Low charging...

Post by **Multiphonikks** » Wed Oct 20, 2004 9:44 am

I noticed earlier today that Hebe's indicator and wipers slow down when we're standing in traffic with the heater, radio, lights, wipers and indicator on...

I took her to the local garage (I've got to drive from Reading to Norwich on Friday night so don't want my battery giving up on me) and they checked out her charge cycle (apparently it's "good") but the battery itself is bringing up about 11.6 volts. (with the car and everything off)

When the engine is revving above idle, we're up to just about 13v (with everything running), but with everything running and the car stationary, it's dropping down to about 10v.

The fan belt doesn't appear to be slipping, but is quite low in the dynamo grove now (so do I need to replace - I've got a spare somewhere from the last service when I didn't replace it....)

Added to this confusion the fact that I seem to have Misplaced my multimeter, and have only just got my dear late dad's battery charger working (first time I've ever needed it and it happens to be the three year anniversary of his death today) - it's currently sitting outside charging the battery on "high".

Question is... I've taken some photographs of the dynamo "spindle" from behind. Can anyone tell me if they think the brushes are worn from this???

Comments? Ideas? Suggestions? Will it be safe to drive Hebe 180 miles on the motorway (bearing in mind that at anything other than stand-still she's producing 13v even with full accessories) if I charge her battery up fully before we leave? Or should I put plan B into operation and go get the Alternator I've been promising Hebe for about 3 months now (I'm going to need the Alternator anyway when we leave for the states as I have plans to upgrade the Candles....)

Nikki

Post by **Cam** » Wed Oct 20, 2004 9:50 am

I don't think the Dynamo is the problem, it sounds like battery. I don't like the dip down to 10 volts. It should not go MUCH below 12 volts. 11.5 or something like that.

If you can't afford a new one at the moment, then charge her up before you go and take your starting handle with you just in case!

Post by **Multiphonikks** » Wed Oct 20, 2004 10:05 am

Cam wrote:I don't think the Dynamo is the problem, it sounds like battery. I don't like the dip down to 10 volts. It should not go MUCH below 12 volts. 11.5 or something like that.

If you can't afford a new one at the moment, then charge her up before you go and take your starting handle with you just in case!

Thing is, they tested the battery and it came out okay, but just very low in charge at the moment :/

Do you mean it shouldn't work below 12 volts?

Post by **pskipper** » Wed Oct 20, 2004 10:11 am

Apparently you should be able to start a minor with one of those square batterys with springy bits on the top (hopefully someone can describe it better than this) if you use the handle. If you are really worried it might be worth popping one of those in the glove compartment!

Post by **d_harris** » Wed Oct 20, 2004 10:27 am

What, one of the old-style 9v ones that are about 2"x2"x4" with the two springs as terminals?

Post by **Alec** » Wed Oct 20, 2004 10:29 am

Hello MP,
with everything running as you describe the load on the system is greater than the dynamo can provide with the engine idling. (Your ignition warning light si probably glowing faintly?) So the car is running off the battery, this will discharge proportionately to the amount of current drawn and time it is discharging. This is the reason that alternators replaced dynamos as they were both larger in capacity and also provide a better charge at slow engine speeds.
If your battery is sound, using a battery charger is quite acceptable to restore the lost charge and you should not have any real problems.
Yes, the fan belt could do with changing if it is very low in the Vee, if it actual contacts the inside of the belt it is totally useless. I can't see how worn your brushes are, but if you can see the flat spring that pushes the brush against the commutator. When it looks deep into the top of the brush box, then there is not much brush left. Also a Minor should start on the handle without using a small battery as someone suggested, unless the dynamo is not working.

Alec

Post by **Cam** » Wed Oct 20, 2004 10:57 am

Multiphonikks wrote:
Cam wrote:I don't think the Dynamo is the problem, it sounds like battery. I don't like the dip down to 10 volts. It should not go MUCH below 12 volts. 11.5 or something like that.

If you can't afford a new one at the moment, then charge her up before you go and take your starting handle with you just in case!
Thing is, they tested the battery and it came out okay, but just very low in charge at the moment :/

Do you mean it shouldn't work below 12 volts?

