Hazard lights and double alternator

[o_teunico]

Hi all,

I have started to build the wiring loom for my Series IIIA project.

I´m going to add hazard lights and I want also to fit two alternators, feeding one battery each.

I rally don´t know much about electricity, so, here the two big questions:

1)What will happen when, with hazard lights on, indicator switch is moved to left or right position (see diagram).

2)If the two separate battery/alternator circuits are joined in pararell (like when jump starting), will this cause damage to alternators if it´s left that way for a long period of time?

[o_teunico]

Here the wiring diagram

[TSD]

2)If the two separate battery/alternator circuits are joined in pararell (like when jump starting), will this cause damage to alternators if it´s left that way for a long period of time?

I'm fairly sure that in the blue book or the red book, Bosch says you can parallel their alternators, if of similar type and set voltage, without any problem.

Parallel connection of batteries is fine if of the same type and capacity and condition. As you move away from the ideal, you probably trade off some performance and service life, but otherwise ok.

[o_teunico]

Thanks!

The idea is to use one battery + alternstor for heater plugs and starter motor, and the other for the rest.

That way, if you need to leave the car all the night with hazards and/or sidelamps on, it will start with no problems in the next morning.

A switch joining both positive poles will be used to jump start the vehicle if the cranking battery goes flat.

[vulcan bomber]

Yes no issues joining 2 alts at the batt +'s. Best way of powering a winchor such like.

Dont use relay's to excite the 2nd alt, but you must use seperate exciter circuits for each alt. 5 watt bulbs are ideal.

[ToyRoverlander]

Why not use a dual battery setup with a cut out switch and a single alternator? Saves a fair bit of fiddling to fit an extra alternator.

That's basically how I've wired up my split 24V system. I can use either batterybank for either starting or auxillary power while I can totally disconnect the other bank.

[o_teunico]

Well, I have that second alterrnator and the fabricated vacuum pump of my IIIA is perfect for adapting that 2nd alternator.

As said, they will be two independent circuits, joined only when one of the system goes flat.

[Adam001]

I have ran a dual alternator system for the exact functionality you mention.

I run a 130amp alternator that powers my primary circuit (Engine, Engine related, features that work only with the engine and the winch) and a 150amp alternator that powers everything else. Both alternators have seperate exciter circuits run from the seperate batteries. The set-up means it is basically impossible to run the primary battery flat. I then have a master battery switch on all aspects (Primary, Secondary, Winch and Cross Over) the Cross Over links the 2 batteries (and hence the alternators) in parallel for jump starting if something goes wrong (Never has ) or so I can send the full 280amps directly to the winch. Might be worth noting, I designed and built my loom from scratch, ignoring everything Land Rover did!!

For example, I have just changed my engine and currently only running a single alternator temporarily, I now have the cross-over switch on all the time, which gives me a normal set-up but with 2 batteries in parallel. Very flexible set-up with massive redundancy.

My understanding is that alternators do not like being connected together in parallel for long periods, can cause issues with the rectifiers, but i'm not an expert.

[vulcan bomber]

You can run 2 alternators into 1 battery if you really want to but theres little point in it.

[zardos]

You can run 2 alternators into 1 battery if you really want to but theres little point in it.

Actually there is lots of point in running 2 alternators to 1 battery (I do)

Yes multiple alternators won't help charging rates as that is a factor of voltage and normally in the maximum current range of about 8Amps is require to charged a battery (thus 1 alternator can easily charge multiple batteries)

The main reason why the standard fit alternator output in cars has increased over the years (from 45Amp to 120Amp) is that really the main function of an alternator is to supply power to electrical devices when the engine is running and not charge the battery (e.g. electric windows, heated windows, heated seats, etc)

Once the engine is running a battery normally supplies no energy to the vehicle (it actually draws power because the alternator output voltage is higher than the battery output voltage)

Thus 2 alternators and 1 battery is good if you have a device like a winch which draws a lot of power as it will delay the point at where the voltage drops to a point where the battery will actually supply power.

e.g. in theory with 2 x 120Amp alternators you can draw 240Amps without taking any power from the battery(s) which is more current than 1 x 120Amp alternator would be able to supply.

(of course in this scenario multiple or bigger batteries would also help once you reach a load greater than your alternator(s) output)