Alternator Charging

John T Carroll

I am posting this in Motorhomes & Campervans because there seems to be a wealth of knowledge here in general re battery charging.
My query: Why doesn't fairly constant high voltage charging damage vehicle batteries, especially car batteries?. The past three cars that I have owned have all done 10 years+, I changed one out as a precaution a few years ago after 12.5 years, this battery and all the others charge at a constant 14.1 to 14.3 Volts even while idling with a "normal" night load, wife is presently driving a car that does all short runs with the original battery, car was bought new in March 2005.
I know plenty of people who have had similar experiences.
I appreciate that these batteries are never deep discharged as the only real load is the starter one, all the other electrical loads are then satisfied completely, in my opinion, by the Alternator.
I did read somewhere that some (in the USA) alternators were 2 stage, ie they charged initially at around 14.3 volts (or higher if temperature compensated) and then fell to a float voltage of around 13.6 volts I think. The Alternators in my cars are certainly constant (> 14) voltage as I monitored them on a few occasions while driving.
Is it possible that the combination of the actual driving time + charging voltage is just enough to keep the battery condition just right by pure luck?, also of course a car driven constantly (taxi or long distance driving) might result in a battery only lasting 3 or 4 years due to overcharging?.
Any thoughts much appreciated.

Aidan_M_M

Volts is only part of it, amps need to be accounted for. It might show 14v, but there'll be feck all amps going into the battery.

@25*C

14.3v isn't high.
gassing voltage is 14.2v @25*C

14.8v is high ( often 15.1v with temperature compensation). Which I use.

I've adapted my alternator to be 3 stage. It makes naff all difference except when the batteries have been a fortnight on charge.
It's nigh impossible fully charge/overcharge a battery with an alternator with normal car use, it can take days to really charge the blighter.
Most batteries deteriorate due to the parasitic load and people leaving the lights on.

John T Carroll

Sir Liamalot wrote: »

14.3v isn't high.
gassing voltage is 14.2v @25*C

14.8v is high. Which I use.

I've adapted my alternator to be 3 stage. It makes naff all difference except when the batteries have been a fortnight on charge.
It's nigh impossible fully charge/overcharge a battery with an alternator with normal car use, it can take days to really charge the blighter.
Most batteries deteriorate due to the parasitic load and people leaving the lights on.

Thats interesting the point re (not) fully charging the battery with an alternator with the car in normal use. Now IF one had/has a fully charged battery would a constant 14.2/14.3 Volts overcharge the battery or would it have to be applied for hours on end to do so, in your opinion.

There's nothing wrong with overcharging if you can replace the electrolyte.

Charging batteries is seriously hard work the chemistry is dreadfully inefficient at end of charge.


Most chargers and alternators do 90%. The super expensive fancy pants ones do 95% in 12 hours. 100% requires intervention or a good solar controller and two weeks or over-voltage and two days.

John T if you are getting 10 years from a starter battery you're obviously doing it right. No need to worry.

DanWall

The battery when it ages loses its capacity not its voltage and will charge up quicker (unless a cell is faulty)

John T Carroll

Sir Liamalot wrote: »

John T if you are getting 10 years from a starter battery you're obviously doing it right. No need to worry.

I'm certainly not worried, I,m just very curious for years now as to why a very basic charging system can result in very long battery life, maybe thats the reason... basic. The 14.1/14.3 Volts coupled with the Irish climate probably helps as well, I think your explanation of the complex chemistry involved coupled with the fact that the battery isnt being charged for days on end goes a long way to explaining it, thanks, I'll sleep well tonight.

DanWall

DanWall wrote: »

The battery when it ages loses its capacity not its voltage and will charge up quicker

Not actually true. Open circuit voltage will rest lower. Convention is to replace them if they can't hold 12.4v.
If you had a well enough engineered charger it would take much longer (cheaper buy 2 or 3 batteries). The battery gets less efficient with age as the surface area of the plates crusts up with sulphates, the electrolyte gets weaker as hard sulphates have fallen permanently outtov solution. More of the charge current is converted to heat inside the battery rather than chemistry. Surface charge becomes more prohibitive as the plates take longer to saturate due to reduced surface area contact with the electrolyte and will fool most of the medium to low end chargers, and so it snowballs..further detioration due to undercharge.
The smaller for longer the charger output the more thorough the charge.
Then there's the filling a bucket with a hole in it effect as the active material is knocked off the plates and piles at the bottom of the cells creating soft shorts and higher self-discharge rates.


