What have I missed?? what is wrong?

[paul connor]

Landrover FFR 24V 1981

 

I have the system for charging working as I think it should be. But I keep getting some odd things happen?

 

Batteries in the front seem to be at a constant 12.6V each. never seems to change?

Rear batteries seem to be 13.2V

 

Yet It only starts off the front as If you isolate the rear It still starts>?

 

Also, now I have wired in the 12v rear spot/work light. When you switch it on my alternator light comes on!! switch off it goes out after a 5 second break..

 

And the rear battery with the main +ve coming in goes up to 16.4V when the light is on? is that safe?

 

Why do the rears always have more voltage? Do I have the +ve's form the ammeter the wrong way round? IE rear should be at the front and vice versa?

 

Its a bit confusing!

 

The the 12V spot light is only off the + off one battery to get 12V. the other battery then goes to 16v? its a bit confusing really.

 

This is all with the engine running, not running no alternator light comes on..

[fv1609]

The alternator light comes on because when you turn the ignition on (but engine not running) it receives 24v + from the feed to the ignition coil. The other end of the bulb gets an earth return through the generator.

 

When the generator is running this earth return for the bulb changes & it is receiving 24v + from the gen output. There is then no difference in voltage to the input of the ignition coil therefore it goes out.

 

The front batteries are for the vehicle, the rear for the radio. The vehicle will run without radio batteries but you must isolate the lead terminals from each other & from accidental earthing.

 

It looks like you have the ammeter in the shunt box, which means it was intended for the transistorised regulator in the Gen Panel No.9 Mk 4. If you are using a Mk 3 or earlier it will work but the charging light will not.

 

The ammeter only measures current to the radio batteries. As they have higher voltage then it looks as if they are charging, but the vehicle ones are not.

 

The most obvious explanation is that one of the contacts on the large BCK relay in the Gen Panel has melted. As when it the engine is running both batteries should have identical voltages.

 

When there is sufficient output from the gen, there is a dedicated 24v + output that only operates the winding to the relay. When activated this relay closes & joins both pairs of batteries in parallel & connects them to the main gen output.

 

When the voltage from the gen dies down or the engine is turned off the batteries are isolated from each other, otherwise the more charged set would discharge into the weaker set. Furthermore there would be a discharge through the windings in the gen which would flatten the batteries.

 

If all else fails bring it round here. (The diagram was a help I had been rather confused by trying to picture it all in words)

[paul connor]

Many thanks Cliv. I'm off to Espania this weekend coming but as soon as I get a free day Ill let you know and prob pop down.

[fv1609]

When you come back I'll need voltage readings (its easier in 24v terms) when the ignition is off, ticking over & revving. Also I need to know what Mk of Gen Panel you are using.

 

Not a fan of the 12v tap across the 24v supply. That way one battery will drain more than the other & will never attain full charge. Once the "upper" battery has attained full charge it cannot pass more current as the batteries are in series, so leaving the "lower" battery under charged. This will bring about premature failure. You can try to offset this by putting a mains charger set on 12v & top them up with charge on a regular basis, but a bit tedious. Better to have a 24v bulb.

[paul connor]

Ok. I shall get the readings when I get a chance this week for you..

/

Be nice to see you, how does Sunday 15th sound?

[fv1609]

Be nice to see you, how does Sunday 15th sound?

 

Probably, but Sundays I sometimes do carboots. Any other times?

[paul connor]

I have sunday-monday-tuesday off that week, but week days the only days I can get to yard to the Pig. Will you know if your at a carboot in advance?