Avoiding sulfation and loss of capacity: How frequently must I charge to 100%?

[Vigo]

Well, looking at alt fans they are 'centrifugal impellers' which means at a low enough speed they barely do anything, and at some point they will start to work, and eventually they may 'cavitate' if spun too fast but i don't know if an alternator really hits those speeds in practice or not. But i would guess the fan performance is on a bell curve and there are places on the steep part of the curve where doubling the fan speed gets you way more than double the airflow.

From memory i think most automotive alternators have a max speed rating of 12000-14000rpm or so, which is why when you put it on an engine that spins to 6-7000rpm, you can't 'pulley' it enough to make it have max output and cooling at idle, or it will kill itself when engine is at redline. If you put it on an engine with a 1000-4000rpm rev range like a typical 'small engine' then you actually could pulley it to make max output at lower rpms and not have it die if you rev the engine all the way up. But then you have to have a small engine which could actually make that power at that lower rpm, and most engines smaller than 400cc probably can't max out even a standard car alternator at much less than the 3600rpm they're governed to from the factory.

Now i do have a couple of Ninja250 engines around here..

 

[rdhood]

I recently replaced an Optima red battery in my car that started failing after 15 months. In 46 years of driving, I never had a battery that cost as much as the Optima, nor degraded as quickly as that Optima. I believe that the answers in this thread is the primary reasons why AGMs are NOT a good choice for automotive applications if the car does a lot of short trips. It is never going to get to 100% after a start, and it is going to start degrading immediately.

 

[Vigo]

Many cars come with AGMs from the factory and are 'programmed' to treat them correctly as much as possible (car doesn't control how short your trip is!). So it is absolutely possible to have long life from an AGM in a car. In general they usually DO live longer than a regular flooded starting battery in a car, even if the car didn't come with AGM and charging characteristics aren't 'optimal' for AGM.

But you rarely get ahead on money. The AGMs often cost 50% over the flooded equivalent, but they don't consistently last MORE than 50% longer. If they cost 50% more and last 50% longer you 'just break even'. Optimas in particular are usually double the money of the flooded equivalent, and rarely last twice as long, making them more expensive over time. So it is usually true that an AGM starting battery in a car is... reasonable.. justifiable.. but not cheaper in the end. It just reduces the frequency of your battery replacements in return for more up-front dollars.

By extension, this is also why the Walmart $64 value batteries are probably the cheapest over time. They cost about half what the 'regular' line costs, but in all likelihood probably last longer than half as long. Making the cheapest battery up front, also possibly the cheapest over time.

 

[Checkthisout]

Many cars come with AGMs from the factory and are 'programmed' to treat them correctly as much as possible (car doesn't control how short your trip is!). So it is absolutely possible to have long life from an AGM in a car. In general they usually DO live longer than a regular flooded starting battery in a car, even if the car didn't come with AGM and charging characteristics aren't 'optimal' for AGM.

But you rarely get ahead on money. The AGMs often cost 50% over the flooded equivalent, but they don't consistently last MORE than 50% longer. If they cost 50% more and last 50% longer you 'just break even'. Optimas in particular are usually double the money of the flooded equivalent, and rarely last twice as long, making them more expensive over time. So it is usually true that an AGM starting battery in a car is... reasonable.. justifiable.. but not cheaper in the end. It just reduces the frequency of your battery replacements in return for more up-front dollars.

By extension, this is also why the Walmart $64 value batteries are probably the cheapest over time. They cost about half what the 'regular' line costs, but in all likelihood probably last longer than half as long. Making the cheapest battery up front, also possibly the cheapest over time.

Yup.

With engine shut down at stops, cars have really big agm batteries now.

 

[Vigo]

There's also a new type of battery called EFB, Enhanced Flooded Battery, for cars with stop-start.

It's not even really a new type. I read this document about them and to me it just seems like 'Regular Flooded Battery except we are trying harder and if we don't attach a new term to it we can't get away with charging more, so it's EFB and that'll be double the money please'. Calling EFB a
'new type' of battery is like when someone's not really doing their job, gets in trouble and actually starts doing their job. You wouldn't exactly double their pay in this scenario for being a new type of employee. ? Maybe i'm just being harsh.

 

[Goboatingnow]

I don’t see AGMs in new cars. Also car regulators are merely power supplies that happen to also recharge a battery they are not configured fir any particular battery type in general

 

[Vigo]

Many, many cars have AGMs. I do think it's true that EFB cuts into the 'market' for AGMs in new cars. But it's also possible that you don't 'see' AGMs as much because they're typically used in cars where the battery is not clearly visible under the hood.

Car charging systems run the full gamut from 'barely functional and pretty stupid' in the 1960s and before, to temperature-modeling and -compensating in the 80s, to modern stop-start vehicles needing to be calibrated with testing info from THAT specific battery, and actually measuring power in and out through inductive current sensors or shunts, and carefully controlling not just the charge, but also discharge of the battery through disabling stop-start under various conditions, to even doing a bunch of other weird little behind the scenes things to manage electrical load.

So you really have to say which car or at least which era of car you're talking about. Some cars have the same level of intelligence in their charging system as a riding lawnmower, and some have a LOT more than what's in the typical DIY off-grid home power setup.

 

[Checkthisout]

I don’t see AGMs in new cars. Also car regulators are merely power supplies that happen to also recharge a battery they are not configured fir any particular battery type in general

Bro, what are you talking about?

You have to go into the battery management system on newer cars and input battery data which includes battery type whenever you replace the battery. Charging strategy for AGM's is different.

2022 F150 in our shop.

 

[rdhood]

Bro, what are you talking about?

