Bigger alternator.

[mat_fenwick]

180 amps! Surely that would be enough for even you?

After a bit more thought I see what you mean, but what you are seeing is tha battery drawing the current it requires rather than the alternator driving[i/] excess current through the battery. If the required current is more than the smaller alternator can provide at those revs, there will be a difference in current flowing.

So yes, a bigger alternator will allow more current to flow but will it damage the battery? I don't think so - my understanding is that the charge rate doesn't matter until the voltage reaches around 2.4V per cell (14.4V for the battery). But I'm always willing to be proved wrong if someone has first hand experience!

[electrokid]

I know it's most unlike me to go for the simple option

Tell me about it

but I've built something using 2 lengths of copper pipe (15 & 22mm), one inside the other. They are joined by reducing T pieces, so you have a water jacket around the 15mm pipe that you connect to the washer circuit, and the 15mm pipe to the coolant system.

A long time ago in a land just down the road, I had a thing called a 'hotwash' - a brass tube the size of heater hose with a plastic water jacket around it - only about 5" long but it worked ok - keep the distance between the hotwash and the washer jets to a minimum and you have hot water to wash the screen - just a bit more effective than cold.

It's fine until you have any overheating problems. The coolant doesn't boil until say 110° because it's at + 10 psi - by which time the water in the jacket is well bubbly It does let you know that the engine is overheating - by squirting steam out of the washer jets

One morning I was whizzing about doing stuff when I realised the engine was about to cook - so I found a side road and parked. Unknown to me beforehand this was a particularly busy kids-walking-to-school road - they hadn't seen steam coming out of washer jets before either

My idea (but unlikely to fly because it's a several clicks away from simple) is to have a separate part of the coolant circuit which is thermostatically (my that's a long word - why is'abbreviation' such a long word too ? ) controlled to say 50° and put a jacket around that - warm enough to do the job but not too hot to crack a screen on an icy day ? and no danger of kids pointing at the mad person in the steaming car - that was embarrassing - and I couldn't drive away from it !

[electrokid]

180 amps! Surely that would be enough for even you?

Finding that had quite a strange effect on me - a weird mix of excitement and sphincter tightening I'm used to 2KW starter motors - both for the 1.9 diesel and the 2.8 granny - but a 2KW alternator - phew !

Fitting that one is well into the realms of belt overload - belt falling off / walking home etc.

The regulator in the alternator stops the output going over 14v or so - when the battery volts are lower than that it stuffs as much as it can into the battery.

When fiddling about with dynamos and Lucarse electromechanical regulators back in the days when ... they has a 'slope' of 10 amps per volt - at 14v no output - at 13v (ie: 1 volt less than 14) 10 amps charge- at 12v 20 amps charge. We found we could improve on that using some electronics to do the regulation and we were getting 100 amps per volt slope. Ie: 13.9v - 10 amp charge, 13.8v 20 amp charge - but that's still eventually up to the limit of the dynamo's output.

Modern alternator regulators have a similar around 100 amp per 'volts below 14' spec but it still depends on alternator speed - an 80 amp alternator will usually only chuck out 80 amps at its max speed - and that is usually designed to happen at the rev limit of the engine so pulley diameters are designed to give max alternator speed at max engine revs.

Fitting a big fella will load the belt - possibly too much for the existing design - and there's no chance I can see of fitting a double pully / wider pulley so I might have to put a resistor between the alternator and battery (very low resistance, very high power) and run the heavy load from the alternator direct.

[electrokid]

Hey Mulley - couple of useful articels about alternators at
http://homepage.ntlworld.com/william.wh ... repair.htm
and
http://www.mk1.connectfree.co.uk/nzunde ... nators.htm
And the update to my quest to rule the world is that I've found a place about 30 miles away that does alternator mods / rewinds for high power audio systems so I hope to chat with them this week.

[MULLEY]

Cheers for those, i'll be doing a bit of reading & may have a go at taking one apart. Any idea on where cheap rectifiers can be purchased from?

[electrokid]

Don't know where to find the diodes but they are very beefy devices as you'd expect. Once you've found the type number you might find equivalents at
http://www.datasheet.org.uk/
but they've recently 'updated' their site so it's now harder to find the info you want

I'd try eBay to start with ?

If you can get at the diodes and separate them from the circuit - and have a meter with a 'diode test' function - this measures the voltage drop across the diode in one direction which is normally about 0.5 to 0.7 volts reading and it should be 'open circuit' in the other direction - or you could use a battery and a bulb and try both directions - the bulb should light in one direction only.

You can only test the diodes individually - not connected to anything else or that will confuse the readings / bulb test.