8 replies to this topic

[gav67]

hi got a 78 mini and want to upgrade alternator to newer one . the newer ones have extra posts b+ and w . do i need to rewire or will standard 3 pin plug be ok . cheers

[Ethel]

I could guess B+ is likely the battery terminal, same as the solid brown wires in the loom, which would leave the other terminal for the exciter feed from the charge light. But look for some confirmation, possibly a wiring diagram from something that uses it a original eqpt.

 

 

 

The exciter feed should be marked D. I think W is just a testing point???

[bpirie1000]

What model of alternator are you/have you purchased?

[gav67]

hi looking at 70 amp -GXE2297 will be running 100w bulbs in headlights and spots. cheers.

[Steam]

To be honest 70A is way overkill and will not be of any use unless you upgrade all the wiring to sizes that will allow 70 to pass. All the standard battery/ solenoid/ wiring is good for about 45A and the alternator about 30A.

[gav67]

cheers, would a 50 amp be ok without rewiring. putting a 45a/h battery in from corsa. any info on B+ terminal thats on newer alts or can i just use original 3 pin plug. cheers

[stuart bowes]

As I understand it amps are not 'forced along the wires' I.e a higher amp rating will not melt the existing cables. Amps are pulled by the items which require the power, Lamps and starter and coil etc etc. So whatever they are rated at is what will be pulled from the alternator. I can only assume the original wiring setup was designed to be sufficient for these needs

However if you then add new things (speaker amps are a common example) THEN you might benefit from (or even require) a more powerful alternator, in that case you would wire those new items with suitable cables, and upgrading any old cabling between that source and the alternator may be necessary.  Although this is a comment about cars in general I do wonder how many additional things are really required in a mini..

It doesn't mean you have to upgrade all the wiring in the car, your headlamps for example will still draw the same amps that they did before (calculatable from the wattage) you might find they are a little brighter if your previous alternator was dying or being overworked for some reason  *corrected see below

The battery being a higher ah rating will not mean it actively 'pulls' more juice per minute, it just means it'll have a larger capacity which will take longer to fill

I assume that any overhead (amount of amps rating not being drawn by electrical items) is available to the battery for charging purposes, which could be beneficial if you have a larger ah rating and you often run electricals with the engine off, for example

The downside would be more effort required at the pulley driving the alternator, and therefore a loss of engine power/efficiency but depending on the alternator size it may be negligible to the point of not being a concern

Edited by stuart bowes, 13 September 2022 - 11:08 AM.

[GraemeC]

Straight fit, no need to rewire anything to add the alternator.

However, you may need to upgrade the wiring for the headlamps as they will draw more current than the old ones - I’d also strongly suggest adding relays as the original switch will not cope.

Edited by GraemeC, 12 September 2022 - 08:17 PM.

[stuart bowes]

hi looking at 70 amp -GXE2297 will be running 100w bulbs in headlights and spots. cheers.

 

just spotted this which contradicts my previous comments about not needing to rewire headlamps, I was assuming keeping standard

 

agreed re: relay etc.

Edited by stuart bowes, 13 September 2022 - 11:08 AM.