second alternator install

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timtheenchanteruk

timtheenchanteruk

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Reet.
quick Q, or possibly...

After researching, it was suggested that installing a second alternator, and have it spinning would be fine as longs as nothing was connected (ie it wasnt "exited") as unless it had exitement it wouldnt produce voltage, I am aware that normally running an alt with no battery will fubar the voltage reg. but if it isnt exited it isnt producing, so all is ok.

So, I went ahead, and yeast installed my second battery, and associated wiring.

now come to this evening, and my second battery was flat, start the engine, and a good 14.4V volts is produced, and battery charging nicely.

The only thing I havnt put in is a charge lamp, is this nessecary, and the cause of my problem.

Or was my research ballcocks and ive knackered the reg in a perfectly good alternator :mad:

if so, can I just change the regulator, cos the alt was brand new, double :mad:

cheers
 
timtheenchanteruk said:
Reet.
quick Q, or possibly...

After researching, it was suggested that installing a second alternator, and have it spinning would be fine as longs as nothing was connected (ie it wasnt "exited") as unless it had exitement it wouldnt produce voltage, I am aware that normally running an alt with no battery will fubar the voltage reg. but if it isnt exited it isnt producing, so all is ok.

So, I went ahead, and yeast installed my second battery, and associated wiring.

now come to this evening, and my second battery was flat, start the engine, and a good 14.4V volts is produced, and battery charging nicely.

The only thing I havnt put in is a charge lamp, is this nessecary, and the cause of my problem.

Or was my research ballcocks and ive knackered the reg in a perfectly good alternator :mad:

if so, can I just change the regulator, cos the alt was brand new, double :mad:

cheers
Click to expand...

On a standard modern alternator .....

yup it needs the charge light to operate ....
Remove the ign warning lamp bulb and you'll get no charge :D
 
Cheer I'll stick a lamp in circuit tomorrow and see what happens, it's charging fine with the engine running, so it works, but it's discharging the battery when it's off, presumably the lamp provides enough resistance to prevent it, if it has self exited I'm annoyed (with mesenteric) nm, voltage regs shouldn't be that hard to change :)
 
can i be cheeky, do you have any wiring diagrams for the 2nd alt (its on my list to do) also will you be running a winch off 2nd battery?
 
dual_alt_split_circuit.jpg
 
I will be running a winch eventually, currently just my aux stuff, I had the alt, and a spare leisure battery from my caravan, so figured I'd save space in me shed and stick it in me fender.

I'll see if the lamp works, otherwise I figure I've damaged the regulator and it's backfeeding :-( I'll take some measurements to check first tho.
 
so if I were to run, 35mm from 2nd alt to boot, then 70mm from batt to winch that would be fine, when under load ( the winch) would that put any extra strain on the other cable considering its approx. 5 meters from alt?

or would I be better running 70mm from front to back and to winch (don't want anything melting lol
 
It won't melt, as long as it's rated for the alternator, a 100A alt can't give more than 100A, any extra is to reduce voltage drop. 70mm for an alt would be overkill, 25mm would be fine. 35 more than enough
 
timtheenchanteruk said:
Cheer I'll stick a lamp in circuit tomorrow and see what happens, it's charging fine with the engine running, so it works, but it's discharging the battery when it's off, presumably the lamp provides enough resistance to prevent it, if it has self exited I'm annoyed (with mesenteric) nm, voltage regs shouldn't be that hard to change :)
Click to expand...
If it's draining the battery, the diode pack is fecked assuming it's wired in correctly. The charge lamp connects to the D+ to provide the exitation current, however there is sometimes enough residual magnetism for the alternator to start charging without it, it has nothing to do with the battery discharging.
If you connected 12 volts to the D+ without the bulb it will have done damage.
 
Last edited:
I have got 70mm2 cables supplying both my front and rear winches, I have 2 battery's wired in parrelle, with 70mm2 cables 85ah each 1000cca that makes it 170ah and 2000cca I've not got a split charge or second alternator and I have a challenge spec 8274 bigger motor ect and use it hard and have never struggled with power,
 
Datatek said:
If it's draining the battery, the diode pack is fecked assuming it's wired in correctly. The charge lamp connects to the D+ to provide the exitation current, however there is sometimes enough residual magnetism for the alternator to start charging without it, it has nothing to do with the battery discharging.
If you connected 12 volts to the D+ without the bulb it will have done damage.
Click to expand...

ahh ballcocks....

im pretty sure you are correct sir...

Dammit...

hooked up a lil 3W rice lamp last night, and its not illuminating, I appear not to have 12V at the D+ when the engine is off either, which I beleive it should have, and I have a 1/4 amp discharge rate (250mA) looks like I'm shopping for a new diode pack :( grrrr.

Bizzarly once its running, its charging fine, voltage is ok, not measured the amps cos my ammeter only goes to 10.
 
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