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Had my 240A alternator for a while and recently running some Electric AC Voltage threshold setting and test.

And I found the out put voltage is lower that what I expect.

At idle without any loads, it was showing 13.7V (measured at the engine bay by tapping rear fuse box and body ground), and the battery terminal voltage is showing 13.5V.

And when the electric AC is switch on, the voltage will dip to 13.2 at the battery terminal.

When the car is running, the battery voltage is showing 13.4V with all RPM range.

I am running a 60AH Antigravity Lithium Battery. 

Just confirm does WOSP alternator have different voltage regulator for lithium battery or I can add some diodes to increase the voltage?





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3 hours ago, classicretrofit said:

Why do you want to increase the voltage - what problem are you having? Is the battery going flat?


Since as per to my knowledge to battery charging voltage, or all the articles about the alternator voltage.

I installed a battery voltage monitor at the battery posts, it gets to 13.4-5V max when the car is running with AC on.

Seems voltage is lower than what I expected thus I think it is not charging the battery, but battery seems stay in full most of the time after the car is sitting for a while.

I can see other case in rennlist with same battery and 175A alternator regular AC and his voltage kept at around 14.0V.

So I would to understand what could be the issue of this difference?

Is it normal I only have around 13.4-5V not above 14.0V  when the car is started in the system?








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Hi Parker,

I don't think there are any issues with your alternator.   

Battery chemistry is a big subject but in a nutshell, the internal resistance of a battery is a function of temperature and also of the state of charge.    Because your battery is in good shape AND you live in a hot climate, the charging voltage is lower than others is colder climates or with varying battery state of charge.  Another factor is the type of battery cell - not all batteries charge at the same voltage.



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Thanks Jonny,


I got your point.

I noticed a user from rennlist had same battery like mine, 175A WOSP alternator, but without Electric AC.

He mentioned he had the voltage up to 14.0V at idle, and yet it is about 13.4V for me.

I understand the temperature might be a factor.

Do you have any theory or testing figures when developing the alternator voltage versus ambient temperature to battery and alternator?

I thought temperature might affect as little as 0.1-0.2V difference.

Do you have any reference about the temperature versus voltage?

Do you think it could be bad grounding in the car (from alternator ground to chassis)? will that possibly cause my concern?









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TBH, we rely on Denso for the alternator internal tech where engineers probably spend more time than you or I can imagine developing this stuff.

Yes, the grounding could be an issue.  Yes, it could be you Li battery holding the voltage down.  Would I worry about it?  Not really, unless you have a drain problem.

We have 3 cars running the 175A alternator in our fleet and they all have different voltages.  Never had a battery drain in years of AC testing running high loads. 


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