Calculating Charging Time for 2x180Ah Batteries Using 90A Alternator and Deutz V8 Engine

Hello
I have the following problem:
How much time should the engine run at least for the alternator to charge the batteries as much as the starter took the current from them. Unfortunately, I do not know what power the starter is, I only know that the alternator is 90 amps and the batteries are 2 x 180Ah, the starter is not a small one because it has to start the 13-liter deutz V8 engine.
The engine works in a construction machine and after about 4 minutes of operation it is turned off, unfortunately it is probably too short time to recharge the power used from the batteries.

A warm engine needs 0.5 seconds of the starter operation, the current flowing in the pulse can reach 1000 A, so you can burn it several dozen times, but these 4-minute working times are probably not enough to fully recharge and it is suitable to connect it to the rectifier overnight with some limitation after charging .
Or let the engine work for about an hour, the on-board ammeter will allow you to assess the state of charge by not leaning to + during operation.

I planned to install the rectifier permanently in the machine because 220v is rather always available on the construction site, but I was wondering how to limit the charging current as the batteries charge (something like the voltage regulator in the alternator limiting the excitation current) and can the rectifier and alternator work together?

A rectifier with automation will help. My guess is the batteries are connected in series so you need a 24V charger. Look around automotive stores, if you have trouble finding, I can give up.
Greetings.

well, 24v, the rectifier even has a quite powerful "dynamic Telwin 620" (a lot of these on the Allegro) but whether it has "automatics" I do not know. It has an ammeter and during charging the arrow gradually moves less and less, but does it actually get less from the rectifier?

A powerful machine, but it seems to me that the device does not have charging control electronics, as a rule, manufacturers are loudly honking about additional product features, and I have not found such information in any descriptions.

hmm ...
what is this machine and what revolutions does it work for these 4 minutes, how many times a day is it burned and with what breaks and how fast the engine starts ... ???

it may turn out that no rectifier is needed ...

Construction crane, engine like in a truck, alternator 28v 90A, "slow" revolutions about 1000 / m, fires normally, i.e. about 1s. The fired, pulled load and extinguished all in order to save today's expensive fuel. Sometimes the engine runs for an hour, sometimes 4 minutes, recently often 4 minutes . I just want to count how much electricity the starter "swallows" for firing and then how much time the alternator has to work to recharge the batteries.

The easiest way is to measure the voltage and concentration of the electrolyte (state of charge) in the morning and the same in the evening. The aerometer costs something over PLN 10.
It is impossible to play with some tedious calculations, which will not give you anything constructive anyway.

And here, however, there will be a problem because the batteries are maintenance-free and do not have plugs, of course, I can measure the voltage, but what next?

Added after 2 [minutes]:

I think there is a formula that is simpler than all this, which will calculate how long the minimum time the engine must run in order to charge it, every 1s the starter operation discharges

If the engine is running for 1 hour then you do not have to recharge the batteries, and if they are frequent firings for only 4 minutes. then you need to provide external charging because you will get expensive batteries.
I suggest buying a 27.6 V power supply (for two series connected 12V / 180Ah batteries). Why 27.6V because this voltage will not overcharge the batteries and at the same time provide full battery power. The power supply does not have to be strong, for example 27.6V / 5A is enough. a lot of it on the Internet, for example
MIXPO MC-140-27.6 universal power supply http://www.volty.pl/276-v-c59.html The power supply can be constantly turned on without fear of damage (battery overcharging). one 12V battery (21V for two) will finish them off.
greetings

If you insisted, it's okay to provide the electricity consumed for the start, I warn you that another will be in the cold, different in the warm, different at the beginning of the filming, different at the end and it plays a role because the differences are great, since the time needed to charge is to be calculated and nothing more? Utopia.

Quote:

tension of course I can measure but what next?

Without miracle, a charged battery has a terminal voltage in the range of 12.7-13.2V. it is to be measured at least after a dozen or so minutes of inactivity.

Sometimes it works for 4 minutes, sometimes 1 hour, so it will be recharged. If you want to charge, use a simple impulse charger, e.g.
http://www.texa.pl/index.php?strona=zb-25
This is what I use for fire engines (with lower current) and ambulances.
Loading from such Telwin, and even more so starting, is very risky.
The charger can work with the engine, but an automatic disconnect can be made using the D + signal from the alternator and a relay.

I plan to buy a voltmeter permanently mounted to the car, I think it will allow you to control the charging of the batteries, which will show me if the charging time was sufficient. I liked the idea of my colleague "K2" with the power supply and my colleague "kkknc" with the connection to D + which will disconnect the power supply. I remember that during one of the first lessons we calculated how much the starter uses and how much time the batteries need to be recharged, but how was it already done? I missed it, in fact it will be better to do it practically and control the tension

Buddy K2 10.5V is the final voltage of a discharged 12V battery. Dangerous voltage below which you must not go down is 8V. At 10.5V, the batteries will not crank the starter in a way that would allow the engine to start.
And the voltage of 27.6V is recommended for buffer operation, not cyclical. Although this voltage is sufficient to keep the battery charged, these power supplies have the option of adjusting the voltage with a potentiometer. There is only a small problem at high load, this power supply will not start and heavily discharged batteries will not be charged.
Buddy arturs75, you twisted my nickname, which is unforgivable, so correct it quickly before you get in ..... This voltmeter is so I will ask what for? A powerful alternator will force the charging with a large current, which will allow you to obtain the correct voltage on the voltmeter. An unloaded voltmeter will show you the electromotive force of the cell, not the charge accumulated in it. A moment after the engine is turned off, the voltage will be very high and then it will drop, so in this mode it will be difficult to deduce whether it will light the next time or not

It is also important that the power supply has a maximum current limiter. In order not to fry (or at best, burn the fuse) of the power supply when turning the starter.