If your charger algorithm is intelligent enough (or dumb enough) it'll persist.
If the output was calculating the difference in the battery internal resistance and compensating the charge current to this it would take a very long time to charge and only desist when the value is constant. Similarly if you charge with constant voltage and a hydrometer it will take an age.
However if it's a cheapo job that is timer based on the length of the bulk cycle or comparator based it'll just say "close enough, I'm done"

Let's not mention some chargers with over-zealous safety margins that compromise their utility. :rolleyes:

John T Carroll wrote: »

I,m just very curious for years now as to why a very basic charging system can result in very long battery life, maybe thats the reason... basic.

Yeah dumb, inefficient and effective.

Let's take my high compression motor as an example.
I've a 90Ah battery which does get fully charged regularly. De-rate 10% for nominal ambient temperature = 80Ah for engine starting.

Starting load = glow plugs 70A for 30 seconds = 70/60/2 = 0.6Ah
Cranking amps = 400A for 2 seconds = 400/60/30 = 0.22Ah

0.82 Ah per start, 1% discharged...minutes to recharge (in a perfect world where electrochemistry is 100% efficient...10s of minutes in the real world)

If used only for starting a starter battery will give ~ 5000 starts = two starts a day for 7 years, or 14 years with two every second day.


Like said it's usually the radio, alarm, computer and park-anywhere-lights that kills batteries....slowly...;)

John T Carroll

Sir Liamalot wrote: »

Not actually true. If you had a well enough engineered charger it would take much longer (cheaper buy 2 or 3 batteries). The battery gets less efficient with age as the surface area of the plates crusts up with sulphates, the electrolyte gets weaker as hard sulphates have fallen permanently outtov solution. More of the charge current is converted to heat inside the battery rather than chemistry. Surface charge becomes more prohibitive as the plates take longer to saturate due to reduced surface area contact with the electrolyte and will fool most of the medium to low end chargers, and so it snowballs..further detioration due to undercharge.
The smaller for longer the charger output the more thorough the charge.
Then there's the filling a bucket with a hole in it effect as the active material is knocked off the plates and piles at the bottom of the cells creating soft shorts and higher self-discharge rates.


If your charger algorithm is intelligent enough (or dumb enough) it'll persist.
If the output was calculating the difference in the battery internal resistance and compensating the charge current to this it would take a very long time to charge and only desist when the value is constant. Similarly if you charge with constant voltage and a hydrometer it will take an age.
However if it's a cheapo job that is timer based on the length of the bulk cycle or comparator based it'll just say "close enough, I'm done"

Let's not mention some chargers with over-zealous safety margins that compromise their utility. :rolleyes:




Yeah dumb, inefficient and effective.

Let's take my high compression motor as an example.
I've a 90Ah battery which does get fully charged regularly. De-rate 10% for nominal ambient temperature = 80Ah for engine starting.

Starting load = glow plugs 70A for 30 seconds = 70/60/2 = 0.6Ah
Cranking amps = 400A for 2 seconds = 400/60/30 = 0.22Ah

0.82 Ah per start, 1% discharged...minutes to recharge (in a perfect world where electro chemistry is 100% efficient)


Like said it's usually the radio, alarm, computer and park-anywhere-lights that kills batteries....slowly...;)

That > 10 year old was left at Cork Airport for 10 days recently, it has from new always drawn a fairly high parasitic loss of 90 MA, ( the other cars in the family that I,ve checked draw 40 to 50 MA) so that battery had drawn down almost 22 AH (10x24x90/1000) from a 44 AH battery and still started the car instantly. It will be at the Airport again shortly for 14 days but NO I will not tempt fate this time, I'll remove the ground terminal, I couldnt face the slagging I'd get if I had to admit that any of my cars failed to start.

John T Carroll

Sir Liamalot wrote: »

That doesnt look like "the wife"

Probably a good thing, bitova kamakaze solution that.

John T Carroll

Sir Liamalot wrote: »

Probably a good thing, bitova kamakaze solution that.

Must be the base model.....no starting handle with them

John T Carroll

John T Carroll wrote: »

...always drawn a fairly high parasitic loss of 90 MA, ( the other cars in the family that I,ve checked draw 40 to 50 MA) so that battery had drawn down almost 22 AH (10x24x90/1000) from a 44 AH battery and still started the car instantly.

That is high, I'd pull fuses to find the heavy consumers. If it's something easy like a radio I'd swap it or add an inline switch.