Yes, it CAN work below 12 volts, although it just means that it is in a low state of charge, and if yours has been 'tested' then it probably just needs a charge. As Alec said, this is perfectly normal (especially during the winter months) for a dynamo system as it does not charge at low revs.

Post by **Multiphonikks** » Wed Oct 20, 2004 10:59 am

Hi Alec,

I drove from Reading down to see Peetee in S'hampton yesterday so Hebe had quite a big drive down. The fact though that she'd got everything going (wipers, lights, heater, radio) may have drawn quite a lot from the battery... I dunno

I've pushed the idle speed up slightly; You're right, it was very faintly glowing.

I've just found my own multimeter and I was getting 13V charging, and just under 12 on full accessories.

I'm off to go and get the fanbelt replaced, and I'll see if that makes any difference....

Post by **doobry** » Wed Oct 20, 2004 11:51 am

Nikki
When you rev the engine the voltage rises to about 13v - that shows normal dynamo operation. You should change the fanbelt periodically anyway so no harm in doing it, but I don't know why you think it is related.
As for the battery - if it showed ok on a battery tester (one of those things that monitors the battery capability whilst drawing high current) then the battery should have some life left in it.
The dynamo doesn't produce much output at tickover, so as mentioned above, you car will be running off the battery. The battery voltage is lower therefore everything runs slower, and when you reve the engine and get 13V, everything runs faster - that's basic physics and not much you can do about it.
A half decent battery battery that is properly charged should read approx 12.2 to 13 volts with no load so if it below that, it may just need charging. As the battery is down to 10v with everything on, then that would show a large change in the speed of the wipers etc.. compared to 13V from the dynamo at higher revs.

Charging the battery in winter is a perfectly normal thing to do, especially if you have lights heater and wipers on a lot, and it is mandatory if you also spend a lot of time in traffic with the engine idling. When I used a mog for commuting I used to charge the battery every 2 months in winter (ie October, December and February).
I was much happier to keep the dynamo and do that to get no problems, rather than to change to an alternator and come home on a recovery truck like so many other people with alternators on mogs, however it's personal choice.

Post by **pskipper** » Wed Oct 20, 2004 12:03 pm

What, one of the old-style 9v ones that are about 2"x2"x4" with the two springs as terminals?

Those are the ones!

Post by **lowedb** » Wed Oct 20, 2004 1:50 pm

Quote:

What, one of the old-style 9v ones that are about 2"x2"x4" with the two springs as terminals?

Those are the ones!

Except those are 6 volt not 9. I wouldn't reccomend connecting one to a car unless you disconnect the coil wire and connect it direct. The dynamo and / or battery could do nasty things to it when the engine started.

You can use the battery voltage to indicate state of charge, but only if it's disconnected from the car, and has been off charge for quite some time (or a short heavy discharge). This removes the surface charge.

12.2 v is about 50% charged. 11.7v is 0% charge, 12.7v is 100%. It's a complex thing that I don't claim to even partly understand, because it's all chemistry!

Post by **doobry** » Wed Oct 20, 2004 3:08 pm

12.2 v is about 50% charged. 11.7v is 0% charge, 12.7v is 100%. It's a complex thing that I don't claim to even partly understand, because it's all chemistry!

yup - I ummed and ah'd about which levels to quote as el-cheapo multimeters have a tolerance and the temperature of the battery and how recently it was subjected to charging volts has an influence. The actual state of charge is a very complex thing and if you charge a battery for long enough it will read 13v (presumably as the temperature is higher), but that will decay down during standing.
Therefore measuring on a cold morning after leaving it overnight and when it is warm underbonnet after an houres drive will give different values for a similar level of charge.

Post by **Multiphonikks** » Wed Oct 20, 2004 3:43 pm

Oh good, cause I just got 14v from mine with the engine running :O

Post by **Kevin** » Wed Oct 20, 2004 3:54 pm

Nikki it looks as though the dynamo is fine if you are getting those sort of outputs

Post by **Multiphonikks** » Wed Oct 20, 2004 4:06 pm

Kevin wrote:Nikki it looks as though the dynamo is fine if you are getting those sort of outputs

Yes, after playing with the idle speed (made it a bit higher- I'll probably drop it a bit in the summer) and trickle charging the battery for a good five hours, she's able to be stationary with all things on and not be loosing too much

Nikki