Mazda BT50 Alternator issues

Bluespot,
How sure are you of the "70 amps of load" ??

I only ask as it sounds like an unrealistic number by general use, unless you are running a washing machine, caravan air-conditioner and a clothes drier etc

A 3way fridge would be ~16 Amps and that is considered big.

Maîneÿ . . .

Hi Bluespot,

the designers of the alternator/regulator/ECU made it work that way for a reason.

If you force the alternator to produce a high current while it spins at a low revs, then it'll overheat and destroy itself.
See, alternators only have an efficiency of around 50 to 70%. So drawing current of 70 amps, that's already 500 Watts of heat generatred inside the alternator. And if the revs aren't there to shove that amount of heat out of it - the diodes get cooked pretty soon...

cheers, Peter

Many modern alternators while they are of quite high output capacity cannot sustain it indefinately due to heat generated and the ability of the components to withstand the heat and current supply.
As you have found the vehicle is capable of the stated output but only under certain parameters. The need for the engine to be over 1500 rpm is pretty normal, it obviously needs to be moving to provide the airflow to keep the alternator cool hence the engine management is doing the right thing to stop the alternator having a meltdown.
Very few vehicles would be able to maintain the full output of the alternator for any length of time.
What you have found is just the tip of the iceberg with vehicles in general, while they are rated to tow and carry loads, climb gradients, etc etc it is never "continuous duty" which is why vehicle wear out prematurely sometimes when subjected to loads and use that they supposedly can handle.

Why would you need such a high amperage?

Friend of mine has a Ford Ranger / Mazda BT50 as well as his son, and both had the issue with the alternator not charging enough. Lucky he is an electrician and traced it to the tiny and pathetic battery terminal connectors not allowing enough current to pass through.

They changed the terminals over to some decent ones and no more problems.

David

hi
agree with the battery value guy, the ecm or alternator regulator will protect it from self destructing. and yes they do need rpm to work efficently and get enough air through to keep cool.
to check your wiring simply place a voltmeter across the battery terminals note the voltage there, then do the same from the alternator casing to the output stud, these readings should be within .3 volts of each other depending on how much the alternator is putting out. this will eliminate any wiring fault.
other than that your stuck with it.
other options include
you could fit a second alternator,
or a voltage sensitive relay to the second battery so your cranking battery doesnt drop too low.
weigh up the costs carefully against fitting more efficent lighting ie LED's you can get beacons and led lighting (assuming your a pilot vehicle) but stick to hella and narva for beacons etc as there is alot of crap out there
cheers stu