[vak]

Dear All,

I am planning to upgrade the alternator in my Bolero Di 4wd. The OE one is a 55amps Bosch unit with vaccum pump. I want to fit atleast 125 amps alternator as I am fitting a winch and other accessories.


But the catch is that, the only 125amp or above alternator with vacuum pump is the Safari alternator. It is a 135amp unit but will cost Rs21,000. But a Bosch 125 amp alternator without vacuum pump is available for Rs10,000. Also a 90amps Bosch unit with Vacuum pump is available for Rs5,500.

I have two choices

1. To replace the OE 55amp unit with a Bosch 90amp vaccum pump unit .

2. To fabricate a new bracket and fit a 125 amps non vacuum unit and connect it parallel to the OE alternator. This will give me a stated output of 125+55 = 180amp. But , Is this kind of fitment electrically stable?

Your suggestions please.

[jeepster]

Originally Posted by vak

1. To replace the OE 55amp unit with a Bosch 90amp vaccum pump unit .

2. To fabricate a new bracket and fit a 125 amps non vacuum unit and connect it parallel to the OE alternator. This will give me a stated output of 125+55 = 180amp. But , Is this kind of fitment electrically stable?

Your suggestions please.

my suggestion will be 125+55A.

but any modifications to electrical system will void your warranty.

please do consider that.

& is there room for another alternator?

rgds,
Nikhil

[Sudarshan]

Originally Posted by vak

1. To replace the OE 55amp unit with a Bosch 90amp vaccum pump unit .

this is the right choice ,will be sufficient for winch operations

2. To fabricate a new bracket and fit a 125 amps non vacuum unit and connect it parallel to the OE alternator. This will give me a stated output of 125+55 = 180amp. But , Is this kind of fitment electrically stable?

Caution : seek expert advise for this --- IMHO & AFAIK two alternators cannot be connected just like that

You can connect two batteries in parallel

Sudarshan

[Aroy]

Originally Posted by Sutripta

Went through them. Thanks. Too elementary, and not really relevant to our discussion.


Is the alternator a voltage source or a current source?

Agreed. But the question is will the current exceed limits on fitting a smaller pulley.
If there is a regulator no, else yes
Alternator Fundamentals - Alternator and Voltage Regulator Operation
if there are four wires then there is a regulator, if two then not (S in the diagram is missing).

Yes. B, F, H. Relevance to our discussion?

Also yes. Also see third comment.

The rectifiers have any role in regulation?
In any case, the question was why alternators do not have current limiters like dynamos. Where it is placed is not relevant.
Rectifiers have only nominal current regulation as they may saturate at high current, but for all practical purpose no.

This alternator has a current regulator
Alternator Fundamentals - Alternator and Voltage Regulator Operation

What current limiting?
Check out the current vs rpm graph in one of your links.

Totally irrelevant to our discussion, I would think.

Remember, our discussion started with this
Regards
Sutripta

Where relevant the replies are in bold.

Back to our initial discussion. I think I got a bit confused while answering the first time. What I had actually wanted to convey is
. If the pulley diameter is smaller then the alternator has capacity to generate higher current at the same RPM.
. If there is a current regulator, it will limit the current to its design value, but this will occur at a lower engine RPM.
. If there is no current regulator the current delivered will rise with engine RPM.
. if the regulator is changed to a higher rating, the alternator will limit the current at a higher value.

In conclusion
- smaller pulley will give higher current at lower engine RPM
- the maximum current delivered by the alternator will be limited by the regulator in the alternator (if there).

[Sutripta]

Originally Posted by Aroy

In conclusion
- smaller pulley will give higher current at lower RPM

OK.

But

the maximum current delivered by the alternator will be limited by the regulator in the alternator (if there).

If you are talking of the voltage regulator, then no, not quite.

If the pulley diameter is smaller then the alternator has capacity to generate higher current at the same RPM.

Engine rpm.
And lets not get into what is it that the alternator produces - voltage or current.

. If there is a current regulator, it will limit the current to its design value, but this will occur at a lower engine RPM.

If there is a current regulator, what does rpm have to do with it?

. If there is no current regulator the current delivered will rise with engine RPM.

Check out the graph in one of your links.

. if the regulator is changed to a higher rating, the alternator will limit the current at a higher value.

If you increase the voltage set point, you are going to fry a lot of things in your electrical system.

Rectifiers have only nominal current regulation as they may saturate at high current, but for all practical purpose no.

Not even nominal, I would think. The V-I relationship of a solid state rectifier is exponential.

This alternator has a current regulator
Alternator Fundamentals - Alternator and Voltage Regulator Operation

Couldn't find the current regulation part in your link!

Regards
Sutripta

[Sutripta]

Originally Posted by Sudarshan

Caution : seek expert advise for this --- IMHO & AFAIK two alternators cannot be connected just like that

Right. Not a good idea.

Regards
Sutripta

[svsantosh]

I converted my 55AH LucasTVS(Alt+Vacuum Pump) to a 90AH Bosch (Alt+Vacuum Pump), costed me 5,000Rs. More details here.

http://www.team-bhp.com/forum/4x4-ve...ml#post3052053

[mohang_j]

I have used a 90A alternator from Indica petrol. Costed 1700. Bought used one from my mechanic. Service and installation was DIY.

[Sudarshan]

Originally Posted by mohang_j

I have used a 90A alternator from Indica petrol. Costed 1700. Bought used one from my mechanic. Service and installation was DIY.

Fantastic .

perhaps ( if at all ) you have missed this thread , will be useful for you WRT fitting a RPM meter ffor your Jeep .

http://www.team-bhp.com/forum/4x4-te...el-engine.html


pls check post #4 , I have fitted a dicor alternator which has facilitated RPM meter function .

Sudarshan

[headers]

A higher capacity alternator can be fitted to a Jeep / Gypsy but one needs to match the pulley size to the Alternator output.

What I mean is the engine pulley to alternator pulley ratio should be such that it helps the alternator generate max voltage at the normal engine operating rpm.

Also, IMO, alternators with vacuum pumps are not great in design and it is better to have a separate vacuum pump if one needs to source vacuum.