More FFR 24V system issues

[BrookyLR]

We have just taken delivery of a generally great condition 1988 FFR from AFM. Having got the car registered last week etc we are starting to delve into the 24V system to use for fridges etc. The maintenance log says that the LHS batteries were replaced in 2016 and the car has only done 700km since then so unlikely to have had radio use since.

On inspection, we find that
1. The RHS batteries are wired in series as they should be.
2. The 2 RHS batteries are together paralleled against the rear LHS battery only! The RHS total voltage is 12.6V and the left rear battery voltage is 11.7V.
3. None of these 3 batteries above are connected to anything else at all.
4. Only the LHS front battery is wired into the 24V system. This battery is showing 12.8V across the terminals and this is what is coming out of the EDB.
5. We disconnected the 28V alternator from the system at the NATO plug and only got a reading of between 3-6V at any engine revs (perhaps the excitation voltage only) and nothing showing on the ammeter.

Leaving aside any thoughts about the awful wiring, from the above I am thinking that the 28V alternator has bitten the dust and that the 24V system output of 12.8V will slowly reduce as the single connected battery discharges with use of the rear interior lights.

I will disconnect the RHS to LHS parallel connection to try and save the rear LHS battery. I will also give the RHS batteries a charge to see if they can be brought back to life.

What is the best way to check the condition and operation of the 28V alternator? Also appreciate any thoughts on a way forwards, best use of FFR batteries etc.

I am having power steering fitted next week at MR Automotive in Brisbane so can have them check it out if necessary at the same time.

[Marlin]

I would be checking the alternator output at the rear of the alternator itself before you condemn it. Also are the input wires connected to the alternator and giving a voltage reading when the ignition is switched on.

[BrookyLR]

Only 0.2V across the outlet with the ignition on and large plug off.

Where are the excitation connections on the alternator?

[dugite]

We have adapted  a FFR distribution box to provide 24v engel connection and 24v led camping lights. I recall that the alternator would not charge dead batteries - at least one 12v battery had to have a nominal charge to begin

[Elliottt]

 To test the alternator first disconnect all the batteries, turn the engine on, idle up to around 1500 rpm then briefly put a voltage across the terminals that connect the lhs battery bank to the distribution box to excite the alternator  [a 12v source is enough to excite the alternator] you should then read 32v across those terminals when there is no load

if you turn the rear 24v light on before doing this, the light will fluctuate with the revs of the engine

Have You got a pic of the current battery wiring setup, it sounds quite strange

the lhs 2 batteries should be connected in series via a short link cable to the distribution box

the rhs 2 batteries should be connected in series via a short link cable

the rhs bank should be connected in parallel to the lhs

[Elliottt]

if that doesn't excite the alternator it would be worth checking the fuses on the top of the dbox as one will prohibit the alternator from charging/exciting if blown 

[Mick_Marsh]

Is it an alternator or generator?
If a generator, shouldn't it be self excited?

[Elliottt]

I've heard it been called both, but I know that it's definitely not self exciting

[Mick_Marsh]

I've heard it been called both, but I know that it's definitely not self exciting

You know they are constructed and operate differently. If it is not self excited, how does it regulate voltage?

[Elliottt]

the emei manuals refer to it as an alternator and the parts book refers to it a generator

I guessing that it's technically a generator, I'm not sure, I haven't pulled it apart, isn't the main difference whether the coil's spinning around the magnet or vice versa?

a generator doesn't necessarily have to be self exciting,  I know that this isn't as Ive tested it many times, if the batteries are flat or disconnected, it won't produce sufficient voltage [around 3 volts]

I don't know how its regulated, I know there is an adjustment screw and the higher the load connected, the lower the voltage, with no load being 32v and no higher than 28v with a battery connected when it has fully charged it, when its charging the batteries at a rate of around 50 amps it produces around 25-26 volts         

[Mick_Marsh]

A generator will have poles with a residual magnetic field and coils around those poles which strengthen the magnetic field when current flows in them.
A generator will pump out power at low revs. I had a Mini with a dead battery. It was dead for months. I push started it often. Couldn't have done that with an alternator.
So, are there other cables apart from the +v and -ve going to it? If no, it must be self excited.
So, I'm thinking there might be a burnt out wire to the poles. That would explain the low voltage.

I don't have a generator or wiring diagram to look at at the moment, so I am just guessing.

[BrookyLR]

So now I have had the time to play with the battery configuration...

- I have removed the right (possibly stuffed) pair of batteries and am trying to resuscitate them separately.
- I have rewired the left (good) pair in series - together 24.5V.
- I have reseated the large plug at the 28V alternator 

and the whole thing (albeit LHS only) creaked back into life! Healthy voltage on the meter on the EDB and the dashboard ammeter showing up to +50A from time to time. I will keep monitoring charging current and battery voltage to see it it all stays healthy.

I can only conclude that the alternator is self exciting and needs an almost full voltage from the battery bank to do its job.

[303Gunner]

The emei manuals refer to it as an alternator and the parts book refers to it a generator

Isn't the main difference whether the coil's spinning around the magnet or vice versa?

The difference is that a generator produces DC current, while an Alternator produces AC (and needs either an internal or external Rectifier to convert it to DC). A Generator does not need an input voltage to excite the fields (and will therefore work with and charge a flat battery), while an Alternator does need an input current to excite the fields (and will not charge at all if the battery does not provide enough voltage to excite).

A Generator that has not been used for quite some time may have lost the magnetism in the iron field coils (and therfore will have a much reduced or even nil output) and may need to have the polarity "Flashed" to reset the magnet fields.

[fc101]

The FFR 24v system looks as if it is different to the 101 24v system where the alternator is excited by the ignition light.  Note that once it has been run correctly with external excitement, most alternators will retain enough flux in their coils to startup up without external excitement but cannot be relied upon as it can fade over time - the green steam leaks out. 

As the 24v system on the FFR is a secondary system, does it have the equivalent of an ignition light - if so that is where the excitement is coming from.  I am excited 

Garry

[Mick_Marsh]

The FFR 24v system looks as if it is different to the 101 24v system where the alternator is excited by the ignition light.  Note that once it has been run correctly with external excitement, most alternators will retain enough flux in their coils to startup up without external excitement but cannot be relied upon as it can fade over time - the green steam leaks out. 

As the 24v system on the FFR is a secondary system, does it have the equivalent of an ignition light - if so that is where the excitement is coming from.  I am excited 

Garry

The alternator on the 101 is a three phase alternator. A normal automotive alternator is only one phase.
Yep, the 101 is very different.

The Perentie FFRs have two separate systems. The vehicle operates from a 12v system powered by an automotive alternator. The radio system is powered from a 28v generator. No, it doesn't have a generator light.

Mr 303gunner has described the difference very well.