Battery Charging Voltage for a Generator

A good trickle charger would be a constant current, not a fixed voltage.

Del

Kitty, can you explain the need for batteries for a generator too?

Nah, that's above my pay scale....
Del

You must be wrong! Its (if any) above you paw scale!

Whatever!

I cannot tell what voltage should be anywhere from the information provided. For all I know you might be getting 24V by putting sixteen AAA carbon zinc batteries in series. Putting a charger on a carbon zinc battery is just a waste of energy, battery and possibly a fire in your near future.

He has in question "(two batteries)", did you not see it? Or was you just trying to say in a roundabout way it would depend on type batteries being used?

Why yes, I am trying to say that the chemistry of the batteries matters.

Since you've casually tossed a challenge to me, please allow me to toss one back at you then. Will you offer me any battery chemistry where a single battery cell produces the needed 12V for two single cell batteries to achieve 24V?

No one ever specified "single cell" batteries. he indicated 2 -12v batteries, not 2 - 12v single cell batteries, and definitely not 2 - 1v cells. So it still not relevant to the discussion, on the part "the chemistry of the batteries matters" is.

The only fault I can see in you response is the application of logic.

Not a fault in itself but there's got to be a more creative answer to a mundane question.

I know of no vehicle that charges a battery at 13.8 for a flooded lead acid battery. In every manufacturer that I have checked right now the spec on right now calls for 14.4. What vehicle uses 13.8?

Correct.

I once worked at a place where we were given new vehicles, from all the big 3 and others, for research.

We put extra loads on them powering microphones, computers, amplifiers and loudspeakers and the alternators all put out at least 14.5-15.5 volts.

Sometimes that wasn't enough.

That may be the voltage at the output of the alternator but it is not the voltage at where the V_sense conductor is terminated.

The regulator's feedback is via the V_sense terminal not the output terminal.

You crank up the load current and the output voltage will go up to compensate for any I²R losses along the way.

Lyn, it's not my generator so why am I caring?

My car for one. Ford Ranger.

One of my vehicles does! '98 Buick LeSabre owned by me but used by a relative. Had car here today doing work on it so I ran an experiment. Details are as follows:

Car has not been run for 4 days

Before start battery voltage 12.2v

Voltage during starting 9.7v

Initial charge by stock alternator at 0:00 time (minutes:seconds)- 14.4v

0:30 times, 14.3v 1:00 time, 14.2v 1:30 time, 14.1v

2:05 time, 14.0v 3:30 time, 13.9v 5:10 time, 13.8v

1:20:00 time, 13.8v 1:30:00 time, engine shut down, 12.8v

4:13:48 time, 12.7v

Readings done with Fluke digital and Simpson analog meters. Regretfully I was not able to take current readings at the times. 14.4v for only 30 seconds or less. Also, why do mechanics use a range of 13.5-cannot be charged to a level greater than the voltage of the supply. To check an alternator a volt meter is put on the output, 13.5v-14.4v good, less than that bad. Battery check (also old school) is charge it for 1 hour, let sit for 10 minutes and take voltage reading, less than 13v is bad or on its way and should be 14.4v as the voltages to determine if an alternator is good (old school method)? We know that a battery replaced soon.

From http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery

Figure 4-4: Charge stages of a lead acid battery
The battery is fully charged when the current drops to a pre-determined level or levels out in stage 2. The float voltage must be reduced at full charge.

Table 4-5: Effects of charge voltage on a small lead acid battery (SLA)

My experience is that 13.8v (2.3v/cell) is good and have never seen a battery hold 14.4v (2.4v/cell).

A 2005 Dodge P/U also demonstrated similar results.

Good Luck, Old Salt

Voltage of any charger has to match that of battery.

Low ampere charging is more beneficial than high ampere charging.

High ampere charging is also called "quick charge" but it is not received well by the battery plates

If you want to "trickle charge" the generator cranking batteries to be sure they are ready when required then a FLOAT voltage of 27 to 28Vdc is what you need.

The current will vary by itself depending on the state of charge.

I assume these are lead acid batteries, the OP neglected to let us know!!!!

What I write here is ONLY for LA Batteries!!!

Trickle charging is fraught with possible errors to my mind. The implication is that the battery can be held at a specific state of charge, not increasing or decreasing.

State of charge is also a voltage.

But the actual trickle needs to take into account the temperature, age, size and type of LA battery, to name but a few....