It will show a lot, but before ignition, and there will be a clear picture of the tendency that the batteries take after subsequent starts, at one time the voltage may be very low and the operator will extend the engine's operation by 20 minutes to recharge or connect a rectifier.
There is such a brand of Volvo and each one has a Voltmeter, every driver knows that if there is 24-26V it will light up without any problem, if 22 is already afraid.
This helps a lot in the economy of electricity with the modern rich equipment of the car: express converters, TV, satellite, laptop, fridge (sometimes the driver stays in this box for 3 days and has to use and rule the electricity)
Such a Voltmeter is wealth.

The EMF in a healthy battery is a relatively good indicator of the state of charge.
They are old sulphated cells and need to be measured as a function of the load.

The charger I proposed is equipped with everything that a colleague has jannaszek He said. She is expensive but professional. Nobody in their right mind will change the battery because the voltmeter is wrong and the car is burning. The real wealth is the ammeter. Woltomierz has many long distance buses because it is cheap. I basically give a reading a little digital will light up or not. In general, I think the topic is a bit blown.
Well, gentlemen, we're here to talk to the author of the post and to the trace.

I am here and because Sunday it was necessary to visit my family. Of course, I apologize for turning my friend's "kkknc". Indeed, when I measured the voltage, it looked as follows: before starting 25v, 27v during engine operation, and after turning off 26v, the latter indication stabilized at 25v after about 2 minutes. This is exactly how he plans to do it, in case of too low a reading before starting the engine, increase the running time of the engine. I don't think these indications turn out badly, how do you think?

Buddy, you still haven't corrected my anyone !!! Should I ask a moderator?
To turn off the charger, you can give a relay with a coil connected to D + alternator and 50 starter, which will disconnect the charger when turning the starter and after ignition, as the alternator works.
Indications are as correct as for idle speed (the question of where you connected this voltmeter - voltage drops in the installation)

I connected the voltmeter in two places and in both the same indication directly behind the main switch next to the batteries and in the cabin in the cigarette lighter socket

Batteries are a bit undercharged, this is what the voltmeter says, it will affect their service life.
A simple solution is to even connect your rectifier on a small range for 2-4 hours every other day and charge it, for example, with a 24V bulb or other resistor, which will prevent overcharging.
Greetings.

What voltage should the charged batteries "have"?

25.8V-26.2V for you approximately, I wrote above.

Relax, arturs75 from what you measured the batteries have a good 25V when you ignite, i.e. 12.5V for one battery, it's great. the motor will drop after a few hours to about 25..26V. So if you have it, you burn from the shot. Lead batteries are chemistry, voltage, internal resistance, inrush currents depend on so many factors that books and doctorates have been written about it. you rarely light up, then connect an external power supply with a voltage of about 27.4V. 27.6V then you will not overcharge them, i.e. they will not gass. In the morning you will come to work, turn on the power supply, turn off after a day's work and do not worry about it, it will be fine. the battery voltage will reach 27.6V and the charging current will drop to a negligible value (maybe a few mA) and that's it. If you want, you can charge cyclically, i.e. up to 14.7Vx2 = 29.4 but why do you take the battery off each cycle? a little bit of life. Just be careful not to let someone else that it kicked the 230V, because it does not sleep. The critical voltage when igniting is 22V to 23V, then you may not ignite it, although it does not know. This voltmeter in the cabin is a good idea. but who wants it today.

jannaszek wrote:

25.8V-26.2V for you approximately, I wrote above.

http://pl.wikipedia.org/wiki/Akumulator_kwasowo-ołowiowy
2x12.6V = 25.2V
Batteries charged and nothing will happen to them, but you can always listen to your friend's advice jannaszek , with this bulb it is already live. as for the "king's candle"
To prevent the batteries from gassing, do not exceed 27.8-28V
I think that you do not need additional charging, if you need good advice from a colleague K2 .

And this power supply with a voltage of 27.4V ..27.6V is what am I supposed to do?

The more the better, but 5A is enough for maintenance charging.

http://www.akumulatory-zelowe.pl/ladowarka-im...owa-24v-8a-do-wozkow-elektrycznych-p-207.html

Quote:

with this light bulb it is already live. as for the "king's candle"
To prevent the batteries from gassing, do not exceed 27.8-28V

Charging by a light bulb is not a candle method, and is very often used by everyone who does not have an appropriate rectifier (the author of the post does not have it either) and want to limit the charging current.

In turn, you need to know what the conserving current is before you write 5A.