Electricity Escaping

[Dollywobbler]

I'm 100% sure it isn't a battery fault.

[RobC]

All this alternator talk reminds me of my need to upgrade my alternator to an a/c one.

Any recommends for the best firm to buy from?

Ta!

(PS yes it sounds like an alternator / charging circuit fault to me too).

[mat_fenwick]

But there is no charge voltage! When you measure the voltage across the battery you are basically directly measuring your alternator output, the fact the reading is 11.5 volts WHEN RUNNING means the alternator is not giving out any charge voltage

I do think we need to be careful giving out (well meaning) advice unless reasonably certain of the cause, as we could be sending people on a wild goose chase when they could otherwise be spending time fixing the known problem.

As for recommendations, I've used QX Components for repairs, and they've been helpful and fixed the problems. No problems since either! I'd be wary of reconditioned parts which seem too good to be true, as the 'reconditioning' may simply consist of a coat of paint...

[vulgalour]

Embarassingly, the earth plug was not attached to the alternator. Plugged it back on and found that its a very strong alternator and a good battery. Tick time continues to improve too.

My battery tell tale still doesn't illuminate and I've literally had the dash apart so that I could climb inside it to change the blown bulb with a good one today.

[kiwi]

Embarassingly, the earth plug was not attached to the alternator. Plugged it back on and found that its a very strong alternator and a good battery. Tick time continues to improve too.

My battery tell tale still doesn't illuminate and I've literally had the dash apart so that I could climb inside it to change the blown bulb with a good one today.

Ha and nearly everyone was saying you need a new battery!

Just goes to show work your way through from the battery backwards to the terminals right up to the alternator before assuming its the alternator or Battery.

As for that Dashboard lamp! Are you saying it does not come on when you first turn the ignition with the syop lamp? Indeed time to replace the bulbs and while you at it replace the important ones at the same time. Pod removal is not an easy task the first time so take it easy.

[vulgalour]

The battery telltale never illuminates, I don't think it has since I got the car I just hadn't noticed until now. Swapping bulbs around doesn't make it illuminate either so I'm not sure what's going on. Dad rang Citroen while I was fettling and they said to take it in and they'll have a look gratis as it's a fault they can't understand either.

[electrokid]

Well - glad you've found the problem - hopefully my previous post...

So if you've checked all the connections to the alternator

may have hinted at it ?

Anyway - there's no such thing as an earth plug on the alternator. There's a big fat connection which is the alternator output - that's a direct connection to the battery so Kevan's comment...

The probe on the battery positive is basically the same as putting the probe directly to the back of the alternator output.

is spot on because the battery and the big terminal on the alternator are connected together by a heavy gauge wire. If that's the one that wasn't connected then the output of the alternator wasn't connected to the battery - you wouldn't expect it to charge in that circumstance.

The smaller terminal is connected to the bulb in the dash. You seem to still have a problem there - I'd advise that when you take the dash off to change a bulb that you go in prepared by buying 4 boxes of 10 bulbs (you should be able to remove the bulbs from the little black plastic holder so you should be able to do the whole job just buying the glass part of the bulb - in 10s they shouldn't be that expensive) and just change the lot in one go.

I'd suggest you check with a meter between the small alternator connection and the wire you think it should go to in the dash and try to apply logic from there.

The alternator earth connection is the metalwork of the alternator itself and the connection is made by the fact that it's bolted firmly to the engine.

[Mothman]

Charge the batt as a precaution.

If it remains charged then your worries are over. I go over all my fleet with the charger on a regular basis for a few days each, then, i do have enough bloody motors.

Andy

[Defender110]

If the main output wire was off perhaps the little feed wire to the lamp has come adrift too?

[Way2go]

Charge the batt as a precaution.
If it remains charged then your worries are over. I go over all my fleet with the charger on a regular basis for a few days each, then, i do have enough bloody motors.

IMHO its not a good idea to perform regular "mains" "top up" charging of car batteries as it can considerably shorten their life. This is because there is little or no smoothing on the rectified output and as a consequence causes a certain shaking of the plates at 50Hz. This in turn causes some of the deterioration on the surface of the plate to be shaken off to the bottom of the battery which builds up and ultimately causes the cell to be resistive or short circuit.