I personally dislike such chargers as there is no guarantee that the charger will do just that, its a complicated procedure and needs to be monitored carefully. Most chargers are unaware of the type, size and age of the battery!!!!

I also think that it makes a battery "lazy"!!! As a non technical way to put it.

I am of the opinion (not proved except to myself!), that letting a battery get charged to about 70% of capacity (around 13.5 volts aprox), then stopping charging and only restart when it dips under 12.6 volts has several advantages:-

1) Battery is not stressed

2) Lead acid battery efficiency is at its best. (LA Batteries are very inefficient users of charging electricity, the higher the end voltage, the worse the efficiency!!)

3) Above 13.4 volts (aprox) gas will start to be formed and therefore water loss.

3) Battery exercises its "muscles" cycling up and down between the two voltage levels. Keeps it fit!!

4) The 12.6 volts lower charging "start" level makes sure that sulphating does not start in most LA battery types. Leisure LA batteries do not suffer from this...

But that is just my opinion.

By the way, it can be dangerous to charge a LA Battery using just current control....

I assume these are lead acid batteries, the OP neglected to let us know!!!!

Seriously Andy? What else could they be other than the cranking batteries of a diesel (or LPG or woodgas or gasoline or some other multi fueled reciprocating ICE ) genset?

These machines can run happily 24/7 for 250 hours straight, if fuel is fed into them, before they are scheduled for an oil change and fuel and oil filter replacements etc, and the whole time that thing is spinning, the alternator is pumping out a reliable 27 to 28Vdc. The current actually being drawn by the battery will depend on it's SOC. No harm befalls these batteries other than normal aging. In the tropics expect or budget to change your battery annually or if your lucky every 2 years.

Float charging the cranking batteries of standby generators at the voltages mentioned above is routine.

The possible reduction in battery life is the price for reliably starting the generator on demand. Otherwise just start the generator once per week and let it run for a half an hour while checking it for other problems just to be sure it is ready to go into service. If you experience frequent interruptions to your primary supply then it will probably keep the batteries charged up nicely on its own. If it mostly sits idle due to uber reliable primary supply then float charging may be prudent or routine starting as I mentioned.

I agree that its unlikely to be another sort of battery, but "never say never.....".

In far off places, Jet engines are started with NICADs or Lithium onboard.....though a starter trailer can also be used if available.

Float charging is done, I know that.

As I said in my post, I don't like that PERSONALLY!!!

Please read more carefully.....

Your answer may be somewhat valid for normal use of a lead acid battery, but a generator is a special case. In general, it does not have any load on the battery at all. The only load on the battery is starting during the periodic tests or when an emergency comes up. Letting the battery just set with a moderate charge will shorten the life, it will sulfate contrary to your statement. The battery chargers that have been developed to combat this, (one called battery minder), send a pulsed voltage/current to the battery to help prevent sulfation which will occur if the battery is left partially charged without movement. It does not have to reach the lower levels you suggested to start sulfating. The use of a solar panel with MPPT controller will be very close to the action of these special type of trickle chargers and have been shown to increase the life of batteries on generators from the 2 years with the method you suggest to 6-7 years. This is the same for automobiles years ago which were rarely driven and there was no load on the battery except when the car was started. (not true today when the electronics can take the charge down in a week)

I have experimented with those pulse desulphators, I do believe they work, but have no actual proof...

With regard to my chargers (that I build myself for many years!) 12.6 volts is not empty......if the battery was reasonably/correctly sized for the job in hand, it will still start an IC engine....

Also, the "bottom" voltage level could be turned up if needed, simple.....

My caravan battery is now almost 14years old (or maybe 13, I forget, its well over 10 I know for sure....). I seems to like my charging methods, but its no proof, one battery.

You need to test using 100 Batteries for 10 years or so.....I won't even live that long.....

But it still "works as designed!" 120 amp LA.....

For lead acid batteries it should be 26.5 volts at 70 degrees ambient temperature. Higher temps the voltage should be lower. Colder temps it should be higher.

