gathermewool
Site Donor 2023
Whats the typical hysteresis? I mean, if it wants to maintain a set SoC, which is pretty tough to do in reality, then it’s going to need to use a higher voltage at times to achieve that.
Any reason to not switch to AGM?
- Thread starter cutlassvillager
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Whats the typical hysteresis? I mean, if it wants to maintain a set SoC, which is pretty tough to do in reality, then it’s going to need to use a higher voltage at times to achieve that.
I got 11 years out of my Red Top in a 2001 Subaru even after a new alternator, lots of jump-starts, and leaving the parking lights on that totally drained the battery. I hope the one I have now lasts as long.
Thanks for all the great feedback everyone. Up until the other day, I haven't had any significant problems that would warrant upgrading to the larger battery. The only thing I've noticed occasionally were my headlights dimming very slightly if I am opening / closing all four windows at once.
Also, Blinker - you are correct. I am not the original owner. I purchased it in July of 2019 with ~13k miles, so it's totally feasible the battery has already been replaced with another Honda one. I haven't found a date code on the battery.
I'll give the local dealer a call to see what their price is and either go with them or a good quality flooded option. If some vehicles have the ability to change charging profiles for AGM, I believe I won't get the full benefits of the different battery technology.
Also, Blinker - you are correct. I am not the original owner. I purchased it in July of 2019 with ~13k miles, so it's totally feasible the battery has already been replaced with another Honda one. I haven't found a date code on the battery.
I'll give the local dealer a call to see what their price is and either go with them or a good quality flooded option. If some vehicles have the ability to change charging profiles for AGM, I believe I won't get the full benefits of the different battery technology.
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yes, exactly -
here’s the thread on it. Note the link to one of the ford engineers with insight into their BMS.
Fiddling with ford’s battery management
I’ve been noticing a change in the starting note in my f150 lately and started paying more attention to the battery voltages. I’ve got a small digital voltmeter mounted. In other posts I’ve noted the stock behavior: - 12.4v cruise - 14.4v deceleration - 13.5v when lights are on or AC is on the 2...
bobistheoilguy.com
gathermewool
Site Donor 2023
Thank you for sharing. I‘ll read that tomorrow.
I wish these jerks would stop messing with this kind of crap. I mean, when I use an external power supply to charge my batteries the current goes to almost nothing when the battery is full. I get that the saturation charge wastes more energy than the bulk charge, but how much are we really talking about here? How much fuel is really saved when compared to a battery that might have its life cut short by X number of days or months?
I‘m not asking for 14.4VDC 24/7, but how much fuel is saved lowering from 13.9VDC to 12.4VDC?
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the fuel is saved when they up the voltage to max again during braking
And my motorhome LifePo4 house batts have a much different charging profile than all the other chemisties.
gathermewool
Site Donor 2023
How much gas is really saved? Honest question.
I guess it also depends on your use case. When I drove the Civic the battery never seemed to be fully charged. It would jump to 14V+ while engine-braking, but wasn't charging at all some of the time, with idle voltages as low as the low 12s. As Meep said, it seemed to default to a low SoC on purpose.
I can see bumping up to a relatively high voltage while engine-braking to compensate for a lower steady-state voltage, but not charging at all or slightly discharging the battery on purpose seems like a gimmick to save a fraction of an MPG, not a sound engineering decision.
gathermewool
Site Donor 2023
What kind of battery is Table 7 for? It doesn’t match Table 3-4 for.
In Table 3-4 it’s interesting that the absorption and float voltages are so low, but the equalizing seems about normal.
Does that mean one will cause chaos as a starting battery in my 2007 Ford?
I like the weight savings but read mixed advice.
I am in a tropical climate and will be trunk mounted.
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A decade or likely more ago some off roading enthusiasts I know moved to AGM's, primarily because they handle vibration better. They had issues with keeping them charged as mentioned, so many went to aftermarket alternators with specifically higher charge voltages to compensate. Mean Green was one of them.
Those same people have indicated to me that the off the shelf AGM's now can tollerate a lower charge voltage and continue to work. They still say best to plug them into the proper maintainer occasionally otherwise they will never top up.
I haven't switched yet either. I do plug my batteries into a float charger on occasion anyway, but I wouldn't want to be needing to.
Those same people have indicated to me that the off the shelf AGM's now can tollerate a lower charge voltage and continue to work. They still say best to plug them into the proper maintainer occasionally otherwise they will never top up.
I haven't switched yet either. I do plug my batteries into a float charger on occasion anyway, but I wouldn't want to be needing to.
here's mine.
The batteries dont erode. They get covered w/the leachate in the chem process. No longer able to interface w/the 'battery acid'. My 'recon' process sorta 'blasts that off' exposing for re-new-ed life. I have no similar process for agm. Will continue to search (& hopefully learn).
gathermewool
Site Donor 2023
What‘s your process? There’s no way to blast off sulphate without also losing some lead, as far as I know.
thought I left that early in the thread, my stick welder...
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Thanks for the explanation on charging voltages for AGMs. This explains why there's a lot of love and hate in the Jeep world - AGMs provide great performance for heavy demands like winching or overland camping draw, but owners end up having to top off routinely via charger. That's too much maintenance for me and I went for a flooded battery when my JKU needed a replacement.
gathermewool
Site Donor 2023
Nope. Just went through the thread and you don’t mention anything about a stick welder. Your posts are a little hard to understand.
