVOmeter here .... fine piece of british kit. weighs a ton.

[SteveD CB500K0]

Thanks for posting that. I tend to forget that we're not all (ex) electronic/electrical engineers on here!

I also have an AVO (its an ancient Model 40 that I inherited from my father who was a real "electrical" engineer. I also have a Fluke digital which I "inherited" from my last employer...)

[BigAl (Alan)]

Hi Tristan,

If you can get hold of My CB 750 Book By Mark Paris page V-10 his explanation with drawings will make things a lot clearer.
The disadvantage with the field coil is that it is using 2 amps @ tick-over (no current is fed back into the battery until 2-3K revs) so if the battery is not fully charged and you put the lights on @ tick-over the voltage drops further...the ignition coils have reduced power to produce a good spark...and then stalls.
You will need a multimeter (ideally an AVO, has 10 amp full scale reading) and some circuit knowledge to find out the voltage or better still the current being used
PS The voltage regulator switches ON or OFF or part ON the field coil

Alan

[Fairview]

Further to my previous post......

Although the battery seemed to hold charge when left overnight it did seem to drain over longer periods and I wasn't convinced that it was sound. I'm fairly sure it isn't the bike draining it but its old so I spunked 40 quid on a new one today (based on Madoc's comment that the charging system is dependant on a decent battery) and ran the tests again. This is what I got -

Ignition off - 12.6v
      "     on - 11.96v
Tick over   -  12.2v
3k rev      -   12.5v
3k & lights -  12.6v

I think this suggests a charging problem? If so where do I start.....

Thanks in advance.

[madoc]

Ok.
I know it sounds droll, but thirty years of bikes always lead me to suspect the regulator.

Anyway , it's either alternator, regulator/rectifier or wiring.

I would check the alternator first and eliminate that.
According to the workshop manual, you can run a resistance check across the three yellow wires:
http://www.scribd.com/doc/14355713/Honda-CB500-CB550-workshop-manual  (page 95)
You maybe want to check to earth as well.

If it's good then check continuity through the loom to the regulator and rectifier (which are separate parts under the left hand side panel).

To be fair, if both alternator and wiring are ok then I'd just replace the original mechanical reg and separate rectifier with a solid state one (what I did).  I got one for £30 and it used the existing mountings and had the right connectors.