Subaru Forester Owners Forum banner

61 - 66 of 66 Posts

·
Registered
Joined
·
121 Posts
@Marv2 Idling a vehicle does very little to recharge a battery especially if it's running a fridge at the same time. And who wants vehicles starting and stopping while you are peacefully camping!
DESIGN: Until I owned my 2016 SUbaru, I never knew that modern Electrical Charging Systems could be so messed up that they would not charge-at-idle (this is what killed off the older DC-Generators .. needing to be at high RPM to get out meaningful Charging Current !): FACT ! But you are right ... that is exactly what happens with a SUbaru Alternator, which will not put out full charging Voltage at Idle ! Please notice that I stated Voltage, and not Current ! Until an Alternator puts out enough Voltage to reverse-flow current thru Battery-Cells, Zero-Current flows back into the Battery. By skimping on copper-turns-of-wire inside the Alternator, SUbaru Charging Systems do very poorly until the RPM's are definately above Low-Idle-RPMs !!!! Dollar-Wise/Pound-Foolish "engineering" ... from one end to the other ... but especially in the Electrical Designs !!!!! KWHr Power Generation is totally based on (sufficient) Copper-Coils, and (sufficient) Iron-Cores ... rotating at a proper designed Magnetic-Flux-Speed (Engineers casually refer to it as "dee-fee-dee-tee"): where Low-Idle 550-RPM is the Design Criteria, you never hear of stuff like SUbaru's Dead-Battery-Issues; but they do not use that more reliable and functional Operating/Design-Specification ... theirs is more like 1100-RPM, and that is the whole mess in a nut-shell ! And that is why thousands of frustated SUbaru Owners are constantly trying to Re-Design their vehicles electrical systems ... just like in this pitiful example !!!!!!!!
PS : there are up-sizing ALTernators available in the After-Market that are properly designed ... but they are not "cheap", like SUbaru's units are. The very first thing that I noticed under the hood was the very small size, and the very high (false) "specified" output of the SUbaru Alternator ..... Size does make a difference ... as it aids in the "dee-fee-dee-tee" !!!!!
 

·
Registered
2019 Forester Limited
Joined
·
1,010 Posts
But you are right ... that is exactly what happens with a SUbaru Alternator, which will not put out full charging Voltage at Idle !
This simply isn't so.
I measured voltage at idle of 14.2 V at the battery with a partially discharged battery, blower on full, and both seat heaters on high. 2019 model. More than enough capacity.
 

·
Registered
Joined
·
121 Posts
"Charging" : Then all the people with dead batteries are ...... ; and all the dedesign work related here is a waste of Time !!!
 

·
Registered
2015 Forester
Joined
·
138 Posts
The real question on charging is not if it's putting out sufficient voltage, but what amperage is it outputting? The battery needs to store electrons to have current flow. Voltage can be an indication of lack of current, but not always. Voltage will definitely drop if something is trying to pull more current that is available. Bottom line, just because you measure the correct voltage at the battery does not mean it is charging.
 

·
Registered
2019 Forester Limited
Joined
·
1,010 Posts
@Marv2, I’m not saying it’s all a waste, just that my car's charging system doesn’t behave as you describe. I believe there’s more in play when it comes to the issues some have encountered.

@commonme , I measured the current with a clamp on meter. It’s charging, with currents similar to what I see with my Victron charger for a similar state of charge (3 amps and lower).
 

·
Registered
Joined
·
121 Posts
CORRECT ! You have a better understanding than most on any of these users venting problems .... ! It is Old-Tech vs. New-Tech: Bottom-Line, when an Alt puts out "pure-DC" ( "modern" undersized ALTs !) it will not maintain SOC anywhere as good as Pulsating-DC,coming from Pulsating ALT Regulator Systems !!!!!

Historical DC Gen/Buzz-Box charging was overwhelming with massive amounts of Pulsating DC, and when occasionally started, and operated was capable of keeping batteries of those days in High-SOC conditions. When the Alt first came into use, designers continued to use the Proven-Technology of Higher Open-Circuit-Voltages, with the newer Electronic-Regulators performing the same function as the Buzz-Box-Regulators: chopping the Higher-Open-Circuit-Voltage into Pulses that were "averaged" by the Battery to arrive at a Proper ("SOC") Level of Charge.

Then the Genusises of the Far East, accompanied with the Euro-Crowd of Upper-Crust Intelligentsia discovered that they could "down-size" the ALT Copper-Content and the Iron-Cores .... save $$$$$$ , and just "SPEC" their components to full time "equivalency" to American Tech which was declared "Ancient" and "Wastefull".

Result, we now have an Industry-Wide problem of Pure-DC ALTs, being controlled by Analog Audio-Type Regulators which are basically Type-A Audio-Amplifiers, just connected to an ALT machine, w/o any meaningful "pulsing" to keep the Sulfation Problem under control, and lots of Vehicle Owners are now stuck with chronically undercharged Batteries.

This is why the Battery-Maintainer-Type of Desulfation works so well ... it is providing the "Pulses" to control damaging crystal formation on Lead-Cell-Surfaces inside the Battery........ pulses that used to be a direct result of Pulsed-ALT DC Charging Systems, that have been replaced by "Pure-DC" ALT-Systems ... which is mandated by poorly designed Sub-Systems that have become standard acc's in most newer Vehicles : GOOD LUCK !!!
 
61 - 66 of 66 Posts
Top