Charging issues

[M0WBY]

Hi

I am having charging issues.

So far I have replaced both parts of the alternator with good second hand parts that were fully tested before putting them on. At the moment it is charging I think. At tickover it has 12.4v across the battery. At 2.5k rpm it has 14V across the battery. At 5k rpm it has 14.8V across the battery. The battery seems to be charging. If I take the battery off the bike and charge it up overnight using my Optimate it charges and if left it stays charged up.

However when switch the lights on it drops a full volt and at tickover it only reads 11.4 across the battery. When switched off and back on again the battery behaves as thought it has dumped all it's power and won't hardly turn over. But if it is left for half an hour or so seems to recover. It does not do this with the lights off and behaves as though it is fully charged.

I don't know what to replace next. I am assuming the reg/rec is ok as it never goes above 14.8v and the manual says as long as it is under 15v it is ok.

I may replace the battery but it is less than a year old!

I don't know why the lights seem to run the battery flat so quickly.

Thanks for any help.

Cheers

John

 

[SteveD CB500K0]

Your charging voltages are spot on. I suspect that your battery is dead.


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[Bryanj]

With the lights on the engine needs to be over 3,500 rpm just to break even

[M0WBY]

Hi

So the battery has to hold a pretty good charge or in stop start traffic with the lights on it would go flat pretty quick requiring a jump start if it cut out for any reason?

Are Honda electrics really that crap?

I still think my battery is duff... I hope so anyway or my bike is getting traded in at the soonest opportunity.

Cheers

John

[SteveD CB500K0]

In the 70's, motorcycle charging systems (in general) were pretty crap - mainly because they couldn't build small, light, powerful generators like they can today.

With the lights on, no Honda of that age will charge at below about 3500 revs (as Bryan says). There's a revs vs charge table somewhere on .net - I'll see if I can find it.

So if you ride with your lights on and in stop/start traffic, your battery will run down.

If the battery is less than 100% it will go flat really quickly!

[SteveD CB500K0]

Found it! It's for a 750 but they're not that different.

http://www.sohc4.net/cb750-faq/indexphp/cb750-charging-rate-chart

[M0WBY]

Hi

I wonder how they coped in the US as you could not switch the lights off they even went as far as removing the on off switch!

I will have to rethink this as I always ride with the lights on. I think it may be time to sell it on and get something else.

Cheers

John

[Bitsa (Ralph Wright - RIP)]

Hi all,
My 2ps worth.
Jap electrics were spot on for their time.Try the old 6v system shit.Its law here to have your lights on all day even though car drivers are blind and makes no difference they still pull out on you.I have never had any electrical problems even when I fixed them back in the 70s unless some bozo had messed with them.I have said this before you have a 70s bike not today's tech .You have to live with this or stay away from classic bikes.Talk to people with 70s cars don't you think they do not have problems.As for electrics the Italian,American and British bikes well what can I say    CRAP.I ride mine maybe twice a week starts first time go for a ride get home battery's fine starts up on starter every time.Albeit it has a gel battery and not a poxy acid thing that does nothing but make your chrome look shit.
Keep this in mind
Cheers
Bitsa

[M0WBY]

Hi

I think I will have to get some night vision goggles...

Cheers

John

[M0WBY]

Hi

You have to admit it is a bit naff... I could ride my 81 GS750 with the lights on and never worry if it was charging the battery. In fact my 1977 Suzuki GT750 always had the lights on and never had a issue and if it did you could always resort to the kick start. Why o why did they do away with a kick start on this model when they knew charging was not up to much!

How much did you pay for a gel battery as I was under the impression they cost more than the bike is worth! LOL

Cheers

John

[Bitsa (Ralph Wright - RIP)]

John,
I think I bought the gel battery of a German on eBay I think it was 45 euros and never regretted it been bloody good.On all winter and started straight up when I uncovered her.
In those days if I remember right the h/light bulb was only 35w don't think you can get them now modern ones are 55 or 60w so the charging system struggles a bit.Tommorrow when after a ride I will do some voltage readings for you lights on/off etc and will let you know what mine does.I do have a 35w fitted stored them up over the years.
Cheers
Bitsa

[Bitsa (Ralph Wright - RIP)]

John,
Forgot to add my xjr1300 which the lights came on as soon as it fired up let me down more times than my Honda albeit through lack of use and try bumping that beast long live the kickstart.
Cheers
Bitsa

[M0WBY]

Hi

I think I have a 55W in the headlight.

Also one of my friends told me to check all the earths are good on it.

Cheers

John

[M0WBY]

Hi

Well the new battery came and it seems a lot happier.

I went for a ride on it yesterday but it started raining so being a fair weather biker I headed home.

Was not flat when I got back but the starter did sound a bit sluggish.

I am wandering if it is possibly the starter motor? It is alright when cold but when the motor is hot it sound a bit sluggish. Does this sound possible? I know the starters on these are well know for having issues. Could my starter cause a major amperage drain when it is warm?

Cheers

John

[Bryanj]

Yes as the resistance of the collected cr*p reduces with heat, most of the time(but not always) stripping the starter down and giving it a clean out with a lube of the bushes (NOT BRUSHES) will sort it out, we used to use a solvent called Armaclean to clean windings and commutators--don't know if its still about