The alternator is kinder to the battery as its frequency is considerably higher by virtue of engine rpm and higher is smoother on the plates. If the battery voltage is low but has sufficient to start the engine then that is enough for a good battery as it should quickly gain charge on the high output of the alternator when taken for anything but a very short run. (Of course if it is known that the battery has insufficient "beef" to turn the engine over then a charger is necessary prior to these occasions or perhaps it is time to start thinking about a new battery?)

[vulgalour]

I can happily report that I'm experiencing no electricity related problems now. I was that confident with how everything is performing that I put the dashboard back together again. There's that much to do on the car, I can't do everything every day so I didn't get around to checking the other connections on the alternator, but I will just to make sure. I'm even finding cold starts aren't always a problem and I don't always have to prime the pump manually, regular use even if it's just turning the car on and using the uppy-downy lever, seems to be something the car responds well to.

I continue to be surprised I paid so little for this Gallic galleon of a car, it really is rather superb underneath it all.

[mat_fenwick]

IMHO its not a good idea to perform regular "mains" "top up" charging of car batteries as it can considerably shorten their life. This is because there is little or no smoothing on the rectified output

I agree and disagree
Most simple battery chargers will overcharge a car battery if left connected once the battery has charged, as they have no control over the charging current. I agree that the output (on mine at least) has poor rectification but I hadn't thought of that as being an issue.
If it's a better (not necessarily more expensive) charger it will have a constant current stage, followed by a constant voltage stage and are designed so you can leave them connected permanently. It will be powered by a switched mode power supply, so the output ripple will depend on the switching frequency which will be faster than mains frequency, and hopefully better rectified.

[electrokid]

I agree and disagree

Me too

Most simple battery chargers use full wave rectification - IE:- they have a bridge rectifier or 4 diodes connected as a bridge cct - so the charge ripple is at 100Hz not 50Hz.

And the minimum ripple frequency of the car charging system ?

1000 rpm tickover is (divide by 60) 16.6 revs per second, the crank pulley is around 100mm and the alternator pulley around 35mm so about 3:1 ratio so the alternator runs at about 3 times the crank speed - 50 revs per second. The alternator is a 3 phase full wave rectified device so the ripple frequency is 6 times that - 300Hz - (each coil produces 2 pulses per revolution) so the same order of magnitude as a basic mains charger except the charge on the car will be at a much higher current and for a much shorter time.

I have no idea which is better for the battery

I've not come across them new fangled switched mode chargers - I'm still using the one I bought in the 1970s - I've only blown up the diodes and had to replace them once.

[Way2go]

300Hz ripple is considerably better and given that you will be driving at a minimum of 2000rpm that becomes 600Hz and when cruising at 3000rpm you are now at 900Hz! (A kHz is easily achievable on the motorway on a standard petrol of all flavours)

If you were ever involved with communication equipment, aircraft electronics was I seem to remember 400Hz. If you powered this externally from a mains arranged supply at 50Hz (OK 100Hz ripple), the hum was objectionable without considerable extra efforts on smoothing. The lower the frequency, the greater the shake! I recall reading about low frequency "resonators" that operated about 7Hz being developed that were supposedly capable of causing a building collapse. Tesla was supposed to have made a breakthrough on an early one of these that was almost pocket sized.

I've no experience of switch mode chargers for automotive use so cannot comment on how smooth they would be but the possibility is there to design them so, however there will likely be a cost premium for a quality unit. On reliability I still would prefer a linear psu. My first charger (long gone) was certainly 50Hz ripple output as it utilized a finned selenium rectifier, the size of which meant there was only room for one in a home sized box.

[mat_fenwick]

[quote="Way2go"there will likely be a cost premium for a quality unit.[/quote]
I should have pointed out that to get a similar sort of current to even a cheap basic charger, you will need to spend more. But if keeping batteries topped up is all you need to do then you don't need a massive current capacity - I use a charger with a 1.8 amp output which cost around £20. This charges at 1.8 amps to start with, then 14.75 V, followed by a float charge at 13.75 V. I've yet to put an oscilloscope on it but as I understand it, typical SMPS switching frequencies are well into the kHz range. Dunno whether this is better or worse...

I do have a cheap 10 amp constant voltage charger for putting charge in more quickly, but I wouldn't leave it connected longer than a day.