For your information: At Silverstone in the collection area, with engine on tickover, a Cup car driver noted that despite having an alternator his battery discharged to 9 amps. Once revs were applied under load the alternator returned to charge.

I am trying to understand this.

a) Are you saying that the alternator was driven by the engine? (as opposed to driven from the prop shaft)
b) Are you saying that at tickover the discharge rate was 9 amps?

I ask as what you have observed is normal, an alternator will not start charging until 2000 rpm ish.

I am however surprised by a 9amp discharge as my K sports discharge is 6 Amps.

Incidentally there is a lot of hogwash around about engines loosing power as the battery discharges near the end of a race, if you look at the ECU (Motorola CPU) the CPU uses a "potted down" voltage of 5 volts derived from 12Volts so the battery has to be pretty much exhausted before the performance of the ECU is affected

I wouldn't dare challenge your electronics knowledge Andy.....however, hogwash or not low batteries do affect Cup cars - perhaps it's the high pressure fuel pump which plays up first?
I have never regretted fitting an alternator.

.....I regretted fitting an alternator on the Phantom after the thing had repetitive failures from the get-go, probably heat related, including the occasion at Silverstone when the V regulator failed and the battery fried costing Alex a good result and nearly costing him his external reproductive organs!

They undoubtedly can and do work to good effect. However, they are also something else to go wrong - witness above and the documentary last night on Discovery Turbo about Creation LMS team in 2005 - 10 mins to change it (therefore crap design by Judd!!) and cost a podium...

Success is about dialling out (repeat) errors...

If you are going to fit one, regardless of chassis make, then make sure it has an adequate supply of direct cooling air - there is a part you can get, used in NASCAR, which provides a duct to connect a 1.5" bore cooling hose direct to the alternator. According to an edition of Racecar Eng magazine about 3 years ago.....

Typical legal ruse to introduce lots of irrelevant data.....

My alternator works fine without any special treatment except being wrapped in aluminised cloth.

You have been watching too many American TV programmes.....'get go'???? I think you will find the English is 'start'!!

Aluminised cloth, that'll retain the heat nicely then just like my fuel tank at Pembrey!!. You're 2nd in the ship at present, hope you don't get a 5volts scenario....

Hang on......I'm talking rubbish, got my rotating machines mixed up - the aluminised cloth is on the starter motor!!! The alternator sits in free air, of course.

I swing both ways

The Mallock runs nude with only a battery
The Gem has an alternator

Certainly the GEM is easier to live with but then there is 2.7Kg to lump around?

Pete, I was told the same as you about low batteries, somehow it does not seem to work that way:-

1) We put the Mallock on a rolling road and decreased the voltage gradually, no loss of power so we gave up at 10Volts.

2) I seem to remember that the ECU is programmed to increase the fuel pulse width when it senses low voltage.

I still don't understand the point that is being made with the 1st posting, BTW who is Technical?

Jamie that's a funny place to mount an alternator?

"Technical" is the driver who noted the voltage drop at Silverstone and who asked that it be shared for exactly the reason of this thread.

See you at Rockingham we hope.
H'

That's the plan, 2 cars with Borat (groan I here) already has his plane tickets.

I'm not "Technical" in the sense of starting this thread but the problem described does apply to me. The sequence of events was this...

1. Gridded up in the pitlane I was warming my engine and oil. My mini voltmeter indicated around 11.5 volts which I would expect as the alternator wouldn't be doing anything useful at idle revs so this would be a true indication of battery volts.

2. At some point the voltage instantaneously dropped to 9.5 volts accompanied by a slight drop in engine revs. Only by revving the engine to 2000rpm could the voltage indication be increased when the alternator cut in, as I would expect.

3. As the engine was becoming quite hot and we were still being held I switched off with the ignition switch and turned the master switch off.

4. When we had to start I put the master switch on only to see 9.5 volts on the meter; unsurprisingly the car wouldn't crank until Ian plugged an external battery in. Thereafter the alternator did its thing and in park ferme the battery volts were back to a little over 11 volts.

My feeling is that this is heat related, with no airflow through the stationary car I suspect something broke down in the alternator control electronics causing a significant battery drain back through the alternator. Once I was moving I imagine the problem corrected itself because of the cooling airflow and the battery was able to charge.

Brian

No groaning - delighted to hear the news, ALMS has been absent too long.

"amps" is a fish of a deep pink hue, it should be "volts"

And the size of Corsica is what......?

Hrrmph!

This looks like a useful document

http://http://www.norbain.co.uk/downloads/others/Yuasa_Little_Red_Book_of_Batteries.pdf

Print it out and take to bed with you for some late night reading.

Pete, thanks for the welcome hope you feel the same way after sharing the track with us

Ah Yuasa - those nice people whose batteries caused the Mitsubishi fires and grounded Boeing's Dreamliner.........not lead acid, I know!

BTW, my alternator probably has a smaller dia pulley (and hence turns faster) but I rarely see less than 13,5 V even at idle.

Regarding the weight of the alternator, this can be at least partially offset by running a much smaller battery....the one I use is 4,1kg less than a Red Top 30.

So after all this 'natter' (spelt with a b up front and an x at the rear, BJ thinks it was heat related due to absence of cooling air. Didn't someone write early in the thread about heat ?????