It'll matter enough to show up during cafe testing, or nedc/wltp in europe
There is a marginal improvement in fuel usage. It's not so much how much fuel is saved but how low can they get the headline emissions figures. They'll do anything to get the emission figures down even if it detrimental to some other aspect like battery life.
I find the net result is that when doing short runs around town the battery is never much more than 80% charged at the end of a trip. After longer runs of several hours driving the battery gets much closer to full charge regardless of the low charging voltage. I'm making that assessment of state of charge based on how long the battery takes to come up when I put a battery charger on it after reaching home. We don't have much choice, Smart alternators are here to stay and have already been around for a long time. My 13 year car has one.
I found this description of a smart alternator algorithm which suggest it's far more complex than simply charging on the overun.
The control module enters Charge Mode whenever one of the following conditions is met:
Under WOT conditions and when the fuel rate (sent by the ECM/PCM) is greater than 21 g/S and the throttle position is greater than 90%.
The headlamps are on, low or high beam.
The wipers are on for more than 8 seconds.
The electric cooling fans are on high speed.
The rear defogger is on.
The battery SOC is less than 80%.
When one of these conditions is met, the control module ramps up the voltage slowly to a level between 13.4 to 15.5V (depending upon the mode of operation the system is presently in) at a rate of 8mV to 50mV per second.
The control module enters Fuel Economy Mode when the following conditions are met:
The calculated ambient air temperature is above 32°F.
The calculated battery current is less than 15A and greater than –8A.
The battery SOC is greater than 80%.
The generator field duty cycle is less than 99%.
This mode’s targeted generator output voltage is 13.0V. The control module will exit this mode once the criteria are met for Charge Mode.
The control module will enter Voltage Reduction Mode when the following conditions are met:
The calculated ambient air temperature is above 32°F.
The calculated battery current is less than 2A and greater than –7A.
The generator field duty cycle is less than 99%.
This mode’s targeted generator output voltage is 12.9V. The control module will exit this mode once the criteria are met for Charge Mode.
After the engine has started, the control module sets a targeted generator output voltage of 14.5V for 30 seconds (Start Up Mode).
The control module enters Battery Sulfation Mode when the battery voltage is less than 13.2V for 45 minutes. Once in this mode, the generator battery control module will set a targeted output voltage between 13.9 and 15.5V for five minutes. The control module will then determine which mode to enter depending on voltage requirements.
In RVC Mode, the control module bases the charging voltage on battery SOC, which is estimated during a key-off event every eight hours, after three voltage measurements every 24 hours thereafter, and then monitored constantly while the ignition is on. These voltage measurements are then compared to estimated battery temperature, as battery temperature vs. battery voltage directly corresponds to battery SOC. While the engine is running, the system uses both the battery voltage and estimated battery temperature to determine the battery current in and out of the battery. The control module then regulates the charging voltage to keep the battery above an 80% SOC.
The control module enters Charge Mode whenever one of the following conditions is met:
Under WOT conditions and when the fuel rate (sent by the ECM/PCM) is greater than 21 g/S and the throttle position is greater than 90%.
The headlamps are on, low or high beam.
The wipers are on for more than 8 seconds.
The electric cooling fans are on high speed.
The rear defogger is on.
The battery SOC is less than 80%.
When one of these conditions is met, the control module ramps up the voltage slowly to a level between 13.4 to 15.5V (depending upon the mode of operation the system is presently in) at a rate of 8mV to 50mV per second.
The control module enters Fuel Economy Mode when the following conditions are met:
The calculated ambient air temperature is above 32°F.
The calculated battery current is less than 15A and greater than –8A.
The battery SOC is greater than 80%.
The generator field duty cycle is less than 99%.
This mode’s targeted generator output voltage is 13.0V. The control module will exit this mode once the criteria are met for Charge Mode.
The control module will enter Voltage Reduction Mode when the following conditions are met:
The calculated ambient air temperature is above 32°F.
The calculated battery current is less than 2A and greater than –7A.
The generator field duty cycle is less than 99%.
This mode’s targeted generator output voltage is 12.9V. The control module will exit this mode once the criteria are met for Charge Mode.
After the engine has started, the control module sets a targeted generator output voltage of 14.5V for 30 seconds (Start Up Mode).
The control module enters Battery Sulfation Mode when the battery voltage is less than 13.2V for 45 minutes. Once in this mode, the generator battery control module will set a targeted output voltage between 13.9 and 15.5V for five minutes. The control module will then determine which mode to enter depending on voltage requirements.
In RVC Mode, the control module bases the charging voltage on battery SOC, which is estimated during a key-off event every eight hours, after three voltage measurements every 24 hours thereafter, and then monitored constantly while the ignition is on. These voltage measurements are then compared to estimated battery temperature, as battery temperature vs. battery voltage directly corresponds to battery SOC. While the engine is running, the system uses both the battery voltage and estimated battery temperature to determine the battery current in and out of the battery. The control module then regulates the charging voltage to keep the battery above an 80% SOC.
Lifepo4 batteries (that I know of) aren't designed to be starting batteries. They have a built-in BMS (battery management system) that limits output and input amperage. They also have special/different charging needs. They would need a special alternator/voltage regulator designed for charging Lifepo4 chemistry.
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