You have to go into the battery management system on newer cars and input battery data which includes battery type whenever you replace the battery. Charging strategy for AGM's is different.

2022 F150 in our shop.
View attachment 117151

I believe it. I have a 2013 Altima. It killed that Optima AGM...

 

[Goboatingnow]

Bro, what are you talking about?

You have to go into the battery management system on newer cars and input battery data which includes battery type whenever you replace the battery. Charging strategy for AGM's is different.

2022 F150 in our shop.
View attachment 117151

Most car stock regulators are power supplies only. They output A fixed voltage and have no battery charging profiles.

Have a look at the L9918 as a modern LIN controlled regulator chip (0r the simpler mC99032 ic ) both have no battery charging profiles.
A car alternator is the primary power source for on board systems a and is designed for that purposes. Charging a starter battery is an secondary non priority activity even in stop start.

 

[Checkthisout]

Most car stock regulators are power supplies only. They output A fixed voltage and have no battery charging profiles.

Have a look at the L9918 as a modern LIN controlled regulator chip (0r the simpler mC99032 ic ) both have no battery charging profiles.
A car alternator is the primary power source for on board systems a and is designed for that purposes. Charging a starter battery is an secondary non priority activity even in stop start.

Right. Just like cars don't use AGMs.

 

[teal95]

I work for an automotive OEM. Batteries are VERY actively controlled. I'm pretty sure that all of ours have shunts that measure current in and out in addition to minding voltage.

 

[Checkthisout]

I work for an automotive OEM. Batteries are VERY actively controlled. I'm pretty sure that all of ours have shunts that measure current in and out in addition to minding voltage.

I'm not an engineer but the pcm has controlled commanded voltage out of the voltage regulator for a couple decades at least?

It's become much more refined now to avoid wasting energy (unnecessary charging load on the engine) and for battery types and to of course avoid killing the battery and probably now the auto stop system has to know battery condition and not just voltage and temperature compensated charging and not charging so much at idle when the battery is depleted to avoid overheating the alternator at low engine speed and a million other things I probably don't know about.

 

[Goboatingnow]

I work for an automotive OEM. Batteries are VERY actively controlled. I'm pretty sure that all of ours have shunts that measure current in and out in addition to minding voltage.

I designed automotive electronics. , never seen a shunt on the regulator. Alternators are voltage controlled. Only current being measured is the field coil current.

Even the latest LIN chipsets for alternator control don’t measure output current. These chips do not have battery profiling, the pcm mechanism was very crude and has mostly been overtaken by LIN

The alternator load in respect of the battery is quite minimal anyway , the major load is the cars electric systems
temperature control is very crude , largely preordained temp step back of the voltage to reduce current.
The layman thinks the alternator charges the battery. That’s an ancillary function the main role is a constant voltage power supply for the car electric systems. The sound system on a high end car draws a considerable current.

Here were I live the motor factors don’t stock AGM , it’s all Bosch or Varta sealed wet lead acid. BMW or Audi are not using AGM to my knowledge , Fiats or Peugeot’s either from memory in a recent garage.

 

[Checkthisout]

I designed automotive electronics. , never seen a shunt on the regulator. Alternators are voltage controlled. Only current being measured is the field coil current.

Even the latest LIN chipsets for alternator control don’t measure output current. These chips do not have battery profiling

The shunt is at the batter negative or in the fuse box on the positive.

The PCM controls charging system regulation as well as the battery management system.

They can tell the regulator what to do.

 

[sunshine_eggo]

I recently replaced an Optima red battery in my car that started failing after 15 months. In 46 years of driving, I never had a battery that cost as much as the Optima, nor degraded as quickly as that Optima. I believe that the answers in this thread is the primary reasons why AGMs are NOT a good choice for automotive applications if the car does a lot of short trips. It is never going to get to 100% after a start, and it is going to start degrading immediately.

In my experience with over a dozen Optima, they are garbage. They used to be a premium brand worthy of praise, but when they moved manufacturing to Mexico with Johnson Controls, they took a nosedive like every other brand made in Mexico.

Optima should be actively avoided unless you have no other choice.

 

[teal95]

Correct, we have a sensor on the negative terminal (IBS, Intelligent Battery Sensor), so it's measuring current in and out of the battery.

 

[Goboatingnow]

PCM is largely a Ford protocol , the German cars are more LIn based these days and some Japanese are still using “ C-Term “

Lin is not optimised for current loop control , far too slow

 

[Checkthisout]

I designed automotive electronics. , never seen a shunt on the regulator. Alternators are voltage controlled. Only current being measured is the field coil current.

Even the latest LIN chipsets for alternator control don’t measure output current. These chips do not have battery profiling, the pcm mechanism was very crude and has mostly been overtaken by LIN

The alternator load in respect of the battery is quite minimal anyway , the major load is the cars electric systems
temperature control is very crude , largely preordained temp step back of the voltage to reduce current.
The layman thinks the alternator charges the battery. That’s an ancillary function the main role is a constant voltage power supply for the car electric systems. The sound system on a high end car draws a considerable current.

Here were I live the motor factors don’t stock AGM , it’s all Bosch or Varta sealed wet lead acid. BMW or Audi are not using AGM to my knowledge , Fiats or Peugeot’s either from memory in a recent garage.

Audis use agm batteries.

Edit: "Most".

They have the battery in the trunk. If it doesn't have a vent tube, it's probably AGM.

 

[Goboatingnow]

Correct, we have a sensor on the negative terminal (IBS, Intelligent Battery Sensor), so it's measuring current in and out of the battery.

Isnt that typically only on start stop ,I never designed for start stop cars.