Battery Electrical Information, Any Year, Any Make

[MrAl]

Hi there,

I thought members here would like to get a purely electrical look inside a battery because the battery is a big part of the correct working of any car and questions come up about this device a lot, so here is some of the logic behind what the battery looks like inside from an electrical point of view.

Note that the two terminals marked plus (+) and minus (-) represent the actual connections to the physical battery, everything else is 'inside' and not accessible except by some electrical measurement usually a bit complicated.

The capacitor on the left is the main storage component and it would have a very large value for an automotive battery.

This model created by the guys listed in the image shows a lot of detail but does not show how the aging process affects the various components. One in particular is the capacitor on the left CCAP decreases in value over time. That's the main one that would be considered in the guarantee because once that decreases too much, the battery no longer holds a decent charge needed to start the car especially in cold weather. That's the main component that decides what the cold cranking amps rating will be. The RS is also important because as that value increases over time the voltage VB drops more and more so the battery delivers less and less current to the starter motor. The value RSD decreases in value so the battery tends to discharge more all by itself, even if it was not connected to anything (sitting on a shelf in the garage or something) and that makes it necessary to charge a battery now and then if it is not being used.
One small note, the variable dVB is really dVB/dIB which is the change in battery voltage with respect to battery current. I'll have to edit that at some point to make it more clear that the change is measured with respect to the current in or out of the battery.

To find out more you can look up the paper that the authors mentioned in the image wrote up. It contains a lot of information.

Maybe this will give some people a better idea what the battery is made up of, from an electrical point of view.

I made this back in 2007 after reading their paper, but i had to correct some spelling errors (ha ha) before posting.

[jreed]

Thanks. It looks like the authors of the 2005 paper (Chen and Rincon-Mora) have put a copy of their work here: https://rincon-mora.gatech.edu/publicat ... tt_mdl.pdf

[abscate]

Just a clarifier, the circuit represents the electrical composition of a battery, not the physical representation. If you open it up looking for a giant capacitor , you are going to be left with that empty, discharged feeling ...

[MrAl]

Thanks. It looks like the authors of the 2005 paper (Chen and Rincon-Mora) have put a copy of their work here: https://rincon-mora.gatech.edu/publicat ... tt_mdl.pdf

Hi,

Thanks for the link i havent read up on this stuff lately and tend to forget over the years.

[MrAl]

Just a clarifier, the circuit represents the electrical composition of a battery, not the physical representation. If you open it up looking for a giant capacitor , you are going to be left with that empty, discharged feeling ...

Hi again,

I know you were just joking but it's amazing how technology has changed and is still changing.
What you can get these days is a "super capacitor" that can store a lot of energy in an actual capacitor, enough to start to mimic some batteries.

Although i dont think anyone has made a super capacitor that can completely replace a car battery, i know that they do make them to add on to your current car battery. That gives the car battery an extra kick when you go to start the car. They are very expensive though equal to the cost of most car batteries today, but i can easily see in the future how they might make a hybrid car battery (if they havent already that is) and that would contain a regular set of plates as well as a large super capacitor.

Right now they are purchased for the purpose of adding to your car yourself and also added remotely (maybe inside the car where the radio is) to aid in providing high surge current to sub woofers.

I dont think i will get one in the immediate future ($200 USD) but it's interesting to think about. The capacitance is rated for about 90 Farads to 500 Farads. That doesnt sound like enough to me but we have to remember that starting a car, if it starts, only takes a few seconds at most. Interestingly, in cold weather the car battery has some trouble providing highest current to the starter and since it only needs a couple seconds of high current to start and the windings are cold, a super capacitor could work wonders here not only in starting the car but prolonging the life of the car battery.

