Dynamo to Alternator

[rogerharrop]

Hello All,

I'm a new member and the proud new owner of an SP250. I'd like to replace the dynamo with an alternator and am thinking of the Dynalite replica. I am negative earth. I understand the regulator will no longer be needed and the battery to alternator wiring needs to be 40A rated - but is it really that straightforward? Any other wrinkles please?

Many thanks

Roger

[John-B]

This topic viewtopic.php?f=34&t=2524 mentions a Dynalite.

Also search for "alternator" which raises a lot of topics.

[Sydsmith]

Welcome Roger and congratulations on buying a proper car.

Your question will earn a hefty response no doubt, but for what it is worth, I have had my SP250 for almost 10 years, it is used irregularly and has done less than 10,000 miles in my keeping.

The Bosch battery was on the car when I got it and has done sterling service. I have a good quality trickle charger which I clip onto the battery every 3-4 months for 24 hours to top it up, if the car has not been used in that time.

The car is standard with the original dynamo. I have used the car at night, for long and short runs, winter and summer in the wet and in the dry in the dark and in day light. The car is fitted with rack and pinion steering so the engine has no cooling fan, but there is a Kenlow fan fitted which gobbles up current.

The reason for the long story is to point out that the dynamo has been ample for the car. Unlike moderns which need hefty current to meet the demand for electronics, there is little demand for current when the car is mobile in day light. The dynamo and it's regulator will cope with demands at night even with head lights, heater fan, the wipers and the engine fan on.

You do need a decent battery and I guess if it is going to be an every day user, there may well be a justification for such a mod, but in my view save your money do not do the conversion.

[grahamemmett]

Damian Mills has just done this on his 57 Conquest Century and it works well. It was a straightforward swap using his existing pulley. His dynamo had failed so it was necessary to do something but as Syd says if it ain’t broke don’t fix it! In my experience starting one job like this uncovers something and so on....

[Phillmore]

Just wondering why it's negative earth if it's still running a dynamo?

[Ian Slade]

There are many reasons why -ve earth with a dynamo, early electronic ignitions didn't have a +ve earth option, newer radios and tape decks let alone CD players were -ve earth only, the battery terminals stay cleaner with less corrosion than +ve earth, I swapped mine in the early 70s