Smug or what

You may be a tad premature......I'm not sure we are quite at root cause yet!

I think you are right Pete in that this no longer seems to be temperature related. I am beginning to suspect that this is a battery and/or alternator control issue. Firstly I have noticed over the weekend that with the master switch on and everything else off the alternator control gets very slightly warm over time. As the only power source is the battery it indicates that there is a slight discharge through this unit although it is too small to trouble my steam driven multimeter. Additionally it seems that my Varley Red top 8 battery copes with this until it drops to around 11 volts when there is a sudden drop to 9.5 volts much in line with what I saw in the pit lane at Silverstone.

....so the V regulator is on the way out then.

I suppose that might be heat related over time; what does anybody else think?

Looks that way. May be heat... could be vibration. It did produce some very interesting symptoms along the way including today a very hot battery as the regulator finally expired. So the battery will no longer be under my seat after reading about Alex's external reproductive organs, you never mentioned his internal ones.

Brian, how old is your battery?

I have now demonstrated this with two batteries, one old and one new. One of them is now bulging having become very sparky and hot in the garage when I was trying to trace the problem. The sparking and hotness extended to the alternator which no longer provides anything useful in the way of electricity.
Your earlier comments about the need for an alternator have been taken on board and rewiring is under way. I am now pretty sure this is similar to the problem Jamie has described elsewhere.

Brian, I too have a bulging redtop, but that was due to overcharging using a generator charger output which clearly was not controlled well enough for gel batteries.

Unfortunately with the bulge, it is a distortion and the Anode and Cathode can touch which heats the battery up and shorts that cell, you then get a step-function drop in voltage. This drop in voltage can stress the charging circuits and if extreme cause them to fault as well.

Once that happens if you replace the battery with a new one you may well still have a faulty charging circuit? That's electronics for you!

I bought a new battery for £95.17 delivery included on eBay from:-


http://www.puredrivebatteries.co.uk/motorcycle-batteries-13-battery-accessories-19-odyssey.html

I've been using a Red Top 15 for the last few years - which has given good service so far and about the same price as the one Andy suggests.

Pete mine was a 20A battery, just wanted to help.

I never doubted your helpfulness Andy

Good luck with the urine test.......

15A batteries aught to be banned for jockeys like you, you should be made to carry at least a 55 ampers, it might slow you down a bit

Get a grip Andy! Lithium battery and a fit, light jockey.well, it seems to work..... alternators = weight. Memo to selves....reduce weight don't add it....

Only the rich (solicitors) can afford Lithium

......not in this case. A dedicated student of his craft who sold something else to buy his batteries ....... probably about the same cost as Kevlar bodywork, I have no idea....

To answer your question, Kevlar is relatively cheap, however the labour time went on and on and......................

......... A bit like this thread then really..........

"Incidentally there is a lot of hogwash around about engines loosing power as the battery discharges near the end of a race, if you look at the ECU (Motorola CPU) the CPU uses a "potted down" voltage of 5 volts derived from 12Volts so the battery has to be pretty much exhausted before the performance of the ECU is affected"

There are a few misapprehensions here:

-Unimportantly, the CPU is not a Motorola CPU. The ECU is produced by (the late) Motorola Automotive and Industrial Electronics Group, but uses an Intel CPU. MEMS 3 uses a Motorola CPU, but this isn't that.

-the voltage for the CPU is derived via a voltage regulator from the battery supply. There are a number of ins and outs, but the final effect is that the ECU needs roughly 6.5 volts for the CPU to have sufficient voltage.

- this isn't the end of the story, however; just because the CPU can work, it doesn't mean that the system really works fully

- as commented elsewhere in the thread, the ECU adjusts the on time of the injectors. As the voltage goes down, the time to get the injectors to switch on increases, but the ECU (mostly) compensates for that

- what is more critical than the injectors is that the time to get sufficient energy into the ignition coil increases. At low rpm, there is still sufficient time to get the correct energy into the coil, but as rpm goes up and voltage goes down you get to the point at which the energy in the coil is marginal for reliable ignition (and the secondary voltage needed is a function of the compression pressure, so you've got rpm, battery voltage, and the amount you've got your foot on the throttle as variable factors and a few other, like coil resistance and quality/topology of the wiring as constant-ish factors, so it wouldn't be a big surprise if the onset came at slightly different points on different vehicles); the bottom line here is at low volts, max rpm at which you get clean ignition _will_ come down

- Rover had a system which cured/delayed the onset of the phenomenon, but, for some reason which has always seemed a bit of a mystery, the Clubmans series didn't take it* (the part that ameliorates this particular effect is 'static distribution' or 'distributorless' operation (different terms for the same thing), and, IIRC, the only standard bulds that had that were the 'MPi' builds. The BMPi builds had the (then) conventional coil 'n distributor set-up, which is more sensitive to this effect, because it can't, obviously, do dwell overlaps).

* Possibly, the Clubmans series took a standard build of ECU for, eg, a Caterham. But that then makes the question 'Why didn't Caterham take the (better) system?' There would have been a slightly greater cost, but compared to the cost of going racing, it would have been negligible. Maybe Caterham didn't see things that way?