Modern car intelligent charging systems: Chronically undercharging battery?

[nobb]

Did some more testing and pulling the connector from the negative battery terminal seems to keep the system at 14.2 - 14.5V, but on deceleration and braking it will still go to 15V.

So I wonder what's the lesser of two evils:
1. Leave it the way the engineers designed it, with the EFB battery undercharged
2. Bypass the intelligent charging, with periodic bits of overcharging at 15V (loss of water, possible increased corrosion on the plates)

 

[D1dad]

I tried a little experiment this morning. My wife’s battery (agm) was 100% charged as was my flooded battery..same car except hers is a 24 and mines a 21.. Both batteries were new in December and both testing @100% state of health. We both drove to the gym separately, at the same time. We get back from a 10 mile round trip, her batteries testing @89%, my deka flooded is testing @93%. I hooked up each car to pretty much identical Pulsetech chargers and mines done in an hour , hers took 4. Conclusion is that I’m never going to buy another agm. I’ve gathered enough data to know that they’re a waste of money, and won’t charge with today’s smart charging systems. If I had stop start, maybe.

 

[goblin]

...won’t charge with today’s smart charging systems...

This is simply not true. If anything, smart charging systems went with AGM batteries when they first came out.
What cars do you and your wife drive, do they require any battery coding/programming when replacing the battery, what type of battery did they come with stock ?
Do your Pulsetech have an AGM mode, if yes - does it have to be selected manually, was it selected ?

 

[f355spider]

I tried a little experiment this morning. My wife’s battery (agm) was 100% charged as was my flooded battery..same car except hers is a 24 and mines a 21.. Both batteries were new in December and both testing @100% state of health. We both drove to the gym separately, at the same time. We get back from a 10 mile round trip, her batteries testing @89%, my deka flooded is testing @93%. I hooked up each car to pretty much identical Pulsetech chargers and mines done in an hour , hers took 4. Conclusion is that I’m never going to buy another agm. I’ve gathered enough data to know that they’re a waste of money, and won’t charge with today’s smart charging systems. If I had stop start, maybe.

Swap batteries between the cars and report back. How do you know it is the battery that causes that condition and not the individual car's charging algorithm.

Also, you are wrong to consider how long a battery takes to reach 100% charge as either a gauge of the quality of the battery charger (you have mentioned this in previous threads) or the state of discharge of the battery. Battery chargers/tenders have different algorithms, and some will modify the algorithm, based not only on the state of charge, but the battery's internal resistance.

There are too many variables for you to make this snap judgement that all AGM batteries do not work with smart charging systems.
As goblin mentioned, many new cars use AGM exclusively, like BMW, Ferrari, Mercedes and many others.

 

[D1dad]

This is simply not true. If anything, smart charging systems went with AGM batteries when they first came out.
What cars do you and your wife drive, do they require any battery coding/programming when replacing the battery, what type of battery did they come with stock ?
Do your Pulsetech have an AGM mode, if yes - does it have to be selected manually, was it selected ?

Swap batteries between the cars and report back. How do you know it is the battery that causes that condition and not the individual car's charging algorithm.

Also, you are wrong to consider how long a battery takes to reach 100% charge as either a gauge of the quality of the battery charger (you have mentioned this in previous threads) or the state of discharge of the battery. Battery chargers/tenders have different algorithms, and some will modify the algorithm, based not only on the state of charge, but the battery's internal resistance.

There are too many variables for you to make this snap judgement that all AGM batteries do not work with smart charging systems.
As goblin mentioned, many new cars use AGM exclusively, like BMW, Ferrari, Mercedes and many others.

Instead of “todays” I should have said “Nissans” smart systems. There have been threads from posters with different makes, posting similar issues. I just can’t see the extra expense for something that’s not working. My tech told me that agms and efbs were a waste on our charging systems and when stock battery (agm) went bad, he would have replaced it with a flooded if it wasn’t under warranty. The swapping batteries isn’t a bad idea and would be an easy way to tell.

I’ve got a trip next week that’s going to be about 700 miles round trip. If the flooded doesn’t run down farther than the agm then I’ll know the tech was right. I did fully charge her agm battery and then drove 600 highway miles only to find the battery had discharged down to almost 80%, so I’ve got a similar scenario to compare to. Both cars use the same alternator with the same algorithm so I’ve ruled that part out and have monitored the voltage on my scanguage. The problem lies in the system itself. The alternator will throttle down to 12,8-13.2 and live there for miles before ramping up above 14 volts. The battery then loses its charge and the agm takes longer and needs more volts than the flooded and what the alternator provides. This equals a depleted battery.

 

[John105]

Not a car, but our FiOS battery backup battery failed, AND, the BBU didn't know (it should alarm).

This is only supposed to support the voice portion of the ONT.

