exciting my alternator ?

[micky44]

Some info please, I am attempting to wire up my 24 volt alternator Now the problem is as follows. i have managed to keep my 12 volt alterntor to supply charge to the starter battery, the starter motor is 12 volt, so i just turn the key, she starts and the alt is charging the start battery, thats all fine. but the problem i have is the 24 volt alt is not of course connected to the 12 volt circuit, so when the engine starts the 24 volt alt spins, which is connected at the moment to batt- and batt+ . can i just take a feed of the batt+ to the exciter terminal and leave it connected ? If you can follow all this your a far better person than me,also if i CAN just leave it connected would it be doing any harm. confussed ? not as much as me !

[Titan]

Some info please, I am attempting to wire up my 24 volt alternator Now the problem is as follows. i have managed to keep my 12 volt alterntor to supply charge to the starter battery, the starter motor is 12 volt, so i just turn the key, she starts and the alt is charging the start battery, thats all fine. but the problem i have is the 24 volt alt is not of course connected to the 12 volt circuit, so when the engine starts the 24 volt alt spins, which is connected at the moment to batt- and batt+ . can i just take a feed of the batt+ to the exciter terminal and leave it connected ? If you can follow all this your a far better person than me,also if i CAN just leave it connected would it be doing any harm. confussed ? not as much as me !

 

I assume the 24v alt is connected to charge a 24v battery bank ? you ought not supply a 24v direct feed to the alternator, you need to create a circuit ideally with a small 24v bulb in line (battery charging bulb ) or a resistor of sorts. If it were me i would hook up a simple 12v relay from an ignition switch fed live, which could then switch the 24v circuit whith the 24v light in the circuit, once engine has started the alternator will charge and exstinguish (battery charging bulb )as normal . i hope this helps, i am sure others may offer far superior advise but i believe this should be a cheep and effective way to solve, good luck

[ditchcrawler]

Some info please, I am attempting to wire up my 24 volt alternator Now the problem is as follows. i have managed to keep my 12 volt alterntor to supply charge to the starter battery, the starter motor is 12 volt, so i just turn the key, she starts and the alt is charging the start battery, thats all fine. but the problem i have is the 24 volt alt is not of course connected to the 12 volt circuit, so when the engine starts the 24 volt alt spins, which is connected at the moment to batt- and batt+ . can i just take a feed of the batt+ to the exciter terminal and leave it connected ? If you can follow all this your a far better person than me,also if i CAN just leave it connected would it be doing any harm. confussed ? not as much as me !

Have you tried just connecting the +ve and -ve or earth return to the battery via a battery isolator switch and run it up. That is how mine is connected and when I increase the engine speed the alternator starts to generate, its output then continues when I drop the speed down to tickover.

Dosen't work for all alternators but you may be lucky.

[micky44]

Thank you very much both of you for your advice.The problem i have have is that there is no ignition switch on the 24 volt system, the 24 volt alt is just conected directly to the 24 volt batter bank. Odviously there is a barrery isolation switch between the battery bank and the alt. would it be ok then (perhaps a bodge ) to conect the exciter terminal to a 24 volt switch, then all i would have to do is flick the swicth on for a few seconds till the alt is spinning then switch it off ? also if i did go down this root would i need a bulb in the circuit? i have a volt metre so i could see what the state of charge is.

[ditchcrawler]

Thank you very much both of you for your advice.The problem i have have is that there is no ignition switch on the 24 volt system, the 24 volt alt is just conected directly to the 24 volt batter bank. Odviously there is a barrery isolation switch between the battery bank and the alt. would it be ok then (perhaps a bodge ) to conect the exciter terminal to a 24 volt switch, then all i would have to do is flick the swicth on for a few seconds till the alt is spinning then switch it off ? also if i did go down this root would i need a bulb in the circuit? i have a volt metre so i could see what the state of charge is.

As I said, I don't have anything connected to the field connection.

I don't have an ignition switch in circuit, I don't have a lamp. I just have two fat cables from the alternator, one black and one red to the batteries.

