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post #11 of 114 (permalink) Old 03-26-2015, 06:10 PM
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Re: Alternator voltage?

Stupid question, but where/how is this installed? I'm having the same issue with my AGM battery.
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post #12 of 114 (permalink) Old 03-26-2015, 08:19 PM
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Re: Alternator voltage?

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brianh previously said: View Post
(snip)


There are some ways to increase the voltage of your alternator but it's not a simple adjustment. .
Can you provide some specific information on these various methods of increasing alternator output voltage ?
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post #13 of 114 (permalink) Old 03-26-2015, 08:26 PM
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Re: Alternator voltage?

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Can you provide some specific information on these various methods of increasing alternator output voltage ?

By putting a diode inline on the field wire, you're dropping the voltage to the alternator by .2vdc which will in its turn out out a higher voltage to the batter/buss.
Haven't looked on the fj schematic for it yet, but I assume this fuse looking deal goes I the alternator (field) fuse slot.
You could do the same with two spade connectors, a good inline fuse and a diode. Adding more diodes inline would raise alternator output even more.
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post #14 of 114 (permalink) Old 03-26-2015, 08:26 PM
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Re: Alternator voltage?

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captinmo previously said: View Post
Stupid question, but where/how is this installed? I'm having the same issue with my AGM battery.
G'day,
I believe you swap it out with your ALT fuse in the engine fuse box.
Cheers
Baz
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post #15 of 114 (permalink) Old 03-27-2015, 12:16 AM
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Re: Alternator voltage?

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G'day,
I believe you swap it out with your ALT fuse in the engine fuse box.
Cheers
Baz
thats what I gathered as well. went ahead and ordered it. this is often an issue with agm battery.
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post #16 of 114 (permalink) Old 03-27-2015, 01:35 AM
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Re: Alternator voltage?

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Monkey_Wrench previously said: View Post
Diode in the field wire? That can be done for a few dollars vs. the $50 eBay link.
Yes, like I said, but I feel the fuse swap much easier. I donīt want to try which diode works best and I like to keep the fuse box/wires as factory look.
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Maybe there are cheaper fixes than the HKB Electronics version, but I do not mind supporting a vendor that has taken the time and done the research.
There is a cheaper model for sale too:
Toyota FJ Cruiser Alternator Voltage Booster MK1 | eBay
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captinmo previously said: View Post
Stupid question, but where/how is this installed? I'm having the same issue with my AGM battery.
Just change the 7.5A fuse of the alternator.

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post #17 of 114 (permalink) Old 03-27-2015, 01:41 AM
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Re: Alternator voltage?

G'day
The other way to do is with a battery conditioner ... such as a Redarc BCDC25 I think that is the model.... but at $500-$600 its a lot more.
Still it does a lot more than a fused diode will do too. solar inputs and other such things....
Cheers
Baz
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post #18 of 114 (permalink) Old 03-27-2015, 08:03 AM Thread Starter
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Re: Alternator voltage?

A great revive on an old thread.

I will look into this further.

Thanks Guys!

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post #19 of 114 (permalink) Old 03-27-2015, 09:15 AM
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Re: Alternator voltage?

Quote:
FJtest previously said: View Post
Can you provide some specific information on these various methods of increasing alternator output voltage ?
X2

It looks like they are giving a false reading to something to get the output to raise

Monkey Wrench, the field circuit is external to the alternator and voltage regulator?


Where is VegasNick? How does this work?

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post #20 of 114 (permalink) Old 03-27-2015, 11:06 AM
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Re: Alternator voltage?

Quote:
Bar3K previously said: View Post
X2

It looks like they are giving a false reading to something to get the output to raise

Monkey Wrench, the field circuit is external to the alternator and voltage regulator?

Where is VegasNick? How does this work?
This is a simple and straightforward solution for raising the alternator output voltage by a few tenths of a volt.

Here's how it works:

1. The alternator has an internal voltage regulator, but it has an external voltage "sensing" terminal that allows the regulator to "see" the actual charging voltage at the battery terminal, rather than just sensing the voltage at the alternator's output terminal. This way the regulator can "compensate" for any voltage drop in the wiring between the alternator and the battery.

2. If we intentionally create a small voltage drop (like 0.5 volt) in this battery voltage sensing line, we can "trick" the alternator into providing a small increase in output voltage. The alternator regulator now doesn't see the true battery voltage, it sees battery voltage minus 0.5 volt. The regulator now boosts its output voltage by 0.5V above its "normal" output voltage.

3. Typical silicon rectifier diodes have a forward voltage drop of around 0.5 - 0.6 volt. If we add one of these diodes in series with the alternator's battery voltage sense line, the alternator regulator now thinks it "sees" a battery voltage that's ~0.5 volt less than the actual battery voltage, and it boosts output voltage accordingly.

4. Conveniently, Toyota has fused the alternator sense line with a standard plug-in fuse. If we make a custom little module that looks like a fuse, but actually contains a silicon diode AND a fuse element, we have a quick, plug-in fix for creating the 0.5V voltage drop, and boosting battery voltage by the 0.5V that we desire. If we want to design the module to be idiot-proof, we can incorporate TWO diodes in parallel, but with opposed polarity, so no matter which way we plug the module in, one of the diodes is of the correct polarity to supply current to the alternator's battery voltage sense line.
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Last edited by FJtest; 10-10-2018 at 09:29 AM.
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