I'm going to do a few calculations to see what it would take to replace a real car battery with a capacitor. Just off the top of my head i think it would take about 450000 Farads, which would mean 1000 of those 500 Farad super capacitors, which would take up probably all the engine compartment space (with no engine that is) and weigh some 8000 pounds and cost about $200000 dollars USD. So i guess we have to wait for some really extreme advances in technology in this area

If anyone is interested, they have some on Amazon part number SB500-34 for the 500F unit. They also have a lot of smaller ones maybe 90 Farads that look easier to install. Im sure they are sold elsewhere also.

Oh and BTW, if anyone has used one of these already it would be very interesting to hear about your experiences with one.

[abscate]

Aren’t the small brick starter packs basically large capacitors? I always though that was the case but they may just just be dense Li technology

[RickHaleParker]

Battery capacity (Listed as Ccap above ) degrades due to sulfation of the battery and shedding of active material. There not to much you can do about shedding of active material other then prevention of sulfation which is the active material converting from Lead into Lead sulfate crystals.

Sulfation can be prevented by keeping the battery fully charged. Sulfation can be reversed by fully charging the battery with a smart charger then leaving it on the charger. Keeping it on the charger and fully charged will slowly convert the Lead sulfate crystals back into Lead.

If the Lead sulfate crystals fall off the plates it is permanently lost.

If you are going to store a battery or don't drive the car much. A $15.00 investment in a battery maintainer is a good investment. Spend the $15.00 or $150.00+ for new batteries.

A battery maintainer is a simple 12.8 - 12.9V regulated float charger .

[MrAl]

Battery capacity (Listed as Ccap above ) degrades due to sulfation of the battery and shedding of active material. There not to much you can do about shedding of active material other then prevention of sulfation which is the active material converting from Lead into Lead sulfate crystals.

Sulfation can be prevented by keeping the battery fully charged. Sulfation can be reversed by fully charging the battery with a smart charger then leaving it on the charger. Keeping it on the charger and fully charged will slowly convert the Lead sulfate crystals back into Lead.

If the Lead sulfate crystals fall off the plates it is permanently lost.

If you are going to store a battery or don't drive the car much. A $15.00 investment in a battery maintainer is a good investment. Spend the $15.00 or $150.00+ for new batteries.

A battery maintainer is a simple 12.8 - 12.9V regulated float charger .

Oh hi there RIck havent seen you around in a while.

What you say about the maintainer is true as far as i know, and i got one a while back and never used it because i didnt have a battery. The garage replaced my battery with a Delco even though it was an Interstate with full warranty and so i had to get the replacement myself. I have it now and use a maintainer i got for around $12 USD. It's a little think a bit larger than a wall wart. It uses 4 stages to charge the battery then go to float charge. The max voltage is about 14.2 volts or something like that, as measured with a quality voltmeter. The float voltage is around 13.8 volts.
I want to keep this battery maintained for use as a backup. I guess it could jump start the car too if needed.

[MrAl]

Aren’t the small brick starter packs basically large capacitors? I always though that was the case but they may just just be dense Li technology

Hi Steve,


Some are super capacitors now yes and some of them are Li-ion or similar.
The Li-ion ones work only if the only problem is a dead battery. If the car wont start easily then they could be worthless. That's because they only allow so many seconds of start time, then they switch into protection mode, which no longer puts out any power. You have to get out of the car and disconnect the thing to get it to reset so you can try to start again. It's a big big pain and never works if the car is hard starting. That's been my experience.
Havent used the super cap ones yet.
I had a Husky jump starter that had a lead acid battery in it maybe around 30 Ahr rating, and it worked very well. It was a lot heavier than the Li-ion jump pack but at least it worked even if the car was a little hard starting.

[RickHaleParker]

The float voltage is around 13.8 volts.

There are different options on what the float voltage should be.

Some people say as low as 12.4V. I say 12.4 is too low because it only a partial charge. I say 12.8 -12.9 because that is the full charge voltage. Keep it at full charge will prevent sulfation. 13.8V is a charging voltage and can slowly evaporate the water in the electrolyte.