Alternarors

[Wil Senior Member Find all posts View Profile Close Wil]

I am after some advice on alternnators.

can the be overloaded?

do they wear prematurely if they are loaded up for a period?

i will shortly be leaving perth for a trip to the cape. Whilst travelling the alternator will be charging/powering
1. the auxillary battery in the prado
2. 100ah battery in the camper
3. 40L engel in the wagon
4. Waeco thermo electric cooler in the wagon
5. Camper 3 way fridge on 12v (power hungry)
6. Charging phones, laptop, camera etc

am i asking too much of the alternator?

will this increase the likelyhood of failure?

cheers,

[120D4D Avid PP Poster! Find all posts View Profile Close 120D4D]

Hopefully LeighW and/or Drivesafe pick up on this, if not, send them a PM.

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Hi Wil and the simple answer is, you can not overload and burnout an alternator. If that's what you are concerned about.

But a little more detail is required.

Alternators can be burnt out but there is almost always a known contributing factor, that has nothing to do with the load being applied to the alternator before it was burnt out.

One of the most common reason for alternator failures in 4x4s, where the alternator is burnt out, is not cleaning a vehicle properly, including the alternator, when you have been off-road, in very muddy conditions.

When going up north, with the many river crossings you will be doing, your alternator is not going to be a problem as it will be kept pretty clean.

As to how much load you can apply to an alternator, with what you have posted above, you can start your day’s drive with very low batteries and your alternator can be power all those devices and be charging your batteries at the same time and no harm will come to your alternator.

All alternators are, by the very nature of the way the operate, are self-protecting.

In all DC circuits, if you have a given current load applied to a specific circuit at a set voltage, if you lower the VOLTAGE, the current load will automatically lower as well.

With an alternator, if you try to apply a current draw that is greater than the alternator’s available output current, the alternator’s VOLTAGE will automatically drop, and it will keep dropping until the applied current draw equals the alternator’s available output current.

I say “available” current out put because this is based on the alternators revs at the time a load is being placed on it.

For example, if you are in traffic and idling, your alternator might be lucky to produce a maximum output of just 40 amps, but it might be a hot night and you could have the air conditioner on, your headlights on and running your sound system at full bast. All of which all probably be way more than a 40 amp load.

The above is a common scenario and you will probably not notice anything unusual, but years ago, when much smaller alternators were used, it was commonplace for the headlights to go yellow and dull, the longer you idled for. The yelling of the headlights was caused by loads greater than the available alternator current output at low revs and the voltage simply dropped.

As soon as you got up to speed, and the alternator was able to produce more current output, the lights would brighten up with the increasing alternator voltage.

So again, you will not overload your alternator.

[Wil Senior Member Find all posts View Profile Close Wil]

Thanks for your detailed response.

truely appreciated.

[Greasemonkey Lurker Find all posts View Profile Close Greasemonkey]

drivesafe

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drivesafe The self protection voltage drop described is in my opinion not so applicable anymore as a large range of loads heave voltage regulated inputs and hence draw more current as voltage drops, this includes also the DC/DC battery chargers added to systems that do not have a reducing current limit based on input voltage sense. In my opinion the outlined loads by Wil are a tall ask for a stock alternator in warmer environment (with air con) and possibly low speed work and also towing, all affecting under bonnet temperatures. I'm very interested in the actual experiences made mid term.