Can anyone explain alternators please

suew · Apr 5, 2017

I'm thinking of changing the alternator on my Defender 200tdi, the current one can be a spare as I don't currently carry an extra one. I have spares of most of the other things which are likely to die on me LOL.

I've looked online and the come in 45A, 65A and 100A, well those are the ones I have seen.

Which of those will my current one be? I might like to upgrade it as I have bought it a split charger and 2nd battery for the winch and other stuff.

I don't want to have to mess around and change things though, it needs to be a straight swap, just more powerful if possible.

Thanks

Kwakerman · Apr 5, 2017

Generally the bigger the better if you are using the winch a lot, however I don't know if the existing 200tdi main alternator cable would be rated at the full current (100A) if it were to be working flat out. Also need to be sure you can physically get a larger alternator in the same space

blue beasty · Apr 5, 2017

As an idiot's guide (which is about all i can manage) the upside of a higher amp alternator is it will keep up better with a large drain on the batteries like using a winch.

The downside is they are physically harder to spin so take a tad off your available injun oomph and increase fuel consumption slightly.

jamesmartin · Apr 5, 2017

suew said:
I'm thinking of changing the alternator on my Defender 200tdi, the current one can be a spare as I don't currently carry an extra one. I have spares of most of the other things which are likely to die on me LOL.

I've looked online and the come in 45A, 65A and 100A, well those are the ones I have seen.

Which of those will my current one be? I might like to upgrade it as I have bought it a split charger and 2nd battery for the winch and other stuff.

I don't want to have to mess around and change things though, it needs to be a straight swap, just more powerful if possible.

Thanks

65 amp is what you want ,your drive belt wont like much bigger unlike the 300 tdi which has the poly vee belt which can cope well with heavy load

suew · Apr 5, 2017

Thank you

I'll go for the 65 then, is that bigger than my current one?

IamRobbie · Apr 6, 2017

if its a disco engine it will be 65 amp, if its genuine defender engine usually 45, unless its been changed by a previous owner. I put a disco 300tdi 100amp on my disco engine and it hasn't set fire yet...

suew · Apr 11, 2017

I was discussing this with Neil at the weekend. He asked if my wiring is up to putting the 65A one on, apparently mine is currently 45A Anyone know the answer

Thanks

discomania · Apr 11, 2017

blue beasty said:
The downside is they are physically harder to spin so take a tad off your available injun oomph and increase fuel consumption slightly.

The alternator will only load the engine harder when actually charging hard. A bigger alt will also charge quicker then drop back to a normal output unless there is continued load, which would load the smaller alternator anyway and or start to deplete the battery, so when the load goes, the smaller alternator is then still loading the engine.

A rough way to work it out is 750W to the HP. So if your alt is making 750W it will be using about 1HP. Which @ 12V that is 62.5A or 52.08A @ 14.4V.

Can anyone explain alternators please

suew

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Kwakerman

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blue beasty

Leaks an prone to bits dropping off

jamesmartin

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suew

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IamRobbie

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suew

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discomania

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