alternator power upgrade

Dont get excited, Im not suggesting that I need to have a more powerful alternator on my D1 , but I was browsing and saw that high power alternators of a similar type as fittted to D1 300tdi were available widely for ice cream vans (!!!) at about 200A and twice the price.Now, I know that if I didnt have A/C on a vehicle it would be easy to put a second stock alt on and achieve the same thing,more or less.But if I couldnt do that,and I wanted more power,well....

....has anyone done this ?Put a higher power,ie over 100A alt on,instead of using two?And has anyone rebuilt a stock 100A unit into a 200A one? I know that its straightforward with the lucas 127 to up the output by changing some easily had internals........

And before anyone says "why do you think you need a more powerful alternator?"....well, I dont....yet.But if it was a straightforward option,then maybe I would,and be able to be independent for longer in the field.But Im not arguing that point, I am just interested in the workings out of pure curiosity !

No one ?

yu will need to change all the wiring on the charging and drain circuits to take that much current, and judging by the way peeps go thru alternators off-roading, not sure that is wise.

Just do the Second alterntor mod and run aux bits off the second alternator, at least if you got a 300tdi you always got a spare to repace a knackered one while your in the filed rather then having no water pump...

Yes I have had an alternator seize on me before while of roading......

I now have two knackered alternators which I am going to refurb and then have a second one under the bonett, and a spare for when I get home

Thanks guys.MHM,the wiring upgrade,as you say,is an essential.But how about if I want to run a single alt on my aircon vehicle that isnt going to do serious offroad but want to charge a lot of batteries to keep me independent of mains hookups ? Would a bigger alt with bigger wiring,in reality (sod the theory!) charge more batteries,or bigger batts,faster ?

shocker said:

Thanks guys.MHM,the wiring upgrade,as you say,is an essential.But how about if I want to run a single alt on my aircon vehicle that isnt going to do serious offroad but want to charge a lot of batteries to keep me independent of mains hookups ? Would a bigger alt with bigger wiring,in reality (sod the theory!) charge more batteries,or bigger batts,faster ?

Click to expand...

The Alternator will supply the required current to charge a (many) batteries (up to the output limit of the alternator.
The cabling has to be capable of taking that current (Amps).
Trying to charge many batteries from one alternator is not a good thing, unless the system comprises of an automatic switching circuit, such that it only charges one battery at a time, and the charging is switched by the voltage drop on any particular battery.
Trying to connect many batteries together is a sure-fire way of ruining any good batteries which will be loaded by any weak ones.

So,voltage sensitive switch? And just one, bigger capacity ,auxiliary battery ,split charge?

I worry about the split charge by relay (the standard way) because (as I understand it) you effectively parallel the batteries and the charge of the alternator will be going to both,so the stronger aux batt will suffer as it equalises with the (smaller) cranking battery.

I have been discussing this at some length (I say discussing,more I am being told and looking stupid) on the 12v forum. I am told there that voltage sensitive switches are pointless since the charge light is effectively telling you your cranking battery is up to its full charge and you van use that circuit to switch the relay.But, I still think that a voltage sensitive switch would send ALL the charge to the aux battery once the cranking battery is "full" and switch back when the cranking batterys level fell too much.

Soooo......wouldnt a bigger alternator make all this happen faster ?Like "fill" the cranking batt,then put all its output into the aux batt, and do it all faster. Given extra huge cabling.Would it ?

Also,one of the other issues.....

....since it is straightforward enough to take alternators apart and reassemble, has anyone attempted a power upgrade by replacing parts ? I have seen it done with a lucas127 where the 50 (?)a was made into a 65a. Also a company I spoke to sill supply a 120a version of the marelli alt,as opposed to the 100, for a similar price. I know that this alt is used extensively in lots of vehicles .....there is even a similar 200a unit for the vw passat, so the parts must be out there.

lots of Q's there.
a battery will only take/demand what it needs. charging two batteries is, normally, not a problem.
voltage switches are perfectly OK - it just depends what voltage it is monitoring!

No - it wont fill anything faster than it needs it.

Thanks mate, Im starting to get there !