It just works, yours may or may not be the same. But its dead easy to try before adding all the other stuff.

If it hadn't have worked I was going to wire a warning lamp via a push button switch to fire it up rather than a 12 volt relay and lamp, but I start my engine in the engine room.

[micky44]

As I said, I don't have anything connected to the field connection.

I don't have an ignition switch in circuit, I don't have a lamp. I just have two fat cables from the alternator, one black and one red to the batteries.

It just works, yours may or may not be the same. But its dead easy to try before adding all the other stuff.

If it hadn't have worked I was going to wire a warning lamp via a push button switch to fire it up rather than a 12 volt relay and lamp, but I start my engine in the engine room.

Thanks once again ! when the new fly wheel comes back, i will try what you have suggested and hope for the best

[blodger]

Yes, you need the bulb to supply the minimal cuurent yhe alt needs for excitation. It will then act as a charge warning light going off when charging OK and coming on if charging fails. The switch will be fine in a live (positive)from the 24v batt to one side of the bulb the other side going to the D+ or IND on the 24v alt. If you wish you can switch it off once the bulb has extinguished having done one of its functions.

[David Mack]

Yes, you need the bulb to supply the minimal cuurent yhe alt needs for excitation. It will then act as a charge warning light going off when charging OK and coming on if charging fails. The switch will be fine in a live (positive)from the 24v batt to one side of the bulb the other side going to the D+ or IND on the 24v alt. If you wish you can switch it off once the bulb has extinguished having done one of its functions.

 

Rather than a separate switch, wire it through an oil pressure warning light sender. That way the excitation circuit switches on and off with the engine, and no risk of forgetting to turn it on/off.

[MtB]

make and model of the 24v alternator? Some are 'self-exciting'.

 

You may be worrying about nothing. How did this all crop up in the first place? Is your 24v battery bank not charging??

 

Mike

[blackrose]

Personally I don't find your alternator all that exciting.

[Gibbo]

The usual way is to take a feed from the ignition switch that is on when the engine is on. That feed is used to energise a relay which connects the new charge warning light to the D+ terminal on the second alternator.

 

It's the way it's always been done. Seen thousands of them. No need for anything else.

[Tony Brooks]

Rather than a separate switch, wire it through an oil pressure warning light sender. That way the excitation circuit switches on and off with the engine, and no risk of forgetting to turn it on/off.

 

Don't they close with the engine off (no oil pressure) and open when there is oil pressure.? He could use a rising oil pressure switch though.

[Gibbo]

Don't they close with the engine off (no oil pressure) and open when there is oil pressure.?

 

Yes.

[Tony Brooks]

Thank you very much both of you for your advice.The problem i have have is that there is no ignition switch on the 24 volt system, the 24 volt alt is just conected directly to the 24 volt batter bank. Odviously there is a barrery isolation switch between the battery bank and the alt. would it be ok then (perhaps a bodge ) to conect the exciter terminal to a 24 volt switch, then all i would have to do is flick the swicth on for a few seconds till the alt is spinning then switch it off ? also if i did go down this root would i need a bulb in the circuit? i have a volt metre so i could see what the state of charge is.

 

 

Having no bulb in the circuit to limit the current on most alternators will result in a permeate drain of about 4 amps (12v) and presumably 2 amps (24v) so although it energises the alternator just fine it has an effect on the batteries state of charge.

 

Use a separate switch as has a been discussed or how about a 12V voltage sensitive relay fed from the 12V side of things for the coil. Use the contacts to switch the 24 volt warning lamp circuit.

[nb Innisfree]

FWIW our 24v large frame Leece Neville is a manual excite one, just requires a live feed to the excite terminal, I use a switched feed so I can start the engine with the alt off load then switch it in when I want - when first started leisure batts put alt into full output and can make slow speed manoeuvring at tickover a bit tricky + it takes some load off starter batt. To remind me to turn off live feed when engine is shut down I also fitted a buzzer from excite switch to D+ otherwise alt will be permanently excited (oh happy memories from when I used to be like that!)

 

Maybe a bit involved but it does give a bit of handy flexibility.