Assuming it has it's plated 44Ah capacity Puekert compensated discharge of 90mA makes it a 57.5Ah battery. So you actually had 35.5Ah in the bucket (@ 25°C)

John T Carroll

Sir Liamalot wrote: »

That is high, I'd pull fuses to find the heavy consumers. If it's something easy like a radio I'd swap it or add an inline switch.

Assuming it has it's plated 44Ah capacity Puekert compensated discharge of 90mA makes it a 57.5Ah battery. So you actually had 35.5Ah in the bucket (@ 25°C)

I'd be delighted if I had that in the bucket in a 10.5 year old battery but I wouldnt push it, I would certainly lean to the view of DanWall above that capacity must surely decline with age. Re the 12.5 year battery that I removed precautionery from another car, I then installed it in the wifes car for a crude test and left the side lights on for 6 hrs which I think would/should have drawn down around 16 AH, (6X2.7). The car then just barely started so I reckon the battery was on its limit and it would indicate (admittedly crudely) that it had a USEFUL equivalent capacity of 16 AH?.
I reckon that this petrol engine draws around 250 amps when cranking so would only deplete any battery by around 0.21 Kwh for a 3 sec crank, (250X3/3600). Yes, this car has always had a high parasitic loss of 90 MA but as it isnt causing a problem, I'm not too bothered, I'll settle for the 10/12 years battery life.

John T Carroll

John T Carroll wrote: »

and it would indicate (admittedly crudly) that it had a USEFUL equivalent capacity of 16 AH?.

Yurp, pretty close to accurate actually.

piuswal

Looking for some charging advice and thought I'd use this thread.

Have an 8 year plus battery in a Ford Transit; see attached photo.

The battery is under the driver seat and difficult to get at.

I can see a positive node under the bonnet but would like to know what is the best place for a negative connection from a charger?

Engine lift hook, alternator casing, gearbox...any part of your chassis not painted.

*Kol*

Sir Liamalot wrote: »

Engine lift hook, alternator casing, gearbox...any part of your chassis not painted.

There is a sticker in the photo on the slam panel showing that the negative should be connected to the engine lifting eye.

piuswal

Thanks for the help so far.

1. I'm putting the van undercover, probably until late March. The 8 year + battery drops below starting capacity in about 4 weeks or so if left unused. Is it advisable to disconnect it while in storage?

2. Does anyone have any experience of battery starter packs? Are t hey worth investing in and if so, what type? Or , should I just invest in a new battery next year?

Disconnect after charging on a mains charger or float charge on a good charger; one that charge rate = discharge rate + load compensation.
If the battery has reduced capacity then I'd replace it. Depends on the parasitic load of the van. Flat after a month might be normal. If you measured it you'd have a better idea.

A starter pack is a battery. Never used or needed one myself.
Use the deep cycles? You don't have to use them to start assist if you'd prefer not to crank from them, you can just link them and let the house battery charge the starter and disconnect to start the engine. If you want to be really frugal light the glow plugs with all the batteries connected.

crabbypaddy

A decent starter pack is over 200 Euro the cheap ones use sealed lead acid batteries and if you don't regularly charge them they're useless and scrap after a while. The snapon ones used to be nicad I know of one that was used and abused in a dealership for about 15 years before needing replacement cells. Not sure if the European union have done away with nicad versions yet but its definitely the way to go.

It's never worth limping along with a ****e battery though just being it for scrap and put the price of a chibese junk starter pack and scrap value into a new battery.

There's some li-ion jobs about as well. High energy density so small size. Nowhere near as good as Ni-Cds for high current discharge survival. Bittova li-ion bandwagon touring these days.


So the EU are gonna ban the Nissan Leaf and cohorts?! What about thin film solar?

crabbypaddy

Sir Liamalot wrote: »

There's some li-ion jobs about as well. High energy density so small size. Nowhere near as good as Ni-Cds for high current discharge survival. Bittova li-ion bandwagon touring these days.


So the EU are gonna ban the Nissan Leaf and cohorts?! What about thin film solar?

The ban came in about 10 years ago automotive and industrial batteries are excluded from the ban its 'portable batteries' that an 'average person' can carry lol There was an exemption for power tools until next year some time. Maybe they can claim a starter pack is an emergency system an therfore exempt
I have some nicd C cells here that are at least 20 years old still working great in my bike light hard to beat them .

crabbypaddy

crabbypaddy wrote: »

...hard to beat them .

Stick one of these on the diff.