I decided to "reboot" the entire system, and inexplicably, the entire interface (ours is from 2009 so it's a large Alcatel hinged box on the wall) now had no power, regardless of being plugged in via AC. Something in the logic went wrong, because tracing the wiring, AC power goes to the Alcatel, and then there is a plug in the ONT going to the BBU.

It's just interesting how unexpected things can happen once logic is introduced into the design. The above should work regardless, when plugged into AC power (battery can be hot swapped etc.).

 

[Jetronic]

I tried a little experiment this morning. My wife’s battery (agm) was 100% charged as was my flooded battery..same car except hers is a 24 and mines a 21.. Both batteries were new in December and both testing @100% state of health. We both drove to the gym separately, at the same time. We get back from a 10 mile round trip, her batteries testing @89%, my deka flooded is testing @93%. I hooked up each car to pretty much identical Pulsetech chargers and mines done in an hour , hers took 4. Conclusion is that I’m never going to buy another agm. I’ve gathered enough data to know that they’re a waste of money, and won’t charge with today’s smart charging systems. If I had stop start, maybe.

you can't fully charge a 93% battery in 1 hour, the 4 hours seem correct.

 

[D1dad]

you can't fully charge a 93% battery in 1 hour, the 4 hours seem correct.

According to my charger you can. The xc400 tests the battery and then registers 75%. An hour, or so later and it’s just pulsing. Whether it’s charged to 100% at that point, I haven’t checked as the surface charge, even with turning the headlights on gives a false reading. But at that point the batteries ready for service. My battery minder isn’t far behind time wise.

 

[Cujet]

On my 2024 F150, Ford did a software update that fixed the battery issue for many owners. I've not had any issues, and I have the update. It seems many manufacturers have a method to change battery charging protocols, if problems arise.

 

[goblin]

... only to find the battery had discharged down to almost 80%...

Again - not sure about what Nissan's system does, but this is precisely what the BMW system does and what is considered normal. It keeps the battery at around 80% charge, charging it to higher percentage only every now and then, whenever it decides. It's a fuzzy logic, it keeps its charge cycles in memory, and there's no repeatabilty from one rid to the other, even if they are identical to the pound of load, foot of distance, degree of temperature, percentage point of tank full - you name it.
Hence the need for coding and programing new batteries and new different batteries - the system needs to know what battery it's dealing with, capacity-wise and age-wise.

The good side of this is that batteries last a really long time. The flip side is that cars that sit a lot and are driven little require more battery tender attention than older cars. But a car that sits a lot and is driven a little requires that no matter what.

Monitoring your percentages and voltages would be like monitoring the coolant temperature on a BMW If you don't know why it's sitting at 110 degrees Celsius in gentle driving then it drops to 95 the second you rev it - you'll get nuts. No wonder they no longer come with temp gauges (or if they do - they no longer work the German way, showing temperature changes, but the Japanese way - showing one value as long as the temp is within specs).

Unless you have some Nissan-dedicated scanner to monitor the charging output in real time - don't sweat it. As long as the car cranks and the battery lasts, you're good.

 

[goblin]

To add to the above - this is part (only part) of the info that can be monitored in my 15-years old BMW:

I very much doubt a recent Nissan would monitor less parameters. So any measurement you might get with a voltmeter will only be accurate for that point in time and that specific component.

These things have endless ways of making us feel old.

 

[D1dad]

I hook up my scanguage on long trips. Cvt temp, coolant and voltage are my main worries. I’d like to have oil temp but that feature isn’t there. I watched my 24 stay around 12.9 volts for an hour. Honestly the only time it reaches above 14v is when I 1st start it.

 

[football]

I’ve noticed that modern cars can turn off the charging circuit in the name of fuel economy. A charging alternator causes friction which reduces fuel economy. Cars will routinely drop to 12 ish volts while driving when back in the day they stayed constant at 14+ volts.

I charge my batteries monthly with a few amps, slow charged. Seems to make the batteries last longer.

 

[meep]

I installed a digital VM in my 2018 Ford and observed that the strategy is complex, and not all bad. Voltage goes way up when coasting or breaking. Voltage stays 12.4 (80% ish state of charge) when underway. It’s 14+ for a minute or so after starting. It’s hard solid at 13.5 when lights are on or high load from A/C. The entire range shifts with temperature. Then once per month, or if the system senses something is amiss, it does a higher-voltage soak for a day … 14.4 or greater. That was very interesting - the attempt at an equalizing or maintenance charge - they put some thought into that.

I messed with it and raised the computers charge strategy to as high as 95% SOC, and didn’t like it. But dyno felt like the vehicle was hampered a little bit. Maybe I was over-sensitive, but I learned to feel it when on a downhill coast it shifted up from 12.4 to 14.6+ charge. It was barely perceptible, like ever so slightly dragging the brakes, but it was indeed there.

I’ve read, and posted here, that they receive more MPG savings with these charge strategies than with AS/S.