Battery charging data

[Bitsyncmaster]

I went to start my D this morning and it cranked over slower than normal but started quickly. I've not done more than 4 or 5 short drives this year so I put a charger on it. I use a linear lab power supply and set 14.50 volts and current limit at 5.000 amps.

I've always had interest in data when charging batteries. Well my battery is defiantly taking a charge since it has taken 6 hours for the current to drop to 1.2 amps. What this means to owners is you really need to make a few long drives during the the year unless you use a battery charger or tender to top off your battery.

Here is some old data I recorded and it will be interesting what my D battery current is when it's fully charged this time.

10/25/2017
Using linear power supply
My test battery charged at 14.50 volts shows 0.115 amps fully charged.
14.0 volts = 0.049 amps
13.5 volts = 0.021 amps
13.0 volts = 0.008 amps
12.9 volts = 0.000 amps

12/28/2016
My D battery charged at 14.5 volts shows 0.12 amps. at 46 deg

1/1/2017
My test battery charged at 13.0 volts shows 0.20 amps. at 70 deg.

1/1/2017
Impala battery charged at 13.3 volts shows 0.20 amps. at 45 deg.

1/3/2017
Malibu battery charged at 12.9 volts shows 0.17 amps. at 47 deg.

[David T]

After years of caring for lead-acid type batteries this is what I have come up with. Using these procedures I can have batteries last for over 10 years.
Use a battery Master Switch so you don't drain the battery when you aren't using the car. A fully charged battery is a happy battery
Use a Battery Tender or other "smart" type battery charger. I hook it up for 1 day every month if the car is not used. I try to do it the 1st day of the month so I don't forget.
If I know in advance I will hook it up the night before I use the car so teh alternator doesn;t have to work hard.
On cars where you can't use a battery master switch because it is newer (not Deloreans) and has a computer, use the battery tender every 2 weeks for 1 day.
If you are not going to use the car for a while (like wintertime in the Northeast) I take the battery out and store it inside where it is warm on a piece of wood and hook it up to the battery tender once a month. Before putting the battery back I test it and clean up the connections. Always use the battery hold down hardware so the battery can't bounce around and damage the internal parts. Do not over-tighten the battery terminals, that will cause the battery to leak. If the sides are bulging or the battery has a smell it is no good. If it ever got completely dead it is no good even if it can be recharged. If it ever got cold enough to freeze and was not fully charged it is no good. (A dead battery's electrolyte is just water and can freeze at 32 degrees F). If the voltage regulator failed and overcharged the battery it is no good. All of these bad things may not kill the battery immediately but severely reduce a battery's useful life by reducing it's capacity significantly. Kind of like a cat. We don't know how many lives are left till the last one is gone. We can get an idea of how much life is left by doing a load test but they are not 100% accurate. Batteries are not like sponges. You can't take all of the electric out and put it back without seriously compromising it's life. In fact, batteries are usually sized/designed so they never have to use more than 50% of their capacity. That leaves enough reserve for cold weather and diminished capacity over it's design life of about 7 years.

[Elvis]

I had a problem today with a Libyen-Bus. The battery only had 6V left.
I checked for currents but there was no drain at all.

So I jump started it, the battery in seconds read 12V but didn't spark at all.
After a few seconds the charging current was <<1A.

The battery is probably less than a year old. I'd like to open the battery to
see what has failed - but I'm afraid of the acid :-(

[Bitsyncmaster]

My battery is now charging with 0.222 amps of current. The current drop is getting pretty slow now so it must be close to 100%.

Anyway this just goes to show you unless you do many hours of driving often your battery won't be 100% charged. Now if your alternator is only putting out less than 14.5 volts your really not going to get a full charge. Note that temperature of the battery determines the voltage needed to achieve full charge. Colder needs higher voltage and warmer needs less. This is why the alternators will change voltage according to the temperature.

A long time ago when I flew RC airplanes I designed a charger for NI-CAD batteries. For that you use a constant current and charge until the voltage peaked and then started to drop. Why it does that is your putting power into the battery and when it's fully charged your still putting power in but it gets converted to heat and the heat made the voltage drop on the battery.

[Bitsyncmaster]

I had a problem today with a Libyen-Bus. The battery only had 6V left.
I checked for currents but there was no drain at all.

So I jump started it, the battery in seconds read 12V but didn't spark at all.
After a few seconds the charging current was <<1A.

The battery is probably less than a year old. I'd like to open the battery to
see what has failed - but I'm afraid of the acid :-(

You would probably find one of cells has a bad connection or the cell got discharged somehow. I've had luck just slow charging those so the discharged cell gets back to full charge.

[David T]

You would probably find one of cells has a bad connection or the cell got discharged somehow. I've had luck just slow charging those so the discharged cell gets back to full charge.

Rarely "fixes" it. The main cause of problems with a cell is that bits of the plates fall off and collect at the bottom of the case in each cell. When enough falls off it reaches the bottom of the plates and shorts them out. The other common problem is inferior manufacture and a bad internal connection. Because the battery is a bunch of cells in series, a bad connection anywhere inside the battery and the whole battery is NG. On old batteries or large industrial batteries you can actually disconnect and remove an individual cell and replace it if it goes bad. The newer sealed type are unrepairable but they are very recyclable. Lead is the most recycled metal of all. Over 90% of all lead is recycled. Good thing, it is very toxic.

[DavidProehl]

That is interesting data, and confirms the need to keep a battery charged to be healthy.

I follow a similar process to David T. When the car isn't driven, it is on a battery tender. Thus, my battery is always fully charged.

I have the cheapest battery I could find, the lowest rated Walmart special that cost about $60. The first one lasted me 10 years, and the second one is still in the car. I check acid levels once a year and pull the battery for the winter.

[Bitsyncmaster]

I have the cheapest battery I could find, the lowest rated Walmart special that cost about $60. The first one lasted me 10 years, and the second one is still in the car.

I agree about using a cheap battery. I've found the expensive ones with high current ratings use thinner plates to pack in more plates and they fail faster.

[David T]

I agree about using a cheap battery. I've found the expensive ones with high current ratings use thinner plates to pack in more plates and they fail faster.

That is what the car was designed for. Those expensive gel cell types like Optima require special charging conditions for which the alternator is not set up for. IMHO not worth the money, at least not for use in a Delorean. If you are that worried about your battery, invest in a battery pack. I have one with a built-in air compressor so it can also inflate a tire. Not only is it good for you, if anyone is in trouble you can use it to help them. On more than one occasion I used it to help another car at a car show. With a battery pack I don't have to give anyone a jump off of my car and take a risk of hooking things up wrong or having to get close to them with the car.

[Bitsyncmaster]

Here is the final result of my charging the D battery.

11/9/2017
Using linear power supply
My D battery charged at 14.50 volts shows 0.151 amps fully charged. At 66 deg.