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Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain. |
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01-03-2023, 04:47 PM | #1 |
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Is alternator output load dependant ???
As I was driving around town, I noticed the voltmeter reading on the dash, is swinging between, 12.4 volts and 14.3 volts. Seems strange as I am used to voltage staying constant all the time around 14.3 in other cars. I get home and let the car idle, check battery voltage with a hand held voltmeter and the readings agree with the in dash meter. So I start turning appliances on and off, lights, brake lights, heater headlights all with the engine idling. The results are when there is no load or minimal load is being applied, the voltage drops to battery voltage of 12.6. When I turn on some load, the voltage increases to 14.3 and stays there until the load is removed, then the voltage again drops down to battery voltage. It appears to me that the alternator output is somehow correlated to the load on the system. It’s as if the alternator knows that the battery is fully charged and does not need to output a higher charging voltage. This may be designed in, to remove some mechanical load for purposes of decreasing fuel consumption. I have no problem whatsoever with the battery going dead. Does this sound normal? Has anyone else noticed this behavior?
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01-03-2023, 05:20 PM | #2 |
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Yes. The ECU will regulate the alternator output. You can even see it go up and down while cruising.
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The Following User Says Thank You to dragoontwo For This Useful Post: | soundman98 (01-03-2023) |
01-03-2023, 05:25 PM | #3 |
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01-03-2023, 08:31 PM | #4 |
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Shouldn't be issue of any sort, with exception of maybe using some 12V>A/C transformator (to eg. power laptop), some models of which due such variances may stop charging. Never had problems with car itself or mobile gadgets charged with 12V cigplug > usb adapters.
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01-03-2023, 08:39 PM | #5 |
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It is smart charging for AGM batteries. It looks at battery amps/temperature to determine if a fast charge is needed. A large system load will not discharge the battery.
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01-04-2023, 08:17 AM | #6 |
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Assuming they still use the updated system from '17.
It would be concerning if it DIDN'T fluctuate.
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01-04-2023, 11:58 AM | #7 |
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Aren't all alternators load dependent? Always have been. In the old days they used a voltage regulator. Now a days I think the ECU controls everything.
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The Following User Says Thank You to WNDSRFR For This Useful Post: | Tcoat (01-04-2023) |
01-04-2023, 01:20 PM | #8 |
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The beauty of the ECU is that the alternator can be sort of fine tuned as to exactly when it does and does not charge. The regulator could say "to much" or "to little" and switch the charging on or off but that was about it.
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01-04-2023, 02:20 PM | #9 |
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I had no idea they changed this. Very cool, learned something today Thank you for posting this
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01-04-2023, 02:40 PM | #10 |
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All the facelift changes are here:
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01-04-2023, 03:38 PM | #11 |
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It's the same. Page 138 of a PDF I can't seem to upload. It's not above the PDF limit.
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01-04-2023, 05:20 PM | #12 | |
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Quote:
Upload the PDF as an image using the "insert image" icon above the text box.
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01-04-2023, 06:41 PM | #14 |
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Odd. I get the same with it. First for me.
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