Trickle charge for a standard lead acid wet cell should be limited to 28.8 volts (much lower than 28.4 doesn't do much good) and also limited to something slightly above leakage current from self discharge and surface leakage. 0.5 amps or so should do nicely. I find solar cells with a controller highly appropriate for this use, since the charge does not have to be continuous. The best charge controllers are the MPPT type since the pulses acctually help to break down and prevent sulfation. You can buy chargers designed to do just that, reduce sulfation, but they are expensive. Experience shows that they do not actually perform better. The cheap chinese mppt chargers are not bad and the 24 volt versions have about the right setting. The use of 26.5 as mentioned earlier would be more appropriate for gel-cel or absorbed mat applications and I have never seen those used on generators. The choice of size of panel would limit the output in amps to that desired.

Unreadable = Useless.

Continuous-preservation (float) charging: 2.23 V for gelled electrolyte; 2.25 V for AGM (absorbed glass mat) and 2.32 V for flooded cells. These voltages are per cell. They do very from the battery manufacture. So I would seek their recommendations.

Also the charger's output could very. Lower end chargers many of which have no adjustment will differ in the output. Better chargers have pots to adjust.

Here is a good article to read on the right way to charge LA batteries.

http://www.powerstream.com/SLA.htm

Despite many opinions the fact is that the applied voltage level is critical when charging any battery.

All batteries are designed to provide "X" volts per cell with Lead Acid being nominally at 2.15 VPC

It is not possible to charge any battery unless the applied charger voltage output level is higher than the battery state voltage.

Example: If a 12 Volt battery has discharged to 9.5 volts you cannot charge the battery (replace the spent electrons) unless the applied voltage is above 9.5 volts.

The higher the applied voltage, the faster the battery can be charged however the applied voltage must be kept within the design limit of the battery charger and as dictated by the type of battery.

E=IR or E=IZ and I=E/R or I = E/Z

I (current) is a direct function of E and R.

By the laws of physics: It is possible to have E or R without I but it is not possible to have I without E and R.

All battery manufacturers provide charging details for free on their batteries and all chargers are "voltage adjustable", but they not current adjustable other than to vary the applied voltage level.

The amount of current flowing from the charger into the battery is dependent on the voltage level applied and the impedance of the battery due to it's discharged state.

I suggest you contact the battery manufacturer and obtain the approproate DATA sheets and the IOM then identify the required Volts-Per-Cell value, and follow their recomendations for setting up the charger.

Any action other than this will not work out in your favor.

If you have a nominal 12V battery showing 9V open circuit voltage then one of the cells has shorted and no amount of magic will restore it.

Recycle it.

Wal-

This is correct in some cases but certainly not all: " If you have a nominal 12V battery showing 9V open circuit voltage then one of the cells has shorted and no amount of magic will restore it." "Recycle it."

If the battery has a bad cell it is correct. If the battery is simply low in charge it is not true. With this condition, where all cells are low to the same voltage, for example 1.5v/cell for a LA battery, all it needs is a charge to bring the total level of the series cells up to the rated voltage. A good scenario for this is when a car has a bad starter and the driver continually try's to start the engine. Since the starter normally reduces the battery level to 8-9v when operating the starter the battery is going to lose charge to that voltage or lower. All that is needed is a charge from an alternator, battery charger or another battery.

Good Luck, Old Salt

Lead acid cell voltage is 2.2V

Let's talk 12V_nom automotive cranking batteries.

My car stops cranking once the voltage drops to 11V andany attempts to crank has the voltage diving still though not to 9V.

If the battery is allowed to rest and cool down the internal resistance drops and the voltage creeps back up to 12V.

Measuring the o/c voltage does not tell you the state of charge or condition of your battery. A battery may show 12v across its terminal but still be dead. As soon as a this battery is loaded the voltage will drop.

If an unloaded 12v battery presents only 9v then I've made a margin on supplying and fitting a new one.

11 to 12V o/c = recharge and try to get a bit more duty from it.

9V o/c = be prepared to replace.

HOW EXACTLY is this bantering helping the OP?

You prove my point eloquently.

Chest beating trumps helping the OP almost EVERY time.

Can you deny this?????

Does, "Lead acid cell voltage is 2.2V

Let's talk 12V_nom automotive cranking batteries.

My car stops cranking once the voltage drops to 11V andany attempts to crank has the voltage diving still though not to 9V.

If the battery is allowed to rest and cool down the internal resistance drops and the voltage creeps back up to 12V.

Measuring the o/c voltage does not tell you the state of charge or condition of your battery. A battery may show 12v across its terminal but still be dead. As soon as a this battery is loaded the voltage will drop.

If an unloaded 12v battery presents only 9v then I've made a margin on supplying and fitting a new one.

11 to 12V o/c = recharge and try to get a bit more duty from it.

9V o/c = be prepared to replace."

help the OP?

Don't you take that bold faced font with me!

Although your technical observations are accurate (and I agree with them!), in the real world they seldom are correct.

The reason being is that all 6 cells in a 12 volt battery are all "individuals" some are weaker and some are stronger. We just assume they are the same, they are not.....

The weakest one will always be discharged first in such situations. When charging, it will be overcharged before the other cells are full. It simply has a lower (the lowest) capacity.

This means that when the battery fails, it will be the weak cell first.......so his comment will actually be correct in the "real" world......my observations over many years support that as well.....

Only Leisure LA Batteries are due to their construction, less affected by this phenomina.....less not "not".....

If the battery is simply low, even without a bad cell, at 9 volts it will probably not be good anymore. Most battery manufacturers for a 12 volt battery recommend not discharging a battery to less than 50% level. This is about 10.5 volts at the amperage in the long term amperage rating (not starting amps). If you allow it to drop below that value, it will have permanent damage to the cells. If you try to charge a 12 volt battery that has dropped to 9 volts, you may get it to charge, but it will never have the capacity it was designed for.

4wsilver-

Yes, most often that is true but not always. The 9volt charge level was only used because that is the level that #33 referenced to. I has also been my observation that a 9v level, 12v nominal, battery correctly recharged can very often be successfully used at applications other than automobiles.

Numerous times I have seen cars with drained down batteries due to leaving appliances such as headlights on for extended periods of time. After a properly administered charge they perform like a battery that has not been exposed to this over withdrawal.

Good Luck, Old Salt

For most LA batteries as far as I am aware, that is true.

Which is exactly why my caravan has a "Leisure" LA battery, they are affected far less.

One should always remember that a normal car battery, when left under 12.6 volts, is starting to get damaged.....but in a car, it is usually recharged by the engine before damage is visibly noticed....the time factor must also be recognised as part of the problem....

There are little 12 volts nominal solar cells available for very little money, that charge the battery as long as there is light.

24 hours a day in summer at the north pole and where places where street lighting is not switched off before sunrise!!

Yes, I agree that this could be the case especially if the battery has been discharged to the point where it enters into "reversal".

The numbers used were just an example.

I have had the opportunity to visit a battery recycling plant and observe some of the methods used to re-generate the chemical reaction inside the cells.

Often the battery cells are not shorted nor open and instead suffer from sulfation and/or oxidation plating of the lead surface. This is usually caused from the battery not getting properly charged and discharged along with too low of charging current and no equalization time. In these cases the re-cycler usually installs new electrolyte then applies very high voltage to the battery while monitoring the specific gravity and temperature. Most of the time the plating is removed and the battery comes back to life.

Wish they could do that with humans.

Just get a "battery tender", should be available from your local automotive supply store. I never checked the output voltage on mine, but they come in various amperages(probably charge at 13-14 volts same as an alternator for 12 volt systems,higher for 24v systems). Rather than charge constantly, they actually measure the battery voltage and only charge when required. Why use power when not required?

As per your last sentence - how true!!

My own chargers actually use a tiny bit of the battery voltage to run a monitor, only a couple of milliamps...it is completely separated from the mains at that point if no charging is needed. Even an unloaded transformer takes more current than my monitor.....though its a very efficient transformer type....

Thats why there is a special switch, which forces the charger on when a battery is so low, the monitor cannot run properly....

I am in the process of using/designing a PIC to do all the heavy stuff in my next version, instead of logic, its not as easy as I first thought!! Keeps the grey matter on the move!!

I laugh, guffaw, shake my head, do palm slaps and chortle at our collective inability to agree on a single thing we "discuss", here and in most threads that we flog beyond all recognition.

I disagree with that Lyn.

We agree fairly frequently.

I haven't seen noticed any disagreements on this thread. Plenty of embellishments but nothing contrary.

I'm surprised it's managed to stay reasonably on topic for so long.

Me too.

Yet I always learn something from the in-depth discussions and usually come away with a better point of view thanks to all that participate.

No denying the wealth of knowledge here. And a few misguided thoughts along the way.

Pity the poor OP who just wants to know what time it is, and gets told how to build a watch.

Yeah but!

Next time would not have to ask!